Effects of oxygation techniques on growth and physiology of vegetable under subsurface drip irrigation

Perched water often leads to a decrease in soil aeration in subsurface drip irrigated crop roots, whereas aerated subsurface drip irrigation (ASDI) provides a source of oxygen in a root environment that suffers from temporal hypoxia and unlocks yield potentials of crops. With Chinese cabbage as test crop, five irrigation treatments were used including Mazzei air injector (MAI) cyclic aeration, 15 mg/L of hydrogen peroxides (H2O2), fluidic oscillator (FO), oxygen concentrator (OC) and a control treatment (CK). The experiment was carried out during September 23, 2015 to October 31, 2015 at the Central Queensland University, Australia (23°22'0.345"S latitude, 150°31'0.53" E Longitude), and subsurface drip irrigation was implemented to systematically monitor soil respiration, crop growth and physiological indexes to clarify the effect of different oxygation techniques on growth and development of potted Chinese cabbage. Compared with the control treatment, the soil respirations in treatments MAI, H2O2, OC and FO increase by 65.87%, 42.07%, 66.79% and 111.62% respectively compared with CK. ASDI improves the leaf chlorophyll content in treatments MAI, OC and FO. The photosynthetic rate, stomatal conductance and transpiration rate are enhanced by SADI. The photosynthetic rates in MAI, H2O2, OC and FO increase by 868.62%, 794.14%, 778.67% and 650.19% compared with CK. The stomatal conductance in MAI, H2O2 and OC increases by 157.14%, 128.57% and 85.71%, the transpiration rates in MAI, H2O2 and OC increase by 55.61%, 32.38% and 19.58%, and there is not statistically significant difference between other treatments. The yield is significantly increased, and the water utilization efficiency (WUE) is improved, too. The yield increases by 56.36% and 38.72% respectively in treatments MAI and H2O2, and the WUE in MAI and H2O2 increases by 48.96% and 36.46% compared with CK. The beneficial effects of ASDI are mediated through greater root activity, especially the root-shoot ratio increases by 49.61% in MAI. In conclusion, ASDI improves the hypoxic environment in crop roots, promotes the growth of Chinese cabbage, enhances the soil respiration and increases the yield as well as water utilization efficiency. Among four treatments, MAI is ranked in the first place