A landscape-scale assessment of the nitrogen and non-nitrogen benefits of pea in a crop rotation
van Kessel, C.
The inclusion of a pulse crop in a rotation could influence the seed yield of a succeeding cereal crop in different slope positions of a field. A landscape-scale study was established in 1993 to examine the N contribution, and the N and non-N rotation benefits, of pea to wheat across a hummocky terrain. Wheat seed yield in the second phase (1994) of the pea-wheat and wheat-wheat rotations was reduced by about 20% in the depressions as compared to the shoulders and footslopes. Soil N availability throughout the growing season was responsible for the landform effect on wheat seed yield in the pea-wheat rotation. The N from pea residue, accumulated by the subsequent wheat crop, met about 5% of its requirements. This response that did not vary across the landscape. Spatial patterns that were detected for N, fixation apparently did not relate to the rate of net N mineralization and, in particular, the greater soil N availability in the depressions of the pea-wheat rotation. In the wheat-wheat rotation, grassy weed infestation in the depressions was the most important landscape-scale control on seed yield. The rotation effect of pea on the succeeding wheat crop apparently shifted the landscape-scale control from a non-N to an N related factor.
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