Sustainable agriculture refers to the creation of a system whereby farmers can farm their land indefinitely. Sort of like a battery that could provide power and be recharged simultaneously. Sustainable agriculture depends upon the ability of farmers to anticipate problems caused both naturally and unnaturally, i.e. as a result of farming, and overcome them.
An example of a natural problem would be drought; an unnatural problem would be nitrogen depletion in the soils as a result of harvesting crops. While man cannot directly control natural occurrences like drought or other extreme forms of weather, they can control their own impact on the land and that’s where the practices of sustainable agriculture are focused.
The common problem of nutrient depletion in the soil can be addressed in a few different ways, some of which are actually feasible right now, some of which are only proposed and depend upon the further development of technology in order to be viable. One possibility is to recycle crop waste and livestock or human manure. Another is to grow legume crops that engage in a symbiotic relationship with nitrogen-fixing bacteria.
A modification of the Haber Process (which produces nitrogen industrially with hydrogen gas) could be sustainable if the hydrogen were obtained from electrolysis powered by wind mills or solar cells instead of getting the hydrogen from natural gas as the Haber Process currently calls for. The last solution, while ideal in many respects, requires greater advancement in the field of genetic engineering.
That solution would be to engineer non-legume crops that produce nitrogen either through symbiosis or without it. Like nutrient depletion problems, the ability to irrigate crops without using up water supplies also demands attention.
Unfortunately for farmers, rainfall does not supply an adequate amount of water for crops in many areas of the world. Irrigation addresses this problem, but when a resource of water is tapped for irrigation and the rate of water use from the resource is greater than rate of water renewal at the source of water, then the water will be depleted. In such situations the sources of water cannot be considered renewable and therefore do not qualify as viable options in creating a sustainable farm.
However, when water can be used at a rate lesser than or equal to the rate of recharge at the source, a farm can be sustainable. Sustainable farms can support those who desire to produce natural products.
Natural products are ones that have not been influenced with inorganic compounds like pesticide or growth hormones in animals. Farmers wishing to market natural meat as a product raise their livestock on sustainable farms in order to be self-sufficient. Some successful farmers, catering to a growing organically inclined market, even sell steaks online.