Nitrogen supply from belowground residues of lentil and wheat to a subsequent wheat crop

Abstract

Lentil (Lens culinaris) production on the Canadian prairies has increased recently with possible benefits to cropping systems in this region. The yield benefit often observed in cereals grown after a pulse crop can be partially attributed to the supply of nitrogen (N) from decomposing pulse crop residues; however, the contribution of belowground residue (BGR) is poorly documented. The purpose of this greenhouse study was to quantify the N input from BGR (i.e., roots plus rhizodeposits) of lentil and wheat (Triticum aestivum) using shoot 15N-labeling and to trace the 15N from BGR into subsequently grown wheat plants. Belowground N (BGN) comprised 34 and 51 % of total plant N in lentil and wheat, respectively. Whereas wheat produced more root biomass than lentil, total amounts of BGN did not differ between species. However, biomass production and N uptake by wheat grown on lentil BGR were 49 and 14 % higher than wheat grown on wheat BGR. Moreover, a higher proportion of added 15N from lentil BGR (14.4 vs. 8.5 %) 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 pulse crops in rotation with cereals, although further research is required to identify non-N benefits of lentil.