What to remember when choosing a cover crop

Cover crops can improve soil and crop health, says Agricol’s KZN sales manager and agronomist Dustin Beckerling, who gives Lloyd Phillips some pointers on selecting appropriate cover crops.

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A Cover crop is any plant population cultivated between the rows of another crop, or planted between periods of regular crop production, to improve soil health and soil moisture retention, prevent soil erosion, and provide nitrogen or organic matter to the soil.According to Agricol sales manger and agronomist Dustin Beckerling, in choosing one or more cover crops, you must know what the desired outcome should be, what the farm’s environment is, what the farm’s existing soil fertility levels are, and what the growth patterns and nutrient requirements of the farm’s commercial crops are. You also need sufficient financial resources to implement a cover-cropping programme.“People ask me what the ideal cover crop is, and I have to tell them that there isn’t one,” explains Dustin. “This is because the potential advantages and limitations of different cover crops vary from farm to farm due to a variety of factors including climate, soil type, fertility and pH levels, the composition and size of stones in soils, soil depth, existing soil surface covering, frost patterns and severity, crop disease and insect varieties and pressure.”

Pros and cons of cover crops
There are many benefits in using cover crops, which include improved soil structure, reduced effects of compaction and plough pans, improved macro- and micro-organism activity in the soil, decreased weed pressure, lower soil temperatures, and a reduction in quantities of pesticides and herbicides used on regular crops.But there are also potential disadvantages, including higher direct input costs and management requirements, more competition for soil nutrients and moisture between the cover crops and the regular crops, a potential rise in weed pressure if cover crops aren’t managed correctly, an increased risk of fire due to the large quantities of dry material left on a land, and the increased need for specialised machinery to manage cover crops.

Choosing cover crops
When establishing one or more cover crops, Dustin says it’s important to choose varieties that establish easily, are easily maintained, are hardy and have vigorous growth. “In planting two or more cover crops together, they should compliment each other, which is why it’s important to determine which cover crops are to be planted. “As it’s important to mix crops with similar growing patterns, ask if the intended cover crops are winter or summer active. Also ask if they are legumes for nitrogen fixation in the soil or if they’re grain crops for a high biomass. “In the event of a mixture, certain legumes can be mixed with forage sorghums. In this case, a consideration would be berseem clover with oats. The berseem clover is an annual winter-growing legume that combines well with oats – the legume will fix nitrogen while the oats provides biomass. Since both can be multi-grazed, good cover can be left as a cover crop when grown out. “Other options include mixing oats, dolichos beans, or vetch with serradella, or forage sorghums with cow peas. Since legumes can climb, sorghum and grains act as a support for legumes providing the best of both worlds.”

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Vetch is an underrated cover crop, says Dustin, as it grows anywhere under almost any conditions and would thrive in KZN if it was given half a chance. “And Brassica species like the white and black mustards make good cover crops. They make high-protein green compost, suppress soil nematode populations and soil pathogens, have a biofumigant effect on soil, and can even suppress certain weed seeds.”

Preparing seedbeds and planting
“Seedbeds must be prepared according to the type of cover crop being planted,” says Dustin. “A fine seedbed is needed for fine seeds, such as clovers, and these seeds must be rolled properly after planting to ensure that they come into contact with the soil. Coarser seedbeds are better suited to larger seeds, such as oats and triticale.”Seedbeds should be weed-free ahead of planting to improve seed germination and reduce competition. This is especially important when planting finer seeds. Minimum tillage methods are the best option. When planting cover crop seeds on sloping soils, direct drilling should be used.“Before planting cover crops, a soil analysis should be done to minimise unnecessary and expensive over-fertilisation. Farmers should also inoculate any legume seeds before they’re planted,” Dustin adds.When planting cover crops, seed size determines planting depth. Fine seed should be planted at around 5mm (no deeper than 2cm), while larger seed germinates best if planted below 2cm of soil depth.Contact Dustin Beckerling on 083 306 5246, e-mail [email protected] or visit www.agricol.co.za.     |fw