Ameliorating Effects of Soil Aggregate Promoter on the Physicochemical Properties of Solonetzes in the Songnen Plain of Northeast China

Freeze-thaw cycles cause serious soil erosion, which makes the prevention, control and management of solonetzic lands in the Songnen Plain challenging. The use of soil-aggregate-promoter (SAP) is highly favoured because of its energy-saving and efficient characteristics; however, SAP is rarely used in the improvement of solonetzic soil in cold regions. To fill this gap, we studied the effects of different experimental conditions on the physicochemical properties of solonetzes; the investigated conditions included the number of laboratory-based freeze-thaw cycles (with 0, 1, 3, and 5 cycles), initial moisture content (0%, 18%, 24%, and 30%) and SAP application amount (0 g/m(2), 0.75 g/m(2), 1.125 g/m(2), and 1.5 g/m(2)). The results showed the following: (1) The soil pH value decreased significantly as the SAP application rate increased, and the effect of the initial moisture content and number of freeze-thaw cycles on soil pH was not significant. (2) SAP effectively reduced the soil electrical conductivity (EC), but a certain threshold was apparent, and the factors studied had significant effects on EC. (3) SAP effectively optimised the soil macroaggregates content and inhibited the damage posed by freeze-thaw cycles to the soil structure. These results provide an important theoretical basis for the effective prevention and control of solonetzes in the Songnen Plain of Northeast China.