Granular straw amendment in improving soil structure and crop productivity in saline soil

Soil salinization represents a significant global threat to agricultural sustainability and the quality of arable land worldwide. This study systematically evaluated the effects of wheat straw applied in different forms-chopped (CW), granular (GW), and biochar (BW)-on soil structure and wheat growth across mild (S1), moderate (S2), and severe (S3) salinity levels in a pot experiment using saline soil from the Yellow River Basin in Inner Mongolia. Results showed that straw amendments, particularly GW and BW, markedly improved soil physical properties: GW most effectively increased the content of large macro-aggregates (>2 mm) and mean weight diameter, while BW best enhanced saturated hydraulic conductivity and the proportion of 2-0.25 mm aggregates. All straw treatments reduced soil bulk density and hardness and increased saturated water content. Compared to the no-straw control, GW, BW, and CW increased shoot biomass by 26.9%, 17.6%, and 19.3%, respectively, and significantly boosted plant nitrogen, phosphorus, and potassium uptake. Soil salinity remained a key constraint, with S1 exhibiting better aggregate stability, hydraulic conductivity, and wheat growth than S2 and S3. Path analysis identified plant potassium and nitrogen content, along with soil hydraulic conductivity and water-holding capacity, as direct drivers of biomass accumulation. In conclusion, granular straw and biochar are effective amendments for enhancing saline soil productivity by improving soil structure and mitigating salt stress, providing a viable technique for sustainable land use and grain security.