Considering belowground nitrogen of crops grown in prairie agroecosystems
Grain legumes can improve the yield of succeeding cereal crops through nitrogen and non-nitrogen benefits. Included among these is the input of symbiotically-fixed N from the remaining legume residues following grain harvest. However, the contribution of fixed-N to the soil system can be underestimated due to inadequate physical recovery of roots and unaccounted N released from living legume roots (rhizodeposition) during crop growth. This paper reports on N partitioning in pea and canola plants using 15N stable isotope methods to track N from the plant into the soil. Results illustrate the importance of accounting for below-ground N, particularly rhizodeposit N, as it accounted for more of the total N that remained in the residues compared to the above-ground residues including straw and chaff. Preliminary results also indicate different allocation of plant N between canola and pea with potential implications for N cycling between these two crops.
15N isotope techniques
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