Population pressure not only disturbing humans but also to the natural resources. Being an agricultural country Pakistan has to feed a growing population with limited resources of land and water. Pakistan has cultivated area 22.6 mha-1 out of which about 17.58 mha-1 is irrigated by canal system and remaining 3.96 mha-1 is dependent on rainfall for crop production. There are millions of hectares of land that is affected by water logging, salinity and sodicity. Erosion is also a major limiting factor in crop production especially in semi-arid regions of the country especially where total crops production is dependent on rainfall. Increasing temperature and intensive cultivation also degrading soil. Reclamation of these problematic soils are very important to increase crop production and ultimately sustainable agriculture can be made possible. Sustainable agriculture provides pants, food, fiber and animals using farming techniques that protect environment, public health and animal welfare. This type of farming provides food without compromising future production ability of the same area. Introduction of beneficial, economically suitable and environmentally viable techniques to ensure optimum crop production on sustainable basis is very important. Green manuring is such type of technique that is very successful under wide range of soil and environmental conditions.
Green manuring is the plowing under or soil incorporation of any green manure crops while they are green and succulent or soon after they flower. Green manures are forage or leguminous crops that are grown for their leafy materials needed for soil conservation. These crops are has ability to fix atmospheric nitrogen and make it available for plants use.
Advantages of green manuring in different soil under different conditions are:
- Improvement in soil fertility
- Addition of plant nutrients and organic matters
- Soil structure improvement
- Improvement in soil aeration
- Green manuring helps to control insects, pests, nematodes and diseases
- Helps control weeds through proving mulch
- Promotes habitat for natural enemies against different insects pests
- Biodiversity of soil is increased by stimulating the growth of beneficial microbes and other soil organisms
Selection criteria for Green Manuring Crops: green manuring crops must meet the following criteria while selecting it as a green manure crop
- Fast growing
- More vegetative growth
- Maximum green matter production
- Succulent
- Nitrogen fixing ability
- Quickly decomposable
- Adaptation in local condition
Green manuring crops: There are many crops that can be grown under wide range of conditions
1-Sesbania 2- Janter 3- Gawar 4- Sun hemp 5- Pigeon pea
6- Berseem 7- Mustard 8- Azola 9- Soybean 10- sweet clover
Time of incorporation:
When the crop is at flowering stage or just before flowering it can be incorporated into soil with maximum biomass. Incorporation can be done by using rotavator in standing water to facilitate decomposition or in dry soil followed by irrigation. Green manure crops usually take 4-6 weeks to decompose depending on temperature and microbes in the soil. Next crop can be sown or transplant just after 1-2 weeks after incorporation of green manure crops.
Conclusion:
Manuring after every three years not only gives improved yield but also make soil fertile. Green manuring may also cause some problems of disease ,insect pest , low germination of succeeding crop in arid region due to moisture depletion and may be loss of one crop as it take 70-80 days in the field and then further time for decomposition. These problems can be overcome by selecting suitable crops for specific region, managing there sowing time in a suitable season and provision of nitrogen to increase decomposition. Sustainable crop production will ensure food security for mankind.
Authors:
Sajid Hanif, Muhammad Irshad, Muhammad Shafique, Azeem Akhtar, Irsa Ejaz and Khadija Tahseen Arshad
