Estimation of water consumption as affected by measurement locations of soil water content in drip irrigated tomato in solar greenhouses

Abstract

Placements of soil moisture sensor have been key considerations in obtaining representative soil water content in crop root zones for irrigation schedules. In this article, the distribution of soil water content in the wetted volume from a line source was studied in drip irrigated tomato in solar greenhouse condition. Through comparison of tomato water consumption determined from measured water content by moisture sensors at different locations, suitable placements of sensors were discussed. The results indicated that irrigation quota range of 14 25 mm increased soil water content in the 0 40 cm soil layer, and daily mean soil water content in wetted soil volume was 75% 100% field capacity throughout tomato growth season. Wetted soil volumes generated by adjacent emitters along the drip lines fully overlapped after several sequential irrigation events, forming lateral zones with approximately uniform distribution of water content around the drip lines. There was no significant difference between mean soil water content along the depth of 0 40 cm layer. The variation tendency of soil water content with time at different horizontal locations from drip lines was synchronous in character, without any obvious hysteresis quality. Assuming that the 0 40 cm layer was the root zone with 80% root concentrated, an irrigation quota range of 14 25 mm caused deep percolation from the bottom of the root zone with a certain spatial variability. Seasonal deep percolation accounted for 13% of irrigation amount during tomato growth season. The differences in tomato water consumption at different locations from drip lines were within 10%, except for the seedling and blossom fruiting stages. The experimental results suggested that high frequency drip irrigation sustained suitable soil water condition in the root zone. One profile of soil water content measured in the proximity of drip lines was adequate for the proper estimation of water consumption of drip irrigated tomato in solar greenhouse conditions.