Landscape-scale variability of N2 fixation by pea

Abstract

The landscape-scale variability of N2 fixation by pulse crops is an important part in the intensity of N cycling in a hummocky terrain. A 100-gridpoint landscape-scale research design was established at a site in the thick Black Soil Zone in the spring of 1993. At the time of seeding, grid points classified as footslope landform complexes had 6.4% more water and 21.7 kg ha-1 more available N than those classified as shoulder. Pea seed yield ranged from 400 to 3750 kg ha-1 and straw yield ranged from 1900 to 12500 kg ha-1. Median seed yield on footslopes was 35% lower than that on shoulders, while median straw yield was 18% greater on footslopes in comparison to shoulders. Total N2 fixed in pea straw and seed ranged from 0 to 239 kg N ha-1. Median N2 fixed on shoulders was 116 kg N ha-1 and 91 kg N ha-1 on footslopes, despite the fact that total N did not show a spatial pattern. Spatial variability of available N, controlled by the redistribution of water, was considered to be the major process controlling the landscape-scale variability of N2 fixation.