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Refer also to the “Biotechnology & plant breeding” chapter
1. Aspects to consider when deciding what to plant
- Make sure the soil is suitable for the proposed crops. Take into account soil depth, texture, acidity and salinity.
- Study the rainfall and temperature pattern over the various seasons when deciding which crop can be grown successfully at different times of the year.
- Make sure of the correct planting dates of each crops and for each region.
- Ensure that the cultivar to be planted is adaptable to the prevailing conditions. Consider yield potential, tolerance to drought and acidity, length of growing season, disease and insect resistance, lodging, sprouting or prolificacy (multiple cobs) and intended use. However, in some instances, rotation of cultivars can be used to spread the risk of entire crop loss from infestation and to maintain a high biological diversity.
- A plough or tined implement can be used for primary cultivation. Ploughing is, however, not recommended for sandy soils that are susceptible to erosion.
- Wind erosion is an important factor that should always be taken into account. In areas where wind is a problem, conservation tillage (zero or minimum cultivation and use of stubble or mulch) is recommended.
- The seedbed should be firm and weed free. In cases where wind erosion is a problem, the seedbed should not be too fine.
Planting spacing and depth
- Planting depth is determined by the moisture status of the soil, as well as clay fraction and the soil type.
- Generally bigger seeds can be planted deep and smaller seeds shallow.
- The spacing between plants is wider in low rainfall areas.
- Most crops can be planted mechanically or by hand. In the latter case, a hand hoe or spade can be used.
- Do not compact the soil, but firm it down to ensure good soil/seed contact.
- Make sure that the soil has sufficient nutrient content for crop growth by using fertiliser before planting and/or top dressing. Compost or organic matter (manure) should be applied three to four weeks before planting.
- Fertiliser can be applied when the results from soil analysis will tell you what nutrients are required in the soil, with the type of fertiliser to use recommended. To have soil analysed, contact the Department of Agriculture or ARC in your area, an extension officer, or one of the role players from the “Soils” chapter. The type of fertiliser best suited often depends on the expected yield and the previous crop (in the case of crop rotation).
- The optimum pH for most crops is 4,5 to 5,5 (KCI). Lime should be applied in the case of soils with a pH of below 4,5. Poultry manure also alleviates low pH problems.
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