Subsurface irrigation with ceramic emitters: Optimal working water head improves yield, fruit quality and water productivity of greenhouse tomato

Abstract

Greenhouses are widely used in Northwest China, especially for tomato, which is the dominant crop. Subsurface irrigation with ceramic emitters (SICE) is a new water-saving technology for continuous low-rate water supply at constant soil moisture. However, a lack of knowledge still existed to define the suitable working water head for SICE to decrease water loss and promote tomato production, fruit quality, and water productivity. In this study, a greenhouse experiment was conducted during spring and autumn cultivation periods under SICE for five working water heads of 0.1 m to 0.5 m with intervals of 0.1 m and subsurface drip irrigation (SDI). The verified HYDRUS-2D model evaluated water balance components and water productivity. A structural equation model (SEM) was developed to determine interactive impacts of SICE and meteorological conditions in greenhouse on tomato yield, fruit quality, and water productivity. The results showed that SICE with a working water head of 0.4 m could be recommended, which created a suitable soil water content of the root zone within 70%–80% of field capacity (FC), resulting in a reduction of water loss from actual evaporation (Ea) and deep percolation (DP) by 12.32% and 21.88% respectively relative to SDI. Fruit weight, yield, water use efficiency (WUE), and irrigation water use efficiency (IWUE) were increased by 8.96%, 8.03%, 19.44%, and 16.05% respectively compared to SDI. Moreover, soluble sugar, organic acid, lycopene, vitamin C, and sugar acid ratio were enhanced by 2.41%, 12.19%, 14.40%, and 2.67% under SICE with the suggested working water head respectively compared with SDI. We recommended that supplemental lighting combined with SICE in autumn cultivation was necessary to ensure tomato production and fruit quality. This study provides an alternative water-saving irrigation method for greenhouse growers to maintain tomato yield and fruit quality in Northwest China.