Cover crops and their impact on soil – shared experience (Part I)

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How three different mixes of roof crops affect the soil, says Boris Koev

How do cover crops affect the soil? In two consecutive articles, part of the joint column of Agri.BG and the specialist in roof crops Boris Koev, share the experience of growing three different mixes of cover crops and their impact on the soil. The experiment was conducted in the 2020-2021 season in the Ruse village of Trastenik.

„When we talk about cover crops, the emphasis is mainly on the soil – what problems we need to address and which types of plants are suitable for the purpose. It is also necessary to take into account both the crop rotation and the microclimatic conditions of the respective fields „, explains Boris.

Initial soil analysis and set goals

The experiment with the three mixes of cover crops begins with an initial analysis of the condition of the soil, which aims to gather detailed and up-to-date information needed to determine both the problematic functions of the soil and suitable plant species.

The analysis examined the mechanical composition, organic carbon content, specific electrical conductivity and soil reaction PH. Soil samples for the initial analysis were taken on 5 June 2020.

The soils have moderately alkaline PH – 7.8, and the relative average content of organic matter – 2.65%. The soil type in terms of mechanical components is sandy-clay soil.

The crop rotation of the field includes the previous crop of wheat and the next crop – corn.

So far, the field has been ploughed, using conventional technology. Due to the specifics of the trail layer, as well as the result in terms of mechanical composition and specific electrical conductivity, the first goal is set – to improve the soil structure.

Since the alkaline reaction of the soil determines the digestibility of vital elements for the next crop – corn (such as phosphorus, zinc, manganese, iron, etc.), it is important to emphasize. Therefore, the next priority is to improve the mineral cycle.

The objectives of the experiment are also to study several conservation practices – cover crops, minimal tillage, direct sowing; mulching and the efficiency of chemical and mechanical termination of roof crops, mulching, etc.

Set mixes and sowing of cover crops

The experiment included three mixes of cover crops, one of which was divided into inoculated and non-inoculated seeds. The mixes are balanced between cereals, crucifers, legumes and other deciduous trees.

Mix 1 – oats, clover, vetch, turnips, millet, sunflower – inoculated
Mix 2 – oats, clover, peas, turnip, coriander, sunflower – inoculated
Mix 3 – rye, clover, peas, vetch, white mustard, silage sorghum, coriander – inoculated and uninoculated

Oat, rye and coriander seeds are inoculated with mycorrhizal fungi, and clover, vetch and peas are inoculated with nitrogen-fixing bacteria.

Root crops are sown directly in wheat stubble with a disc seed drill. No other tillage was done before sowing. Sowing took place on October 1, 2020, and rain on October 2-3 provoked the germination of seeds next week.


In the mixes, given the date of sowing, we selected freezing and overwintering crops in different combinations and norms. We sowed each of the mixes on an area of ​​about 25 decares, says Boris Koev.

It is important to note that due to late planting, especially sensitive to low temperatures crops do not emerge (sunflower, silage sorghum, millet).
Expect the continuation of the material to find out more about:

The development and termination of cover crop mixes
Planting of the main spring crop – corn
The main indicators in the subsequent soil analyses and the conclusions about the mistakes and benefits of the cover crops applied in the experiment!