Inoculating Legumes: Practice and Science

Atmospheric nitrogen (N) is fixed by symbiotic root-nodule bacteria (rhizobia) associated with pasture and pulse legumes and has a national value of about $3.5 billion annually.

This is based on nitrogen fixation rates of about 70 kilograms per hectare per year, crop and pasture legume areas of close to 50 million ha and fertiliser N costed to the grower at $0.76/kg, which equates to $1.00/kg plant-available N in the soil after accounting for N losses. The price of carbon-based fossil fuels, used in the production of nitrogenous fertilisers, is expected to increase in the future which will push fertiliser costs higher. Added to that are the environmental costs associated with the production, distribution and application of nitrogenous fertilisers. Therefore, the historical and ongoing interest by Australian farmers in using legumes which fix nitrogen in their farming systems makes good economic and environmental sense and needs to be sustained into the future.