The rate of increase in food production is too slow to cope with the rapidly increasing population and with that the rising demand for food. The need of the hour is to increase food production.
The present system of sole cropping has failed to meet domestic needs of small farmers. Monoculture is associated with several problems that intercropping can solve. Intercropping has the potential as an economic and ecological alternative fully compatible with modern agriculture.
Intercropping, the practice of growing more than one crop simultaneously on the same piece of land at a time, may be used extensively in most of the developing world where farmers have limited access to agricultural equipment and products. The modern agriculture, based on monoculture, has increased yield enormously in developed countries, but the improvement has not been without its costs.
The production and operation of machines and synthesis of fertilisers and pesticides involve a huge amount and energy. Other costs can be high as well, ranging from degradation and disruption of environment to human pesticide poisoning. A majority of agricultural scientists are sufficiently aware of environmental and health risks of modern agricultural practices.
Problems: The low cost of synthetic fertiliser may have been a double-edged sword. The inexpensive and seemingly inexhaustible supplies helped to create a false sense of security among farmers, contributing to abandonment of soil conservation practices. Soil lost from erosion is occurring at an alarming rate, exacerbating the need for synthetic fertilisers.
Addressing problems of soil erosion and soil quality is the top priority now. Discontinuation of crop rotation also increases weed problem. Weed species are able to proliferate that can be readopted to the fixed annual planting and harvesting schedules for growing monocultures in continuous sequence. Although mechanical cultivation to remove weeds continues, herbicides rapidly become the primary means of weed control. Pesticides can be extremely useful, but recognition of complications is growing that arise when pesticide especially insecticides are abused. More pests have developed resistance to insecticides than other pesticides but all forms of pesticides have been affected.
Apart from agricultural complications, pesticides’ use is a health risk. There are direct risks in producing pesticides, a greater number of people including, farmers, fieldsmen and labourers are being poisoned from pesticide use.
Advantages: Better use of growth resources, including light, nutrients and water. Better yield stability. Intercropping offers the possibility of yield advantage relative to sole cropping through yield stability and improved yield. It meets diversified needs of small farmers, stability of yield over different seasons, better control of weeds, insect pest and diseases as well as control of soil erosion.
Companion plant: Perhaps the most obvious advantage of growing two crops simultaneously is the substantially reduced risks of total crop failure. Crops differ in their response to physical and environmental stress and it is not uncommon for one crop species to do poorly while a different crop grown under the same conditions thrives. In fact even varieties of the same species differ enormously in their response to the variable climatic condition that typically occurs.
Planting two crops together through intercropping provides an additional benefit because the resources that become available through the failure of one species can be used by the surviving crop. The remaining companion crop can use resources, such as synthetically produced fertiliser, which would otherwise have been lost due to leaching or run off, thus increasing the efficiency with which these expensive inputs are used.
Differential resources: When the distance between plants reaches some critical point, they begin to compete for at least some of their resources .Given a set of fine conditions (environment, planting pattern etc.) competitive interactions between two intercropped species can have three possible outcomes:
Intra-specific competition can be less than inter-specific competition for both species.Intra-specific competition can be greater than inter-specific competition for both species.Intra-specific competition can be less than inter-specific competition for one species,While reverse is true for other species.
Fertiliser requirements: In many situations the presence of second species may actually enhance nutrient availability for the first, although competition is present between a legume and non-legume in an intercropping system. In an intercrop, inevitably competition occurs for some resources, the legume through a mutual association with nitrogen fixing bacteria (rhizobium) may provide additional nitrogen to the associated non-legume. Legumes also form association with a fungal group, vesicular arbuscular mychorrhizae (VAM). Furthermore rhizobium and VAM can act synergistically for the host legume, greatly increasing nutrient availability. Intercrops can also reduce the need for synthetic fertilisers by alleviating soil erosion. Most soil is lost between harvesting and establishment of next crop. Differences in the phenologies of intercrops allow for continuous plant cover. Furthermore, the diversity of root systems of two crops enables them to use and stabilize a broader soil zone.
Reducing pesticide: Intercrops have been shown to reduce the population of numerous herbivore species under a wide range of conditions. Risch et al 1983 reported that in 150 intercropping studies involving 198 herbivore species, 53 per cent of the herbivore species were less abundant in the intercrop.
An advantage of intercropping has not received much attention is the reduction of weeds, but evaluating this benefit may be complex. If a species used to control weeds, it will probably also compete with its companion crop. Therefore, we might expect that crops yield to be less than it would be if grown in weed free monoculture. However, the economic and ecological cost of maintaining a weed-free monoculture may be excessive.