Cover Crops, a user’s guide

January 23, 2024

Modern farming has recently rediscovered the benefits of cover crops, with their many advantages for the production cycle, especially of monocultures. These crops improve the sustainability of the agricultural production process and generate considerable benefits in agronomic terms. In this article we’ll explore what cover cropping is, its benefits and which crops are most advantageous.

Why sow a cover crop?

Cover crops are all crops sown for the specific purpose of improving the properties of the soil, without actually being harvested. They are interval crops grown between two main crops so that the soil is not left bare, a state in which, over time, it would lose all its nutrients, be invaded by weeds and suffer erosion, especially in winter.

Instead of leaving the soil exposed to degradation, this cover of live vegetation is used to improve fertility and achieve a large range of results which vary depending on the cover crop chosen, stimulating the activity of microorganisms and conserving biodiversity. Thanks to these properties, cover crops are becoming more and more important within farmers’ agronomic strategies, especially for those who pursue conservation agriculture objectives.

Farmers can choose the best cover crop for their purposes bearing in mind the characteristics of each species and of the other crops within the rotation cycle, and weather and environmental factors.

Cover crops, all the benefits

Often, after a crop is harvested the field is left exposed to the weather without the protection that a layer of vegetation would provide. This may be the wrong strategic choice, because it leads to the loss of residual water and nutrient resources within the soil. In these cases it is useful to encourage the uniform growth of a cover crop, in view of the many agronomic benefits this can provide in the medium term. However, for this crop to be productive it is important to choose the right combination of cover crops and cash crops in the growing cycle, also considering now much biomass will be created for the following crop.

The right choice has to be made from the many crops available on the basis of a variety of factors: seasonality; soil type; benefit required; preference for mixtures or single seeds; possible weak points of the species or effects on other main crops; and production costs.

What are the benefits of cover cropping?

Improvement of soil structure to prevent erosion. This is perhaps the best known function and is of primary importance, because soils left bare during the winter are subject to the erosive action of often torrential rain. They can be protected by sowing crops with a good root structure, such as ryegrass, oats or other grasses. Their roots give structure to the soil and defend it from the action of the weather.

Permeability. These crops don’t only block weed growth but also, especially in areas with heavy rainfall, provide permeability, making it easier for water to enter the soil. This cover crop benefit is even more significant in view of the current climate crisis, with its extreme weather events and torrential rain.

Enrichment with organic matter. Cover crops do not impoverish the soil but rather increase its fertility due to their vegetative processes and the presence of microorganisms. What’s more, the destruction and ploughing-in of cover crops creates rich biomass, which boosts fertility levels. This is true of both rye and ryegrass, for example. It is important to remember that this process also generates large amounts of humus, fundamental for the soil and the next crop.

Nitrogen enrichment. The crops which follow require a good nitrogen level for their healthy growth, especially in the initial germination phases. Leguminous plants like field bean, field pea or clover, which are nitrogen fixers and tend to degrade more quickly, are ideal for this purpose. The nitrogen-enriched soil will be a benefit for the next crop and the farmer will be able to reduce the use of fertilisers.

cover crop

Additional benefits

Nitrogen capture. The situation here is the opposite of that in the previous point: excessive nitrogen in the soil due to the fertilisers used may be harmful to the next crop. The roots of specific cover crops such as grasses capture nitrogen compounds from the soil.

Weed control. A cover crop helps to control weeds, which are no longer able to access nutrients and have to compete for water resources and space to grow. This is even more the case with faster-growing cover crops such as rye, vetch or mustard. As we will see later, mulching fulfils the same purpose, starving weeds of light and oxygen.

Pest limitation. Some plant families have a biocide action, releasing aggressive substances that attack harmful insects into the soil. These include the Brassica genus, to which horseradish and mustard belong.

Pollinator insects. The sowing of some cover crops is also encouraged for another purpose, as they are particularly attractive to pollinator insects, such as bees for honey production. This category includes borage and buckwheat, which grow fast and flower abundantly, or horseradish.

Mixtures can be used to sow combinations of different species, such as a blend of ryegrass, field pea and vetch, to provide the soil with multiple benefits by exploiting the key qualities of each species.

Mechanical procedures

Choosing the right, high-performing machine is fundamental, so Alpego has designed solutions ideal for cover cropping.

Depending on the needs and the desired benefits, cover crops may be sown at different times of year. They may be sown directly on firm or on semi-tilled or tilled soil, using seed-drills or combined seed-drills and hoppers, with different combinations At the end of the cover crop’s cycle, rotary tillers or flail mowers are used.

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