Effects of straw returning on rice growth and yield under water-saving irrigation

Abstract

Straw returning (SR) is an important means of straw utilization, which has been tested and is helpful for improving soil fertility and crop production. However, the effects of SR on plant growth and yield of paddy rice (Oryza sativa L. subsp. japonica Kato) under water-saving irrigation (WSI) are rarely investigated. In the 2015 and 2016 rice seasons, field experiments were conducted with four treatments, namely controlled irrigation with conventional fertilization (CI-CF), controlled irrigation with straw returning (CI-SR), flooding irrigation with conventional fertilization (FI-CF), and flooding irrigation with straw returning (FI-SR). The objective of the present study was to investigate the response of plant height, number of tillers, biomass, and yield to SR and irrigation management. Results indicated that SR enhanced rice yield on average by 7.9% and 7.5% and improved irrigation water use efficiency (IWUE) by 6.3% and 8.3% in 2015 and 2016, respectively. The CI-SR combination significantly increased IWUE compared with FI-CF. These results suggested that SR could offset the inhibition of rice growth caused by CI, and the CI-SR combination could be an effective measure to enhance soil fertility, maintain the rice field, and increase IWUE. Furthermore, rice growth (plant height, number of tillers, and biomass) was slightly inhibited by SR during the first 20 d of the rice season, but increased after the jointing stage (approximately 40 d after transplanting). This implied that diverting some top-dressed chemical N fertilizer into basal application may be necessary for fertilizer management to better meet crop nutrient uptakes in rice fields with SR application, especially with CI.