Green Manure

Green Manure

Green manure improves soil quality and fertility. When soil is left uncovered, its fertile layer is washed away and dried out by rain and wind. Green manure is an important protection for soil resources. Annual plants with short growing periods are most commonly sown for green manuring. Shallow-rooted plants, when dug in, enrich the soil with humus. Deeper-rooting species (broad bean, clover) loosen the soil more than the length of a spade. Broad bean is a plant whose nodule bacteria enrich the soil with nitrogen. Sow green manure thoughtfully, considering what you will sow on the bed after incorporating it. Mustard and rapeseed should not be planted where you will later grow brassicas. If you plan to grow legumes, don't sow vetch, broad bean or clover before them. The most universal green manure is phacelia, which has no relatives among commonly grown vegetables. Phacelia is also a fast-growing plant, needing only 6 weeks to grow, has a rich root system that loosens the soil, and tolerates drought well. Green manure naturally regulates the physical properties of soil. It aerates heavy soils and improves water supply and nutrient provision to dry soils.

We sow green manure immediately after harvesting vegetables and other productive plants. We don't leave the bed bare so that soil erosion doesn't have time to begin. We can progressively mow green manure on the bed and always leave it lying as mulch. We mow green manure during flowering, when their content is most valuable. We can let the plants flower as long as possible, precisely because they attract the most insects and bees. However, we must not let them flower so long that the blooms mature into seeds. We don't dig seeded green manure into the soil, but remove it from the bed. If we have a lawn mower, we can shred the green manure while mowing, which makes the soil enrichment process faster. Annual plants usually decompose and break down on the bed by themselves.

We can mix different green manures when sowing. For example, we can sow marigold and calendula together, which suppresses nematodes, mix in sunflower and oil radish, which loosens the soil, and add peas, broad beans, vetch, beans, or clover, which enriches the soil with necessary nitrogen.

Which Green Manure to Sow and When

In spring - which is currently relevant - we sow plants that are resistant to cold: oats, peas, broad beans and spring vetch. We sow these plants very early in spring, as soon as the last snow melts. We sow green manure on beds where we will later grow peppers and tomatoes.

In summer - as soon as we harvest early vegetables and potatoes from the beds, we sow sunflower, phacelia, buckwheat, calendula, mustard, rapeseed and turnip rape on the harvested field. Or various combinations of these useful plants. Lettuce, spinach, beans or brassicas are also suitable for summer green manuring.

In autumn - we sow winter crop species such as rye or winter vetch. The plants will cover the soil and create a resistant soil cover. This soil cover protects the soil from erosion. In spring, we can dig these plants into the soil or use them for feeding.

Leguminous plants can be sown in beds where we grow tomatoes. These plants can fruit alongside each other and, for example, broad beans will provide tomatoes with sufficient nitrogen in the soil during growth.

Commonly used green manure:

• For gardens (peas, vetch, mustard, marigold, calendula, buckwheat).
• In agriculture (peas, clover, broad beans, vetch, mustard, rapeseed, oats, rye).

Why sowing green manure is important

• Protection of soil from drying out, effects of rainwater and weather conditions.
• It is a universal fertiliser that can replace up to 50% of farmyard manure.
• Limits weed growth and thus reduces weed infestation in beds.
• Loosens and roots the soil, revitalises it and improves its structure.
• Supports humus formation.
• Neutralises pests and fungal diseases.
• After digging into the soil, it improves its nutrient richness.
• Leguminous plants enrich the soil with nitrogen.
• A bed planted and revitalised in this way will attract many beneficial insects.

For soil quality, not only the above-ground part of green manure plants is beneficial, but also their root system. Plant roots suitable for green manure have microscopic rootlets that gradually grow and die off. Dead rootlets become food for soil organisms. These rootlets and organisms play a major role in humus formation and thus soil fertility. This process is called "root hairiness".

You can repeat sowing green manure several times a year. After harvesting potatoes, you can sow mustard in the bed, for example. When it grows to a height of 50 cm during flowering, you can dig it into the soil and sow again. Plants suitable for green manure are undemanding in terms of watering, are drought-resistant and flower naturally. After digging in, you can water the beds with plant slurry, which accelerates the decomposition (rotting) of green manure and adds additional nutrients to the soil.

With the right choice of plants, you can also sow green manure on ornamental beds. However, mulching with bark is most commonly used on these beds.

You may be discouraged by the time and effort you will spend sowing the bed with green manure and its subsequent incorporation. However, consider the ecological impact on growing plants in your garden, on what you eat, and what you fertilise crops intended for consumption with. Green manure is ecological, it nourishes the soil, and additionally protects its upper fertile layer from leaching and erosion.

Author: Hana Michalíková