Water use efficiency was improved at leaf and yield levels of tomato plants by continuous irrigation using semipermeable membrane

Continuous irrigation (CI) is a newly developed irrigation technique that utilizes semipermeable membrane to release water into the plant root zone slowly and continuously. In order to investigate the effects of CI on plant gas exchange and water use efficiency (WUE) compared to conventional intermittent irrigation (II) under different soil water conditions, a field experiment was conducted on tomato plants during two growing seasons in the arid region of northwestern China. Gas exchange parameters were measured during fruit enlargement stage, which showed that the net photosynthesis rate of tomato leaf was similar between CI and II, while the stomatal conductance was significantly higher under CI for most measurements, resulting in significantly lower intrinsic WUE under CI compared to II. However, the non-stomatal limitations and lower vapor pressure deficit (leaf to air) caused significantly lower transpiration rate under CI, leading to slightly higher instantaneous WUE compared to II. Consequently, the total water consumption was reduced by CI. Moreover, CI also had significantly greater yield than II and therefore, CI improved WUE at both leaf and yield levels compared to II. CI can be used to reduce irrigation water use and increase WUE in crop production in northwestern China.