Abstract:

To explore the straw returning amount suitable for high and stable yield of double cropping rice in South China, the effects of rice straw returning amount on tiller number, plant weight, dry matter accumulation and early and late rice yield were studied through a 2 years (2016 to 2017) field experiment. 5 different ratios of straw returning were set up in the experiment: no straw addition (CK), 25% straws returning (S1), 50% straws returning (S2), 75% straws returning (S3) and 100% straws returning (S4). The results showed that 100% straws returning inhibited early rice tillering and promoted late rice tillering; 25%, 50% and 75% straws returning treatments had no significant effect on early and late rice in early growth period, but showed positive effect at the middle and late growth stages. The late rice plant height of 75% and 100% straw returning treatments were significantly higher than that of no straw addition treatment, with the average increase of 8.15 cm. Compared with no straw addition, the dry matter accumulation of early and late rice under all straw returning treatment increased, and the difference of 50% straw returning treatment in early rice was significant (P<0.05), which was 8.0% higher than that of CK; 50%, 75% and 100% straw returning treatments averagely increased the dry matter accumulation by 13.3%, and the difference was significant (P>0.05); however, no difference of dry matter accumulation was observed between different amounts of straw returning. Both the yield of early and late rice in straw returning treatments were higher than that of CK, among them, 50% straws returning treatment had the highest early rice yield, with the increase of 6.92%; for late rice, 50%, 75% and 100% straw returning treatments increased the yield by 5.33%, 7.50% and 8.23%, respectively; however, no difference was observed between different amounts of straw returning treatments in both early and late rice. Under this experiment, rerunning 50% straw is the best for increasing early rice yield while 100% is the best for late rice in short time. The long-term effect of straw returning on rice yield needs to be further explored.

Key words: double cropping rice in south China, straw returning, retuning amounts, growth, yield components