Cover cropping is the growing of crops that provide a soil cover either during or after the cropping season, including fallowing events.
Common cover crops include water melon, pigeon pea (cajanus cajan), sweat potatoes, beans (mucuna), pumpkins, forage grass, lablab among others. Maintaining a permanent soil crop cover throughout the year is called permaculture. Under permaculture, a crop is usually planted towards the harvest of or alongside an annual crop.
There are numerous advantages that come with cover cropping as presented below:
* Cover cropping provides a permanent soil cover throughout the season or year to protect against soil erosion. By reducing the speed of run-off, cover crops increase soil water infiltration and movement.
* Cover cropping cuts down the evaporation of soil moisture to the atmosphere, reducing crop stress and hence facilitating sustained production, even during the dry spell.
* Cover cropping provides a blanket against the impacts of raindrops and blowing wind that would otherwise cause rain and wind erosions respectively.
*Sustained moisture content within the soil, as a result of cover cropping, facilitates the growth, multiplication and activity of soil micro-organisms like earth worms. These are useful in recycling nutrients, providing soil aeration, barrowing, and foster crop root development among others.
* Cover cropping provides an insurance to the farmer against total loss due to failure of one given enterprise.
* Cover cropping provides a balanced food base for the farmer’s family as well as his or her animals or birds, hence increasing the productivity of a given piece of land.
* Cover crops suppress the growth, development and multiplication of weeds and related species that would otherwise lower crop yields.
* By stopping erosion and binding soil particles together, cover cropping improves the soil physical properties like soil structure and soil texture.
* Cover plants that react through allelopathy (generating chemicals that inhibit the development of other species) have the capacity to inhibit the growth and development of some crop pests.
* Cover cropping practiced on the river banks improves on the water resources life and downstream water quality by reducing sedimentation and silting.
* Cover cropping promotes maximum utilisation of land and space available on the farm and could spur sustainable rural economic growth.
* In cover cropping there is increased organic matter available to the farmer to use in mulching which increases soil nutrient recycling and soil fertility.
* Cover cropping enables regeneration and rebuilding of soil organic matter and nutrient reserves since the soil is kept under fallow for some time.
* Cover cropping enables farmers to adapt and become more resilient to climate change vagaries by fully conserving soil, water and biodiversity while simultaneously increasing food production and restoring productive natural resources and ecosystems.
* Cover crops that are leguminous, like beans, and nitrogen-fixers, help to fix plant nutrients like nitrogen.
* Soil cover helps to maintain normal soil temperatures that are a necessity for the development of soil microbial organisms and plant roots.
How to harness maximum benefits
The cover crop should be planted as soon as tillage is complete so as to remain beneficial. However, it could also be done towards the harvesting period to avoid nutrient competition with the main crop and maintain a soil cover.
The desirable cover crop is one from a variety that maintains minimum competition with the main crop by having a slowed growth.
The desirable cover crop is one that easily grows and spreads and multiplies to cover the whole soil surface such as pumpkins.
A cover crop should be cheap and easy to establish and eradicate at the beginning and end of its requirement.
Cover crops to be considered also include those that derive other multiple uses such as fodder, herbs and food.
In arid or semi-arid lands with total annual rainfall of below 500mm, cover cropping practices should be avoided to avert excessive competition for the limited available soil water.
It is cheap and appropriate, at times, to keep natural vegetation including weeds as plant cover for sustainable soil water use.
Nitrogen-fixing species are preferred to those that consume nitrogen.
The cover crop must not develop a high canopy so as to fully perform the roles of cover cropping.
Cover crops should be easily manageable for the time they are still required.
Cover crops that are most desirable are those with deep root system and low water consumptive use.
It is advisable to plant cover crops which fit in the local cropping system.
The writer is a practicing agricultural engineer.