What to plant in a greenhouse in the fall after tomatoes?

Organic farming advocates consider green manure to be one of the best ways to increase soil fertility.

Using plants as fertilizers is environmentally safe and improves not only the composition but also the structure of the soil. Sowing green manure in a greenhouse is advisable, as it partially replaces crop rotation, addressing the problem of intensive soil depletion and the accumulation of harmful microflora.

The effect of green manure on the soil

Green manure crops are sown between main crops to restore fertility and improve soil quality. Plants that produce large amounts of humus during decomposition are suitable for this purpose. This substance, which is found in high concentrations in black soil (10-15%), determines soil fertility.

Green manure crops are valuable not only as fertilizer, which can be applied as compost. The plants are grown directly in the garden bed, as they improve soil properties already during the growing season:

• structure – loosens the soil, increasing its permeability to oxygen and moisture;
• microbiological indicators – stimulate the growth of beneficial microorganisms that synthesize nitrogen and suppress pathogenic microflora in the soil;
• Cleanliness – suppresses weed growth, some species cleanse the soil of fungi, viruses, soil pests or larvae.

Green manure for tomatoes in a greenhouse

In most cases, the lack of beneficial effects or even damage to the planting due to the use of green manure is due to the incorrect selection of crops. When selecting plants, consider the following:

• main culture;
• soil character;
• sowing dates;
• presence of pests or diseases.

Green manure for tomatoes

Vegetable plantings should not be alternated with solanaceous green manure crops (physalis, datura), as tomatoes belong to the same family and therefore have similar nutritional needs and are susceptible to the same diseases and pests. Instead of enriching the soil with nutrients and cleansing it, solanaceous plants will deprive the tomatoes of nutrients and aggravate fungal and insect damage.

The most effective options for improving soil depleted by years of tomato planting are legumes (especially peas and broad beans) and cruciferous crops (mustard and rapeseed). Vetch, clover, rye, oats, buckwheat, goat's rue, rapeseed, sweet clover, lupine, alfalfa, and phacelia also perform well.

Don't sow a single type of grass annually; rotate or mix crops from different families (legumes, cereals, cruciferous). One common mistake is mixing crops from the same family, which results in plants competing for moisture and nutrients, poor growth, and reduced nutrient release. Avoid using perennials, as removing them from the area can be difficult, and the green manure will become a weed.

Soil characteristics

Green manure can be used to adjust soil parameters to those optimal for the main crop. Tomatoes require loose, slightly acidic soil (pH 6.0-6.8). Suitable soil types include black soil, sandy loam, or loamy clay.

1. Heavy clay soil. It's necessary to loosen the soil, and among other measures, you can sow plants whose roots will soften the soil structure. Suitable green manures for tomatoes include beans, alfalfa, and lupine. Alfalfa is the best choice as it provides phosphorus, a deficiency of which is likely in clay soil, especially with high acidity. To enrich the soil with phosphorus, you can sow peas, phacelia, or white mustard.
2. Sandy soil. This type of soil is characterized by a deficiency of humus and biomass. In such areas, green manure crops are most beneficial, especially lupine. Sandy soils quickly lose nitrogen, which can be replenished by sowing vetch, peas, or beans. Alfalfa, phacelia, and lupine are second-best nitrogen sources.
3. Peat soil. As with sandy soil, it's important to increase the humus content. It also needs to be enriched with potassium, which phacelia is rich in.
4. Acidic soil. Mustard, phacelia, and alfalfa have the ability to reduce acidity, but to achieve significant results, crops must be sown over several years.
5. Alkaline soil. In this case, green manure can be useful as a source of sulfur, which is often deficient in low-acid soils. White mustard is recommended, while legumes and cruciferous crops should be avoided.

Sowing dates

Green manure crops can be divided into winter, early, and heat-loving varieties. Sowing time is determined not only by the plant but also by the green manure cultivation method.

1. Winter sowing. In late autumn, the plot is sown with winter crops, which are mown in the spring. Suitable crops include rye, alfalfa, rapeseed, clover, and oats.
2. Spring sowing. This is done when the average daily temperature reaches above zero. Phacelia or mustard are used, and should be harvested 2-3 weeks before planting.
3. Companion cropping. Heat-loving green manure crops (vetch, legumes, lupine) can be sown between tomato rows, and the beds can be mulched after mowing.

4. Autumn sowing. Plants are sown after the harvest and mown before winter. The same crops are suitable as for spring sowing, plus vetch – a plant too heat-loving for planting after winter, it will emerge well in late summer, and its rapid growth will allow it to gain the necessary green mass before the cold weather sets in.

Pests and diseases

Some crops have the ability to repel harmful insects or attract beneficial insects that feed on pests. Furthermore, some plants produce fungicidal and antibacterial substances, making them useful for disease prevention and recurrence in garden beds.

Autumn sowing of green manure in a greenhouse

The timing of sowing herbaceous fertilizers in the fall depends on the region and the thermal insulation of the greenhouse. Plants should reach 10-15 cm in height before freezing temperatures set in. For northern and central regions, the optimal time for sowing is late August, while in southern regions, the procedure can be carried out in early September. Winter green manure crops are sown in late September or early October, before the onset of frost.

Sowing technology

Before planting green manure, all necessary sanitary work is carried out - removing tops and weeds from the beds, cleaning, and disinfecting the greenhouse.

1. The soil needs to be loosened to a depth of 5-7 cm and leveled with a rake.
2. You can make furrows, but sowing in a continuous layer is also acceptable.
3. Sow as densely as possible. For even seeding, it's recommended to mix the seeds with sand in a 1:1 ratio.
4. The seeds are raked into the soil. If sowing winter crops, it is recommended to cover them with a thin layer of compost.
5. The crops need to be watered.

Subsequently, the planting should be watered generously once a week.

When and how to cut

Green manure crops are cut in the fall or, if winter crops are being planted, in the spring, when the plants reach 20-30 cm. Crops with shallow roots (sweet clover, lupine, alfalfa, mustard) are cut and incorporated into the soil with a subsoiler, loosening the soil to a depth of 10 cm. After planting deep-rooted crops (rye), plowing or deep digging of the soil is required, which is done before planting tomatoes. Experienced gardeners prefer not to resort to this method, as the movement of soil layers destroys beneficial microorganisms.

If mowing is done in the spring, three weeks before planting the seedlings, the soil should be watered with EM preparations to speed up the digestion of plant residues. Watering should be repeated weekly, but it is only effective when the average daily temperature is at least 8°C.

Between the rows of tomatoes, you can lay the mown stems of plants grown elsewhere, using them as mulch.

Advantages and disadvantages of green manure

This method of soil fertilization has its supporters and detractors. Arguments in favor of using green manure include:

• absolutely natural fertilizer, guarantee of the purity of the future harvest;
• low interference with natural processes, safety for soil microflora and beneficial insects (earthworms, etc.);
• greater benefits of plant nitrogen for tomatoes compared to the mineral form;
• high stability of organic substances with which green manure saturates the soil;
• the relative cheapness of the method (in comparison with the purchase of manure or mineral fertilizers);
• replacement for crop rotation, which is impossible in greenhouses.

The downside of this method is its labor-intensive nature. Some gardeners believe the results don't justify the time and effort.

Don't expect immediate results from using green manure. Sowing must be continued for several years before the soil is fully restored, especially in poor, severely depleted soils. Subsequently, with regular use, tomato yields can almost double. However, improper green manure application, particularly when choosing the right plants for sowing, can reduce tomato yields.