Effects of exogenous material additions on the improvement of cultivated sodic-saline soil in West Liaohe Plain

Salinization has become an important factor restricting the development of agriculture in the West Liaohe Plain.In order to explore the effects of soil improvement measures for cultivated sodic-saline soil in the West Liaohe Plain, field control micro-area tests were carried out on sodic-saline cropland fields with different salinization degrees.Various exogenous materials (decomposed cow dung, biological bacterial fertilizer, humic acid, desalinization gypsum and compound conditioner) were added in the soils with different salinization degrees.Soil physical and chemical properties (soil bulk density, porosity, hardness, three phase ratios, pH, alkalinization degree, sodium adsorption ratio, total alkali) and maize yield were analyzed.The results showed that 6 000 kg·hm^-2 humic acid in light cultivated sodic-saline soil increased the maize yield by 8% and decreased the soil bulk density by 4.3% on average.In addition, the soil structure was close to ideal.The 22 500 kg·hm^-2 compound conditioner in moderate cultivated sodic-saline soil decreased the soil bulk density at 0~ 40 cm soil layer by 2.8% on average, soil structure was significantly improved, soil pH decreased by 0.61 units on average, soil alkalinity and sodium adsorption ratio decreased by 31.4% and 19.8% on average, respectively.In addition, maize yield increased by 11.8%.Application of compound conditioner 22 500 kg·hm^-2 with humic acid 6 000 kg·hm^-2 in severe cultivated sodic-saline soil significantly increased total soil porosity at 0~10 cm soil layer, decreased soil hardness at 0~30 cm soil layer and increased soil liquid with a better effect on soil structure than other treatments.In addition, soil pH at 0~ 40 cm soil layer decreased 0.29 units, soil alkalinity, soil total alkalinity and sodium adsorption ratio decreased by 19.1%, 30.8% and 20.7% on average, and maize yield increased 29.8%, respectively.Based on the soil improvement and yield-increasing effect, the humic acid (6 000 kg·hm^-2) in light cultivated sodic-saline soil, the compound conditioner (22 500 kg·hm^-2) in moderate cultivated sodic-saline soil, and the compound conditioner (22 500 kg·hm^-2) combined with humic acid (6 000 kg·hm^-2) in severe cultivated sodic-saline soil would be the optimal improvement measures.