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Effects of growth stage and irrigation depth on alfalfa canopy water interception under low-pressure spray sprinkler

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  2018 ASABE Annual International Meeting  1800659.(doi:10.13031/aim.201800659)
Authors:   Yunling Wang, Maona Li, Yangyang Meng, Haijun Yan
Keywords:   canopy interception, alfalfa, growth stage, irrigation depth, sprinkler

Abstract. For a sprinkler system, water losses through the wind drift and evaporation losses as well as interception loss were usually considered as a main problem. Canopy interception as a part of water loss has great influence on the water use efficiency analysis for sprinkler irrigation system. A study was conducted to determine alfalfa canopy water interception and its influence factors. Canopy interception for three growth stages of alfalfa (S1- Early vegetative stage, S2-Late vegetative stage and S3- Bud stage) were measured under two kinds of low-pressure spray sprinklers. At the same time, Dynamic process of canopy interception and interception rate with irrigation depth were observed. In this observation, the total irrigation depth was around 8mm. A device for interception measurement was installed outdoor and integrated with the sprinkler at 1m height and 20-psi pressure. All the measurements were conducted under low wind conditions by weighing method. The results showed that alfalfa canopy interception capacity (Im) and interception rate significantly increased with the development of growth stage (P<0.05). Im ranged from 0.46 mm to 1.46 mm, and the largest Im occurred during the bud stage. With the irrigation depth of about 8mm, the interception rate of alfalfa ranged from 5.44% to 17.45%. With the irrigation depth increased, alfalfa canopy interception showed a trend of firstly rapid increasing and then tending to be stable. Interception rate decreased as the irrigation depth increased. Function models for the dynamic process of canopy interception and interception rate with irrigation depth were established and well fitted. Effect of application rate and droplet diameter combination was significant (P<0.05) during stage of S2 and S3. The fresh weight, plant height and LAI had the significantly positive correlations with canopy interception capacity (P<0.01), and a liner regression model was developed with the main factor of plant height but which needed further verification.

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