Soil quality as affected by long-term cattle manure application in solonetzic soils of Songnen Plain

Abstract: Poor soil structural properties and nutrient status, and low enzyme activities are common in the solonetz. This is caused by excessive exchangeable Na+ and high soil pH value in soils. Long-term application of cattle manure is an important management practice that can affect soil quality in the solonetzic soils. Experiments were carried out in a randomized complete block design comprising 5 treatments according to the cattle manure application history: Corns (Zea mays L.) with manure applied for 2, 6, 13, and 18 years were used as the experimental treatments and corn without manure application was used as a control treatment. Soil physic-chemical properties and enzyme activities were measured across all treatments. The effects of long-term manure application on soil quality were assessed using factor analysis. Results indicated that long-term manure application significantly improved soil physic-chemical properties and enhanced soil enzyme activities. Two factors were selected for the measured soil attributes, which were "soil structural properties" (Factor 1) and "saline-alkaline properties" (Factor 2), respectively. Compared to untreated soils, soils treated with manure for 13 and 18 years were characterized by improved soil structural properties (Factor 1) and decreased soil saline-alkaline properties (Factor 2), while soils treated with manure for 2 and 6 years were characterized by decreased soil saline-alkaline properties (Factor 2). Soil quality was increased with the number of years of manure application judging from the soil quality indices, with the highest value observed for 18 years of manure application. We conclude that soil structural and saline-alkaline properties are the key factors that limit soil quality, and promotion of soil quality is characterized by the decrease in bulk density, pH value and electrical conductivity in the solonetz, especially for bulk density.