Ammoniated straw improving soil structure and winter wheat yield

Abstract: As an important organic resource, straw returning into soil is a most economic and feasible method to improve soil structure and crop yield. Many problems occur in the utilization of straw resources, such as the slow decomposition of straw and the competition of nitrogen between straw and crop when the straw is applied into soil, thereby negatively affecting the crop yield. These problems can be affected by straw-incorporation methods, and an appropriate method may result in few problems. Therefore, this study aimed to select an efficient straw incorporation method to improve soil structure and increase crop yield in semi-arid region of Shaanxi China. To achieve this goal, a 2-year field experiment was carried out in the year of 2011- 2013. Summer maize straw was used. Two control treatments included long straw returning by covering soil (CK1), long straw plowed into soil (CK2). Four straw treatments were long-ammoniated straw plowed into soil (CN), powdered-ammoniated straw plowed into soil (FN), long-ammoniated straw mixed with inorganic soil amendment (calcium sulfate) plowed into soil (CNT) and powdered-ammoniated straw mixed with inorganic soil amendment (calcium sulfate) plowed into soil (FNT). The soil bulk density, total porosity, water stable aggregates, mean weight diameter (MWD), geometric mean diameter (GMD), and fractional dimension of soil aggregates were determined before experiment in 2010. Winter wheat was planted after straw returning. After harvesting winter wheat and measuring its yield, we collected soil samples at the depth of 0-30 cm and determined the soil structure-related indicators as above. The results showed that compared with CK1 and CK2, the treatment FN in the plough layer (0-15 cm) significantly (P<0.05) reduced the soil bulk density by 6.30% and 7.03%, respectively, and significantly (P<0.05) increased soil porosity by 5.07% and 6.40%, respectively. The treatment of powdered-ammoniated straw had no significant effect on the soil bulk density and porosity at the >15-30 cm. In 0-15 cm soil layer, the application of powdered-ammoniated straw (P<0.05) increased the content of soil aggregates (>0.25 mm), significantly (P<0.05) decreased soil fractal dimension, and improved MWD and GMD, improving the stability of soil structure. The correlation coefficient between grain yield and grain number, efficient panicle, 1000-grain weight, and above-ground biomass was 0.30 (P>0.05), 0.76 (P<0.01), -0.89 (P<0.01) and 0.88 (P<0.01), respectively. It indicated that the increase of its efficient panicle or aboveground biomass may primarily contribute to the increase in the yield of winter wheat. Among all the treatments, the treatment FNT had the most significant effect on increasing the yield of winter wheat. Its yield was increased by 11.12% (2011-2012) and 17.85% (2012-2013) compared with the CK1, and by 7.39% (2011-2012) and 16.59% (2012-2013) compared with the FN. Therefore, the treatment FNT was the best straw-incorporation method in this study. The results above could provide valuable information for selecting efficient straw-incorporation method to improve soil structure and crop yield in semi-arid regions of China.