Sustainable agriculture integrates three main goals: environmental stewardship, farm profitability, and prosperous farming communities. These goals have been defined by a variety of disciplines and may be looked at from the vantage point of the farmer or the consumer.
Description
Sustainable agriculture refers to the ability of a farm to produce perpetually. Among other requirements, this means that any outside inputs employed for agriculture must be available indefinitely, so non-renewable resources are avoided. While air and sunlight are generally available in most geographic locations, crops also depend on soil nutrients and the availability of water. When farmers grow and harvest crops, they remove some of these nutrients from the soil. Without replenishment, the land would suffer from nutrient depletion and be unusable for further farming. Sustainable agriculture depends on replenishing the soil without using non-renewable resources, such as oil and natural gas, or deforestation. In some areas, sufficient rainfall is available for crop growth, but many other areas require irrigation. For irrigation systems to be sustainable they must be managed properly and not use more water from their source than is naturally replenished, otherwise the water source becomes, in effect, a non-renewable resource.
Conventional agriculture is often considered unsustainable for two reasons:
1 - Reliance on non-renewable resources
2 - Concern that some practices may cause long-term damage to soil, such as erosion from excessive tillage. Long-term experiments provide some of the best data on how various practices affect soil properties essential to sustainability. Organic farming is a promising alternative, but most organic food production currently uses both fossil fuels (for tractors) and tillage. Hydrogen made by electrolysis, using electricity from solar cells or windmills, may someday replace fossil fuels most farmers use to power tractors and the natural gas used in the manufacture of synthetic nitrogen fertilizer but this will invariably introduce other problems. Reducing erosion and restoring the human-nature relationship are research priorities for both conventional and organic systems.
Improvements in water well drilling technology and the development of submersible pumps have made it possible for large crops to be regularly grown where reliance on rainfall alone previously made this level of success unpredictable. However, this progress has come at a price, in that in many areas where this has occurred, such as the Ogallala Aquifer, the water is being used at a greater rate than its rate of recharge.
To make replenishment of nutrients sustainable, the best though difficult alternative may be to recycle crop waste, use livestock or human manure, and grow plants such as legumes, peanuts, or alfalfa that utilize special nitrogen-fixing bacteria called rhizobia
source : hydroponicsearch
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