Final draft2

Climate-Smart Agriculture _ Training Manual Water Resources and Wetlands Vegter JR (2001). Groundwater Development on South Africa and an Introduction to the Hydrogeology of Groundwater Regions. WRC Report No. TT 134/00. Water Research Commission, Pretoria, South Africa. Wetland Management Series: WET-RoadMap. 2007. Report TT 321/07, Water Research Commission; WET-Origins. 2009. Report TT334/09, Water Research Commission; WET-Priorities. 2009. Report TT337/09, Water Research Commission; WET-legal. 2009. Report TT338/09, Water Research Commission; WET-Ecoservices. 2009. Report TT339/09, Water Research Commission; WET-Health. 2009. Report TT340/09, Water Research Commission; WET-RehabMethods. 2009. Report TT341/09, Water Research Commission; WET-RehabEvaluate. 2009. Report TT342/09, Water Research Commission. Winter TC (1999). Relation of streams, lakes, and wetlands to groundwater flow systems. Hydrogeology Journal. 7(1): 28-45. 150

Climate-Smart Agriculture _ Training Manual Water Resources and Wetlands LIST OF FIGURES Figure 1 Illustration of the water balance components in a catchment. 129 Figure 2 Palmiet (Prionium serratum). 131 Figure 3 Swamp forest. 131 Figure 4 Reeds (Phragmites australis). 132 Figure 5 Illustration of where inland wetlands could occur in the landscape. 133 Figure 6 Illustration of the different HGM wetland units. 134 Figure 7 Decomposition stages of the peat horizon: A) Fibric, 135 B) Hemic and C) Sapric peat from Karst system. Figure 8 National Wetland Map version 5. 136 Figure 9 Wetland confidence map and categories. 136 Figure 10 Peat ecoregions with Palmiet systems (wetlands dominated 137 by Prionium serratum) occur along the Southern Coastal Belt (A). The Mfabeni Mire (oldest system) occurs in the Natal Coastal Plain (B). The map also shows known peat sites in the National Peatland Database (C). Figure 11 Ecosystem drivers and responses influencing the ecosystem services provided. 139 Figure 12 Bodibe (North West Province); MUZI: Peat/Hard Carbonate. 143 Figure 13 Peat loss due to erosion (Kromme, Western Cape Province), 143 KROMME: Peat/Hard Rock. Figure 14 Locations of peat fires and desiccated peatlands reported across South Africa since 1996. 144 Figure 15 Water and carbon storage lost due to peat desiccation and subsurface fire. 146 LIST OF TABLES Table 1 Drivers and impacts on wetlands and peatlands with examples. 140 145 Table 2 Extent of peat fires and desiccated peatlands reported across South Africa since 1996. 151

MODULE 4 Grain Crops Production Compiled by Zaid Bello, Molefe Thobakgale, Phonnie Du Toit and Edzisani Nemadodzi Agricultural Research Council – Grain Crops

Climate-Smart Agriculture _ Training Manual 154 Grain Crops Production 156 156 Table of Contents 156 157 1 INTRODUCTION 157 2 PERCEPTION ON CLIMATE CHANGE AND CLIMATE VARIABILITY, AND CSA 159 2.1 Perceptions on climate change and climate variability 160 2.2 Climate-Smart Agriculture 162 3 SELECTED GRAIN CROPS PRODUCED IN THE TARGET PROVINCES 163 3.1 MAIZE 165 3.2 SORGHUM 166 3.3 SUNFLOWER 166 3.4 GROUNDNUT 167 3.5 COWPEA 167 3.6 DRY BEANS 169 4 CSA TECHNIQUES/APPROACHES 174 4.1 CONSERVATION AGRICULTURE 174 4.1.1 Minimum till 174 4.1.2 Crop rotation 175 4.1.3 Cover crops 176 4.2 CROPPING SYSTEMS 176 4.2.1 Crop varieties 176 4.2.2 Intercropping 177 4.3 Integrated Pest Management (IPM) 177 4.4 AGRONOMIC PRACTICES 178 4.4.1 Planting dates 179 4.4.2 Weeding 180 4.4.3 Fertilisation 184 4.4.4 Mulching 185 4.4.5 Adjusting plant population 4.5 IMPROVED STORAGE AND PROCESSING TECHNIQUES 5 REFERENCES AND RESOURCES LIST OF FIGURES LIST OF TABLES 153

Climate-Smart Agriculture _ Training Manual Climate Change refers to a Grain Crops Production change in the state of the climate that can be detected 1 INTRODUCTION (e.g., by statistical tests) by changes in the mean and/or Agriculture is one of the most important variability of its characteristics economic sectors in South Africa. It is critical and that lasts for an extended to the process of economic development and period of time, often decades significantly contributes to household food or longer. Climate change may security. Smallholder farming benefits the be caused by natural internal economy in both commercial and subsistence processes or external forcings ways. Agriculture in South Africa includes such as solar cycle modulation, animal husbandry, fisheries, forestry, and crop volcanic eruptions, and chronic production. Crops are grown throughout the country in both eTcohstneavsbeelnistlhioomnngea-nltetcrromopfph2ctio0uanrm0emg7npat)sdo.nryassscidtthieicoatmlinneogoanterhrsllayiandtneaidisnftiumcdnsooieecmsda(pItpPheClebeCryti,tcehleay irrigated and dryland areas. Crop production is unprepared for the level of climate change that feasible on roughly 13% of South Africa's land grain farmers are currently confronted with. area. Irrigation affects 1.3 million hectares of Only since 2008/09 have organized agriculture land. Crops grown in South Africa include grain, and research institutions, such as Grain SA, tubers, fiber, fruits, horticultural, and oil crops. begun to provide substantial support for the Because of the long-standing emphasis on need for a more climate-smart and sustainable maize production, research, and the industry grain production system, such as conservation as a whole, the vast majority of grain-producing agriculture (CA). Due to the wide range of land in South Africa is still controlled by a maize climatic conditions, grain crop production in mono-cropping system. This has largely resulted South Africa can be divided into two categories: in the neglect of other important crops, as summer crops and winter cereals. well as a lack of a strong commitment to crop diversification and crop rotation, both of which Summer crops that are important include are essential for a sustainable and resilient grain maize, soybeans, sunflower seeds, groundnuts, business. Between 1980 and 2008, a significant and sorghum, which are grown in areas with mechanization industry arose. high summer rainfall. To maintain and stabilise maize output, the growing mechanisation sector concentrated The semi-arid and arid regions of South Africa on high traction power and heavy tillage produce the majority of grain crops. Semi-arid instruments that encouraged aggressive field and arid regions, for example, accounted for preparation. Furthermore, the introduction of more than 60% of total area grown for maize, GMO maize (1998–2004) shifted attention to sorghum, and sunflower, whereas wet regions maize, resulting in increased maize production accounted for 30% of total area grown for the at the expense of reduced crop diversity. Out of same crop set (DAFF, 2019; Haarhoff et al., all the legume and oil seed crops, only soybeans 2019). Because grain crops are grown in South benefited from GMO technology. Africa's semi-arid and arid regions, they are subject to a low, unreliable seasonal rainfall regime with high variability in both time and space, necessitating a special emphasis on soil water storage and water use efficiency. 154

Climate-Smart Agriculture _ Training Manual Grain Crops Production High summer temperatures, low, erratic rainfall, Where grain crop production is consistent, and high evaporation rates frequently limit crop its sustainability is called into question due yields and, in some cases, cause crop failure to the impact of agronomic practices such (Beukes et al., 1999; Bennie & Hensley, 2001; as fertiliser application, mono-cropping, and Stroonsjder, 2003). Farming practices in these indiscriminate field irrigation on yield, soils, areas are complicated by climate variability and and the environment. Grain crops have recently climate change events. The unpredictability of gained prominence as the world's population the climatic conditions has made these areas continues to expand at an exponential rate, unsuitable for cultivation of any of these grain increasing demand for food production. Crop crops over the years, resulting in a decrease in production should be increased to meet total land area cultivated. Within 20 years (1998- demand while ensuring long-term productivity, 2018), the total land area under cultivation for all while taking climate change and current maize was reduced by nearly 20%. (DAFF, 2019). environmental conditions into account. Training objectives • Extension Practitioners (EPs) are expected to be familiar with the importance of Climate-Smart Agriculture (CSA) to grain crop production by the end of the training. • Show a thorough understanding of the importance of conservation agriculture (CA) as a Climate- Smart Agriculture (CSA) relevant system. • They should also be able to use CSA knowledge to advise farmers on how to solve problems or address production challenges that are weather, climate, crop, soil, or a combination of these. 155

Climate-Smart Agriculture _ Training Manual Grain Crops Production 2 PERCEPTION ON CLIMATE CHANGE AND CLIMATE VARIABILITY, AND CSA 2.1 Perceptions on climate change growth and spread of most pest species by and climate variability providing a warm and humid environment as well as the moisture they require for growth. To solve any problem, you must first understand Extension officers play an important role in what is causing it. Extension staff are expected educating farmers on how to cope with and to know and understand the subject of climate respond to climate change. As a result, they change and climate variability in order to educate must understand climate change issues such as farmers about the effects of climate change on causes, effects, vulnerability, and mitigation. grain crop output. Unrestricted greenhouse gas emissions cause the earth's temperature 2.2 Climate-Smart Agriculture to rise, glaciers to melt, precipitation to increase, extreme weather events to occur, and Agricultural productivity issues are one of the seasons to shift. Understanding how vulnerable issues posed by climate change. To prepare agricultural productivity is to climate change for the possibility that climate change will and unpredictability is critical. bring about a new set of weather patterns and extremes that local communities in South Africa Temperatures above the grain crop threshold may not be able to deal with, several measures have the same effect on crop growth and for efficient and sustainable grain crop development as low and variable rainfall. production will be put in place. Climate smart Another effect of extreme weather is the failure agriculture addresses these issues holistically of some crop protection strategies, resulting in order to produce grain crops in a sustainable in yield losses. This is due to the unpredictable manner, increasing production and meeting the impact of extreme weather events on crop, increasing demand for food, particularly grain pest, and disease interactions. Increases in crops. temperature and precipitation encourage the 156

Climate-Smart Agriculture _ Training Manual Grain Crops Production 3 SELECTED GRAIN CROPS PRODUCED IN THE TARGET PROVINCES A brief overview of six grain crops that are 3.1 MAIZE relevant and highly produced in the three provinces represented is provided below. These South Africa's most important grain crop is crops were chosen based on the potential maize (Zea mays L.). It is the primary food application of CSA to the challenges that consumed in many rural households, and it is smallholder farmers face in producing these widely grown by the majority of farmers. crops in these provinces. While it is impossible South Africa is the leading maize producer in to present all of the grain crops produced in the Southern African Development Community these provinces, the ones chosen are chosen (SADC) region (Durand, 2006). Currently, based on their representativeness of grain regardless of the type of maize, South Africa crops in the country, particularly in the regions produces approximately 9 million tons of maize where the EPs work, namely the Eastern grain per year on approximately 1.7 million ha Cape Province, Limpopo Province, and North of land. More than half of the crop is white West Province. Maize, sorghum, sunflower, maize for human consumption. groundnut, cowpea, and dry beans have been chosen as grain crops. Figure 1 Cultivar maize trial field. 157

Climate-Smart Agriculture _ Training Manual Grain Crops Production Smallholder farmers produce a much smaller Maize is highly susceptible to changes in share (15%) of the country's total maize precipitation and temperature because it is a production (Greyling and Pardey, 2019). summer crop (Durand 2006; Benhin 2006). In Lack of good storage infrastructure, better general, the temperature range for optimum credit, better technologies and know-how, as maize growth and development is between 6°C well as difficulties in accessing better land, are and 45°C, with different cultivars falling within some of the reasons for smallholder farmers' this range (Moloetsi, 2010). As a result, maize is low contribution to the country's total maize sensitive to extremely low temperatures (frost), production. which can harm the crop (Ofori & Kyei-Baffour, With the exception of early maturing cultivars, 2009; Trasmonte et al., 2008). Though warmer which can take less than 100 days, and others temperatures hasten maize development, at high altitudes, which can take up to 300 days resulting in shorter vegetative and reproductive from sowing to maturity, maize has an average phases, high temperatures can also have an growing cycle of 120 to 140 days (Frere & Popov, impact on maize by reducing pollen viability, 1986). which in turn reduces kernel numbers, one of In terms of soil nutrient status, nitrogen, the most important yield components of maize phosphorus, and potassium, as well as other (Lisazo et al., 2017). micronutrients like baron, calcium, magnesium, Water stress has a general impact on flowering manganese, and molybdenum, are the most synchrony and, as a result, grain yield (Herrero important nutrients influencing maize growth & Johnson, 1981; Hall et al., 1982). This could and yield (Reid et al., 2006; Ofori & Kyei-Baffour, occur during periods of low rainfall or high 2009). Though nutrient availability is critical for rainfall variability. maize yields and productivity, these variables Climate change can also cause biotic issues are also influenced by environmental conditions in maize, such as pest and disease outbreaks. as well as pest and disease management (Ofori The incidence of fall armyworm in maize is & Kyei-Baffour, 2009). an example of the effect of climate change The Free State Province is the most productive, on pests. The incidence of fall armyworm in followed by the North West and Mpumalanga maize crops has increased dramatically in the provinces. The majority of the maize is grown Vhembe district of northern South Africa over under rainfed conditions, accounting for up to the years (Phophi et al., 2020). The increased 90% of the total maize produced in South Africa incidence was attributed to more dry spells and (Greyling and Pardey, 2019). The climate of warmer conditions, as the pest requires warmer South Africa's major maize-producing regions environments to survive and reproduce. is classified as semi-arid or arid. The common occurrence of low precipitation in these areas is exacerbated by the high evaporative demand of the atmosphere. 158

Climate-Smart Agriculture _ Training Manual Grain Crops Production 3.2 SORGHUM In South Africa, cultivated sorghum is grown in the drier areas of the northern provinces, Sorghum (Sorghum bicolor L. Moench) is a where it is planted between mid-October and gluten-free grain and the world's fifth most mid-December. This hardy crop provides better widely grown grain crop, after wheat, rice, corn, household food security than maize in South and barley. Sorghum is an African crop, and Africa's more drought-prone areas. Bitter and while commercial needs and uses may change sweet sorghum cultivars are the two types of over time, it will continue to be a basic staple sorghum. Sweet cultivars are given preference. food for many rural communities. Sorghum is Bitter sorghum is planted in areas where birds used for human consumption (cereal, flour, and are a problem because it contains tannin, which beer) as well as animal feed as silage or hay. gives it a bitter taste, and birds avoid feeding on Sorghum is also used to make biodegradable it as a result. packaging, wallboard, baskets, and brushes. Grain sorghum has a starch content that is 7 to 10% higher than maize, making it ideal for ethanol production. Figure 2 Sorghum field at early maturity stage. 159

Climate-Smart Agriculture _ Training Manual Grain Crops Production Sorghum production in South Africa ranges crops and can be attributed to exceptionally between 100,000 and 155, 000 tons per well developed and finely branched root year from a land area of approximately 50 system, which is very efficient in the absorption 000 ha. The provinces of Free State and of water. Also, small leaf area per plant, which Mpumalanga contribute the most to the area limits transpiration is another attribute that planted to sorghum and sorghum production. contributes to the crop drought tolerance. Furthermore, Free State Province produces The crop has a more effective transpiration roughly half of South Africa's sorghum. The system in comparison to maize. The epidermis average grain seed production yield is 2 tons/ of sorghum leaf is corky and covered with a waxy ha. In recent years, sorghum production has layer, which protects the plant form desiccation. shifted from the drier western production areas The stomata close rapidly to limit water loss to the wetter eastern areas. during dry periods and has the ability to remain This shift in production area has resulted in the in a virtually dormant stage and resume growth identification and development of cultivars that as soon as conditions become favourable. Even are more temperature tolerant. To maximize though the main stem may die, side shoots can yield potential, sorghum plants require a deep develop and form seed when the water supply well-drained fertile soil, a medium to good and improves. fairly stable rainfall pattern during the growing season, temperate to warm weather, and a frost- 3.3 SUNFLOWER free period of approximately 120 to 140 days. Sorghum is a warm-weather crop that needs The sunflower (Helianthus annuus L.) is the high temperatures to germinate and grow. most important oilseed crop in South Africa. It As a result, a temperature range of 27 to 30 ºC is was South Africa's third largest grain crop after required for optimal growth and development. maize and wheat before being surpassed by Temperatures as low as 21 ºC, on the other soybeans (Grains South Africa, 2019). Sunflower hand, have no discernible effect on growth and seed is primarily used in the production of yield. After germination, temperature plays an sunflower oil and oilcake for animal feed. In important role in growth and development. The South Africa, sunflower is primarily grown as minimum temperature for germination ranges a single crop for commercial purposes (Botha, from 7 to 10 ºC. At a temperature of 15 ºC, 80 2006). Sunflowers have earned the reputation % of seeds germinate in 10 to 12 days. When of being an ideal crop to grow in South Africa there is enough water in the soil and the soil under low-input farming and marginal cropping temperature is 15 ºC or higher at a depth of 10 conditions over the years. cm, it is the best time to plant. The ability of sunflowers to produce relatively Sorghum is produced in South Africa on a wide consistent yields under adverse weather range of soils, and under fluctuating rainfall conditions, as well as their overall drought- conditions of approximately 400 mm in the drier tolerance, makes it an appealing crop for western parts to about 800 mm in the wetter producers in dryland production regions. eastern parts. Drought tolerant Sorghum is able Sunflowers can also produce a crop on marginal to tolerate drought better than most other grain soils with very little or no additional fertiliser. 160

Climate-Smart Agriculture _ Training Manual Grain Crops Production Sunflower seed can be planted from the oil (Grain SA, 2015). However, in the long run, beginning of November to the end of December sunflower is said to have a higher average gross in the eastern production areas and until the margin than maize (Grain SA, 2015). middle of January in the western production Sunflowers are drought resistant, making areas. Sunflowers grow best when planted in them an ideal crop for South African growing the middle of summer, when less moisture is conditions and an alternative crop in the face lost from the soil during the critical growing of climate variability and change. Because of periods. its extensive root system, the crop can access Production is concentrated in the Free State water from deep within the soil. This means (FS) and North West Province (NW), which that the crop can still produce successfully account for 79 percent of the national even in dry conditions. This could be one of the sunflower planting area. Over the last two reasons for the observed increase in sunflower decades, both production and production land cultivation land area. The main problem with areas have steadily increased in the country, sunflower cultivation is high temperatures. High but this has not resulted in significant growth soil temperatures can have a negative impact in the South African sunflower industry. Though on crop quality in terms of grain oil content both production and production land areas (Rondanini et al., 2005). This is one of the most are increasing, they are not increasing at the significant challenges confronting the major same rate as demand for oilcake and vegetable producing provinces of this crop. Figure 3 Sunflower cultivar trial field. 161

Climate-Smart Agriculture _ Training Manual Grain Crops Production 3.4 GROUNDNUT Groundnut is one of the most important grain legumes grown by both subsistence Groundnut (Arachis hypogaea L.) is a major grain and commercial farmers in South Africa legume in arid and semi-arid areas (Chibarabada (Chibarabada et al., 2017). The majority of et al., 2017). It is well-known for its versatility, groundnut produced in South Africa is grown in as it can be eaten as a snack or processed the North-West and Free State provinces, which into peanut butter or cooking oil. Because have seen a decline in total production and groundnut is a legume, it has been linked to high production land areas. The gross production of nitrogen fixation, making it a strategic crop for groundnuts in 1991 was 79 000 tons, compared long-term intensification. Its suitability to these to the current production of 19 500 tons (2018). environments has been demonstrated by its production in major semi-arid and arid regions of South Africa, but it has also demonstrated instability across environments and seasons (Sahay and Sarma, 2005; Mekontchou et al., 2006; Nawaz et al., 2009). Figure 4 Groundnut field at the vegetative stage. 162

Climate-Smart Agriculture _ Training Manual Grain Crops Production The temperature of the soil is just as important Groundnuts that come after small grains usually in groundnut production as it is in other grain have fewer diseases. To prevent sclerotium crops. In groundnuts, the lower limit for rot from becoming a problem, previous crop germination is around 18°C. Germination occurs stubble must be thoroughly incorporated into at temperatures ranging from 20 to 30 ° C, but the soil. at 33 ° C, germination drops to 84 %. Optimal Aflatoxin contamination is another risk to germination temperatures are thus between 20 groundnut yield and quality. Aflatoxins are a and 30 ° C, with a minimum of 18 ° C. group of mycotoxins, produced by fungi called In the literature, water has been identified as a Aspergillus species. Aflatoxin is a carcinogen, limiting factor in groundnut production. Despite immune system modulator, and cause of its drought tolerance, production is subject to malnutrition in both humans and livestock significant fluctuations due to rainfall variability. (Rushing and Selim, 2019). As the fungi that However, the availability of water at various produce aflatoxins prefer warm tropical stages of groundnut growth has a different and subtropical conditions, global warming, effect on grain production (Subramanian et al., particularly in temperate climates, encourages 2000) discovered that applying stress during the fungi and their toxin production. Groundnuts the seed-filling phase reduced kernel yield the are more susceptible to aflatoxin accumulation most. When compared to fully irrigated growing when exposed to high temperatures during pod seasons, reduced irrigation during the early maturation and when it rains (Milani, 2013). growth phase increased pod yield. Drought conditions can cause groundnut pods Variation in dry matter partitioning to pods has to crack, providing entry points for aflatoxin. been reported (Greenberg et al. 1992), and it was discovered that large variation in response 3.5 COWPEA of genotypes more tolerant to midseason drought is due to differences in recovery after Cowpea (Vigna unguiculata (L.) walp.) is drought relief (Williams 1994). All of this can thought to have originated in West Africa and be factored into the production plan, taking South Africa, though another source claims it into account the planting date as influenced by originated and was domesticated in Southern rainfall and variety selection. Africa before spreading to East and West Agronomic practices such as crop rotation are Africa and Asia. Small-scale farmers working also important for groundnut production. There in dryland farming conditions are the primary should be a good crop rotation program in place producers of cowpea. The annual global cowpea to protect against diseases and improve soil crop is estimated to be grown on 12.5 million health. Groundnuts should be grown in rotation ha, with a total grain production of 3 million with other crops, particularly grass type crops, tons, though only a small portion is exported. to reduce risk in the farming system. Groundnuts West and Central Africa is the world's leading should be planted after a main crop like maize, producer of cowpeas. These regions produce small grains, sorghum, or millet. 64 % of the estimated 3 million tons of cowpea seed produced annually. 163

Climate-Smart Agriculture _ Training Manual Grain Crops Production Cowpea is primarily grown in the provinces day length varies, with some being insensitive of Limpopo, Mpumalanga, North West, and and flowering within 30 days of sowing when Kwazulu Natal in South Africa. Cowpea is grown at temperatures around 30°C. The regarded as an underutilised indigenous crop flowering time of photosensitive varieties varies in some provinces. Cowpea offers numerous depending on the time and location of sowing benefits to both small-scale and commercial and can last more than 100 days. Even in early farmers. Cowpeas can be eaten as a spinach, flowering varieties, warm and moist conditions green bean, protein-rich seed, meat, or coffee can prolong the flowering period, resulting in substitute. asynchronous maturity. Many cowpea cultivars have a vining growth Cowpea is a drought-tolerant crop that habit, but modern plant breeding has resulted outperforms many others. It can thrive in rainfall in more upright, bush-type cultivars as well. The ranging from 400 to 700 mm per year. Cowpea vining variety is preferred for forage or cover is also very resistant to waterlogging. Rainfall crops, whereas the bush variety is better suited that is evenly distributed is essential for cowpea for direct combining. growth and development. Cowpea production Summer is the best time to grow cowpea. The in South Africa is hampered by the infrequency starting temperature for germination is 8.5°C, and unreliability of rainfall. In some areas, the and the starting temperature for leaf growth frequency of rains is excessive, resulting in is 20°C. Cowpea is a drought-tolerant and flooding, whereas in others, it is so unreliable heat-loving crop. The ideal temperature for that moisture conservation is critical for crop growth and development is around 30 degrees production. Cowpea is more drought-tolerant Celsius. The response of different varieties to than groundnuts, soya beans, and sunflowers because it efficiently utilises soil moisture. Figure 5 Cowpea at the pod filling stage. 164

Climate-Smart Agriculture _ Training Manual Grain Crops Production 3.6 DRY BEANS The Lowveld region of Mpumalanga produces the most seeds, followed by the Limpopo and Dry bean (Phaseolus vulgaris L.) is regarded as Northern Cape provinces. one of South Africa's most important field crops In frost-prone areas of South Africa, planting due to its high protein content and dietary dates range from November to mid-January. benefits. It is less expensive and contains more March and April are ideal months for planting protein than an equal amount of red meat. beans in frost-free areas. The large white kidney Other advantages of dry beans include quick bean is an exception; it is planted from mid- production due to a short cultivar growth cycle November to mid-December and is not adapted of 85-95 days, which can result in an early to winter production. harvest. Dry beans can grow in an upright, bush, The dry bean is an annual crop that grows well creeping, or indeterminate manner. Dry beans in warm climates. It grows best at temperatures get their name from the fact that they mature ranging from 18°C to 24°C. Extremely hot on the plant until the pods have dried and split. weather (30°C or higher) during the flowering South Africa produces 75% of the country's dry stage causes flower abscission (shedding) bean consumption. In lieu of this, efforts are and a low pod set, reducing yield. A daylight being made to increase its production in order to temperature of less than 20°C, on the other meet the ever-increasing demand for the crop. hand, will cause maturity to be delayed and According to the Crop Estimates Committee, an result in empty seed pods. The length of the estimated 53 360 ha of dry beans were planted cultivar's growing season is determined by the for commercial markets, yielding 69 360 tons temperature, particularly at night. Based on in 2017/18. The Free State Province produced the influence of the night temperature, these 41,2 percent (28 600 tons), Limpopo produced cultivars are classified as Short (85-94 days), 21,6% (15 000 tons), Mpumalanga produced Medium (95-104 days), and Long (105-115 14,1% (9 800 tons), and North West produced days). 13,8% (9 600 tons). The other provinces produced the remaining 9.2% (6 360 tons). Figure 6 Well established dry beans field with the farmer. 165

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4 CSA TECHNIQUES/APPROACHES 4.1 CONSERVATION AGRICULTURE CA has been used in the commercial, small- scale, and subsistence cultivation of various Conservation agriculture (CA) is one of the major grain crops around the world for many years. components of Climate-Smart Agriculture. CA Moldboard ploughing and hand hoeing are is a farming system that promotes no-till or common practices in smallholder agriculture in minimal soil disturbance during preparation, Southern Africa, and they are often blamed for mulching (crop residue retention) and/or land degradation and nutrient losses (Fowler planting cover crops to keep the soil surface and Rockstrom 2001; Knowler and Bradshaw covered, and crop rotation. Above and below 2007). ground, CA promotes biodiversity and natural Reduced tillage, permanent soil cover, and crop biological processes. These factors lead to rotations are all being promoted as ways to increased water and nutrient use efficiency, combat this scourge (FAO 2008). Conservation which leads to long-term crop improvement. agriculture's effectiveness in controlling Because traditional farming methods have a excessive water run-off and soil erosion has negative impact on all aspects of soil quality, been well documented (Adams 1966; Alberts finding an alternative system that will ensure and Neibling 1994; Choudhary et al. 1997; Lal the land's long-term viability has become a top 1998; Barton et al. 2004; Scopel et al. 2004), and priority. Dry periods may become more common this contribution is expected to be measured in the future as a result of global climate change in terms of crop yield. Other advantages of trends. In this regard, dry land grain farmers conservation agriculture include lower crop face a significant challenge in minimizing any input costs and profit maximization (Dumanski type of water loss from the soil surface. Water et al. 2006; Knowler and Bradshaw 2007). loss through runoff and evaporation should be Soil organic matter (SOM) improvements can avoided as much as possible because it reduces help these soils improve their nutrient storage the amount of plant-available water in the soil, capacity, nutrient availability, biological activity, which is a major cause of low grain yields in soil structure, and erosion resistance, among many cases, especially during dry seasons. other things. The use of crop residue retention CA aids adaptation by reducing the risk of methods or the planting of cover crops has rainfall runoff and soil erosion, as well as helping been proven numerous times to increase SOM. to buffer against drought by increasing water The profitability of conservation agriculture will storage in the soil profile. This is especially always be influenced by a variety of factors, critical in areas where future climates are including market trends, climatic conditions, expected to become drier and/or extreme farmer attitudes, knowledge, and skills. rainfall events will become more common. CA Improved soil health and eco-efficiency under CA can help to mitigate climate change by storing systems, in this case, are critical for maximizing carbon in the soil. agronomic production and profitability while also enhancing ecosystem services. 166

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.1.1 Minimum till Another advantage of a no-till system is that the Tillage systems management is one of the CA residues can withstand the impact of raindrops, principles that involves no-till /zero-tillage, reducing the risk of water runoff. The term minimal /reduced soil disturbance during \"minimum tillage\" refers to systems that use land preparation for crop cultivation. Soil as little soil manipulation and/or turn over as tillage has been used to prepare seedbeds, possible (reduced intensive tillage). It causes kill weeds, incorporate nutrients, and manage little disruption to the soil structure in order to crop residues. The tillage system's goal has maintain and improve soil properties. Primary been to provide a suitable environment for tillage is completely avoided in these practices. seed germination and root growth for crop 4.1.2 Crop rotation production. However, tillage is said to have had Crop rotation is the practice of growing a a negative impact on field productivity over the different plant species each year on the same years. plot of land. Conservation Agriculture includes As a result, farmers must evaluate the reasons it as one of its components. Crop rotation has for tillage because the negative effects of re-captured the world's attention as a way to tillage operations on the soil and environment address growing agro-ecological issues like must be thoroughly considered. No-till crop declining soil quality and climate change caused production systems leave the most residue on by short rotation and mono-cropping (Liu et al. the field, which serves as mulch or a source of 2016). Crop rotation is an important production biomass for soil protection from direct sunlight practice for weed control, interrupting insect and radiation. This system has consistently and disease cycles, and maintaining productivity. proven to be one of the most profitable crop production methods. Table 1 Example of crop rotation sequence for two provinces.   Provinces Year Limpopo North West 1 Cowpeas Groundnuts 2 Maize 3 Dry beans Maize 4 Sorghum* Dry beans Sunflower *Sorghum in sorghum production area 167

Climate-Smart Agriculture _ Training Manual Grain Crops Production (a) (b) Figure 7 Example of Cereal- legume crop rotation. Maize; soybean; cowpea; maize crop rotation field in one of the demonstration trial fields. (a) Early stage (b) Later stage. 168

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.1.3 Cover crops CA if cover crops were successful. Similarly, Knot Cover crops are beneficial for weed control, soil (2014) discovered that cover crops increased organic matter (SOM) generation, soil fertility infiltration and soil water content (Myburgh improvement, and moisture conservation. 2013; Knot 2014) while decreasing runoff and It was hoped that if farmers produced a lot associated soil loss (Bennie and Hensley 2001). of cover crop biomass, they would be able to (Russel 1991; Mchunu et al. 2011). solve weed problems, soil fertility problems, soil erosion problems, and soil moisture retention problems. Farmers would be encouraged to use Figure 8 Mavize grow faster and healthier due to mycorrhiza left following soybean than maize following canola (non-mycorrhiza). Figure 9 Sunflower plots under no- till tillage system at ARC-GC, Potchefstroom. 169

Climate-Smart Agriculture _ Training Manual Grain Crops Production • CSA Relevance Several projects have been launched to raise A good soil structure increases the soil's water awareness and facilitate the adoption of CA holding capacity, which aids in the retention and principles in the production of various grain storage of water during periods of low rainfall. crops. Part of the project, which was funded Cover crops and mulch help to keep the soil by The Maize Trust in collaboration with the cool by preventing evaporation. CA improves Riemland (Reitz) and Ascent (Vrede) study climate adaptation and resilience by increasing groups, was reported to be very successful soil organic matter (SOM), sequestering soil after the first two seasons of the project were organic carbon (SOC), and lowering greenhouse completed. For many years, conventional soil gas emissions (GHG). tillage methods, with a mould board plough as the most commonly used implement, have • Case study been a major cause of soil degradation in South The vast majority of soils in most of South Africa. Africa's grain production areas have been Soil manipulation is not only highly destructive subjected to conventional soil tillage methods to soil structure, but it also results in a decrease for many years, resulting in soils with poor in soil fertility, reduced SOM, a decrease in physical, nutritional, and biological status. The beneficial soil organisms, and, as a result, a task is to restore these soils so that they are low water-holding capacity of the soil. Soils more protected, richer in organic matter, fertile, subjected to these levels of manipulation biologically vibrant, and productive. Several are also more susceptible to wind and water case studies on how farmers and researchers erosion. used CA to increase grain crop productivity on commercial fields or marginalized soils have been published. Figure 10 Erosion within the field as a result of bare soil and continuous tillage of the soil. 170

Climate-Smart Agriculture _ Training Manual Grain Crops Production These conditions necessitate deliberate for smallholder farmers in some parts of the measures to improve the physical, chemical, and country when it comes to maize production. As biological quality of the soil, thereby reducing a result, CA has been recommended to address the destructive occurrence of soil erosion. this issue, particularly in terms of increasing soil Poor soil fertility has always been a problem organic matter (SOM). Figure 11 In this photo, despite good weed control, no measures were taken to conserve moisture for the planned crop. The conventional system of soil tillage and the resultant bare soil contributed to the high risk this farmer (Siyabuswa area in north west of Mpumalanga) had to face in the dry season of 2011. Figure 12 A mulch (soil cover) of 41% established after the first season (2013/14) at the Dipaleseng Municipality in the south western part of Mpumalanga. 171

Climate-Smart Agriculture _ Training Manual Grain Crops Production Figure 13 Soybeans established in a no-till rotation with maize planted at Carolina in Mpumalanga. Figure 14 Lablab planted as cover crop in one of the trials at ARC-GC Potchefstroom. 172

Climate-Smart Agriculture _ Training Manual Grain Crops Production (a) (b) Figure 15 (a) Example of a converted planter. An old conventional John Deere planter converted into a no-till planter (b) No-till planter in action. Minimum soil disturbance applied, leaving the crop residue on the surface. 173

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.2 CROPPING SYSTEMS The most common type of intercropping practiced by most smallholder farmers is cereal- Cropping systems refer to a variety of legume mixtures. Intercropping conserves agricultural field management practices that soil water by reducing evaporation losses and are used to maximise yield in any form. Some increasing organic matter in the soil, which of these systems can be combined in CSA improves soil structure, infiltration, and water farming to produce grain crops in a sustainable retention, as well as aiding in soil erosion and environmentally friendly manner. In some prevention. cases, this may result in or serve as integrated pest management. The Push-Pull cropping • CSA Relevance system is an example. As a CSA practice, interacting and integrating 4.2.1 Crop varieties different cropping systems and crops allows The selection of crop varieties prior to planting for environmental manipulation for sustainable is an important aspect of the planting process. grain crop production. Drought-tolerant crops CSA prioritizes low-input, high-yielding, integrated into a crop rotation program can resource-efficient varieties that are also cope with reduced rainfall scenarios, and sustainable. These crops are usually improved legumes and cover crops help to improve soil varieties that are site or location specific. Crop nutrient status and structure, which aids water selection must take into account the frequency storage and cooling of the soil by shielding the of erratic rainfall, dry spells, late rain onset, soil surface from direct sunlight and heat. rising temperatures, terminal heat stress, and Due to high rainfall variability in an area, there heavy rainfall, among other factors. Changing may be a call for a crop switch, such as cultivating from maize to sorghum or millet, which are a more drought tolerant crop, sorghum instead more drought-tolerant, could improve climate of maize, as a result of climate change and resilience. variability. Cropping systems must maintain soil 4.2.2 Intercropping fertility and sequester greenhouse gases in the Diversified cropping is when two or more plant long run to mitigate climate change's negative species are grown in the same field in the effects. In general, cropping systems should same year and at least partially at the same be used to increase water infiltration and soil time. Intercropping has become an important moisture conservation, reduce soil erosion, run- management strategy for enhancing crop offs, and evaporation, and improve soil fertility, resource use efficiency and maximizing plant which will improve fertiliser response rates, productivitythroughthedeliberatemanipulation increase carbon sequestration, and reduce of interspecific species interactions. It's popular greenhouse gas emissions. IPM is exemplified in rain-fed agriculture, where resources are by the push-pull cropping system. Push-pull limited, because one crop can take advantage technology is a biological intensification system of a resource that the other can't. In densely that involves attracting gravid female stem borer populated countries, mixed or intercropping moths along the border (pull) with a trap plant, as a method of crop intensification is used to either Napier grass or Brachiaria, while driving produce more food per unit area. them away (push) from the main crop, either maize or sorghum, using a repellent intercrop of Desmodium (Cook et al., 2007). 174

Climate-Smart Agriculture _ Training Manual Grain Crops Production • Case study implemented in an Ethiopian district with the ARC-GC has collaborated with a variety of ultimate goal of increasing food security among organisations and countries to develop maize smallholder farmers. During the study period, varieties that are more water efficient (Water maize grain yields in the climate-adapted Push- efficient maize for Africa - WEMA). These Pull plots were significantly higher than those in varieties are better suited to production in the the maize monocrop plots (Kumela et al., 2019). country's drier climate zones. The Executive The control of stem borer damage in Push-Pull Council for Cultivation in South Africa has technology plots was credited with the increase approved a new drought trait maize variety, in grain yield. with small holder farmers as the primary target. Another example is the use of drought-tolerant 4.3 Integrated Pest varieties or crops in place of other crops when Management (IPM) drought strikes. Figure 16 shows that a drought-tolerant cowpea Pest population size, survival rate, and variety was still green when compared to geographic distribution can all be affected another variety planted the same day that had by climate change, as can disease intensity, already dried and yielded nothing. development, and geographical distribution. There hasn't been enough research into Push- As a result, pest and disease control for grain Pull technology in South Africa, but there has crops should be done in a way that promotes been some in other African countries. A push- soil conservation, water conservation, and long- pull technology targeting maize stem borers was term crop production for each geographical location. This is in the form of climate-smart pest control. Figure 16 Effect of dry seasons on different cowpea varieties planted on the same day. 175

Climate-Smart Agriculture _ Training Manual Grain Crops Production Pest population size, survival rate, and These practices are commonly considered basic geographic distribution can all be affected practices in the implementation of other CSA by climate change, as can disease intensity, principles in CSA. Biological processes that development, and geographical distribution. cause nitrate leaching and greenhouse gas As a result, pest and disease control for grain (GHG) emissions can also be controlled through crops should be done in a way that promotes agronomic management. soil conservation, water conservation, and long- 4.4.1 Planting dates term crop production for each geographical Climate-Smart Agriculture also includes location. This is in the form of climate-smart adjusting planting dates and manipulating crop pest control. growth stages to coincide with rain events. The Integrated pest management is a strategy that planting date also aids in avoiding some extreme employs a variety of management tools with weather conditions that could be detrimental the goal of reducing pest populations to levels to the crop's growth and development. Frost that are both environmentally and economically is an example of the condition. Farmers must sustainable. Identification of pests, weeds, and plan crop planting dates so that critical growth diseases, as well as timely control during the stages do not coincide with any extreme most critical periods for crop development in a weather conditions. given field, are critical components of the IPM 4.4.2 Weeding program. Weed control is an essential part of agronomic Integrated pest management employs all practices. Because no-tillage and minimum- available pest management techniques as part tillage systems limit weed seed redistribution of a comprehensive crop or pest management to the top zero to five centimetres of soil, program that takes into account all potential aggressive weeding is recommended for CA pests that may impact the crop during its practices to reduce plant competition. Because growth and production. Pesticides are only used different situations and farmers require when absolutely necessary, and determining different approaches, no specific weeding when pesticides are actually needed is an method is recommended. To ensure continued important part of integrated pest management. weed control in CA systems for the farmers Reducing the use of pesticides is one way to who are most vulnerable to weed pressure, a help with GHG reduction. According to the combination of chemical and cultural control Intergovernmental Panel on Climate Change, practices should be investigated, particularly agricultural activities account for approximately for resource-poor and cash-constrained 30% of global emissions contributing to climate smallholder farmers. change, owing primarily to the use of chemical As a result, proposed weed management fertilisers and pesticides. strategies, as in Figure 17, should take into account a variety of site and farmer conditions. 4.4 AGRONOMIC PRACTICES Crop production can be made more sustainable and environmentally friendly by implementing a variety of agronomic practices and management. 176

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.4.3 Fertilisation 4.4.4 Mulching Fertilisers applied in the right amount, at the Mulching is a common and effective practice right stage of crop growth, and with the right for artificially reducing evaporation in arid/ method can significantly reduce the amount of semiarid ecosystems in order to conserve water. fertiliser that reaches water bodies or is wasted. Mulching is a common and effective solution Farmers can prevent periods of bare ground on for not only conserving soil moisture but also farm fields by planting cover crops or perennial improving soil properties and plant production species, which protect the soil (and the nutrients in dryland areas. it contains) from erosion and loss. Farmers can Mulch cover associated with no-tillage practices reduce the frequency and intensity with which increases soil water retention (Blevins et al. their fields are tilled. This can assist in reducing 1971) and decreases soil temperature (Burrows erosion, runoff, and soil compaction, as well as and Larson 1962), delaying maize emergence the likelihood of nutrients reaching waterways. and early-season growth. When residues were Organic fertilisers, such as manure, compost, completely removed, maize yield reductions and green manures, are superior in a variety of were attributed to decreased soil water storage ways, including. and excessive surface soil temperatures, particularly in climates where moisture stress • Provision of nutrients for plants uptake conditions existed during the growing season • They help to increase SOM, (Doran et al. 1984). Leaving a mulch of crop • reduce erosion, extract nutrients from the residue on the soil surface to act as a protective cover, as done in CA, is an effective way to limit deep down the soil and deposit them on these losses. the topsoil. CA systems with residue retention increase • There is no chance of eutrophication from water infiltration and maintain higher soil organic fertiliser. moisture levels due to reduced evaporation (Roth et al., 1988). Figure 17 An example of a Glyphosate pre-plant application. In a no-till system, this creates a weed-free seedbed at planting time. 177

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.4.5 Adjusting plant population Locally, the majority of farmers, particularly Plant density is a critical management practice small-scale farmers, do not adhere to the for successful grain and forage production recommended plant densities, resulting in yield (Karunatilake et al. 2000) and has been identified declines (Lithourgidis et al., 2005). Farmers as a major factor determining the degree of must reduce plant density during these periods nutrient competition between plants (Kgasago of rainfall pattern in order to sustain and better et al., 2006). Plant population is important utilise the available precipitation. In areas with because it determines the amount of nutrients little rainfall, it is highly recommended to widen needed by the plant for maximum yield. row spacing and reduce plant population as Low plant population and wider row spacing shown in Figure 18. are recommended in areas with low annual rainfall because there is less competition for CSA Relevance nutrients by the plants (Mashiga et al., 2013). Too much inorganic fertiliser may cause an Plant population has a significant influence on increase in the acidic level of the soil, causing growth parameters and is regarded as the most degeneration of the soil structure and, as a important factor in determining the level of result, a reduction in the soil's water holding competition between plants (Sangakkara et al., capacity and nutrient availability. Mulching is 2004). According to Abuzar et al. (2011:694), similar to cover cropping in that it protects the high plant population results in low grain yield. soil during extreme weather conditions such as As the number of plants per unit area increases, high temperatures or low rainfall. so does the competition among plants for light intensity and nutrients (Sangakkaras et al., 2004). Figure 18 Example of wide row spacing in the North West, (Sannieshof area). 178

Climate-Smart Agriculture _ Training Manual Grain Crops Production 4.5 IMPROVED STORAGE AND from the field as well as the development of PROCESSING TECHNIQUES insects and pathogens. Grain crop production does not stop in the • South Africa case study field. In the food chain, storage and processing Cowpea is grown as a vegetable in South Africa, techniques play a significant role. Crops are and the leaves are picked four weeks after grown seasonally in most places, and after planting and dried to store for the dry season. harvesting, grains are stored for short or long They are usually steamed or boiled first, but this periods as food reserves and seeds for the is not always the case. Sun-drying takes 1 to 3 following season. The majority of these grains days; storage for up to a year is possible because are stored in bags in traditional structures made dried, cooked leaves are less susceptible of locally available fronds, grasses, or woods. to insect damage than dried seeds. Excess Moisture content and temperature are the P-carotene, vitamin C, and the amino acid lysine two most important factors influencing storage are frequently lost in sun-dried leaves; however, life. Mold growth is slowed by low moisture these losses can be reduced by minimal cooking levels, which keep relative humidity below 70%. followed by drying in the shade. Depending on the direction of air convection in To avoid insect damage, properly dried seed of the traditional storage structure, temperature cowpea grown for grains is kept in a container. fluctuations caused by weather changes cause During storage, insect pests in particular can moisture to accumulate at the top or bottom be devastating to cowpea. There are storage of the grains' bulk. This can be avoided by insects that cause damage to the seed; minimising the temperature difference between therefore, it is critical to store seed in a secure the inside and outside of the storage structure. location. Cowpea weevil, Callosobruchus Grain should be harvested when the moisture maculatus, is a serious pest during storage. As content is less than 15% to minimize losses. the use of chemicals in controlling these insects Otherwise, grains should be dried to about 13% becomes a problem, the growing popularity of moisture content before storing. organic produce lines has sparked interest in Insects are another issue with storage. Infestation non-chemical disinfestation treatments. of insects is the most serious problem in grain Cowpea storage life is determined by its moisture storage facilities. It is well known that insect content prior to storage. The lower the moisture infestation can reduce the value of maize by content, the better the storage quality of seeds. up to 1%. In order to avoid this, insect-resistant Cold storage is an option in areas where it is seed varieties are recommended for cultivation. cost-effective. Pest numbers can be reduced by Spraying against specific insect infestations is more than 99 % by exposing them to -18°C for also advised during a specific period of storage. 6 to 24 hours. Short-term storage at 12 percent • CSA Relevance moisture or less is recommended, with 8 to 9 % recommended for long-term storage. In terms of storage, moisture and temperature are critical in order to protect against damage 179

Climate-Smart Agriculture _ Training Manual Grain Crops Production 5 REFERENCES AND RESOURCES Adams JE (1966). Influence of mulches on runoff, erosion, and soil moisture depletion. Soil Science Society of America Journal. 30: 110-114. Alberts EE & Neibling WH (1994). Influence of crop residues on water erosion. In: Unger PW (Eds) Managing agricultural residues. Lewis Publishers, Chelsea. 19-39. Barton AP, Fullen MA, Mitchell DJ, Hocking TJ, Liu L, Bo ZW, Zheng Y & Xia ZY (2004). Effects of soil conservation measures on soil erosion rates and crop productivity on subtropical Ultisols in Yinnan Province. China Agricultural Ecosystem and Environment. 104: 343-357. Benhin JKA (2006). Climate change and South African agriculture: Impact and adaptation options. CEEPA Discussion Paper #21. University of Pretoria, South Africa. Bennie ATP & Hensley M. (2001). Maximizing precipitation use efficiency in dryland agriculture in South Africa - a review. Journal of Hydrology. 241: 124-139. Beukes DJ, Bennie AT & Hensley M (1999). Optimization of soil water use in the dryland crop production Areas of South Africa. In: N. van Duivenbooden, M. Pala, C. Studer & C.L. Bielders (Eds.), Efficient soil water use: the key to sustainable crop production in dry areas of West Asia, and North and sub-Saharan Africa. Proceedings of the 1998 (Niger) and 1999 (Jordan) workshops of the Optimizing Soil Water Use (OSWU) consortium. Aleppo, Syria: ICARDA; Patancheru, India: ICRlSAT. 165-191. Blevins RL, Cook D, Phillips SH & Phillips RE. (1971). Influence of no tillage on soil moisture. Agronomy Journal. 54: 19-23. Burrows WC & Larson WE (1962). Effect of amount of mulch on soil temperature and early growth of corn. Agronomy Journal. 54: 19-23. Botha JJ (2006). Evaluation of maize and sunflower in a semi-arid area using in-field rainwater harvesting. PhD thesis, University of Free State, Bloemfontein, South Africa. Botha JJ, Van Rensburg LD, Anderson JJ, Van Staden PP & Hensley M (2012). Improving maize production of in-field rainwater harvesting technique at glen in South Africa by the addition of mulching practices. Irrigation and Drainage. 61: 50-58. Chibarabada TP, Modi AT & Mabhaudhi T (2017). Expounding the Value of Grain Legumes in the Semi- and Arid Tropics. Sustainability. 9: 60-84. Choudhary MA, Lal R & Dick WA (1997). Long-term tillage effects on runoff and soil erosion under simulated rainfall for a central Ohio soil. Soil and Tillage Research. 42: 175-184. 180

Climate-Smart Agriculture _ Training Manual Grain Crops Production Cook SM, Khan ZR & Pickett JA (2007). The use of “Push-pull” strategies in integrated pest management. Annual Review of Entomology. 52: 375-400. Doran JW, Wilhelm WW & Power JF (1984). Crop residue removal and soil productivity with no-till corn, sorghum, and soybean. Soil Science Society of America Journal. 48: 640-645. Dumanski J, Peiretti R, Benetis J, McGarry D & Pieri C (2006). The paradigm of conservation tillage. In: Proceedings of World Association of Soil and Water Conservation. FAO, Rome. 58-64. Durand W (2006). Assessing the impact of climate change on crop water use in South Africa. CEEPA Discussion Paper #28. University of Pretoria, South Africa. FAO (2008). Conservation Agriculture. Available at: http://www.fao.org/ag/ca/ (Accessed 11 December 2019). Fowler R & Rockstrom J (2001). Conservation tillage for sustainable agriculture: An agrarian revolution gathers momentum in Africa. Soil and Tillage Research. 61: 93-108. Grain South Africa (2015). Available at: https://www.grainsa.co.za/ (Accessed 20 January 2020). Greenberg DC, Williams JH & Ndunguru BJ (1992). Differences in yield determining processes of groundnut (Arachis hypogaea L.) genotypes in varied drought environments. Annal of Applied Biology. 120: 557-566. Greyling JC & Pardey PG (2019). Measuring Maize in South Africa: The shifting structure of production during the twentieth century, 1904-2015. Agrekon. 58: 21-41. Hall AJ, Vilella N, Trapani N & Chimenti C (1982). The effects of water stress and genotype on the dynamics of pollen shedding and silking in maize. Field Crops Research. 5: 349-363. Herrero MP & Johnson RR (1981). Drought stress and its effects on maize reproductive systems. Crop Science. 21: 105-110. Kassam A, Friedrich T, Derpsch R & Kienzle J (2015). Overview of the worldwide spread of conservation agriculture. Facts Reports. 1-11. Knot J (2014). Promoting conservation agriculture: commercial farmers in the eastern Free State. PhD thesis, University of the Free State, Bloemfontein, South Africa. Knowler D & Bradshaw B (2007). Farmers’ adoption of conservation agriculture: A review and synthesis of recent research. Food Policy. 32: 25-48. 181

Climate-Smart Agriculture _ Training Manual Grain Crops Production Kumela T, Mendesil E, Enchalew B, Kassie M & Tefera T (2019). Effect of the Push-Pull Cropping System on Maize Yield, Stem Borer Infestation and Farmers’ Perception. Agronomy. 9 (452): 1-13. Lal R. (1998). Mulching effects on runoff, soil erosion and crop response on alfisols in western Nigeria. Journal of Sustainable Agriculture. 11: 135-154. Lizaso JI, Ruiz-Ramos M, Rodríguez L, Gabaldon-Leal C, Oliveira JA, Lorite IJ, Sánchez D, García E & Rodríguez A (2018). Impact of high temperatures in maize: Phenology and yield components. Field Crops Research. 216: 129-140. Mchunu CH, Lorentz S, Jewitt G, Manson A & Chaplot V (2011). No-till impact on soil and soil organic carbon erosion under crop residue scarcity in Africa. Soil Science Society of America Journal. 75: 1502- 1511. Milani JM (2013). Ecological conditions affecting mycotoxin production in cereals: A review. Vetinary Medicine Journal. 38: 405-411. Moeletsi ME (2010). Agroclimatological Risk Assessment of rainfed maize production for the Free State Province of South Africa. PhD thesis, University of the Free State, Bloemfontein, South Africa. Mupambwa HA & Wakindiki IIC (2012). Winter cover crop effects on soil strength, infiltration and water retention in a sandy loam Oakleaf soil in Eastern Cape, South Africa. South African Journal of Plant and Soil. 29: 121-126. Myburg PA (2013). Effect of shallow tillage and straw mulching on soil water conservation and grapevine response. South African Journal of Plant and Soil. 30: 219-225. Nawaz MS, Nawaz N, Yousuf M, Khan MA, Mirza MY, Mohmand AS, Sher MA & Masood M (2009). Stability performance for pod yield in groundnut. Pakistan Journal of Agricultural Research. 22: 116-119. Ofori E & Kyei-Baffour N (2009). Agrometeorology and maize production: Chapter 12 of Guide on Agricultural Meteorological Practices (GAMP). 3rd Edition of WMO No. 134 by the World Meteorological Organisation/Technical Committee for Agro-Meteorology (WMO/CAgM). 1-22. Phophi MM, Mafongoya P & Lottering S (2020). Perceptions of Climate Change and Drivers of Insect Pest Outbreaks in Vegetable Crops in Limpopo Province of South Africa. Climate. 8: 27. Reid J, Pearson A & Stone P (2006). Land Management for Grain Maize: recommended best management practices for New Zealand. Crop & Food Research Report No. 31, Christchurch, New Zealand Institute for Crop & Food Research Limited. Rushing BR & Selim MI (2019). Aflatoxin B1: A review on metabolism, toxicity, occurrence in food, occupational exposure, and detoxification methods. Food Chemistry Toxicology. 124: 81-100. 182

Climate-Smart Agriculture _ Training Manual Grain Crops Production Russel WB (1991). The effect of various tillage methods on soil and water losses from maize lands. South African Journal of Plant and Soil. 8: 160-163. Sahay G & Sarma BK (2005). Yield stability of some groundnut (Arachis hypogea) genotypes in Meghalaya. Indian Journal of Agricultural Research. 39: 221-224. Scopel E, Silva F, Corbeels M, Affholder F & Maraux F (2004) Modelling crop residue mulching effects on water use and production of maize under semi-arid and humid tropical conditions. Agronomie. 24: 383-395. Swanepoel PA, du Preez CC, Botha PR, Snyman HA & Habig J (2015). Assessment of tillage effects on soil quality of pastures in South Africa with indexing methods. Soil Research. 53: 274-285. Subramanian V, Gurtu S, Rao RN, & Nigam SN (2000). Identification of DNA polymorphism in cultivated groundnut using random amplified polymorphic DNA (RAPD) assay. Genome, 43(4), 656-660. Tesfuhuney WA, van Rensburg LD & Walker S. (2013). In-field runoff as affected by runoff strip length and mulch cover. Soil and Tillage Research. 131: 47-54. Trasmonte G, Chavez R, Sergura B and Rosales, JL (2008). Frost risks in the Mantaro river basin. Advances in Geosciences. 14: 265-270. 183

Climate-Smart Agriculture _ Training Manual Grain Crops Production LIST OF FIGURES Figure 1 Cultivar maize trial field. 157 Figure 2 Figure 3 Sorghum field at early maturity stage. 159 Figure 4 Figure 5 Sunflower cultivar trial field. 161 Figure 6 Figure 7 Groundnut field at the vegetative stage. 162 Cowpea at the pod filling stage. 164 Figure 8 Well established dry beans field with the farmer. 165 Figure 9 Figure 10 Example of Cereal- legume crop rotation. 168 Figure 11 Maize; soybean; cowpea; maize crop rotation field in one of the demonstration trial fields. (a) Early stage (b) Later stage. Mavize grow faster and healthier due to mycorrhiza 169 left following soybean than maize following canola (non-mycorrhiza). Figure 12 Sunflower plots under no- till tillage system at ARC-GC, Potchefstroom. 169 Figure 13 Erosion within the field as a result of bare soil and continuous tillage of the soil. 170 Figure 14 Figure 15 In this photo, despite good weed control, no measures were taken to conserve moisture for the planned crop. The conventional system of soil tillage and the resultant bare soil contributed Figure 16 to the high risk this farmer (Siyabuswa area in north west of Mpumalanga) Figure 17 had to face in the dry season of 2011. 171 A mulch (soil cover) of 41% established after the first season (2013/14) 171 at the Dipaleseng Municipality in the south western part of Mpumalanga. Soybeans established in a no-till rotation with maize 172 planted at Carolina in Mpumalanga. Lablab planted as cover crop in one of the trials at ARC-GC Potchefstroom. 172 (a) Example of a converted planter. An old conventional John Deere planter converted into a no-till planter (b) No-till planter in action. Minimum soil disturbance applied, leaving the crop residue on the surface. 173 Effect of dry seasons on different cowpea varieties planted on the same day. 175 An example of a Glyphosate pre-plant application. In a no-till system, 177 this creates a weed-free seedbed at planting time. Figure 18 Example of wide row spacing in the North West, (Sannieshof area). 178 184

Climate-Smart Agriculture _ Training Manual 167 Grain Crops Production LIST OF TABLES Table 1 Example of crop rotation sequence for two provinces. 185

MODULE 5 Wheat Production Compiled by Dr Rorisang Patose, Dr Tarekegn Terefe and Hestia Nienaber Contributors: Dr Astrid Jankielsohn and Dr Justin Hatting Agricultural Research Council – Small Grain Institute

Climate-Smart Agriculture _ Training Manual Wheat Production Table of Contents 1 INTRODUCTION 188 2 IMPACT OF CLIMATE CHANGE ON WHEAT PRODUCTION 189 2.1 EFFECTS OF CLIMATE CHANGE ON WHEAT DEVELOPMENT, 189 YIELD AND GRAIN QUALITY 189 2.1.1 Germination and emergence 190 2.1.2 Tillering 190 2.1.3 Stem elongation 190 2.1.4 Heading/flowering 191 2.2 SOIL HEALTH 191 2.3 CROP PESTS AND PATHOGENS 191 2.3.1 Insect pests 196 2.3.2 Diseases 199 2.3.3 Weeds 203 3 INTERVENTIONS ON THE IMPACT OF CLIMATE CHANGE 203 3.1 SOIL HEALTH 204 3.1.1 Organic matter 207 3.1.2 Conservation agriculture 212 3.2 CROP PESTS AND PATHOGENS 212 3.2.1 Insect pests 213 3.2.2 Diseases 213 3.2.3 Weeds 215 5 REFERENCES AND RESOURCES 218 219 LIST OF FIGURES LIST OF TABLES 187

Climate-Smart Agriculture _ Training Manual Wheat Production 1 INTRODUCTION tonnes per hectare. Wheat production, on the other hand, has been declining in recent years. The Western Cape (winter rainfall), Free State Table 1 shows that, under dryland conditions, (summer rainfall), and Northern Cape (winter the number of hectares planted with wheat rainfall) are the three main wheat-producing has decreased in the three provinces over the provinces in South Africa (SA) (irrigation). last three years, with yields fluctuating. South Wheat is grown primarily under irrigation in the Africa is a net importer of wheat, importing a Eastern Cape, Limpopo, and North West, as well large amount each year to meet local demand as in Mpumalanga. South Africa produces 1.5 to because it does not produce enough. 3 million tonnes of wheat per year, with dryland productivity rates of 2-2.5 tonnes per hectare and irrigation productivity rates of at least 5 Table 1 Wheat production overview over three seasons. Source: Southern African Grain Laboratory, 2018 & 2019. Type of 2016/2017 2017/2018 2018/2019 production Province Hectares Yield Hectares Yield Hectares Yield Eastern Dryland planted (t ha-1) planted (t ha-1) planted (t ha-1) Cape Irrigation Limpopo Total 700 2.43 600 2.33 400 2.5 North Dryland West Irrigation 1500 6.2 1300 6.23 1250 7.78 Total Dryland 2200 1900 1650 Irrigation Total 850 2.35 1000 3.6 1000 2.5 16150 6.3 19000 6.76 19000 6.61 17000 20000 20000 80 2.5 80 2.5 -- 11920 5.8 13420 6.22 1200 6.5 12000 15500 1200 188 Agrometeorological applications for Climate-Smart Agriculture

Climate-Smart Agriculture _ Training Manual Wheat Production 2 IMPACT OF CLIMATE CHANGE ON WHEAT PRODUCTION Climate change causes environmental changes Climate change-induced temperature that have a negative impact on crop production increases, according to Easterling et al. (2007), around the world. Temperature changes, are expected to reduce wheat production in rainfall variability, changes in atmospheric gas developing countries by 20-30%. The region's composition, and changes in solar radiation low productivity (2t/ha) is primarily due to abiotic are all examples of environmental changes (drought and heat) and biotic (yellow rust, stem that affect crop, pest, pathogen, and weed rust, septoria, and fusarium) stresses that are relationships, as well as soil health (Myers intensifying and occurring more frequently as a et al, 2017). The net effect of climate change result of climate change (Tadesse et al, 2018). on crop yields and quality is determined by the interactions of all of these factors, and Climate change's impact on crop production as adaptation and mitigation measures are must be understood in order to adapt and implemented, the cost of inputs will rise. mitigate it. The following section discusses the impact of climate change on wheat production. Globally, average temperatures have risen, resulting in higher rates of evaporation and Climate change affects the health of the soil on drier soil conditions (Girvetz and Zganjar, 2014; which crops grow, as well as the distribution and Girvetz et al, 2019). While temperatures are occurrence of pests, pathogens, and weeds, all expected to rise as a result of climate change, of which have an impact on wheat development, rainfall projections differ between global yield, and quality. Wheat development, yield climate models (GCM) ( Flato et al., 2013 ). The and grain quality, soil health, and crop pests magnitude of these changes was expected to and pathogens will all be covered in this section vary greatly between regions ( CSIRO and Bureau (insect pests, diseases and weeds). of Meteorology, 2015 ). In the next 30–80 years, 5at5m0opsaprhtesripceCrOm2 illelivoenls. are expected to exceed 2.1 EFFECTS OF CLIMATE CHANGE Protein, iron, and zinc ON WHEAT DEVELOPMENT, content in many food crops grown below 550 YIELD AND GRAIN QUALITY ppm are reduced by 3–17%, potentially causing protein, iron, and zinc deficiency in people. 2.1.1 Germination and emergence Since 1975, temperatures in Africa have risen Seed germination and seedling emergence are at a rate of about 0.03 degree Celsius per year influenced by a variety of factors, including (Girvetz et al, 2019). And the new normal for available moisture and soil temperature. To temperature is higher than any other time in germinate, seed must consume a significant history. Much of Africa is drying out, according amount of water in relation to its dry weight. to precipitation patterns (Hartmann et al, 2013). Wheat seed must have a minimum water In comparison to other parts of Southern Africa, content of 35–40% by weight in order to such as Zambia and Zimbabwe, South Africa has germinate. Seed that germinates at a lower received more rain. moisture content may make it through the first 189

Climate-Smart Agriculture _ Training Manual Wheat Production stages, but it will not perform to its genetic 2.1.4 Heading/flowering potential. Excess moisture, on the other hand, causes germination to be delayed or prevented To flower, winter wheat must be exposed to cold due to a lack of oxygen. Photosynthesis requires temperatures (vernalisation). Furthermore, a constant supply of water after emergence. an increase in temperature shortens the Soil temperature also plays a significant role vernalisation period and reduces flowering. in the rate at which germination proceeds. Water deficiency during flowering reduces Germination can take place at temperatures pollen viability, stigma receptivity, and seed ranging from 4°C to 37°C, but the best development. Increased temperatures cause temperatures for germination are 12°C to shorter seed formation periods, resulting in 25°C. Temperature has an impact on the rate of lower yields. imbibition. Temperatures below the optimum result in lower germination and longer Air temperatures above 30°C are generally germination periods, whereas temperatures associated with lower yields for rain-fed crops above the optimum reduce or prevent such as dryland wheat (Carlson,1990; Schlenker germination by denatureing cellular protein and & Roberts, 2009). High temperatures can killing the seed. reduce yields by accelerating crop development 2.1.2 Tillering (Asseng et al, 2014; Butler & Huybers, 2015) and A temperature increase of 10–25°C increases can cause direct plant cell damage (Sanchez et the total number of leaves and tillers, whereas a al, 2014). Climate variability in terms of rainfall temperature increase of more than 25% reduces (drought, excess rains) and terminal heat (high leaf development. Temperature fluctuations temperature during grain filling stage) have cause increased leaf senescence, which can a significant impact on wheat production. reduce grain yield by 50%. High temperatures For example, if wheat is planted late in the cause crop water loss due to increased season, high temperatures at the end of the respiration rates, resulting in lower biomass season hasten maturity and reduce grain yield production and, as a result, lower yields. Lower (commonly known as terminal heat stress). leaf area occurs as a result of water stress. Wheat matures earlier than usual, resulting in 2.1.3 Stem elongation yield loss. Water stress results in fewer nodes, lower stem dry weights, and a decrease in height. The High temperatures and terminal drought have increase in average temperature during the a negative impact on wheat biomass and grain growing season typically causes plants to use yield. Drought stress brings down crop yields more energy for respiration and less for growth.. significantly due to dry weight accumulation decreases. Increased carbon dioxide pe(CrOfo2r)mainnce the atmosphere improves crop by increasing photosynthesis rates and water use efficiency, but significantly reduces wheat grain 190

Climate-Smart Agriculture _ Training Manual Wheat Production q(Zuna)l,itayn. dEliervoante(FdeC) Ole2vreelsd,uacneds grain protein, zinc extremes, and higher soil temperatures can their responses to encourage fungal growth. setlreevsasteadnCdOn2 ilteroveglesnar(eN)als(Mo yreedrsuceetd by water iInncgreeanseerapl,ersitsioncgcuCrOre2 nlecvee, lsseavnedrittyemofpdearamtuargees, AlHadeethi et al, 2019). al, 2014; and pest infestation winter survival, as well as the spread of disease and pest-carrying 2.2 SOIL HEALTH organisms. Increased rainfall may result in leaf wetness and humid conditions, which can aid Climate change and variability have a large in the development and spread of a variety of impact on crop growth and yields because of diseases and pests. their impact on soil health and crop varieties' 2.3.1 Insect pests ability to adapt to changing climate and weather Aphids, mites, false wire worms, Bagrada bugs, patterns. A healthy soil for wheat development African bollworms, leaf miner flies, and false must have sufficient essential nutrients, water, armyworms are among the wheat insect pests. a suitable temperature, oxygen (air), and the Their significance, however, is determined by ability to support plant roots. Heavy rain causes the wheat production area and the climatic runoff and soil erosion, resulting in significant conditions in which they can thrive. As a result, losses of soil organic matter and poor crop it is difficult to rank these pests in terms of production (GrainSA, 2015). overall importance across the country, though Soil erosion causes changes in soil structure, three insects or insect groups can be highlighted as well as leaching and nutrient loss. The loss as being important in almost every production of salts and nutrient cations during leaching area of the country. The three will be discussed increases salinization in areas where there is in greater depth. net upward water movement due to increased 2.3.1.1 Aphids evapotranspiration or decreased rainfall or Aphids are the most common insect pests of irrigation water supply (Chandra et al, 2013). wheat and other small grains, and they can be Because the production, transport, and found in nearly every wheat-growing region. application of fertiliser emits more carbon This group contains about five prominent dioxide, soil fertilisation used to improve species, the importance of which varies by essential nutrients does not typically generate a region depending on weather conditions. net sink for carbon. Fertilisers cause less water, The first is the Russian wheat aphid (RWA) (see air, and life in the soil (GrainSA, 2015). Figure 1), which thrives in dry, water-stressed environments. They are particularly important 2.3 CROP PESTS AND PATHOGENS in the Free State and Western Cape's dryland environments. With the rise in dryland wheat Plant-pest interactions are changing as a result of production, this pest may become more climate change. Plants that grow in waterlogged important. soil are more susceptible to viruses and soil- borne diseases. The distribution of insect pest pests is influenced by temperature. Plant pathogens' ecology can be altered by climate 191

Climate-Smart Agriculture _ Training Manual Wheat Production RWA is the most damaging aphid on wheat due RWA is the most damaging aphid on wheat to its feeding damage resulting in considerable because of its feeding damage, which results yield losses. Managing RWA also proved to be in significant yield losses. Managing RWA has a challenge. Resistance in crops is an effective also proven to be difficult. Crop resistance is an management tool for insect crop pests. effective tool for controlling insect crop pests. A drawback of this management option is that One disadvantage of this management option is the insect can overcome the resistance in the that the insect can overcome crop resistance, crop, which will result in new insect biotypes resulting in new insect biotypes capable of able to damage the resistant crop plant. This damaging the resistant crop plant. This was proved to be the case with RWA resistant wheat demonstrated by RWA resistant wheat cultivars. cultivars. South Africa currently has five RWA biotypes. RWASA1 has been present in South African wheat production areas since 1978 and has been able to overcome the Dn3 resistant gene in wheat (see Table 2). Figure 1 Russian wheat aphid. Source: Dr Goddy Prinsloo. 192

Climate-Smart Agriculture _ Training Manual Wheat Production In 2005, RWASA2 was recorded in the Eastern Table 2). RWASA5 was recorded in 2018 and has Free State. This RWA biotype was able to the Dn6 and Dnx genes added to its virulence overcome the Dn1, Dn2, Dn3, Dn8, Dn9, and profile. Currently, RWASA5 is the most virulent Dn y resistant genes in wheat (see Table 2). RWA biotype. RWA biotypes are found in a RWASA3 was recorded in the Eastern Free State complex, primarily in the Eastern Free State. in 2009 and has a Dn4 resistant gene added to Only RWASA1 is found in wheat production its virulence profile. RWASA4 was recorded in areas in the rest of the country (Western and the Eastern Free State in 2011 and has a Dn5 Central Free State, Northern Cape, and Western resistant gene added to its virulence profile (see Cape). Table 2 Resistance(R)/Susceptibility (S) of wheat germplasm with resistant genes against five South African biotypes (RWASA1-RWASA5). Source: SA Grain, March 2019. Resistant gene RWASA1 RWASA2 RWA biotype RWASA4 RWASA5 Dn1 R S RWASA3 S S Dn2 R S S S Dn3 S S S S S Dn4 R R S S S Dn5 R R S S S Dn7 R R S R R Dn8 R S R S S Dn9 R S R S S Dnx2006 R R S R S Dny2006 R S S S S R S 193

Climate-Smart Agriculture _ Training Manual Wheat Production The second most important group of aphids there is a lot of rain in the fall. The humid climate includes the oat aphid (shown in Figure 2), rose is ideal for these aphids. These aphids are not grain aphid (shown in Figure 3), and brown ear as dangerous as the Russian wheat aphid, but aphid (shown in Figure 4). They thrive in the feeding damage of 12% to 15% may occur Western Cape's humid winter rainfall, and they during heavy infestations. They are, however, are common in all irrigation areas. They occur known to be effective virus vectors, particularly sporadically in the Free State during years when for the Barley Yellow Dwarf Virus (BYDV). Figure 2 Oat aphid. Source: Dr Goddy Prinsloo. Figure 3 Rose grain aphid. Source: Dr Goddy Prinsloo. 194

Climate-Smart Agriculture _ Training Manual Wheat Production Figure 4 Brown ear aphid. more damaging in irrigated wheat, significant Source: Dr Goddy Prinsloo. infestations occur sporadically in dryland 2.3.1.2 African bollworm conditions in the Western Cape and Free State. The African bollworm, pictured in Figure 5, ranks Larvae have been observed moving into the second among insect pests of wheat and other heads at an early stage, where they feed on the small grains because it is a voracious feeder kernels, causing them to be damaged. found in all production areas, albeit not on a regular basis. Although this insect is potentially Figure 5 African bollworm and the damage it causes. Source: Dr Goddy Prinsloo. 195

Climate-Smart Agriculture _ Training Manual Wheat Production 2.3.1.3 Leaf miner flies 2.3.2.1 Rusts The leaf miner fly first appeared as a wheat Diseases are more likely to occur and spread pest in irrigated wheat fields in the Prieska and as temperatures and rainfall rise. When there Douglas areas in 2000. This is a local indigenous is an abundance of free water, for example, insect that began infesting wheat and barley wheat stem and leaf rusts increase with rising for unknown reasons. Initially, the pest spread temperatures. Stripe rust infection, on the other north along the major rivers to Vaalharts and hand, is most common in cool weather (below Bloemhof. Since then, it has gradually spread to 15°C). As a result, stripe rust is more common Lichtenburg and the Brits area. It first appeared in cooler wheat-growing regions (e.g., Eastern on dryland wheat in the Western Cape in 2016, Free State), while stem rust and leaf rust are where one to two life cycles were completed more common in wheat-growing regions with early in the wheat growing season. Despite mild winter temperatures (e.g. Western Cape). their presence in KwaZulu-Natal production When conditions are favorable, susceptible areas, they are not a problem, owing to natural cultivars are planted, cultural practices are enemy action. altered, and these three factors combine, rusts 2.3.2 Diseases can cause severe losses. The environmental The latitudinal range of pathogens shifts as conditions required by the three rust diseases, temperatures change. Extreme weather events namely leaf rust (shown in Figure 6), stem rust can destabilise agricultural systems, weakening (shown in Figure 7) and stripe rust (shown in crop defenses and allowing pathogens to Figure 8) are summarized in Table 3. establish themselves in niches. Figure 6 Leaf rust. Source: Dr T. Terefe. 196

Climate-Smart Agriculture _ Training Manual Wheat Production Figure 7 Stem rust. Source: Dr T. Terefe. Figure 8 Stripe rust. Source: Dr T. Terefe. 197

Climate-Smart Agriculture _ Training Manual Wheat Production Table 3 Environmental conditions required for the wheat rusts. Source: Roelfs et al., 1992. Stage Temperature (oC) Light Free water Germination Minimum Optimum Maximum Low Essential Germling Low Essential Appressorium 2 Leaf rust None Essential Penetration 5 No effect Essential Growth - 20 30 High Sporulation 10 High None 2 15-20 30 None Germination 10 Low Germling 15-20 - Low Essential Appressorium 2 None Essential Penetration - 20 30 High Essential Growth - High Essential Sporulation 15 25 35 High 5 None Germination 15 25 35 Low None Germling Low Appressorium 9 Stem rust None Essential Penetration - Low Essential Growth - 15-24 30 High Essential Sporulation 2 High Essential 3 20 - 5 None 16-27 - None 29 35 30 40 30 40 Stripe rust 9-13 23 10-15 - - (not formed) 8-13 23 12-15 - 12-15 - 2.3.2.2 Barley Yellow Dwarf Virus (BYDV) combined with moist conditions. Because this Virus infections such as BYDV, such as shown in virus is only transmitted by aphids, aphid control Figure 9, are common in some irrigation areas, is critical early in the growing season, when resulting in a 33% yield loss. The occurrence wheat is most susceptible to BYDV. The oat and incidence of barley yellow dwarf virus aphid, rose-grain aphid, and English grain aphid are influenced by environmental factors. The are the most common aphids on small grains in disease thrives in cool temperatures (10° - 18°C) South Africa that can transmit BYDV. 198

Climate-Smart Agriculture _ Training Manual Wheat Production These aphids are all present on wheat that has defenses and creating niches for weeds to thrive. been irrigated, as well as in Kwazulu-Natal and Because of their diverse gene pool, weeds are the Northwest province, where BYDV infections banedtterrisiandgatpetmedpetroaturirseins gasCaO2recsounltcoenf tcrlaimtioantes have occurred on a regular basis in recent years. change. Weeds can be classified as C3 or C4 Climate change will have an impact on the weeds, and their responses to higher CO2 levels population dynamics of these vectors, as well and temperatures differ. as the prevalence of BYDV. 2.3.3 Weeds This will have an impact on crop-weed Weed control in any small grain production competition dynamics. Furthermore, climate system can be difficult, especially with the change factors may impact the efficacy of emergence of herbicide-resistant weeds. Weed many herbicides, making weed management infestations in wheat have been shown to a significant challenge for sustainable crop reduce wheat yield by up to 33%. Several post- production. Chemical control methods are emergence herbicides have been shown to no heavily used in wheat production. Herbicides longer control grassweeds in recent seasons. accounted for nearly 25% of total pesticide Many farmers were forced to implement an use worldwide in 2011. (Grube et al., 2011). integrated weed management system (IWM) Herbicides have become the primary tool for and are now focusing on pre-emergence weed management due to their ease of use, herbicide control strategies. higher efficacy, and, most importantly, lower Extreme weather events can destabilise control costs due to labor and time savings agricultural systems by undermining crop (McErlich and Boydston, 2013). Figure 9 Barley yellow dwarf virus infected wheat leaves. Source: https://www.gardeningknowhow.com/edible/grains/barley/barley-yellow-dwarf-virus.htm. 199