ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
A CROP COEFFICIENT MODEL FOR TREES AND VINES |
| Authors: | R.L. Snyder, M.L. Ferreira, K.A. Shackel |
| Keywords: | Evapotranspiration, crop water use, irrigation, scheduling. |
| Abstract:
Information on tree and vine crop coefficient (Kc) values is often contradictory and confusing. Differences in Kc recommendations are often site- and year-specific and depend on local ETo rates, rainfall frequency, and crop management. When using Kc values to estimate crop evapotranspiration (ETc), it is assumed that ETo is a measure of the evaporative demand and the Kc values account for crop and management factors. The main variables affecting the difference between ETc and ETo are (1) radiation interception, (2) presence of ground cover, (3) aerodynamic roughness, (4) irrigation method and frequency, and (5) rainfall frequency. Without a ground cover crop, the Kc values are higher from a wet than a dry soil surface because of increased water availability for evaporation. The model uses a new method for estimating soil evaporation during the off-season. With a ground cover, the ETc from an orchard or vineyard is similar to that of a wet soil surface. In this paper, a model for crop coefficients that accounts for all of these aspects of estimating ETc is presented and compared with field measurements. | |
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