Guan'gai paishui xuebao (Mar 2022)
The Effects of Water Deficit on Root Growth and Water Uptake of Mulched Greenhouse Tomato under Drip Irrigation
Abstract
【Objective】 Facility vegetable production in China relies on drip irrigation with the seedbed mulched. How roots grow and its consequence for water uptake is an issue that is not fully understood. The aim of this paper is to investigate the change in root traits and water uptake of tomato under deficit irrigation, as well as the effect of initial soil water on demand of the crop for water. 【Method】 The experiment was conducted in a solar greenhouse, and the irrigation amount in each treatment was calculated based on the cumulative evaporation (EP) measured from a 20 cm standard evaporation pan installed inside the greenhouse. There were three treatments: irrigating 90% of EP with the soil mulched (FM-0.9) and not mulched (WM-0.9) by plastic film, and irrigating 50% of EP with the soil mulched (FM-0.5). In each treatment, we measured root distribution and change in soil water content. The root water uptake was calculated inversely using HYDRUS-1D, from which we analyzed the factors which impacted root water uptake as well as the consequence for fruit yield. 【Result】 Root length in the top 20 cm soil in WM-0.9, FM-0.9 and FM-0.5 accounted for 58.6%, 56.2% and 78.9% of their total root length, respectively. The mean root square error of the soil moisture content simulated by HYDRUS-1D was less than 0.010 cm3/cm3, and the regression coefficient between the measured and simulated soil water content was in the range of 0.867~1.076. The mean root square error of the measured transpiration and the simulated total root water uptake was less than 0.581 mm/d, and the regression coefficient between them was higher than 0.890. The largest root water uptake was in FM-0.9, totaling 240.9 mm, 24.4% and 26.7% more than that in WM-0.9 and FM-0.5, respectively. Roots took most of the water the crop transpired from the 0~40 cm of soil, accounting for 84.2%, 85.7% and 83.2% of the total transpiration for WM-0.9, FM-0.9 and FM-0.5, respectively. Water use efficiency and irrigation water use efficiency of FM-0.5 were 59.0 and 70.3 kg/m3, 34.4% and 55.5% above that of WM-0.9, and 11.3% and 30.4% higher than that of FM-0.9, respectively. FM-0.9 gave the highest fruit yield at 147.7 t/hm2, 19.3% and 23.6% higher that of WM-0.9 and FM-0.5, respectively. 【Conclusion】 Our experimental results showed that irrigating 90% of EP combined with film mulching is optimal to increase the use of deep soil water for greenhouse tomato production.
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