1 Department of Agriculture and Food Western Australia, 10 Dore Street, Katanning, WA, 6317, firstname.lastname@example.org
Subterranean clover may be under stress as a result of current cropping systems leading to sub-optimal nitrogen fixation. The aim of the study was to survey farmers’ paddocks to examine the health of the nitrogen fixation process. Subterranean clover from twenty one pasture paddocks, with a range of management histories, were sampled for assessment of nodule numbers, rhizobial strain in sampled nodules, pasture composition and nitrogen fixation rate. The results showed that the current rhizobial strain was the most common strain in pasture paddocks. The amount of nitrogen fixed was above industry standards. For each tonne of legume biomass there was 20 kg of nitrogen fixed in the shoots per ha. The major factors limiting nitrogen fixation were legume plant density and legume composition of the pasture. Rhizobial strain occupying the nodules and the percentage of nitrogen fixed had relatively small impacts on the amount of nitrogen fixed. The conclusion is that subterranean clover in in this part of Western Australia appears to be in a healthy state fixing sufficient nitrogen to support crop production.