Role of straw mulching in non-continuously flooded rice cultivation

Rice (Oryza sativa L.) cultivation under non-flooded (NF) condition is a new alternative to the conventional flooded (CF) rice cultivation system in the regions where rainfall and fresh water resources are limited. Non-flooded rice cultivation may mediate rice growth performance and mulching may be good practice to reduce evapotranspiration and increase water use efficiency (WUE). The research objectives of this study were to investigate the effects of non-flooded cultivation with straw mulching on the rice agronomic traits and water use efficiency of the second rice cropping season (late rice). The treatments were conventional flooded rice cultivation, non-flooded rice cultivations without (NF-ZM) and with rice straw mulching (NF-SM). Irrigation water was 19950 m3 ha−1 in 2003 and 15,850 m3 ha−1 in 2004 in the CF treatments and 7200 m3 ha−1 in 2003 and 5045 m3 ha−1 in 2004 in the non-flooded rice fields (NF-ZM and NF-SM treatments).The field measurements showed that water seepage was 13,442 m3 ha−1 in the CF treatment, 5510 m3 ha−1 in the NF-ZM treatment and 5424 m3 ha−1 in the NF-SM treatment. Rice straw mulching decreased evapotranspiration by 33% and 63% (in 2003), 36.5% and 57.1% (in 2004) to the NF-ZM treatment and CF treatment, respectively. Compared with the NF-ZM treatment, mulch application significantly increased the leaf area per plant, main root length, tap root length and root dry weight per plant of crop. The yield of the NF-SM treatment (2003: 6489 kg/hm2; 2004: 8574.8 kg/hm2) was similar with the value of the CF treatment (2003: 6811.5; 2004: 8630.5 kg/hm2), and much higher than the NF-ZM treatment (2003: 4716; 2004: 6394.8 kg/hm2). The order of irrigation water use efficiency (IWUE) and water use efficiency were as follows: NF-SM > NF-ZM > CF.