Effect of Water and Nitrogen Coupling on the Characteristics Photosynthesis and Growth in Maize Reproductive Stage in Yuanmou Dry-hot Valleys

Purpose Jinsha River dry-hot valleys (DHV) of Yuanmou in Yunnan Province Southwest of China have high temperature and drought all the year round. A plot experiment was designed in this area to research the water-fertilizer coupling of sweet corn (Zea mays L.).

Method There were three irrigation levels low (W1), 55%-90% field capacity (Fc); medium (W2), 70%-90% Fc; and high (W3), watering 2 hours every 5 days (approximate 2.270 5 m³), four nitrogen fertilizer levels F1 (75 kg/hm²); F2 (75 kg/hm²+foliar fertilizer); F3 (150 kg/hm²); F4 (150 kg/hm²+foliar fertilizer). The twelve irrigation and fertilization treatments were T1(W1×F1), T2(W1×F2), T3(W1×F3), T4(W1×F4), T5(W2×F1), T6(W2×F2), T7(W2×F3), T8(W2×F4), T9(W3×F1), T10(W3×F2), T11(W3×F3), T12(W3×F4), respectively. Some parameters of maize were determined. They were net photosynthetic (P_n), intercellular CO₂ concentration (C_i), atomatal conductance (G_s), transpiration rate (T_r), water use efficiency (WUE), morphological parameters and yield.

Results The photosynthesis and morphological parameters were no significant differences (P>0.05) in the early reproductive stage of sweet corn in different watering and fertilizing treatments, but there were significant differences (P>0.05) in the later reproductive stage, in which stage the high water treatment groups showed a significant advantage in photosynthesis. TheP_n was higher in W3 treatment group, compared with other groups, the maximum value was 35.06 μmol/(m²·s). For water use efficiency, the irrigation water use effciency (IWUE) was higher in the W1 groups the maximum value was 4.203 2 kg/m³(FW), while lower in the W3 groups the minimum value was 2.292 8 kg/m³(FW). There was no significant difference (P>0.05) in the yield.

Conclusion The study area was characterized by high temperature, drought with little rainfall, so water was the main limiting factor. The IWUE increased with the decrease of irrigation quantity. The water treatment significantly effected on the physiological of sweet corn, while the fertilizer treatment was the secondary factor, as it had a little effect on the physiology of sweet corn.