Relay cropping can be called an American variation on undersown crops. This system, which is gaining popularity, is intended not only to allow “squeezing” the maximum production capacity from a unit of area, but also to bring agrotechnical and environmental benefits.
Overlap cultivation
Undersown crops, intercropping, companion plants… There are many ideas and names, but one idea is that the main crop should not be “lonely” in the field. In the United States and Western Europe, a system called relay croppingwhich also fits this idea.
Like other undersowing variants, relay cropping is also based on growing two species of plants in the same field at the same time. Characteristic of this system is the sowing of the second crop in specially left empty rows between the rows of the first crop when the first crop enters more advanced stages of generative development, relatively soon before harvest.
The easiest way to explain this is with an example. In the system relay cropping most often, cereals are sown together with legumes – in the USA, mainly winter wheat and soybeans. Cereal is sown in the usual autumn time (September or October), with the sowing coulters set to leave rows free for soybean sowing. Importantly, soybean sowing is carried out no earlier than the earing phase of wheat (May). Depending on the farmer’s decision, wheat and soybeans grow in the following arrangement: two rows of wheat – two rows of soybeans or four rows of wheat – two rows of soybeans. For a while, grain and soybeans grow together. After the wheat harvest (July), the legume remains in the field until the soybean harvest (September-October).
Translating the English name of this system, in Polish it can be called relay cultivation, which quite well reflects the idea. relay cropping. Like in a relay race, the wheat leaving the field gives up the baton to the already developed soybeans in the further race to harvest.
One of the well-known farmers in the United States practicing this cultivation system – Jason Mauck from Indiana – thus obtains approximately 5-7 t/ha of wheat grain and approximately 4-4.5 t/ha of soybean seeds.
Advantages and disadvantages of relay cultivation
American supporters of the relay cropping system point out that such cultivation makes it possible to harvest two crops in one season in those latitudes where it is impossible to grow two species consecutively in one year. Relay cropping is intended to be a way to maximize production capacity per unit of area, increase profitability and diversify risk in the face of uncertain sales markets.
It is also said that such cultivation is a way to increase biodiversity, which is associated with reducing the pressure of pests, and in the case of using a legume as a second species, you can benefit from nitrogen fixed from the atmosphere. Practicing farmers relay cropping with cereals and legumes indicate a narrowing of the C:N ratio of plant residues left, which is supposed to favor the activity of microorganisms and the decomposition of residues.
This action allows you to maintain soil cover and the so-called “living roots” under its surface. We wrote more about the effects of living roots in the text below:
Of course, there is also the other side of the coin. Depending on the latitude, the main factor limiting the popularization of the relay cropping system is the average annual rainfall. Maintaining two species in the main crop in the field at the same time requires significant water resources in the soil, which is not feasible everywhere.
Another difficulty in this system is the development of a chemical protection plan for crops, primarily herbicides, that will be safe for the second plant species. Relay cultivation also involves the risk of competition in the canopy, which may ultimately lead to a significant reduction in the yields of both crops.
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