The long-term effects of cattle manure application to agricultural soils as a natural-based solution to combat salinization

Excessive exchangeable sodium and high soil pH result in structural destabilization of sodic soil. The long-term application of cattle manure is an important management practice that can affect the physical properties of sodic soil. Experiments were carried out using a randomized complete block design comprising five treatments according to the cattle manure application history: corn (Zea mays L.) fields with annual manure application since 2011 (M2011), 2006 (M2006), 2001 (M2001) and 1995 (M1995) were used as the experimental treatments; manure was applied at a rate of 10,000 kg ha−1 yr−1 on an oven-dry weight basis, and corn without manure application was used as the control. The results indicated that long-term application of manure to sodic soil resulted in significant increases in soil porosity, water-holding capacity, and saturated hydraulic conductivity (Ks) and a decrease in bulk density in comparison to the control treatment. In addition, manure application significantly increased macro-aggregate formation and the mean weight diameter (MWD). Based on stepwise regression analysis, the dominant independent variable that affected aggregate stability was water-stable aggregates (WSAs) of 0.5–1 mm, and the dominant independent variable that affected both capillary porosity (ƒc) and non-capillary porosity (ƒn) was WSAs of 0.25–0.5 mm. MWD, ƒn and especially soil organic matter (SOM) were the dominant attributes that affected Ks. It was concluded that improved soil physical properties are related to soil aggregation, resulting mainly from macro-aggregate formation, particularly WSAs of 0.25–0.5 and 0.5–1 mm. This is due to binding-agent production and increased SOM from annual manure application.