Potential for Increasing N2Fixation of Field Pea through Soil Management and Genotype

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Abstract
The effects of incorporation of straw in soil, liming and genotype on N2 fixation by field pea were evaluated in glasshouse experiments using the 15N isotope dilution technique. Soil treatment with the equivalent of 2.5 to 10 t straw ha−1 reduced soil N03 -and soil N uptake by pea, which increased the proportion of pea N derived from N2 fixation: from 0.67 (nil straw) to a maximum of 0.96 (10 t straw ha−1). Total fixed N was increased depending on Rhizobium inoculation method and cultivar. When soil and seed were both inoculated, fixed N increased from 153 mg N pot−1 (nil straw) to 240 mg N pot−1 (10 t straw ha−1) when the cultivar was Dundale. The amount of N2 fixed by pea in response to fertilizer N addition (the equivalent of 50 kg N ha−1) varied significantly with genotype. Total fixed N increased with increasing pH over the range of 3.9 to 4.5 or 4.1 to 4.7 in two soils. In one of these (Book Book) the increase in fixed N was nearly 50% of the nil lime control.