Nitrogen application modified the effect of deficit irrigation on tomato transpiration, and water use efficiency in different growth stages

Abstract

Nitrogen (N) application affects the relationships between tomato transpiration (T), water use efficiency (WUE) and soil water content (SWC), and is important for practical agricultural management. This study investigated T (hourly, Th, and daily, TC) and WUE (leaf scale, WUEL, and plant scale, WUEP) differences of tomato grown in a solar greenhouse in response to different N and irrigation treatments. Three N application rates (0, 100 and 200 mg N kg−1 soil) were applied with four irrigation levels (full irrigation, Wck; and deficit irrigation, half amount of Wck, happened in different growth stage, W1, W2 and W3 respectively). Results showed that N application partly alleviated reductions in T associated with deficit irrigation, and it enhanced the promotion of deficit irrigation in WUEL. In tomato fruit late growth stage (stage 3), a balance is needed between irrigation and N application rate, higher N application can improve T and WUEL under higher irrigation water available. The positive effects of N2 and N3 on T were more pronounced when SWC was in the range of 0.19 − 0.22 cm3 cm−3 and 0.22 − 0.26 cm3 cm−3, respectively in this study. In tomato fruit early growth stage (stage 1), N application aggravated the reduction in WUEP due to deficit irrigation, while in tomato fruit middle and late growth stages (stage 2 and 3), N application enhanced the promotion of deficit irrigation on WUEP. Generally, in tomato early growth stage, there should be no water shortage and N excess; in fruit middle and late growth stages, more N can be applied along with the increase of SWC. This study proposes a prospect to implement integrative management of irrigation and N application during tomato growth, promoting transpiration and water use efficiency in a scientific way.