Long-term effects of cattle manure application on the soil aggregate stability of salt-affected soil on the Songnen Plain of North-Eastern China

Purpose Poor soil structure and instability are primary problems in salt-affected soil, which is formed by excessive amounts of exchangeable Na+ and inadequate cementing substances in the soil. Long-term cattle manure application is a management practice for salt-affected soil that can change the distribution of soil aggregates and increase the stability of soil aggregates. Methods Experiments were carried out in a randomized block design comprising 5 treatments according to the number of years of cattle manure application. Soils to which cattle manure was applied for 7, 12, 15 and 18 years were used as the experimental treatments, and soil without cattle manure application was used as the control treatment. Soil aggregate destruction, organic matter contents, and exchangeable cations were measured, and the soil percentage of aggregate destruction was calculated. Results The results indicated that the application of cattle manure to the salt-affected soil significantly increased the organic matter content and the exchangeable Ca2+ and Mg2+ in water-stable aggregates and significantly decreased the exchangeable Na+ and soil pH compared to those in untreated soil in all fractions (P < 0.05). The abundance of water-stable microaggregates (WSAs < 0.25 mm) was reduced, while that of mechanically stable microaggregates (MSAs < 0.25 mm) increased with increasing years of cattle manure application. Conclusion We concluded that applying cattle manure to salt-affected soil led to a reduction in exchangeable Na+ and increases in exchangeable Ca2+ and organic matter contents in soil aggregates; these changes caused the agglomeration of soil aggregates and thus a decrease in the soil percentage of aggregate destruction and an increase in soil aggregate stability, ultimately resulting in an increase in macroaggregate (WSAs > 0.25 mm) abundance.