Modelling the Soil Water Dynamics under Micro-sprinkling Hose Irrigation for Distorted Roots of Transplanted Cotton

Information on root zone water dynamics is essential to optimize irrigation strategies. The study on root is an important step for the research of root zone water dynamics. A field experiment was carried out to study the root development of transplanted cotton and simulate root zone water dynamics under micro-sprinkling hose irrigation (MHI) with different irrigation regimes during 2013-2015. The irrigation regimes were set as: high irrigation (HI, 80 mm), medium irrigation (MI, 60 mm) and low irrigation (LI, 40 mm). Analysed data disclosed that the root system of transplanted cotton consisted of some claw-shaped branch roots, and was distributed in shallower soil layer (0-30 cm) than that of direct-seeded cotton. The average root length density in the MI treatment was 12% and 41% larger than that in the HI and LI treatments. MI also increased the average root biomass density by 18% and 53% compared with HI and LI. By inputting the calibrated data on distorted root, HYDRUS-2D model simulated the soil water content well. The mean average absolute errors, root mean square errors, model efficiencies, and Rs in the HI treatment were 0.009 m m, 0.015 m m, 0.825 and 0.839; these in the MI treatment were 0.011 m m, 0.017 m m, 0.859 and 0.863; and these in the LI treatment were 0.010 m m, 0.015 m m, 0.900 and 0.894, respectively. In summary the HYDRUS-2D can be used to simulate the root zone water dynamics in transplanted cotton field and irrigation regime of 60 mm proved better than 80 and 40 mm to promote the root growth of transplanted cotton under MHI. © 2018 Friends Science Publishers