Influence of different amounts of irrigation water on salt leaching and cotton growth under drip irrigation in an arid and saline area

In order to evaluate the effects of different amounts of water, applied by drip irrigation, to a saline–sodic soil (surface ECe > 40 dS/m; SAR > 40), on cotton growth and soil salinity, a three-year experiment was conducted on a saline wasteland in Xinjiang Northwest China during 2008–2010. Five water treatments were used for this experiment based on the soil–water matric potential (SMP) measured 20 cm beneath a drip emitter located close to the plant: the SMP levels used to determine when to irrigate were −5 kPa (S1), −10 kPa (S2), −15 kPa (S3), −20 kPa (S4), and −25 kPa (S5). After three years, both the soil salinity (ECe) and sodicity (SAR) declined significantly in 0–120 cm depth and more reduction were achieved in 0–40 cm soil depth than in 40–80 and 80–120 cm depths. Moreover, the reductions of SAR were smaller than those of ECe. Additionally, the amount of salt removed from the 0 to 80 cm depth decreased with decreasing SMP threshold. The S1 treatment resulted in the highest lint yields in 2009 and 2010. Considering the effects of leached salts on the environment of deep soil layer and the yield of cotton, an SMP of −10 kPa can be used to trigger irrigation for cotton in the first three years for saline wasteland reclamation in Xinjiang Northwest China.