Nitrogen supply from belowground residues of lentil and wheat to a subsequent wheat crop
Lentil (Lens culinaris) plants can form an association with rhizobia and thereby biologically fix much of the nitrogen (N) required for their growth. This not only reduces the need for expensive N fertilizer when the lentil crop is grown, but there is a potential to contribute a net increment of N to the soil that can be utilized by the subsequent crop. However, estimating this net increment of N remains a challenge, because of the difficulty in estimating the amount of root and root-derived N. The purpose of this greenhouse study was to quantify the belowground N (BGN) of lentil and wheat (Triticum aestivum) using shoot 15N labeling and to trace the 15N from BGN into subsequently grown wheat plants. Belowground N comprised 34 and 51 % of total plant N in lentil and wheat, respectively. Biomass production and N uptake by wheat grown on lentil belowground residues (BGR) were 49 and 14 % higher than wheat grown on wheat BGR. Moreover, a higher proportion of added 15N from lentil BGN was recovered in the succeeding wheat crop, indicating that lentil BGN was more readily mineralized than wheat BGN. The disproportionately high increase in yield vs. N uptake for wheat grown on lentil BGR, however, indicates that non-N factors also contributed to the increase in wheat yield. This study highlights the importance of including estimates of BGN when evaluating the positive effects of including lentil crops in rotation with cereals.
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