Farming operations cause land degradation and can be unsustainable over time. Reliance on heavy machinery and synthetic inputs have negative impacts on soil health.
Heavy machinery navigating around farms causes soil compaction which, over time, reduces the productivity of the land. Synthetic fertilizer, chemical herbicides, and pesticides can destroy soil health and the negatively affect the environment. For example, excessive uses of chemicals kill beneficial organisms, like earthworms, and contaminate water sources.
During fallow periods, between growing seasons of commercial crops and right after land clearing, bare lands are prone to soil erosion, nutrient leaching, and spreading of weeds.
Cover cropping is one of the ways to counter this problem. By planting cover crop, it provides ground cover to minimize soil erosion, capturing nutrients in the soil to be used as green manure. The rapid growth of cover crops also suppresses weed growth.
Some cover crop fixes nitrogen and increases nutrient availability in soil. They also host beneficial organisms and produce allelochemicals to control pests and diseases. Reducing the use of synthetic products, saving costs and benefit the environment.
Additionally, cover crop helps farmers reduce greenhouse gaseous emission by sequestering carbon into the soil. That also increases soil health by increasing soil organic matter. Soil organic matter improves field trafficability by making the soil more robust.
One interesting fact: Food produces from farms that are heavily reliant on pesticides can be toxic for consumption. Check out: Dirty dozen, clean 15 lists released for 2021.
Advantages and Disadvantages of Cover Crop
Cover crop has many benefits but it also has some disadvantages. Understanding cover crop and its management is important to fully utilize the benefits of cover crop. The advantages often outweigh the disadvantages. Here are lists of advantages and disadvantages of cover crops:
- Reduce soil erosion
- Reduce soil compaction
- Increase residue cover
- Increase water infiltration
- Increases soil organic carbon
- Improve soil physical properties
- Improve field trafficability
- Recycle nutrients
- Legumes fix nitrogen
- Suppress weeds
- Increases populations of beneficial insects
- Reduce some diseases
- Increases mycorrhizal infection of crops
- Increases yields on proceeding crops
- Improve landscape aesthetics
- Must be planted when time(labor) is limited
- Additional costs (planting & killing)
- Increase evapotranspiration & reduce drainage
- Reduce soil moisture
- May increase pest populations
- Creating a green bridge for disease & pest
- May increase risks of diseases
- Difficult to incorporate with tillage allelopathy
Types of cover crops
Cover crops are plant species with allelopathic potential, rapid growth, high biomass, and good soil cover. There are four classes of cover crops: grasses, legumes, brassicas, non-legumes broadleaves.
- Grasses – Grasses are a good choice of cover crop to scavenge nutrients with fibrous root systems, especially nitrogen, leftover from the previous crop. Also, good to hold soil in place and improving soil structure. They are high in carbon content and it takes longer for the residue to break down. Thus, it is good for weed control and increases soil organic matter for the longer term. Yet, they are easy to kill. However, it is less likely to release nitrogen as it breaks down.
- Legumes – The most popular legume cover crop is used to fix atmospheric nitrogen, prevent erosion, and add organic matter to the soil. Legumes are generally lower in carbon and higher in nitrogen. Thus, it is easier to break down releasing nitrogen and other nutrients faster than grasses. But, legumes are not effective in removing excess nitrogen and their residue does not last as long. Resulting in a lower soil organic matter and weed control ability than grasses.
- Brassicas – The least popular brassicas have some unique benefits as a cover crop. Brassicas are known for rapid fall growth and good biomass production, reducing erosion and absorbing excess nutrients in the soil. Uniquely of their natural pest management characteristic – most brassicas release chemicals that can be toxic to soil-borne pathogens and pests. However, pest control cannot solely depend on brassicas as it is not as effective as commercial pesticides.
- Non-legumes broadleaves – Mainly used as green manure crops and providing different plant species and root systems for soil building. They cannot fix N from the air, but takes up large amount of nutrients from the soil. However, do not let them seed, or it will become a potential future weed problem.
The four types of cover crops have different benefits and each type of cover crop has a number of plant species with different characteristics.
Cover crops in Malaysia
Legumes are widely used in Malaysia, primarily in palm oil, and rubber plantations. The common leguminous cover crop in Malaysia is uniquely dense in biomass and is good for suppressing weeds in the plantation. For more information visit Chemiseed.
Here are some leguminous cover crop species used in Malaysia:
- Centrosema pubescens sp
- Pueraria phaseoloides sp
- Calopogonium mucunoides sp
- Calopogonium caeruleum sp
- Mucuna bracteata sp
- Stylosanthes guainensis sp
- Desmodium ovalifolium sp
- Leucaena leucephala sp
- Arachis pintoi sp
All of these species have some distinct characteristics. Depending on the characteristics of the crop and if it fits the farmers’ goals, then a particular cover crop will be chosen.
Sometimes a mixture of different types and species of cover crops will be used for better performances. For example, Pueraria phaseoloides sp can withstand 4-5 months of the dry season and Calopogium Mucunoides sp can withstand a flood. Both these species can be mixed together to also provide ground cover during drought and flood.