Effect of irrigation and nitrogen supply on physio-morphologicalindices of broomcorn millet at seedling stage

The effects of irrigation and nitrogen application on physio-morphological indices of broomcorn millet at seedling stage was studied in a pot experiment. The results indicated that plant height, leaf area, total root surface area, root volume and root length increased with increasing nitrogen supply at equivalent moisture. However, root to shoot ratio decreased with increasing nitrogen supply. All indices were similar in trends to the water and nitrogen supply, with each treatment significantly different from the control. Chlorophyll content of broomcorn millet at seedling stage remarkably changed under different water and nitrogen conditions. High water and nitrogen treatments at soil moisture of 70%~80% field capacity and urea nitrogen at 4.6 g·kg^-1(soil), W3N3 had the maximum chlorophyll content while low water and nitrogen treatments at soil moisture of 30%~40% field capacity and 0 g(urea)·kg^-1(soil), W1N1 had the minimum content. At constant moisture, chlorophyll content increased with increasing nitrogen supply. Also at constant nitrogen supply, chlorophyll content increased with increasing water supply. Hence water and nitrogen had an apparent synergetic effect on leaf chlorophyll content of broomcorn millet at seedling stage. Electrolyte leakage rate showed the reverse tendency. Root SOD activity of broomcorn millet at seedling stage was maximum 213.71 U·g^-1(FW) under W1N2 soil moisture of 30%~40% field capacity and 2.3 g(urea)·kg^-1(soil) and minimum 72.93 U·g^-1(FW) under W3N3. POD activity, MDA content and soluble sugar content decreased with increasing nitrogen at constant soil moisture and decreased with increasing water at constant soil nitrogen. The reverse was noted for root activity with each treatment significantly different. Under drought stress conditions, increase in nitrogen fertilizer proportionately improved chlorophyll content and root activity of broomcorn millet at seedling stage. It also increased total root surface area, root volume and root length. Increase in nitrogen fertilizer, however, reduced root MDA content. To a certain extent, increased nitrogen fertilizer responsively relieved the impact of drought stress.