Terminating cover crops: when green manuring is the right option

February 19, 2024

Cover crops are one of the strategies adopted by conservation farming and are encouraged by the European regulations on agriculture and soil tillage in general. They aim to improve soil quality by reducing the number of tillage procedures required, by crop rotation and by covering the soil with both crop residues and cover crops. There is a wide choice of cover crops with different purposes and benefits. There are also various options with regard to cutting, residue management and green manuring.

Why is termination so fundamental?

Using cover crops is a way of protecting the soil and preparing the ground for the subsequent seeding of cash crops. To achieve this, cover crops must be terminated in a specific phase in order to make sure of their positive effects for the rest of the crop sequence. Choosing the right time for cutting or green manuring is important, since the methods used may influence the rate at which the crop will break down and be transformed into nutrients, also depending on the microclimate conditions of the environment concerned.

The two options available

There are two possible choices for termination:

  1. The action of seasonal frost, effective for “frost-tender” cover crops (such as mustard or clover), which die off at low temperatures. If this method is used the initial choice of the type of cover crop is fundamental, because not all species are affected by low temperatures in the same way. It is also preferable for the cover crop to be in a more advanced, frost-sensitive phase of its growth, a factor which must be borne in mind initially, when choosing the seeding period. In this case the farmer will decide whether to perform direct seeding or use alternative processes.
  2. Mechanical action, using agricultural machinery such as rotary tillers or flail mowers. This strategy reduces or eliminates the need for chemical weedkillers, so it is suitable for farmers who use organic growing methods. Machines can be used to bury the biomass or it can be left on the surface, as we will see in later points.
green manuring

Mechanical action, when should cover crops be terminated?

Depending on the variety chosen and leaving aside “frost-tender” species, cover crops can be terminated during flowering or just before, as in the case of pulses. It is essential to produce a large amount of biomass, so it is fundamental to choose the optimal time for seeding and cutting: only a few weeks earlier or later may make all the difference.

Once shredded, the cover crop can be left on the field as a mulch or buried in the soil prior to seeding of the following crops. The choice between these two options will depend on the aims of the farmer, who must also consider the costs of the process and its timing. The next crop can generally be seeding within the next 2-3 weeks.

Terminating cover crops without burying

Once the cover crop has reached the optimal phase for cutting, the flail mower is used to cut up all the organic material and spread it evenly as a mulching crop residue. This strategy has two agronomic benefits: since the cash crop cannot be seeded for a few weeks, the biomass present will protect the soil from the weather and also start to break down, enriching the soil with nutrients in the uppermost layer, where the seed will then be placed. What’s more, the mulch limits the spread of weeds and protects the soil from the erosive action of rain.

On large areas, a front-mounted and a side-mounted flail mower can be combined to increase the working area and reduce the procedure’s times and costs.

Afterwards, if the surface of the ground is to be prepared, the farmer can perform combined seeding by pairing a power harrow with a seed-drill with multifunctional hopper, for simultaneous preparation of the seedbed and mixing of the organic residue, seeding and fertilisation; fewer passes, with environmental and economic benefits.

cover crops

Burying cover crops: green manuring

The benefits of cover crops – such as the nutrient input of grasses and the biocide action of varieties of brassica – are most complete when the crop is mechanically buried, in the practice known as green manuring. With this method the vegetation is mown, chopped into smaller pieces and immediately buried, so that the biomass can break down to produce a fertile soil, rich in microorganisms and nutrients.

One of the best agricultural machines for green manuring is the rotary tiller, which finely chops the biomass and tills the ground, guaranteeing excellent performance on hard soils. Alpego has a wide range of patented rotary tillers suitable for all types of soil thanks to the variety of rotors available, which provide excellent preparation of the seedbed for the main crop. The professional models FG and FG-BIO, recommended for cover crops and green manuring, are chosen by our customers all over the world: watch the complete interview with a German farmer!

To conclude

Cover crops and green manuring are becoming more and more popular with agricultural policy-makers, a fact also reflected in the new CAP 2023-2027. They are a fundamental aid in achieving sustainable farming with low environmental impact, which supports biodiversity. Alpego is committed to being an integral part of this green transition by offering versatile, professional agricultural machines, the essential support for every operator in the field who wants to produce with greater awareness and the highest benefits.

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