Improvements of soil salt characteristics and nutrient status in an impermeable saline–sodic soil reclaimed with an improved drip irrigation while ridge planting Lycium barbarum L.

Abstract

Takyric solonetz is spread widely across the arid area of northwest China. The extremely poor soil structure and low hydraulic conductivity (Ks < 0.1 mm day−1) hinder its amelioration. The purpose of this study was to investigate the soil salt leaching characteristics, nutrient contents, and distributions in the impermeable saline–sodic soil reclaimed with an improved drip irrigation method, and to explore the impacting mechanisms of agronomic practices involved on the amelioration. A 3-year field experiment was conducted to investigate the success of planting Lycium barbarum L. in the highly saline–sodic wasteland of takyric solonetz using drip irrigation. The soil beneath the drip emitters near the plants was replaced with sand in niches that were 0.2 m in ground diameter and 0.2 m deep. Five treatments based on soil matric potential (SMP) were designed to find the optimal irrigation schedule: −5 kPa (S1), −10 kPa (S2), −15 kPa (S3), −20 kPa (S4), and −25 kPa (S5). A significant improvement was found in soil infiltration capability, which was demonstrated by the increasingly enlarged wetted area beneath the drip emitter. This improvement was resulting from the combined affects of all the agronomic practices involved, including drip irrigation, sand-filled niches, film mulching. After 3 years, soil salt leaching rates in S1–S5 root zones were 68.16 , 39.45 , 26.56 , 25.14 and 10.40%, respectively, indicating that the higher SMP improved soil salt leaching. The increased soil ECe/SAR ratio reflected the amelioration of soil physical properties. After planting, the soil nutrient status considerably improved. N fertilizer, which often was leached away, should be applied in the latter half of an irrigation event. Available P content in the soil was relatively low and it was necessary to apply adequate P fertilizer to meet crop growth needs, while the studied soil was rich in K and moderate supplement of K fertilizer was proposed. After 3 years, S2, S3, and S4 produced the significantly higher dry fruit yields (∼900 kg ha−1), which were close to those produced by local farmland. Our findings indicated that an improved drip irrigation made the reclamation of an impermeable saline–sodic soil possible. The key operations included drip irrigation, sand-filled niches beneath drip emitters, ridge tillage, film mulching, and the use of thresholds to control SMP.