Agriculture Reference
In-Depth Information
4.10.3 GREEN MANURING AND COVER CROPPING
Growing cover crops and green manure crops can be viewed as a type of
crop rotation, where adding a nonrevenue generating crop between annual
cash crops extends the growing season
.
Green manures, also referred to
as fertility building crops, may be broadly defined as crops grown for the
benefit of the soil. The terms cover crop and green manure are frequently
used synonymously. They perform many similar functions and many of
the same plant species are used as both cover crops and green manure
crops. The main difference between the two is that the primary purpose of
growing a cover crop is to protect the soil surface from raindrop impact,
runoff, and erosion and the primary purpose of a green manure is as a soil-
building crop to produce organic material for incorporation into the soil.
Although green manuring crops have many roles, they are still often under
utilized by today's organic farmers. However, recent emphasis on reduc-
ing the environmental impact of all farming systems has led to a growing
interest from the conventional sector. Green manuring can bring a number
of advantages to the grower like: (1) Adding organic matter to the soil,
(2) Increasing biological activity, (3) Improving soil structure, (4) Reduc-
tion of erosion, (5) Increasing the supply of nutrients available to plants
(particularly by adding nitrogen to the system by fixation), (6) Reduc-
ing leaching losses, (7) Suppressing weeds, (8) Reducing pest and disease
problems, (9) Providing supplementary animal forage, (10) Drying and
warming the soil. N (%), P
2
O
5
(%), K
2
O (%) composition of some green
manuring crops are as follows: Sunhemp - 0.75, 0.12, 0.51; Mung - 0.72,
0.18, 0.53, Cowpeas - 0.71, 0.15, 0.58, Black gram - 0.85, 0.85, 0.53.
4.10.4 USE OF ORGANIC MATTER
The use of organic manures (farmyard manure, compost, green manure,
etc.) is the oldest and most widely practiced means of nutrient replenish-
ment in India. Prior to the 1950s, organic manures were almost the only
sources of soil and plant nutrition. Owing to a high animal population,
farmyard manure is the most common of the organic manures. Cattle ac-
count for 90 percent of total manure production. The proportion of cattle
manure available for fertilizing purposes decreased from 70 percent in
the early 1970s to 30% in the early 1990s. The use of farmyard manure
