In irrigation experiments these two are important components.
Crop water use efficiency is the yield of the crop (y) per unit of water lost through evapotranspiration of the crop (ET) whereas field water use efficiency is the ratio of yield of the crop to total amount of water used in the field (or in other words water requirement - WR). This WR includes water used in evopotranspiration (ET) + application loss + water needed for special operations like pre-sowing irrigation, land preperation, transplanting, leaching of excess salts, etc.
WR can be calculated in another way also where WR = IR + ER+S where,IR = irrigation requirement, ER = Effective rainfall, S = soil profile contribution (in case when water table depth < 2m)
Crop water use efficiency is the yield of the crop (y) per unit of water lost through evapotranspiration of the crop (ET) whereas field water use efficiency is the ratio of yield of the crop to total amount of water used in the field (or in other words water requirement - WR). This WR includes water used in evopotranspiration (ET) + application loss + water needed for special operations like pre-sowing irrigation, land preperation, transplanting, leaching of excess salts, etc.
WR can be calculated in another way also where WR = IR + ER+S where,IR = irrigation requirement, ER = Effective rainfall, S = soil profile contribution (in case when water table depth < 2m)
The simple difference is consideration of other losses such as percolation, leeching etc. Most of the times, WUEf is always lower than WUEc and WUEf is more useful for designing irrigation systems.
The former is more important for farmers (growers), while the latter - for scientists.
Soil property and humidity also strong impact to field water use efficiency.
Since only water taken up by the plant contributes to growth and consequently to economic yield, crop water use efficiency (WUE) should be related to transpiration (water going through the plant and lost through the stomata but with a small amount
Thank you Akwilin sir for your brief expalnation and i here want to put one more question. for ex: in paddy field what is the proportion of evaporation and transpiration losses of water?
Shantu, in a paddy field we add water to the brim (unless you are considering upland rice), which means that the only useful index of water use would be the ratio of yield to the transpired water during the period of growth. If we consider the total irrigation water applied during the season, then rice will have the poorest water use efficiency (WUE). Paddy is the poorest absorber of water although it grows well in flooded lands. We maximize production of paddy in flooded lands where other crops cannot perform well, which means in the production of this type of rice, water (either rainfall or irrigation) should not be a limiting factor.
It depends what scale is in your mind. While field WUE mainly focuses on water budget and water balance components the crop WUE is mostly dependent on net water use by the crop community. The field WUE could be interesting for the hydrologist who would like to calculate how available water is used at a lump scale (field, area, watershed) but the last one is interesting for the irrigationist and agronomist. However, you can consult more with the book "Water Productivity in Agriculture: Limits and Opportunities for Improvement ". Hope it helps as a primary definition.
We get all efficiency values in %. If we take the definition as given by Sabyasachi Mitra we dont get the value of field water use efficiency crop water use efficiency in % values. Please suggest a method to get this in % values.
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