Effects of partial root-zone irrigation at different water-control duration on physiology and water use efficiency of maize

【Objectives】Partial root-zone irrigation (PRI) is a water-saving irrigation method, including alternate PRI (AI) and fixed PRI (FI) or partial root-zone drying irrigation (PRD). With PRD, half of root-zone is fully irrigated while the other not irrigated during the growth stage of crop. With AI, the both sides of root-zone are alternatively irrigated depending on the growth stage and soil water condition. The effects of PRI at different water-control durations during the early jointing to tasseling stages on the physiological indices, dry matter accumulation and water use efficiency (WUE) of maize were investigated under different fertilization conditions, so as to provide scientific basis for rational irrigation and fertilization of maize. 【Methods】 A pot experiment was conducted. Three irrigation methods with two irrigation levels each and two fertilization treatments were designed. The three irrigation methods include: conventional irrigation (soil was evenly watered), alternate PRI (the two halves of a pot soil were alternately watered) and fixed PRI (only half of the soil in the pot was watered); two irrigation levels include: conventional irrigation (70%-80%f, f is field capacity) and mild water deficit (60%-70%f); two fertilization treatments were 100% chemical N and 80% chemical N + 20% organic N. The three water-control durations were 12, 24 and 36 days from the jointing stage to tasseling stage. The leaf photosynthetic rate, stomatal conductance, the contents of chlorophyll, carotenoid, soluble sugar and proline, total dry mass, water consumption and WUE of maize were measured. 【Results】 Different irrigation methods, irrigation levels and ratios of inorganic to organic N do not significantly affect leaf photosynthetic rate, stomatal conductance, contents of chlorophyll, carotenoid and soluble sugar of maize at the early and middle jointing stages and tasseling stage, and irrigation level does not significantly affect proline content of maize at the tasseling stage either, indicating that PRI, mild water deficit and combined application of inorganic and organic N do not significantly affect physiological indices. Compared to conventional irrigation, PRI at different water-control duration does not significantly affect total dry mass and WUE, but significantly reduces water consumption at the early jointing to tasseling stages in most cases. However, under normal irrigation (70%-80%f) and only chemical N treatment, PRI increases the WUE by 24.4% and 16.3% at 24 d (later jointing stage) and 36 d (tasseling stage) after water control, respectively. Moreover, mild water deficit (60%-70%f) and combined application of inorganic and organic N (80% chemical N + 20% organic N) do not significantly affect physiological indices, total dry mass and WUE. 【Conclusions】 Partial root-zone irrigation at the jointing to tasseling stages significantly reduces water consumption, while it has limited effect on physiological indices and total dry mass, thus it enhanced water use efficiency significantly under normal irrigation with only chemical N.