Question

if the crop coefficient is 0.8, wetted area factor as 0.50, pan evaporation is 8mm/day and pan coefficient is 0.7 the per square metre water requirement for crop is​

Answer 1

Answer:

Crop coefficients are properties of plants used in predicting evapotranspiration (ET). The most basic crop coefficient, Kc, is simply ratio of ET observed for the crop studied over that are observed for well calibrated reference crop under same conditions.

${\displaystyle PET=K_{c}*RET}{\displaystyle PET=K_{c}*RET}$

Potential evapotranspiration (PET), is evaporation and transpiration that the potentially could occur if a field of the crop had an ideal unlimited water supply. RET is reference ET often denoted as ET0.

Even in agricultural crops, where ideal conditions are approximated as much as practical, plants are not always always growing (and therefore transpiring) at their theoretical potential. Plants have growth stages and states of health induced by the variety of environmental conditions.

RET usually represents PET of the reference crop's most active growth. Kc then becomes a function or series of values specific to crop of interest through its growing season. These can be quite elaborate in case of certain maize varieties, but tend to use the trapezoidal or leaf area index (LAI) curve for common crop or vegetation canopies.

Stress coefficients, Ks, account for diminished ET due to the specific stress factors. These are often assumed to the combine by multiplication.

${\displaystyle ET_{estimate}=K_{w}*K_{s_{1}}*K_{s_{2}}*K_{c}*ET_{o}}{\displaystyle ET_{estimate}=K_{w}*K_{s_{1}}*K_{s_{2}}*K_{c}*ET_{o}}$

Water stress is most ubiquitous stress factor, often denoted as Kw. Stress coefficients tend to the functions ranging between 0 and 1 simplest are linear, but thresholds are appropriate for some toxicity responses. Crop coefficients can exceed 1 when crop evapotranspiration exceeds that of RET.

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