Nitrogen Contribution of Pea Residue in a Hummocky Terrain
1997
Stevenson, F. C. | van Kessel, C.
Topography influences the distribution of soil water and inorganic N, which could affect the availability of N from legume residue to the subsequent crop. A study assessed the landscape-scale variability of the N contribution by pea (Pisum sativum L.) to the soil (N₂ fixation in residue minus seed N derived from the soil) and the subsequent wheat (Triticum aestivum L.) crop. In situ ¹⁵N-labeled pea residue was used to monitor the contribution of pea residue to the succeeding crop. A 100-point sampling grid, with 10-m spacings, was established in a field with hummocky terrain. Each sampling point was classified as a shoulder or a low-catchment or high-catchment footslope. The N contribution by pea to the soil was 45 kg ha⁻¹ in the shoulders and 63 kg ha⁻¹ in the footslopes. Recovery of ¹⁵N in the microbial biomass was greater in the footslopes (71%) vs. the shoulders (51%), and related to greater soil water content in the footslopes. The N contribution by pea to wheat, as assessed by the ¹⁵N that wheat derived from the residue of the preceding wheat crop, was 11% and similar among landform complexes. Therefore, the N contribution of pea to wheat did not explain the greater N accumulation by wheat in the high-catchment areas than the other landform complexes. The N contribution of pea to a succeeding wheat crop apparently will be a small component of the rotation benefit by pea in a hummocky terrain. Contribution no. R789 of the Saskatchewan Centre for Soil Research.
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