Effect of granulated straw incorporation on soil nutrient and grain yield of winter wheat

To clarify the feasibility of incorporation of granulated straw into soil in Huang-Huai-Hai region, a micro-plot field experiment was conducted in winter wheat/summer maize rotation cropping system at Dezhou Agricultural Research Academy of Shandong Province. The effects of granulated straw incorporation on soil nutrients contents, wheat growth and yield components were investigated. A total of three treatments were included in the experiment—no straw incorporation (CK), conventional chopped straw incorporation into the 0-15 cm soil layer (CCSI) and granulated straw incorporation into the 0-15 cm soil layer (GSI). All the treatments were arranged in a completely randomized design with three replicates. The indexes determined during the winter wheat season included wheat tiller number, chlorophyll content and net photosynthetic rate of flag leaf, dry matter accumulation and its contribution to yield, and soil nutrients contents, and wheat yield after harvest. The results showed that compared with CK, CCSI and GSI treatments had significantly higher soil nutrients contents. The contents of soil organic matter, available nitrogen and available phosphorus under GSI treatment were higher than those under CCSI treatment by 8.54%, 6.12% and 6.25%, respectively. GSI treatment also improved seedling emergence and increased tiller number. The number of basic seedlings under GSI treatment increased by 1.63% and 19.39%, tiller number increased by 3.16%-13.23% and 11.28%-16.64%, fertile tillers rate increased by 9.88% and 4.92%, and spike number increased by 13.23% and 16.64% over those of CK and CCSI treatments, respectively. Meanwhile, GSI treatment delayed leaf senescence and increased leaf area index at filling stage by 21.79% and 16.97%, increased chlorophyll content by 7.56%-47.24% and 0.53%-12.88%, increased net photosynthetic rate of flag leaf at grain-filling stage by 15.76% and 3.33%, respectively, over those of CK and CCSI treatments. Improvement in leaf photosynthetic characteristics contributed to the increase in aboveground dry matter production and translocation from vegetative organs to grain. Compared with CK and CCSI treatments, GSI treatment increased aboveground biomass at flowering stage by 17.09% and 6.33%, aboveground biomass at maturity stage by 18.91% and 9.85%, translocation of accumulated dry matter after flowering stage to grain-filling stage by 19.65% and 14.75%, respectively. Finally, GSI treatment had the highest grain yield, which was 9.69% and 10.71% higher than those under CK and CCSI treatments. Further analysis showed that grain yield had no significant correlation with kernel number per spike and thousand-kernel weight, but it had significant positive correlation with effective spike number. This indicated that spike amount was the main reason for the grain yield increasing. Therefore, the granulated straw incorporation was an effective option for straw return to the soil in agricultural production in Huang-Huai-Hai region.