Browsing by Author "Simwanza, Hopeson Isaac"

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Evaluation of rainfall interception models in a maize field
(Sokoine University of Agriculture, 1996) Simwanza, Hopeson Isaac
Rainfall interception is a component of effective rainfall and is an important component in agriculture because of the latter's use in irrigation and drainage projects. A rainfall interception study was carried out at Kabanana farm plot no. 2952 M, a peri urban area in Lusaka, Zambia. The objectives of the study were (a) to measure rainfall interception by maize crop growing in a freely drained soil and (b) to evaluate and validate the models developed to represent rainfall interception loss. Standard raingauges placed adjacent to the study area and beneath the canopy of the maize plant were used to measure rainfall amounts. Funnel like collars were used to measure stemflow. A planimeter was used to measure leaf area required for the calculation of leaf area index and the data from the nearby University of Zambia meteorological station was used to estimate crop evapotranspiration. The results of the study showed that the interception process by a maize plant brought about an interception loss of 10%. Interception loss without stemflow was 27.4% implying that 17.4% of the incident rainfall reached the ground by flowing down the stalk of the maize plant as stemflow. Of the four models tested the models developed by Merriam (1960) , Leonard (1965) and De Jong and Cameron (1979) did not represent the process of interception by a maize plant. The linear regression model adopted by Gash (1979) which is insensitive to canopy structure was 93% significant for a two sided t-test at 95% confidence interval. It is highly recommended that the models should be calibrated before being adopted and a model should be developed that includes among the usual measurable parameters, leaf area configuration and branching patterns.