Effect of straw mulching on drought resistance of summer maize in upland red soils

An upland red soil experiment was conducted from 2006 to 2012 to determine the effects of rice straw mulching on seasonal drought resistance of summer maize. The study was conducted at the Taoyuan Agro-ecological Experimental Station of Chinese Academy of Sciences, Hunan Province, China. Rice straw was applied at the rates of 0 (CK), 5 000 kg·hm^-2 (T1), 10 000 kg·hm^-2 (T2) and 15 000 kg·hm^-2 (T3) in field plots. The results showed that compared with CK (control), total soil available moisture in T1, T2 and T3 increased by 6.8% (P > 0.05), 19.3% (P > 0.05) and 28.4% (P < 0.05), respectively. In 2012, maize photosynthetic rate at filling stages in T1, T2 and T3 respectively increased by 24.1%, 40.3% and 53.8%. Also T1, T2 and T3 were respectively higher in photosynthetic rate than CK by 20.0%, 40.3% and 37.9% at maturity stage. At drought occurrence rate of 18.2% per ten days, there was no significant difference in maize yield between rice straw mulching and CK. Yield difference was significant (P < 0.05) when drought occurrence rate was 18.2% 63.6% per ten days. When drought occurrence rate was 18.2% 36.4% per ten days, T1 had the maximum yield. When drought occurrence rate reached 54.5% per ten days, T3 produced the maximum yield. When drought occurrence rate exceeded 63.6% per ten day, rice straw mulching was no longer suitable for resisting drought. The recommended amount of straw mulch in the southern hilly red soils was 5 000 kg·hm^-2.