Enhancing soil fertility: The role of green manuring in soil health

Legumes as green manure. (Julio César García/Pixabay)


Soil health is important for successful crop growth and sustainable farming. One eco-friendly and cost-effective method to improve soil fertility is through green manuring. 

Green manuring is a practice that dates back centuries, utilizing leguminous plants known for their nitrogen-fixing abilities. The process involves growing specific plants and later turning them into the soil before they reach full maturity. The plants then decompose, enriching the soil with essential nutrients.

In the Philippines, some of the common leguminous plants used for green manuring to improve soil fertility include munggo or mung bean (Vigna radiata) cowpea (Vigna unguiculata), and bataw (Lablab purpureus).

Benefits of green manuring

Nitrogen Fixation. Leguminous plants have symbiotic relationships with nitrogen-fixing bacteria called rhizobia, allowing them to convert nitrogen gas from the atmosphere into a usable form for plants. This process enhances soil fertility and provides an additional source of nitrogen for subsequent crops.

Increased organic matter. As leguminous plants decompose, they contribute organic matter to the soil. This organic matter improves soil structure, water-holding capacity, and nutrient retention, promoting a healthier and more productive environment for crops.

Weed suppression. Green manure crops can outcompete weeds, reducing the need for chemical weed control and ensuring that the cultivated plants have a better chance to thrive.

Guide to green manuring

Select the area. To begin the green manuring process, carefully choose a plot that would benefit from soil improvement or designate a fallow area where you intend to cultivate crops soon. It’s essential to avoid selecting areas with heavy weed growth or diseased plants, as these conditions may hinder the success of green manuring. 

Clear the land. Once the area is chosen, the next step involves clearing any existing vegetation. Ensure that the leguminous plants, which will serve as the green manure, are trimmed to a manageable height of nor more than six inches tall. This preparation will facilitate their easy incorporation into the soil later on.

Plant leguminous crops. Proceed to sow the selected leguminous seeds evenly across the designated area. Take care to maintain proper spacing between the seeds to allow for healthy growth and development of the green manure crops.

Growth and development. Regular monitoring is crucial during this stage. Provide the leguminous crops with adequate water and care to support their healthy growth and development. This attention ensures that the green manure plants thrive and fulfill their role in enriching the soil. 

Incorporate the green manure. Timing is vital for this step. Before the leguminous plants reach full maturity, which is typically when they start flowering, incorporate them into the soil using a spade or plow. This process allows the organic matter and nutrients from the green manure to become available to the soil.

Decomposition period. After incorporating the green manure, allow the crops to decompose in the soil for several weeks before planting the main crops. This decomposition period ensures that the nutrients released from the decaying green manure are ready and accessible to support the subsequent plant growth. Patience during this stage ensures optimal results for your crops.

Green manuring offers a sustainable and effective approach to improving soil fertility, making it a valuable practice for farmers. It can enhance soil nutrient content, organic matter, and weed control. This, in turn, contributes to healthier crops, reduced environmental impact, and long-term agricultural sustainability.


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