Legumes in Crop Rotations Reduce Soil Nitrous Oxide Emissions Compared with Fertilized Non-Legume Rotations

摘要

Soil nitrous oxide (N_2O) emissions were measured from a range of and crops and crop rotations in the northern grains region of ralia. The objective was to compare N20 emissions associated the growth and post-harvest residue decomposition of a nitron-fixing legume crop with that from N fertilized non-legume 1 From 2009 to 2012 a dryland crop rotation experiment was ducted on a black Vertosol (cracking clay soil) representative of main soil type used for grain growing in the region. Crop rotation tments were: canola + N_wheat + N_barley + N (CaWB), chick-.wheat + N_barley (CpWB), chickpea_wheat_chickpea (CpWCp), chickpea_sorghum + N (CpS). Soil emissions of N20 were moni-din the field seven to eight times per day using an automated 'em of chambers connected to a gas chromatograph. Soil mineral and plant N uptake were measured by regular field sampling. Dur-the project, extremes of cold, hot, wet and dry weather were weed that were often well below or above long-term averages the site. Cumulative N20emissions from the four rotations were the order CaWB > CpS = CpWB > CpWCp. Emissions from CaWB 523 g.N_2-N/ha~(-1)), where all crops were N fertilized, were more n twice those of CpWCp (614 g-N^O-Nha~(-1)), where legume N2 fixation was the external N source. As a proportion of anthropogenic Ninput, legumes emitted less N20 than N fertilized non-legumes, emissions from N fertilized crops occurred during early crop growth, while most emissions from legumes occurred during post-est decomposition of cropresidues. These differences should be n into account when devising strategies to reduce N20 emissions cropping.