Green Manure in Organic Farming

What is green manure?

Green manures are crops sown specifically to be incorporated into the soil in order to improve its fertility, structure, and microbial biodiversity. This practice is essential in organic farming due to its ability to supply organic matter, fix nutrients such as nitrogen, and protect the soil. It also contributes to biomass generation.

Most Effective Types of Green Manure in Organic Farming

Legumes (rich in nitrogen)
Examples: Vicia sativa (common vetch), Lupinus albus (white lupin), Trifolium spp. (clovers), Medicago spp. (alfalfa).
These fix atmospheric nitrogen through symbiosis with nitrogen-fixing bacteria of the Rhizobium genus.

Grasses (rich in biomass)
Examples: Avena sativa (oats), Secale cereale (rye), Hordeum vulgare (barley).
They produce large amounts of dry matter and help improve soil structure.

Cruciferae / Brassicaceae (biofumigant effect)
Examples: Brassica napus (wild turnip), Raphanus sativus (forage radish).
These help control soil-borne pathogens and nematodes due to sulfur compounds such as glucosinolates.

When to Use Grasses or Legumes?

Goal	Use Legumes	Use Grasses
Increase available nitrogen	✅	❌
Provide large biomass amounts	⚠️ (less than grasses)	✅
Improve compacted soil structure	⚠️	✅
Prepare soil for demanding crops	✅	⚠️
Weed control and quick soil coverage	⚠️	✅
Enhance microbial biodiversity	✅	✅

Benefits of Green Manure

• Increases biomass and organic matter, improving water and nutrient retention..

• Fixes nitrogen (in the case of legumes), reducing the need for external fertilizers.

• Improves soil structure thanks to deep roots that break compaction.

• Controls erosion by covering soil from rain and wind impact.

• Reduces weeds and diseases through competition and allelopathic effects.

• Attracts beneficial fauna such as pollinators and natural pest controllers.