Ammoniated Straw Incorporation Improves Soil Structure with Increasing Grain Productivity in Dryland Areas

To meet the increasing challenges for food security, agricultural management should aim to maximize grain yield and export from the field while improving soil fertility. However, the effects of different straw incorporation on soil aggregates, grain yield and soil C and N contents as well as their potential linkages remain poorly understood. In this study in China, we simultaneously investigated soil aggregates, SOC and TN and grain yield. The three treatments: (i) no straw (CK, the local traditional practice), (ii) straw plowed into the soil (SP), and (iii) ammoniated straw plowed into the soil (ASP, straw with low C/N ratios). The SOC content in the macro-aggregates (> 5 mm) and the micro-aggregates (≤ 0.25 mm) differed among the CK, SP, and ASP plots after 5 growing years, i.e., ASP > SP > CK. In addition, the ASP treatment had the highest grain yield, 5-year mean grain yield and aboveground biomass compared with CK and SP treatments. The ASP treatment significantly increased SOC and TN content in topsoil layers, relative to CK and SP treatments. These results suggest that we could potentially shape soil structure, increase yield stability, soil C and N content under ASP treatment. Our results highlight the importance of optimal crop straw returning on soil structure, grain yield and SOC and TN content, whereas long-term continuous measurements and observations are still required to have a good understanding of sustainable agriculture.