Interactions between non-flooded mulching cultivation and varying nitrogen inputs in rice–wheat rotations

Abstract: A 3-year field experiment examined the effects of non-flooded mulching cultivation and traditional flooding and four fertilizer N application rates (0, 75, 150 and 225kgha-1 for rice and 0, 60,120, and 180kgNha-1 for wheat) on grain yield, N uptake, residual soil Nmin and the net N balance in a rice–wheat rotation on Chengdu flood plain, southwest China. There were significant grain yield responses to N fertilizer. Nitrogen applications of >150kgha-1 for rice and >120kgha-1 for wheat gave no increase in crop yield but increased crop N uptake and N balance surplus in both water regimes. Average rice grain yield increased by 14% with plastic film mulching and decreased by 16% with wheat straw mulching at lower N inputs compared with traditional flooding. Rice grain yields under SM were comparable to those under PM and TF at higher N inputs. Plastic film mulching of preceding rice did not affect the yield of succeeding wheat but straw mulching had a residual effect on succeeding wheat. As a result, there was 17–18% higher wheat yield under N0 in SM than those in PM and TF. Combined rice and wheat grain yields under plastic mulching was similar to that of flooding and higher than that of straw mulching across N treatments. Soil mineral N (top 60cm) after the rice harvest ranged from 50 to 65kgha-1 and was unaffected by non-flooded mulching cultivation and N rate. After the wheat harvest, soil Nmin ranged from 66 to 88kgNha-1 and increased with increasing fertilizer N rate. High N inputs led to a positive N balance (160–621kgha-1), but low N inputs resulted in a negative balance (-85 to -360kgha-1). Across N treatments, the net N balances of SM were highest among the three cultivations systems, resulting from additional applied wheat straw (79kgha-1) as mulching materials. There was not clear trend found in net N balance between PM and TF. Results from this study indicate non-flooded mulching cultivation may be utilized as an alternative option for saving water, using efficiently straw and maintaining or improving crop yield in rice–wheat rotation systems. There is the need to evaluate the long-term environmental risks of non-flooded mulching cultivation and improve system productivity (especially with straw mulching) by integrated resource management. [Copyright &y& Elsevier]