Potential for Increasing N₂ Fixation of Field Pea through Soil Management and Genotype

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.