Effect of alternate irrigation on root-divided Foxtail Millet (Setaria italica)

Improper irrigation management is a major factor contributing to water shortage problem. A pot experiment was conducted in order to evaluate water use efficiency of partial root zone drying in root-divided foxtail millet. The study was conducted as a factorial experiment based on randomized complete block design (RCBD) with three replications. We tested three irrigation methods (conventional, fixed and alternate irrigation) which applied at three intervals (2, 3 and 4 days). In conventional irrigation, the whole root system was evenly dried. In fixed irrigation, water was always applied to one part of root system, and in alternate irrigation watering was alternated between two halves of root system. Results showed that forage fresh yield were reduced by increasing irrigation interval. Under conventional irrigation, irrigation interval of 3 and 4 days had a dry biomass reduction of 5% and 34% compared with irrigation interval of 2 days, respectively. Under irrigation interval of 3 and 4 days, less water was used by the alternate and fixed irrigation, compared to conventional irrigation, but plant growth in terms of dry biomass, plant height, leaf to stem ratio, specific leaf weight, leaf area, root dry weight, root volume, root surface area and root length, was not affected. Under irrigation interval of 3 days, fixed and alternate irrigation used 29% and 20% less water compared with conventional irrigation, respectively. However, water stress increased specific leaf weight, but reduced leaf area, leaf dry weight and leaf relative water content. Root growth was less sensitive than shoot to water stress. Under mild water stress, alternate irrigation performed better than fixed irrigation compared to all irrigation methods under non-water stress, so to achieve acceptable yield along with efficient use of water, alternate irrigation under mild water stress is recommended.