Effects Of Whole Year Straw Returning And Soil Tillage Management On Rice Yield, Quality And Greenhouse Gas Emissions In Paddy Season

This study was carried out in Suzhou Modern Agriculture Rice Demonstration Zone in Xinzhuang Town, Changshu City, Jiangsu Province from 2008 to 2009 with split-plot designs. Main plots included crop straw returning to field composed of whole year straw returning (WS) and whole year straw not returning (WNS). Split plots included rotary tillage before wheat sowing (RTW) + rotary tillage before rice transplanting (RTR), rotary tillage before wheat sowing (RTW) + plow tillage before rice transplanting (PTR), plow tillage before wheat sowing (PTW) + rotary tillage before rice transplanting (RTR), plow tillage before wheat sowing (PTW) + plow tillage before rice transplanting (PTR). Changyou 1, a early ripening rice cultivar, was used as the tested rice cultivar. The effects of the above-mentioned treatments on rice grain yield and quality and the emissions of greenhouse gases were studied. The main results are as follows:1. Effects of whole year straw returning and soil tillage management on rice yield and yield componentsCompared with WNS treatments, the grain yield of WS treatments was increased by 2.64%. The rice yield of the treatments of RTW + RTR, RTW + PTR, and PTW + RTR was increased by 8.10%, 1.77%, and 1.97%, respectively, while the yield of the PTW+PTR treatment was slightly decreased by 1.45%. Compared with WNS, WS significantly reduced the number of panicles per area by 5.77% in 2008. However, the number of panicles per area increased by 1.04% compared with the WNS treatments in 2009. The treatments of WS increased significantly the number of spikelet per panicle by 5.58% and 3.68% in 2008 and 2009, respectively. The seed setting rates of WS treatments were very significantly increased by 2.22% in 2008 and were significantly reduced by 3.11% in 2009. The 1000-grain weights were significantly increased by 0.41g under WS treatments in 2008 and were slightly increased by 0.16g in 2009. The differences in grain yield, the number of panicles per area, the number of spikelet per panicle, seed setting rate, and 1000-grain weight were observed significant between different tillage treatments.2. Effects of whole year straw returning and soil tillage management on rice biomass at maturity and harvest indexCompared with WNS treatments, the biomass amount at maturity of WS treatments was increased by 26.30 g·m-2 in 2008 and reduced by 37.19 g·m-2 in 2009. But the differences didn't reach significant levels. WS increased the harvest index by 0.011 in 2008 and 0.010 in 2009. But the differences didn't reach significant levels. There were no observable differences in rice biomass at maturity and harvest index between the different tillage treatments.3. Effects of whole year straw returning and soil tillage management on nutrient uptake and utilization of nitrogen (N), phosphorus (P), and potassium (K)Compared with WNS treatments, nitrogen accumulation at maturity of WS treatments was insignificantly reduced by 0.05 g·m-2 in 2008 and by 0.45 g·m-2 in 2009; the N use efficiency for grain of WS treatments was insignificantly increased by 1.97 g·g-1 in 2008 and by 1.34 g·g-1 in 2009. The P accumulation at maturity of WS treatments was insignificantly increased by 0.19 g·m-2 in 2008 and slightly reduced by 0.02 g·m-2 in 2009. The P use efficiency for grain of WS treatments was insignificantly reduced by 2.21 g·g-1 in 2008 and slightly increased by 2.41 g·g-1 in 2009. The K accumulation at maturity of WS treatments was insignificantly reduced by 0.45 g·m-2 in 2008 and by 0.51 g·m-2 in 2009. The K use efficiency for grain of WS treatments was insignificantly increased by 2.33 g·g-1 in 2008 and by 1.29 g·g-1 in 2009. The differences in N, P, and K accumulation, P and K use efficiency for grain at maturity between different tillage treatments were significant at the 0.01 probability level. There was no significant difference in N use efficiency for grain between different tillage treatments.4. Effects of whole year straw returning and soil tillage management on rice qualityCompared with WNS, the brown rice rate of WS treatments was insignificantly reduced by 0.06% in 2008 and by 0.05% in 2009. The milled rice rate of WS treatments was insignificantly reduced by 0.17% in 2008 and was slightly increased by 0.16% in 2009. The head rice rate of WS treatments was insignificantly reduced by 0.14% in 2008 and was slightly increased by 0.40% in 2009. The rate of chalky rice rate of WS treatments was insignificantly increased by 0.42% in 2008 and by 2.17% in 2009. The rice chalkiness of WS treatments was slightly increased by 0.44% in 2008 and by 0.31% in 2009. The protein content of WS treatments was insignificantly reduced by 0.03% in 2008 and was significantly reduced by 0.11% in 2009. The content of amylose of WS treatments was insignificantly increased than WNS by 0.34% in 2008 and was slightly reduced by 0.22% in 2009. The rice taste value of WS treatments was increased by 0.08 in 2008 and was increased significantly (P < 0.01) by 1.00 in 2009. The differences in brown rice rate, milled rice rate, rice chalkiness, protein, and amylose contents between different tillage treatments were insignificant. But the differences in head rice rate, chalky rice rate and rice taste value were significant at 0.01 or 0.05 probability level.5. Effects of whole year straw returning and soil tillage management on greenhouse gas emissions in paddy seasonMethane emissions in all treatments increased at the early stages of rice growth and declined in the following stages. Little N2O emission was observed in paddy season. Methane emissions were significantly influenced by whole year straw returning treatments. As compared with the WNS treatments, CH4 emissions were 110.9% higher in WS treatments. Total CH4 emissions of the treatments RTW + RTR, RTW + PTR, PTW + RTR, and PTW + PTR was increased by 149.9%, 107.4%, 126.9%, 70.5%, respectively. Compared with WNS, total N2O emissions was 1.41% higher in WS treatments. Total N2O emissions of the treatments of RTW + RTR, RTW + PTR and PTW + RTR were decreased by 1.83%, 1.49% and 2.00%, respectively, while PTW+PTR was increased by 10.02%. Total N2O emissions were significantly influenced by soil tillage management treatments. Soil tillage management treatments, the interaction between whole year straw returning and soil tillage management treatments on total CH4 emissions was not significant. Whole year straw returning treatments, the interaction between whole year straw returning and soil tillage management treatments on total N2O emissions was not significant.