Abstract
Film hole irrigation is a relatively low cost and high efficiency irrigation method, which can significantly improve the efficiency of agricultural water use. In order to establish the quantitative model of film hole irrigation between cumulative infiltration and the wetting body and the irrigation volume model of crops, the infiltration process and wetting body characteristics of four different soils (Xi’an silt loam, silt, silt loam and loam) were studied in laboratory experiments and numerical HYDRUS simulation experiments. The relationship between cumulative infiltration and wetting body radius was established using a mathematical method, and a crop irrigation volume model was proposed based on the root distribution and the required water content of different crops. The experimental results showed that the shape of the wetting body of film hole irrigation is approximately half of the rotating ellipsoid, and the curve shape of the wetting front can be expressed using an elliptic equation. From the center of the film hole to the surface of the wetting front, the soil water content of the wetting body gradually decreases, and the change rate of water content gradually increases, reaching its maximum value near the wetting front. Furthermore, the distribution of water content in the wetting body can be accurately expressed using an elliptic curve equation. The cumulative infiltration of film hole irrigation is proportional to the third power of the equivalent radius of the wetting body, and the equivalent radius is equal to the geometric mean of the horizontal and vertical migration distances of the wetting front. In addition, based on the distribution of crop roots and the demand of crop roots on soil water content, the irrigation model of crops was established. This study provides a theoretical basis for the calculation of the irrigation volume for film hole irrigation under the condition of experiment, and has a guiding significance for the field experiment and application of film hole irrigation in different crops in future.
Highlights
Water resources are crucial for the production and preservation of human beings, and the shortage of water resources throughout the world is becoming increasingly severe [1,2]
This study provides a theoretical basis for the calculation of the irrigation volume for film hole irrigation under the condition of experiment, and has a guiding significance for the field experiment and application of film hole irrigation in different crops in future
Wang et al [31] showed that the distribution of soil water one-dimensional vertical infiltration can be represented by elliptic curve, and we discovered that the content under one-dimensional vertical infiltration can be represented by elliptic curve, and we water content distribution of film hole irrigation has similar properties
Summary
Water resources are crucial for the production and preservation of human beings, and the shortage of water resources throughout the world is becoming increasingly severe [1,2]. The arid and semi-arid region in Northwest China has low rainfall and large evaporation capacity, so water resources, agricultural water, are scarce in this region [3,4]. To solve the problem of water shortage in this area, water-saving irrigation technologies, such as sprinkler irrigation and drip irrigation, are widely used. For farmers in poor areas, the cost of advanced irrigation systems is relatively high, which is not conducive to their promotion and application. A relatively cheap and efficient irrigation technology is urgently required in poorer areas [5]. Mulch irrigation has become a high-yielding and efficient agricultural practice, with global applications which can reduce water evaporation, maintain soil temperature and humidity, Water 2020, 12, 1226; doi:10.3390/w12051226 www.mdpi.com/journal/water
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