Prospects of using drip irrigation for ecological conservation and reclaiming highly saline soils at the edge of Yinchuan Plain

Reclaiming saline soils at the edge of Yinchuan Plain is of paramount importance for ecological conservation. Therefore, efficiency of drip irrigation method was evaluated in a field experiment. The experiment using drip irrigation as reclamation method was carried out that included five soil matric potentials (SMPs) controlled at -5, -10, -15, -20 and -25 kPa (treatments S1-S5, respectively) directly under drip emitters at 20 cm depth. Measures including vegetation collocation, high-raised ridge and three-stage drip irrigation scheduling were adopted. Results showed that SMP thresholds significantly affected the spatial distributions of both electrical conductivity (ECe) and sodium adsorption ratio (SARe) based on extracts of saturated paste. The low salinity and SARe zones either kept enlarging or remained stable when SMP thresholds were above -20 kPa. However, for treatment S5(-25 kPa), these gradually shrank with time. By the end of the second year, the average ECe values in treatments S1-S5 were 2.05, 2.59, 3.36, 3.05 and 3.9 dS m(-1), respectively, indicating that ECe increased linearly as SMP threshold decreased. The SARe showed the same trend, with corresponding values of 9.56, 10.48, 12.26, 12.82 and 15.23 (mmol L-1)(0.5). The pH of the saturated soil extract (pHe) in all treatments increased from 7.64 to around 8.00 and was not significantly affected by treatments. Moreover, the two-year survival rates of the dominant trees were > 87.5% when SMP threshold was above -20 kPa. The growth indexes of plants reduced with the decrease in SMP thresholds and statistical analysis suggested that -20 to -17 kPa was an important SMP range, below which the forage yield of the herbaceous legume Astragalus adsurgens dropped sharply. This study suggested the SMP threshold of -20 kPa was important for drip irrigation scheduling and the drip irrigation, combined with ridging plantation, was efficient for both vegetation reclamation and reclaiming saline soils in these saline areas with shallow ground water.