The soil water balance of rainfed and irrigated oats,Italian rye grass and rye using the CropSyst model |
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Authors: | Michael G Abraha Michael J Savage |
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Institution: | (1) Soil-Plant-Atmosphere Continuum Research Unit, Discipline of Agrometeorology, School of Environmental Sciences, University of KwaZulu-Natal, Private Bag X01, Scottsville, 3209, Pietermaritzburg, South Africa |
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Abstract: | Crop growth models have been used in simulating the soil water balance for purposes of irrigation management and yield predictions.
The application of CropSyst, a cropping systems simulation model, was evaluated for Cedara, South Africa. Simulations included
soil water balance of fallow land and rainfed and irrigated winter crops oats (Avena sativa), Italian ryegrass (Lolium multiflorum) and rye (Secale cereale)]; and irrigation scheduling of the winter crops. Soil, plant, weather and management inputs were used for the soil water
balance simulations. Model crop parameters were used from past experiments or obtained from model documentation, with a slight
modification to account for varietal differences. The fallow land soil water simulations were more accurate for dry than for
wet soil. For all three winter crops, the model consistently over-estimated the soil water content in the upper layers, with
a good agreement for the deeper layers until a large precipitation event occurred to which the model responded more slowly
than that observed. Simulations using model-scheduled irrigation based on 0.4 and 0.6 maximum allowable depletion criteria
indicated that the observed applied irrigation in the field was more than that required. Soil water depletion and accumulated
transpiration simulations were similar in both the observed and model-scheduled irrigations, but total soil evaporation and
percolation were greater in the case of the observed than the model-scheduled irrigations. Irrigation scheduling using crop
growth models may assist in avoiding over- or under-application of irrigation applications by ensuring efficient utilization
of rain and irrigation. |
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