Soil mulching as an effective method for improving soil fertility in a greenhouse

In natural conditions, the soil is always protected by a layer of organic matter — fallen leaves, needles, and dead plants. Applying this technology in greenhouses allows an agronomist to solve several problems at once: maintain soil structure, protect roots from temperature stress, and activate beneficial microflora. Without cover, greenhouse soil quickly overheats in summer, overcools in winter, becomes covered with a dense crust, and gradually loses soil fertility.

How mulch protects the soil and improves its structure

The mulching layer works as a natural insulator. It retains soil moisture, reducing the need for irrigation, and eliminates the need for frequent weeding. Sunlight does not penetrate through organic matter, so a hard crust does not form on the surface of clayey soils, and plant roots can breathe freely. To maximize moisture retention, the mulching material should be applied immediately after irrigation.

Under the organic cover, soil bacteria and earthworms develop actively. In summer, microorganisms process a layer of green mulch in just a few weeks, turning it into available nutrients. After this, it is sufficient to slightly loosen the soil and apply a new layer of organic matter. As a result, the humus content in the soil increases, the land becomes loose and does not seal during irrigation.

Organic cover also performs a protective function for plant health. Mulch protects plantings from onion and carrot flies and repels moles. According to field research data, surface mulching significantly reduces the nematode population. Furthermore, in winter, the organic layer retains heat, protecting the root system of perennials from freezing.

Mulch application technology and working with different soil types

The optimal time for mulching in a greenhouse is late April or early May. Work should be carried out on warm and moist soil. Before applying the material, be sure to prepare the plot.

1. Clear the beds of debris.
2. Thoroughly weed the area.
3. Remove the rhizomes of perennial weeds.
4. Evenly spread a complex fertilizer.
5. Lightly incorporate the granules into the soil using a rake.

The prepared soil is covered with organic material. The layer thickness depends on the density of the chosen raw material. In summer, the mulch is left undisturbed, and under perennial vegetable crops, such as asparagus or rhubarb, it is left for the winter, with a new layer added on top annually.

• Layer thickness of dense materials (bark, sawdust) — 5 cm
• Layer thickness of light materials (leaves, needles) — 7–8 cm
• Radius of the mulching circle around a plant — 45 cm
• Maximum layer thickness on heavy loams — 2 cm
• Rate of compost formation on light soils — 1 cm per year

When working with heavy loams, the structure can be noticeably improved after two to three years of regular mulching with thin layers. On light soils, the effect is visible faster: thanks to microorganisms, a centimeter-thick layer of fertile compost is formed in just one year.

Annual vegetable crops are handled individually at the end of the season. If the beds were mulched with well-decomposed low-lying peat or humus, they are incorporated into the soil during autumn ploughing. The same is done with chopped straw, but with the mandatory application of nitrogen fertilizers. Coarser materials, such as sawdust, bark, or flax shive, are sent to the compost pile in autumn for further processing by worms.

Choosing mulching material: from film to organics

Black polyethylene film has become the primary mulching material in global vegetable growing over the last 50 years. It completely blocks weed growth, retains moisture, and does not obstruct gas exchange between the soil and the air. However, organic mulch remains indispensable for improving soil structure and nutrition. The main thing is to correctly select the material for a specific task and soil type.

Each type of organic matter has its own application characteristics:

• Peat. Suitable for mulching rows of winter garlic and sown vegetable crops. It prevents the formation of a crust, and its dark color accelerates soil warming in spring. Peat loosens heavy clayey soil and makes sandy soil more moisture-retentive.
• Decomposed manure and compost. Manure must be lightly incorporated into the top layer of soil; otherwise, it quickly loses nitrogen. Compost works more gently: it protects roots from temperature fluctuations and gradually releases nutrients.
• Mown grass and weeds. Grass must be dried in the sun before application to avoid rotting. Weeded plants can be spread on beds only before they start flowering.
• Green manure (siderates). The green mass of lupine or oilseed radish is distributed over the field surface. The maximum effect is achieved by subsequently incorporating them into the top layer of soil with disc implements.
• Sawdust and straw. Suitable mainly for perennials. Applying fresh sawdust under annual crops leads to soil acidification and nitrogen deficiency. Chopped straw is affordable but is often contaminated with weed seeds.

Combined Mulching Technologies

Combined methods are used to protect against weeds and accelerate fruiting. Two-layer mulching was tested in field experiments on cucumber and pumpkin crops. Plant rows were covered with a 3—4 cm layer of chopped straw, and non-woven material (spunbond) was stretched over it. This combination allowed for the total suppression of weed vegetation while maintaining normal conditions for the development of crop seedlings.

When using alternative materials (flax shives, wool waste, paper), strictly monitor their ecological purity. To prevent disease on berry bushes, use potato haulms and tomato suckers. Spread these residues under black currant and gooseberry bushes — this will reduce the risk of fungal diseases.

High yields, minimal costs, no "chemicals" — such is organic farming. The main principle is a reasonable approach to the land and plants, through which stable yields are achieved with minimal expenditure of resources, without the application of mineral fertilizers and toxic chemicals. Its essence lies in organizing the farm like natural ecosystems, in which every creature has its purpose and lives in harmony with other creatures. For hundreds of millions of years, our Earth has nourished vast forests, meadows, and steppes. No one specifically ploughed or fertilized the soil, and its soil fertility was inexhaustible. In the 20th century, due to active improper tillage, soils began to deplete. In the final decades of the 20th century, scientists realized many of their mistakes. As a result, organic farming began to develop, based on the understanding that soil, plants, livestock animals, and the forces of nature are in a very specific interaction.

The basic principles of organic farming are simple. Firstly, the land should be loosened no deeper than 5 cm, i.e., it should not be dug or ploughed. The earth is a living organism. It is like a sponge, but permeated with many small roots and saturated with a huge number of worms and microorganisms. Charles Darwin wrote about the decisive role of worms in forming soil fertility in his book "The Formation of Vegetable Mould through the Action of Worms": "Long before man arrived on the scene, the soil was regularly ploughed by earthworms, and will continue to be so." In a single 100-square-meter plot of land, untainted by chemicals, there are about 200 kg of bacteria and approximately the same amount of worms and other life that produce more than 500 kg of humus per year. It is these "natural farmers" that fertilize and feed the plants. Deep ploughing and digging suppress the activity of worms and microorganisms, destroy the soil structure, and reduce its soil fertility. With deep ploughing and digging, the soil is saturated with oxygen, which encourages soil bacteria to process humus into mineral elements available to plants. This ensures high yields on ploughed virgin lands only in the first 2-3 years, and then the amount of humus drops rapidly, yields decrease, plant immunity weakens, and pests and diseases spread. And then fertilizers and toxic chemicals become necessary.

The second basic principle of organic farming is mulching. Mulch, as a reminder, is everything that covers the soil: hay, straw, leaves, sawdust, or simply weeds cut down with a flat cutter. In nature, there is no bare black earth; it is always covered by foliage or grass. Bare, unprotected soil overheats in the sun and evaporates soil moisture very quickly, turns into mud after rain and stops breathing, gets overcooled during frosts, and is subject to erosion. Mulch protects the land, creates favorable conditions for worms and microorganisms, and eventually turns into humus.

Finally, the land needs to be revitalized by feeding the worms and soil microorganisms. The easiest way to do this is to use "green manure", cover crops, which successfully replace manure, compost, and mineral fertilizers.

Invaluable assistance in increasing soil fertility is provided by effective microorganism preparations. These are beneficial microbes and fungi that, when applied to the soil, actively multiply, utilize organic matter, process it into a form easily assimilable for plants, suppress pathogenic bacteria and fungi, and fix mineral elements.

Thereby, a striking effect of accelerating plant growth, increasing fruit mass, and extending their storage life is achieved. This technology was developed by the Japanese scientist Higa Tera and has been successfully applied in many countries around the world for over 15 years.

Of course, organic farming has its own nuances and agrotechnical practices:

• natural and effective methods of plant protection against diseases and pests;
• bed planning;
• crop rotation;
• cultivar renewal and much more...