The contributions of legumes to reducing the environmental risk of agricultural production

Fertilizer nitrogen (N) produced by the Haber-Bosch process using fossil fuels has played a key role in improving global food production. Unfortunately, less than half of the 109 million tonnes of fertilizer N currently consumed by agriculture each year is assimilated into the aboveground biomass of crops. While some fertilizer N will also be recovered by roots, much of the remainder is either leached or lost as environmentally harmful gas emissions. This chapter examines how legumes can improve biodiversity and ecosystems services outcomes while also reducing the risk of environmental damage associated with the present high reliance on N fertilizers by the following: (1) providing a renewable input of N to agricultural soils through symbiotic N2 fixation, (2) lowering the fertilizer N requirements and fossil energy use of farming systems, (3) reducing the net release of greenhouse gases into the atmosphere, and (4) slowing the rate of decline in soil organic carbon or improving the capacity of soils to sequester carbon.