Rangjian Qiu

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.

Effects of water stress at different growth stage on greenhouse multiple-trusses tomato yield and quality

In order to explore the effects of deficit irrigation (DI) on yield and quality of solar greenhouse multiple-trusses tomato and determinate optimal deficit irrigation scheduling, a field experiment was conducted with different water deficit levels applied at three growth stages, i.e. seedling stage, flowering and fruit development stage and fruit maturation and fruit harvesting stage. The results showed that based on the normal irrigation amount of 21mm (CK), applying 1/3 or 2/3 irrigation amount of CK at seedling stage did not affect the tomato yield and quality; applying 1/3 or 2/3 irrigation amount of CK at fruit maturation and harvesting stage significantly improved tomato fruit quality, but decreased market yield by 48.2% and 38.0% respectively, which resulted in water use efficiency (WUE) drop. Considering the yield, quality and water saving amount, applying 1/3 irrigation amount of CK at the flowering and fruit development stage, normal irrigation at other growth stages, i.e. totally 12 irrigation times with 196 mm, could obtain the comprehensive objects of higher fruit quality, acceptable yield and water saving, which could be recommended as the suitable deficit irrigation scheduling for the multiple trusses tomato in solar greenhouse spring to summer season cropping season.