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Estimating crop coefficients from fraction of ground cover and height
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Autores
Orientador(es)
Resumo(s)
The FAO-56 procedure for estimating the crop
coefficient Kc as a function of fraction of ground cover and
crop height has been formalized in this study using a
density coefficient Kd. The density coefficient is multiplied
by a basal Kc representing full cover conditions, Kcb full, to
produce a basal crop coefficient that represents actual
conditions of ET and vegetation coverage when the soil
surface is dry. Kcb full is estimated primarily as a function of
crop height. Kcb full can be adjusted for tree crops by
multiplying by a reduction factor (Fr) estimated using a
mean leaf stomatal resistance term. The estimate for basal
crop coefficient, Kcb, is further modified for tree crops if
some type of ground-cover exists understory or between
trees. The single (mean) crop coefficient is similarly estimated
and is adjusted using a Ksoil coefficient that represents
background evaporation from wet soil. The Kc
estimation procedure was applied to the development
periods for seven vegetable crops grown in California. The
average root mean square error between estimated and
measured Kc was 0.13. The Kc estimation procedure was
also used to estimate Kc during midseason periods of
horticultural crops (trees and vines) reported in the literature.
Values for mean leaf stomatal resistance and the Fr
reduction factor were derived that explain the literature Kc
values and that provide a consistent means to estimate Kc
over a broad range of fraction of ground cover
Descrição
Palavras-chave
crop coefficients ground cover crop height
Contexto Educativo
Citação
"Irrigation Science". ISSN 0342-7188. 28 (2009) 17-34
Editora
Springer