Nitrogen Special Issue: Summing up of papers and recommendations for future research

The 12th Australian Nitrogen Fixation Conference was the third in a series of national workshops that began in 1991 and dealt with aspects of the nitrogen dynamics of Australian pastures and croplands. The conference and the papers published in the Special Issue addressed, at least in part, the slow progress that is evident in improving the rate of biological nitrogen fixation by enhancing inoculating techniques and Rhizobium strains. An important output from the conference was an analysis of nitrogen supply and demand in Australian dryland crops, indicating less reliance on biological nitrogen fixation due to higher wheat yields, the increased use of canola in crop rotations and problems with pulses. In 3 keynote reviews, the factors affecting the fixation and release of biologically fixed nitrogen to non-legume crops were comprehensively detailed. These factors included the frequency of legumes in rotations and their individual biomass rather than the efficiency of nitrogen fixation itself. The further development and use of models is a way of predicting outcomes for various combinations of management and crop rotations. The present trend towards fewer years of legumes in phase farming in Australia may reverse, resulting in renewed interest in ley pastures and pulse crops.