Green manure is a vital element of every home vegetable patch or allotment plot within the UK. It is an investment in your soil that will yield future benefits in the form of healthier, more productive crops and higher yields at harvest.
The advantages for using Green Manure are outlined below:
Enhance soil fertility.
Nutrient Accumulation and Recycling: Green manure crops, such as legumes (e.g., clover, peas, beans), have the ability to fix atmospheric nitrogen through symbiotic relationships with nitrogen-fixing bacteria. This nitrogen fixation enriches the soil with essential nutrients, especially nitrogen, which is a vital element for plant growth.
Organic Matter Addition: Green manure crops contribute to increasing organic matter content in the soil when they are incorporated or decomposed. Organic matter improves soil structure, water retention, and nutrient-holding capacity.
Microbial Activity: Green manure fosters a healthy soil microbial community. The roots and residues of green manure crops provide a favorable environment for beneficial microorganisms that aid in nutrient cycling and decomposition, further promoting soil fertility.
Soil Aeration: The growth and subsequent incorporation of green manure crops into the soil can enhance soil aeration. The roots of green manure plants create channels, improving the movement of air and water in the soil.
pH Regulation: Some green manure crops can help regulate soil pH, making it more suitable for the growth of certain crops. For example, crops like clover can help increase soil acidity in alkaline soils.
Mitigate soil erosion by ensuring the ground is covered during winter/off-cycles.
Physical Ground Cover: Green manure crops, with their dense vegetation and root systems, act as a protective cover for the soil surface. The plant material effectively shields the soil from the impact of raindrops, preventing them from dislodging soil particles and initiating erosion.
Root Systems: The extensive root systems of green manure plants help bind the soil particles together. These roots penetrate the soil and create a network that stabilizes the soil structure, making it more resistant to erosion caused by water runoff.
Reduced Runoff: The plant cover formed by green manure slows down the movement of water across the soil surface. This reduced runoff decreases the velocity and erosive force of water, minimizing the likelihood of soil being carried away.
Enhanced Infiltration: The roots of green manure crops create channels and pores in the soil, enhancing water infiltration. This allows water to penetrate into the soil instead of running off the surface, reducing runoff and associated erosion.
Absorption of Excess Water: Green manure plants can absorb excess moisture from the soil, preventing waterlogged conditions. This absorption reduces the risk of soil erosion that can occur due to saturated soils.
Suppress weeds on bare soil, acting as "smother crops."
Shade and Competition: Green manure crops grow rapidly and create a dense canopy of foliage. This shade inhibits sunlight from reaching the soil surface, making it difficult for weed seeds to germinate and grow. The green manure crops compete with weeds for resources like sunlight, water, and nutrients, limiting weed growth.
Allelopathic Effects: Some green manure crops release chemicals or allelopathic substances that hinder the growth of nearby weeds. These substances can deter weed germination, root development, and overall weed growth, providing a natural weed-suppression mechanism.
Physical Barrier: The vigorous growth of green manure crops forms a physical barrier that prevents weed seeds from making direct contact with the soil. Without access to the soil, weed seeds struggle to establish themselves and are less likely to grow.
Cover and Smothering: Green manure plants cover the soil, effectively smothering emerging weeds and preventing them from establishing a foothold. This layer of vegetation physically restricts the growth of weeds, keeping the soil surface covered and minimizing weed competition.
Crop Residue and Decomposition: After green manure crops are incorporated into the soil or left as surface mulch, the residue contributes to a protective layer on the soil. As the residue decomposes, it enriches the soil with organic matter, improving soil health and structure while continuing to inhibit weed growth.
Absorb nutrients that would otherwise wash away or seep into groundwater, acting as "catch crops."
Nutrient Uptake: Green manure crops have vigorous root systems that extend into the soil, actively absorbing nutrients such as nitrogen, phosphorus, potassium, and other essential elements. This nutrient uptake process helps to capture excess nutrients from the soil.
Reduced Leaching: By absorbing nutrients from the soil, green manure crops help prevent these nutrients from leaching down into the groundwater. Leaching occurs when excess nutrients move through the soil profile and can contaminate water sources. The roots of green manure plants act as a barrier, minimizing nutrient movement and leaching.
Retained in Biomass: The absorbed nutrients are stored within the biomass of the green manure crops. When these crops are incorporated into the soil, the nutrients are recycled and released back into the soil, contributing to the fertility and nutrient content of the soil.
Biomass Incorporation: When green manure crops are tilled into the soil or incorporated as mulch, the accumulated nutrients in their biomass are reintroduced to the soil. This ensures that the nutrients remain within the soil ecosystem and are available for future crops.
Enhance soil tilth.
Organic Matter Addition: Incorporating green manure into the soil adds organic matter, which improves soil structure. Organic matter binds soil particles together, creating aggregates that allow for better air and water movement through the soil.
Soil Aeration: The roots of green manure plants create channels and pores in the soil as they grow and then decompose. These channels facilitate air movement into the soil, promoting aeration. Well-aerated soil is crucial for root development and overall soil health.
Enhanced Water Retention: The organic matter from decomposed green manure acts like a sponge, enhancing the soil's water-holding capacity. This ensures that the soil retains adequate moisture, which is essential for plant growth and resilience during dry periods.
Improved Drainage: Green manure helps improve soil drainage by preventing soil compaction. The organic matter in decomposed green manure keeps the soil loose and porous, allowing excess water to drain away, reducing the risk of waterlogged conditions.
Microbial Activity: Green manure supports a thriving community of beneficial soil microbes. These microorganisms break down organic matter, releasing nutrients in a form that plants can readily use. This microbial activity further enhances soil tilth by promoting nutrient availability and cycling