Increasing biodiversity in the agro-ecosystem through cover cropping

By Bob Aston

Increased importance of cover crops in the sustainability of agro system attributes provides an enabling environment for improving the quality of neighbouring natural ecosystems but also enables smallholder farmers to manage soil erosion, soil fertility, soil quality, water, weeds, pests, diseases, and biodiversity.

Despite the many advantages of growing cover crops, most smallholder farmers have not adopted them in their cropping systems. Few smallholder farmers have realized the economic importance of cover crops.

Farmers weeding at Matwiku area of Githiga Ward, Laikipia County,Kenya

Cover cropping is particularly important in conservation agriculture. Some of the uses of cover crops include suppressing weeds, protecting soil from rain or runoff, improving soil aggregate stability, reducing surface crusting, adding active organic matter to soil, breaking hardpan, fixing nitrogen, scavenging soil nitrogen, suppressing soil diseases and pests.

Planting cover crops is an easy way to revitalize the soil, and help soil tilt and subsequent plant growth.  They reduce erosion by protecting the soil from impact energy of raindrops; their root stabilizes slopes, slows down the runoff speed, and improves soil structure thus allowing water to infiltrate soil more quickly.

They improve soil quality by increasing soil organic matter levels through the input of cover crops biomass over time. This helps to enhance soil structure and increase soil carbon sequestration.

Leguminous cover crops such as dolichos, cowpeas, pigeon peas, and desmodium, are typically high in nitrogen and can often provide the required quantity of nitrogen for crop production. Legumes also help prevent erosion, and they can increase the amount of organic matter in soil.

Some cover crops held to retain and recycle nitrogen already present in the soil as they take up surplus nitrogen remaining from fertilization of the previous crop thus preventing it from being lost through leaching.

Non-legume cover crops like rye, wheat, barley, oats, pumpkin, and sweet potatoes are useful for scavenging nutrients, suppressing weeds and producing large amounts of residue that adds soil organic matter. They are ideal for planting when a field has excess nitrogen.

Cover crops can reduce infestations by insects and diseases. Some are able to break disease cycles and reduce populations of bacterial and fungal diseases as well as parasitic nematodes as they are able to attract pests away from the main crops. Pest-fighting cover crop systems help minimize pesticide use, and as a result break disease, cut costs and reduce your chemical exposure.

In addition, cover crops help to stabilize yields and improve moisture availability through evapotranspiration. In addition, they help improve soil water-holding capacity in any tillage system. When used as mulch, they conserve water by shading and cooling the soil surface, this reduces evaporation of soil moisture.

Some cover crops suppress weeds as they compete with them for available space, light, and nutrients. They can prevent most germinated weed seeds from completing their life cycle and reproducing.

Flowering cover crops can support the habitat requirements of bees and other pollinating insects by providing a food source. The many advantages of cover crops show that smallholder farmers can immensely benefit through their cultivation.