Effects of drip irrigation strategy on cotton root distribution and water use efficiency

The effects of different drip irrigation parameters on crop growth and transportation of soil water and salinity are important for designing scientific irrigation strategies and rational utilization of water resources in arid area. Drip tape arrangement and irrigation water quality are two important factors of mulched drip irrigation. In order to investigate their influences on distribution of soil salinity and roots, and water use efficiency, field experiment was conducted in the north of Xinjiang in 2010. Two drip tape arrangements (a tap for four lines, Ms; a tap for two lines, Md) and three levels of irrigation water quality (0.24 dS/m, 4.68 dS/m, 7.42 dS/m) were designed. The results showed that drip tape arrangement played an important role in change of soil salinity and cotton roots distribution. Under the same condition of water quality, Ms reduced the salinity accumulation in root zone, and lower salinity concentration was observed in 0 ~ 40 cm soil layer of Ms treatment than that in Md treatment. Cotton roots mainly distributed in 0 ~ 40 cm layer in all the treatments. Stronger stress on cotton root growth was observed in Md treatment than in Ms treatment under irrigated with the same saline water. However, the saline water only affected the distribution area where the cotton root density was higher than 0.5 kg/m3. The cotton water consumption appeared no significant relationship with the drip tape arrangement under the same irrigation amout, and decreased with the increase of irrigation salinity. Moreover, the saline water reduced the cotton yield but improved the water use efficiency (WUE); saline water irrigation reduced both the WUE and cotton yield in Md.