Use of Cattle Manure as Auxiliary Material to Gypsum to Ameliorate Saline–Alkali Soils

Soil salinization is a major threat to agriculture and food security globally. The effectiveness of amendments on soil quality and crop production is management-dependent, and low-cost management practices are essential for developing countries. In this 3-year field study, the effects of cattle manure and gypsum amendments on the physicochemical properties of saline–alkali soil were evaluated. We found that both single gypsum and mixed amendments significantly reduced soil hardness, bulk density, pH, and soil salt content in 20–40 cm in 2015 and 2017. A more significant decrease in soil EC and density was observed with the mixed amendments compared to single gypsum after three years of reclamation. Specifically, applying mixed amendments (M-G15) led to a significant increase in Hordeum yield by 60.94%, whereas the application of single gypsum increased Hordeum yield by 25.20–53.14%. This indicated that co-application of cattle manure can reduce the amount of gypsum needed to achieve similar improvements in soil properties and Hordeum yield, with a long-term cumulative effect. Na+/(Ca2+ + Mg2+) showed the largest negative contribution to Hordeum yield under amendments, while soil bulk density showed the second largest number of negative effects on Hordeum yield under mixed amendments. Single gypsum improved the soil’s physical quality during the early stage of saline–alkali soil remediation, and mixed amendments improved the soil’s physicochemical properties and Hordeum yield during the late stage of remediation. Na+/(Ca2+ + Mg2+) in topsoil was confirmed to be the dominant factor under the mixed amendments affecting Hordeum yield, followed by the soil bulk density. These results confirm that the co-application with cattle manure achieves a similar reclamation effect with a reduced gypsum dosage, thereby lowering the reclamation costs of saline–alkali land in semi-arid areas.