Naturelly Alternatives to Fertilizer (IFA’s Literature)

Legumes (soybean) play an important part in world agriculture in two ways: First they contribute to food supply directly (grain legumes) and indirectly through the animal (forage crops and clover in mixed grassland swards). Second, through the process of nitrogen fixation they add nitrogen to the soil. Though grain legumes are an important source of protein for the human diet, these crops are, in comparison to cereals, relatively unproductive and it would be impossible to cover the world’s protein needs by growing them in place of the cereals and other non-leguminous crops which cover most of the world cropped area. It is also unfortunately true that grassland, certainly in temperate zones, can rarely sustain enough clover to be as productive as grass which receives N fertilizer. The nitrogen contributed to the soil by these crops offers a source of economy but it is not sufficient to support the high yields of arable crops which can now be grown using N fertilizer. The nitrogen provided by legumes is obtaine d without cash expenditure, but energy is expended in the fixation process in the plant. In a properly nourished crop, 400 kg of carbohydrate is used up in fixing every 100 kg N from the atmosphere.