Soil residual water and nutrients explain about 30% of the rotational effect in 4-yr pulse-intensified rotation systems

Diverse crop rotations enable the best use of residual soil water and nutrients, thus decreasing necessary production inputs. Here, we determined the effect of cropping sequences on soil residual water and nutrients and the performance of subsequent wheat (Triticum aestivum L.). Nine rotation systems were evaluated at Swift Current, SK, and Brooks, AB, from 2010 to 2014. Pea (P, Pisum sativum L.) and lentil (L, Lens culinaris Medik.) as preceding crops before wheat (W) or the rotation systems with pea (P-P-P-W) or lentil (L-L-L-W) included more than once in the 4-yr rotations had the highest residual soil water and N in the 30-90 cm depth and continuous wheat (W-W-W-W) had the lowest. Preceding pea and lentil increased the grain yield of the subsequent wheat by 26% and 18%, respectively, as compared with continuous wheat. Variance partitioning of redundancy analysis revealed that soil residual water and residual N explained 12.4%-42.7% (average 30%) of the yield variation observed in the subsequent wheat, with the rest of the rotational benefits unexplainable by soil residual water and residual nutrients. Investigation of the factors other than soil water and nutrients that contribute to the succeeding wheat yield may further enhance the rotational effect.