Improvement of soil nutrient and biological properties and establishment of Lycium barbarum L. in an impermeable saline-sodic soil using drip irrigation

A sodicity-induced degraded wasteland, classified as takyric solonetz with low permeability (Ks <0.1 mm d–1), is spread widely across the arid area of north-west China. A 3-year field experiment was conducted to evaluate the improvement of soil properties and growth performance of Lycium barbarum L. Drip irrigation of 5 mm was triggered in each irrigation event by controlling the soil matric potential above –15 kPa, and urea, phosphoric acid and potassium nitrate were applied with irrigation water. Soils were sampled intensively in soil transects in different years. Results showed that the soil total nitrogen and organic carbon contents in the root zone increased by 63.9% and 16.3% after 3 years respectively, due to the addition of fertiliser and the return of more residue with plant growth. Similar increases occurred in soil nitrate contents, which showed obvious mobility with water flow. After reclamation, the reduced soil pH helped activate the original unavailable phosphorus caused by the presence of calcium carbonate in native soil, and increased the soil phosphorus availability. Soil urease, alkaline phosphatase and sucrase activities in the root zone were enhanced significantly by reclamation. Remarkable increases in soil respiration rates occurred within the horizontal 20-cm-distance from the drip line. Compared with the perpendicular direction to the drip line, more plant roots developed in the parallel direction, and their spatial distribution appeared in the range of 40-cm-width and 60-cm-depth beneath the drip line. An acceptable survival rate (>80%) and dry fruit yield (866 kg ha–1) were obtained at 3 years. The findings provide an alternative for reclaiming the saline-sodic soil with low permeability.