Green manure improves soil fertility by increasing soil organic matter, improving soil structure, fixing nitrogen (if legumes), and enhancing nutrient availability.
Green manure crops, which are plants grown specifically to be incorporated back into the soil, provide a multitude of benefits that contribute to improved soil health and fertility. Here's a detailed breakdown:
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Increased Soil Organic Matter: Green manures significantly boost the organic matter content of the soil. After termination (e.g., cutting down and tilling into the soil), the plant material decomposes, adding carbon and other essential nutrients back into the soil. This increased organic matter acts like a sponge, improving water retention and drainage. The reference mentions how these crops remove carbon dioxide from the atmosphere and build soil organic matter.
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Improved Soil Structure: The root systems of green manure crops help to bind soil particles together, improving soil structure and aggregation. Improved soil structure leads to better aeration, water infiltration, and root growth, making the soil more hospitable for subsequent crops. The reference highlights that legume crops "build" soil structure over time. A well-structured soil is less prone to erosion.
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Nitrogen Fixation (Legumes): Leguminous green manures, such as clover, alfalfa, and vetch, have a symbiotic relationship with nitrogen-fixing bacteria in their root nodules. These bacteria convert atmospheric nitrogen into a form that plants can use. When the green manure is incorporated into the soil, this fixed nitrogen becomes available to future crops, reducing or eliminating the need for synthetic nitrogen fertilizers.
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Enhanced Nutrient Availability: Green manures can scavenge nutrients from deeper soil layers and make them available to subsequent crops. As the green manure decomposes, these nutrients are released into the soil, enriching it and making it more fertile. They can also help to solubilize phosphorus and other essential minerals, increasing their availability to plants.
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Reduced Soil Erosion: The dense cover provided by green manure crops protects the soil from the impact of rain and wind, reducing soil erosion. This is particularly important on sloping land or in areas prone to heavy rainfall.
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Weed Suppression: Green manure crops can compete with weeds for resources like sunlight, water, and nutrients, suppressing their growth and reducing the need for herbicides. A dense stand of green manure can effectively smother weed seedlings.
In summary, green manure provides a natural and sustainable way to improve soil fertility by adding organic matter, improving structure, fixing nitrogen (in the case of legumes), enhancing nutrient availability, reducing erosion, and suppressing weeds.
