A global meta-analysis of pulse crop effect on yield, resource use, and soil organic carbon in cereal- and oilseed-based cropping systems

Globally, pulses are important crops that are used to diversify cereal- and oilseed-dominated cropping systems and provide nitrogen (N) benefits during their growth phase and to the succeeding crops. A comprehensive synthesis is needed to better understand how the type and frequency of pulses in a rotation sequence affect the productivity and resource use of subsequent cereal and oilseed crops. A meta-analysis of global studies was conducted to determine the effect of the type and frequency of pulses in rotation on yield and resource use of subsequent cereal and oilseed crops. Three pulses (chickpea, Cicer arietinum L.), (lentil, Lens culinaris L.), and (pea, Pisum sativum L.) were selected for this study from 82 published articles with 749 pairwise comparisons. Wheat (Triticum aestivum L.) accounted for 70% of cereal pairwise comparison while canola (Brassica napus L.) was our only oilseed crop. Including pulses in a crop rotation sequence significantly increased wheat grain yield, N removal, N fertilizer use efficiency (NFUE), and water use efficiency (WUE) relative to the control (cropping systems without pulses) by 16%, 31%, 21%, and 14%, respectively. Similarly, pulse-inclusive rotations significantly increased grain yield, N removal, and WUE of canola by 10%, 26%, and 16%, respectively compared to the control. The inclusion of pulses in rotations did not significantly change soil organic carbon (SOC) for wheat (0.2%) relative to the control. The increase in grain yield of wheat in pulse-inclusive rotations was in the order of lentil > pea ≈ chickpea. In comparison, the increase in grain yield of canola in pulse-inclusive rotations was not significantly different among pulse types. In terms of pulse frequency, the effect of including pulses in rotation on grain yield, N removal, and NFUE was most pronounced in a rotation of 1-yr pulse in a 2-yr crop sequence than in any other pulse frequency, particularly for wheat. We found that (i) the increase in grain yield in the pulse-inclusive rotation was more pronounced for wheat than canola, (ii) lentil in rotation provided a greater yield increase for subsequent wheat than chickpea and pea, (iii) wheat and canola showed greater grain yield and N removal responses when they were individually grown in an alternate year with a pulse crop than any other pulse frequency, and (iv) including pulses in rotation may not increase SOC, at least in the short term. This study demonstrated relative benefits that exist am