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 ECH_2O 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 ECH_2O 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.

Improvement of Plant Growing Techniques in Drying up and Water Scarcity Conditions

Due to its specificity, seasonality and location of large areas, the crops are exposed to the greatest degree of risks posed by climate change. To maintain stability and increase yields, it is imperative to implement an innovative approach by which to optimize certain processes such as tillage, sowing and irrigation. The main tasks of innovative solutions are proposed to increase the soil water holding capacities in the root layer over a prolonged period of time, and improve the accuracy of the drilling process for row crops and vegetables by using biodegradable materials, and on this basis to optimize the irrigation by use of specialized software products to determine irrigation scheduling and irrigation requirements.

Total phosphorus accident pollution and emergency response study based on geographic information system in Three Gorges Reservoir area

In recent years,sudden water pollution accidents in China's rivers have become more frequent,resulting in considerable effects on environmental safety.Therefore,it is necessary to simulate and predict pollution accidents.Simulation and prediction provide strong support for emergency disposal and disaster reduction.This paper describes a new two-dimensional water quantity and the quality model that incorporates a digital elevation model into the geographic information system.The model is used to simulate sudden water pollution accidents in the main stream of the Yangtze River and Jialing River in the Chongqing section of the Three Gorges Reservoir area.The sectional velocity distribution and concentration change of total phosphorus are then analyzed under four hydrological situations.The results show that the proposed model accurately simulates and predicts the concentration change and migration process of total phosphorus under sudden water pollution accidents.The speed of migration and diffusion of pollutants is found to be greatest in the flood season,followed by the water storage period,drawdown season,and dry season,in that order.The selection of an appropriate water scheduling scheme can reduce the peak concentration of river pollutants.This study enables the impact of pollutants on the ecological environment of river water to be alleviated,and provides a scientific basis for the emergency response to sudden water pollution accidents in the Three Gorges Reservoir area.