Cover Crops in South Africa: A Regenerative Way to Build Soil Health
Modern, industrial agricultural production contradicts natural laws and principles, including the practice of growing a single species on a patch of land, and then removing this plant durring the harvest. Neither of these is a natural occurrence. In nature, on the other hand, if a field was to be left bare for some reason, ‘pioneer’ plants would quickly grow over the soil. In regenerative farming, we can replicate this natural process through cover cropping.
Greater plant diversity benefits your crops by unlocking nutrients, enhancing resilience and improving soil structure. In South Africa, methods such as cover crops and intercropping increase the diversity of the ecosystem to help improve biodiversity and achieve these outcomes.
What is meant by cover cropping?
Cover crops are different from cash crops (plants that a farmer sells for profit); they are plants that are used primarily to slow erosion, enhance water availability, smother weeds, help control pests and diseases, improve soil health, increase biodiversity and bring a host of other benefits to your farm. Farmers plant cover crops in fields that would otherwise be bare; in between growing seasons, for example.
What’s the difference between intercropping and cover cropping?
Intercropping refers to the cultivation of two or more crops simultaneously on the same field; while cover cropping refers to planting ground cover between harvests to avoid leaving fields bare.
When it comes to commercial farming, both of these methods increase overall diversity in a field, thus providing a foundation for organic nutrient management, natural weed suppression, biological pest control and improved soil health.
What are the advantages of cover crops in South Africa?
Every time a farmer grows a cash crop, the plants draw nutrients out of the soil. After the harvest, those nutrients need to be returned for the next crop. Certain cover crops have the unique ability to return nutrients to the soil, making them an indispensable tool in maintaining and increasing soil fertility without the use of chemical inputs.
Farmers should consider cover crops as a long-term investment in improved soil health and regenerative farm management. Sometimes farmers see a return on investment in the first year of use; others may need a few years to see a net positive return.
Some of the benefits of cover cropping include:
Improved soil fertility
One of the primary uses of cover crops in regenerative farming is to increase soil fertility. Using legumes as cover crops return nitrogen to the soil, and other cover crops can balance soil fertility by using excess nitrogen and other nutrients. If the farmer incorporates the cover crop as green manure or mulch, the nutrients are slowly released back into the soil during decomposition. The breakdown of green manures also facilitates nutrient availability through the formation of organic acids by microbial activity.
Soil quality management
Over time, cover cropping can improve soil quality by increasing soil organic matter levels. Cover crops also improve soil structure by facilitating the breakdown of organic matter to create well-aggregated soils with high water infiltration rates.
Cover crops provide a high percentage of ground cover to slow down the velocity of rainfall before it contacts the soil surface, preventing erosive surface runoff. The root networks of the cover crops also anchor the soil in place and reduce soil movement.
- Cover crops can reduce the rate and quantity of water draining off a field by acting as a physical barrier at the soil surface
- Cover crops improve the stability of soil aggregates, reducing the break-up of aggregates with raindrop impact
- During rainy periods, more water can infiltrate into the soil instead of causing soil runoff.
- Cover crop root growth results in the formation of soil pores, allowing water to filter through the soil profile rather than draining off as surface flow
- Mulch remaining from a killed cover crop reduces water evaporation from the soil surface
- Increased water infiltration can improve the potential for soil water storage and the recharging of aquifers
Weed, disease & pest management
- Cover crops take up space and light, thus shading the soil and reducing the opportunity for weeds to establish themselves
- Some cover crops (known as ‘trap crops’) attract pests away from the crop of value
- Other cover crops can be used to attract the natural predators of pests
- If a farmer leaves a cover crop to form a mulch, it can provide significant weed control and provide a habitat for beneficial insects
- Increased numbers of beneficial insects have been noted to be associated with cover crops, acting as natural pest controls
How does cover cropping in agriculture work?
In nature, pioneer plant life provides several benefits:
- Feed the soil life with their sugar exudates
- Provide a living root mat to stabilise the soil to prevent leaching
- Protect the soil from the direct impact of the sun
- Their roots mine minerals from deeper down in the soil profile
This regenerative approach can be emulated by cover cropping and rotating the species planted on a piece of land. Cover crops provide ground cover to avoid leaving fields bare. They take on the role of the pioneer plants by providing weed competition, taking up excess moisture, maintaining soil nutrients, improving salinity and reducing wind and water erosion of soil.
The foundation of organic no-till
Cover crops are extremely important to organic no-till. In a no-till system, farmers also use cover crops as mulch for weed control.
But won’t cover crops rob moisture from the main crop?
The answer is ‘no’. There is still a widespread belief that cover cropping causes competition for moisture and nutrients with crops. But, in fact, you often get improved moisture management with a cover crop. This is because cover crops increase organic matter (humus), which holds its own weight in water. They also deed and stimulate bacterial populations, which constantly release a sticky substance that works just like water crystals
What is an example of a cover crop?
Legume cover crops
Beneficial for nitrogen-fixing
- Red clover
- Crimson clover
Non-legume cover crops
Beneficial for scavenging nutrients
- Cereals: Rye, wheat, barley, oats, triticale
- Forage grasses such as annual ryegrass
- Broadleaf species: Buckwheat, mustards, brassicas
How do I choose the right cover crop?
It is important to identify what you require from a cover crop in order to determine the best species to use.
Here are three steps and some key questions to consider:
#1 Identify your primary objectives for adding cover crops to your system
Do you want to:
- Add nitrogen to your soil?
- Increase organic matter to improve soil health?
- Reduce erosion?
- Provide weed control?
- Manage nutrients?
- Conserve soil moisture?
While cover crops provide many of these benefits, some species or mixes of species are better suited to certain objectives than others. The choice of cover crop will depend on the goal for that field.
Examples of cover crops and their application:
Grassy cover crops act as green manure
- Sorghum that can be composted in-field to build organic matter
Nitrogen-fixing cover crops can increase soil nitrogen levels
- Planting legumes before planting a cereal crop provides significant amounts of nitrogen.
- Legumes also release organic acids into the soil to release calcium and phosphorus (the two most important minerals for photosynthesis) in a plant-available form.
#2 Identify the best time and place to fit cover crops into your rotation
Take your long-term objectives into account to create a new rotation or modify an existing one.
- Are you looking for winter cover crops to scavenge nitrogen?
- Or summer cover crops to break soil compaction?
- Need a window in a small-grain rotation to supply essential nutrients?
- Or a full-year cycle to improve soil or suppress weeds?
#3 Think through the logistics
- How and when will you seed?
- When will you plant and terminate your cover crop?
- Have you got a reliable source for cover crop seeds?
- What will the weather be like?
- Can you get into the field?
- What labour and equipment will you need?
Cover cropping as part of a regenerative farming solution for South African farmers
Cover cropping and intercropping are critical ways to improve soil quality (and thus create a better yield). At RegenZ, promoting sustainable agriculture through improved regenerative agriculture is one of our main focus areas, and we advocate for some form of cover cropping or intercropping as part of a sustainable farming solution.
Get in touch to learn more about how we’re transforming human health through innovative and regenerative farming.
About the Author: Justin Platt
Justin is the Founder & CEO of Zylem and RegenZ. Justin has a BSc in Plant Pathology and Botany from UKZN. He has been involved in the agricultural services industry since graduating in 1979. Justin has a passion for regenerative agriculture.