Abstract
Estimating canopy interception of water by plants during rainfall or sprinkler irrigation is a critical step for evaluating water-use efficiency. Most existing experimental studies and mathematic models of canopy interception have paid little attention to the interception losses of water by herbaceous plants. To better understand the canopy interception processes of herbaceous plants and to estimate the interception losses, a process-based dynamic interception model for alfalfa canopy was developed and validated by an experiment under conditions of simulated sprinkler irrigation. The parameters of the model included the maximum interception, the rate of interception of the alfalfa canopy, and the duration of sprinkler irrigation. The model demonstrated that the amount of interception increased rapidly with duration in the early stage of sprinkler irrigation, and then gradually leveled off until the maximum retention capacity of the canopy was reached. The maximum interception by the alfalfa canopy, ranging from 0.29 to 1.26 mm, increased nonlinearly with the increase of leaf area index (LAI) and sprinkling intensity. The rate of interception increased with the decrease of LAI and the increase of sprinkling intensities. Meanwhile, a nonlinear equation based on sprinkling intensity and plant height was proposed in order to more practically estimate the maximum interception by alfalfa canopy.
Highlights
The area of planted alfalfa in China has increased rapidly since 2012 [1]
Our objectives are to: (1) construct a dynamic interception model for alfalfa canopy and validate it experimentally with a simulated sprinkler irrigation system during different vegetative stages and under different sprinkling intensities; and (2) estimate the maximum interception of water by alfalfa canopy based on the variables of morphological indices and sprinkling intensity
Across different vegetative stages of alfalfa under the same sprinkling intensity, the rate of interception and the maximum interception tended to increase as the vegetative stage at cutting increased
Summary
The area of planted alfalfa in China has increased rapidly since 2012 [1]. Currently, there are over 4 million hectares of alfalfa, mainly distributed in northwestern and northern parts of the country [2].These regions dominate alfalfa production in China because of the availability of large-sized lands with appropriate climatic and soil conditions. The area of planted alfalfa in China has increased rapidly since 2012 [1]. There are over 4 million hectares of alfalfa, mainly distributed in northwestern and northern parts of the country [2]. These regions dominate alfalfa production in China because of the availability of large-sized lands with appropriate climatic and soil conditions. The major constraint to alfalfa growth in these arid and semiarid regions is the shortage of natural rainfall. Irrigation is essential for the production of alfalfa, and the center pivot is the most popular irrigation system [3,4]. A major concern about overhead sprinkler irrigation (like center-pivot systems) is the loss of water. While some water is lost due to wind drift and evaporation before reaching the plants and the soil [5,6], a significant amount of water can be intercepted by the canopy and lost through evaporation [7,8]
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