UNDER THE circumference of global warming and climate change, emanations of various gases seem to be played most destructive role in changing climate. In agriculture, so called chemical fertilizers or synthetic harmones are considered most effective candidates for instant availability of nutrients. However, complete utilization or uptake by plants is still a question. Not all amounts of available nutrients are used by the plant then where they go.
Excess nutrients either deteriorate water quality via eutrophication, leaching or release into environment thus increasing temperature so nutrient management is raised as new issue in global warming scenario. CO2 emissions are considered the primary cause of global warming but under anaerobic conditions CO¬2 is converted in methane gas which is 25 times more dangerous than CO2. Furthermore, release of nitrous oxide from soil is 300 times more vicious than CO2. Nitrogen and phosphorous are considered two most important nutrient and they are applied in very high amount in crop production. Small amount of them are used while great amount of these nutrients loss through eutrophication, soil erosion, leaching, volatilization or immobilization. All these processes disturb sustainability of an ecosystem and deteriorating soil, air and water quality. The challenges when dealing with environmental issues that are perplexed by crop production and profitability of a farm. Identification of any environmental problem takes time before it may become a possible concern.
To combat these herculean problems and ensuring sustainability of an environment, an integrated approach should be used. Possible solution may reduce utilization of synthetic fertilizers which is not possible for small land holding farmers or may be use of additional crop in main crop just to use excess available resources which has potential to be accepted. Different case studies revealed that relay cropping has potential to reduce the effectiveness of these problems. The inclusion of any scavenger crop in main crop at a stage when main crop is at its maturity looks like to be a reliable and approachable technique. That scavenger crop not only uses excess nutrients from soil that might be lost latter but also produce biomass which is a source of additional income for the farmer.
Relay cropping is actually a synonym of crop diversification with aims to increase planting intensity per unit area and net profit. Use of grain legumes in standing main crop is an old approach but has little attention due to less productivity of main crop. Farmers intention is to produce more from cash crop and for that he applies extra nutrients and takes extra care of that crop but does not take care of his soil. A famous line is used by many agronomists that use the land according to its capability. This means that apply nutrient to soil according to nutrient retention capacity of soil. Excess nutrient may disturb chemical and physical properties of soil and in future might be unable to cultivate any crop. Under all such situations, relay cropping system is more productive one.
For instance, Corn production is the most favourable business in world due to high price of corn. To get high yield farmers are using hybrid which are more fertilizer responsive. Several studies in different countries demonstrated that soils on which corn is produced have lost their retention capacities and underground water has more EC and pH due to high concentration of salts in it. Later, few scientist experimented wheat and soybean relay intercropped in maize in different regions of world on different soil series at farmers field level and they found that excess amount of nutrient unused by maize was used by wheat and soybean. Thus that nutrient reduced the cost of production and increased profitability of farm. They showed that wheat removed 146 Kg N/hac that could be lost via leaching. Wheat saved that amount of nitrogen by two reasons: (1) it absorbed fall and spring precipitation, reduced available water for nitrate in soil (2) By driving force of wheat roots, nitrates retained in rhizosphere thus made it available for itself. However, the contribution of wheat towards overall profitability of farm depends on amount of nitrogen availability and which depends on management practices, taken previously. In this way relay cropping works and optimize net profit, sustain the environment, conserve the resources. A lot of research in needed to examine the effectiveness of relay cropping system in spatial variation of nutrients, in various agro ecological zones.
The writer can be reached at <Mohsin_1728@hotmail.com>