The Green Manuring
Since ancient time, green manuring has been known to its positive role in crop production. This soil ameliorating practice expands its importance in recent years because of the high cost of chemical fertilizers, environmental pollution and necessity of sustainable cropping systems. Green manuring supplements the use of compost. When you need additional organic matter and readily available nutrients, you can use green manures. Green manuring is the practice of turning under the soil living plants at the peak of their growth. This peak is reached right before flowering. Young, leafy part of trees can also be used as green manure. All the plant materials recommended for composting can also be used in green manuring. Wild sunflower is a favorite green manure in Benguet. Legumes, plants that can take in nitrogen from the air through the bacteria that live in the roots, are a favorite material for green manuring.
The roots of green manure plants break down soil clods and greatly increase the porosity of the soil. Millions of tiny plant roots penetrate every part of the soil and loosen it up. Green manures have their limits. Farmers will find it difficult to control the quality of humus. Such is not the case in composting where the process of decay can be directed so that effective humus can be produced in large quantities. Green manure also does not necessarily improve the long term structure of the soil. Wrong use of green manures can lead to a decrease in soil organic matter. Leguminous green manure can lead to a further break down of soil organic matter.
There are different methods of green manuring, depending on the size of the farm and type of tools available. For vegetable farmers with small land, the following method can be used.
• Using a hoe, cut the green manure plants at the base. Start cutting at one end of the bed. Place the cuttings on the opposite side of the bed. On the space that no longer contains the green manure plants, dig a trench (4 inches deep, 6 inches long and as wide as the size of the bed). Also place the soil at the opposite side of the bed.
• Turn to the nearest area where the green manure is growing. Again, using a hoe, cut the green manure at the base. This time, drag the cuttings into the trench. Cover the green manure cuttings with soil obtained by the digging a new trench.
• Continue the process until you reach the opposite end of the bed. Into the last trench, place both the soil and green manure cuttings that were dug in the beginning of the bed. This completes the process of green manuring.
Green manures require adequate water to decay properly. Thus, the beginning of the rainy season and the end of the rainy season are among the best times to green manure. The height of the rainy season is not a good time to green manure because the soil is too wet. It will destroy the good structure of the soil if you till it when it’s too wet.