When green manure can be harmful

Soil in garden plots requires a constant supply of nutrients essential for plants. This is achieved by adding organic matter and chemical fertilizers. Green manure crops are often used instead of fertilizers, although this is not a quick way to restore soil fertility. They must be used correctly—if used incorrectly, the harm will outweigh the benefit.

What are green manure crops used for?

Green manure is a term used to describe plants with a special chemical composition – they are specifically planted to enrich the soil with various macro- and microelements, improve its structure, saturate it with nitrogen, and protect it from erosion and windblown air.

Beneficial properties:

• a developed root system loosens the soil and promotes the movement of nutrients to the upper soil layers;
• when decomposing, they saturate the soil with microelements;
• necessary for the reproduction of earthworms, which participate in the creation of the humus layer;
• prevent the soil from drying out, improve moisture and air permeability;
• strengthen sandy and loose soils and slopes;
• prevent weed growth;
• prevent the spread of insect pests, fungal infections, and harmful microorganisms;
• create a mulching layer.

Features of application

A variety of plants are planted as green manure—around three hundred varieties in total. Like chemical fertilizers, each has a specific effect on the soil—this can be determined by examining the characteristics of the crop used as green manure. Vegetable growers most often use plants from the legume, cereal, and brassica families—their seeds are readily available.

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Examples of use green manure:

• oats + vetch - unpretentious and cold-resistant, can be sown before winter, in early spring, the greatest effect is achieved when sown together, they perfectly loosen the soil, prevent the growth of weeds, are rich in protein, vetch - in nitrogen;
• rapeseed - after it, the yield of vegetable crops is higher, it supplies the soil with phosphorus, sulfur, nitrogen, and a large volume of green mass;
• annual lupine – saturates with nitrogen, potassium, phosphorus, the effect can be compared to the effect of manure;
• Buckwheat is undemanding to soil, has a short growing season (can be sown several times per season), prevents the growth of weeds and the spread of aphids, and cleanses the soil of harmful microorganisms;

• white mustard – has a fungicidal and bactericidal effect, helps clear the area of ​​insect pests (wireworms, aphids), attracts beneficial insects, is rich in sulfur and phosphorus;
• Phacelia - can be planted before any vegetable crop, saturates the soil with microelements (nitrogen, potassium, phosphorus, etc.), grows in drought, in the shade and in the sun, gives the greatest effect when used with legumes;
• Oilseed radish – can grow in any soil and has an effect similar to fungicides and antibacterial drugs.

The benefits of these plants, if planted correctly, taking into account crop rotation, are undeniable, but thoughtless use can cause significant damage to crops, affecting the quantity and quality of the harvest.

When green manure is harmful

Each plant leaves behind a specific set of microelements, altering the chemical composition of the soil and promoting or, conversely, inhibiting the development of beneficial (or harmful) microorganisms. Therefore, crop compatibility in a plot must be considered when developing a crop rotation plan. Furthermore, there are a number of side effects from improper use of green manures:

• After green manure, the soil must rest so that the plant residues can rot and produce maximum effect, but in small areas this is not always possible;
• late cutting leads to seed dispersal and clogging of the area, the stem becomes hard and takes a long time to decompose;
• scattered seeds will attract birds - in large quantities they can harm the quality of the harvest and destroy beneficial insects;
• oats sown after beets will either absorb excess moisture or dry out before flowering, because beets dry out the soil, so it is recommended to plant them before planting beets - they take up a lot of moisture and retain it;

• Rapeseed grows poorly in acidic soils, so it will not give the expected results. It is not sown after cruciferous crops due to common diseases. Beets should not be planted after it, since rapeseed promotes the spread of nematodes.
• You shouldn't expect any benefit from buckwheat in a cold and dry climate - it grows poorly in such conditions, and as a precursor it is not suitable for all vegetable crops;
• White mustard, as a member of the cruciferous family, suffers from the same diseases as cabbage, so they cannot be combined; in addition, many birds fly to its plantings;
• oilseed radish, mustard, and rapeseed are not planted before or after cabbage or beets - they have the same pathogens;
• Sowing the same green manure for several years oversaturates the soil with microelements, such as phosphorus and potassium.

In summary, we can conclude that using green manure is beneficial for vegetable crops and improves the quality of the harvest, but it must be planted at a specific time, according to a crop rotation plan, cut on time, and incorporated into the soil at the right time.