WUE/NUE Based on Yield Biomass
Creators: name: Savvas Dimitrios, Ntatsi Georgia
Publisher: name: Zenodo
Year: 2018

description: <strong>Water Use Efficiency based on yield biomass</strong> Water Use Efficiency (WUE) is the ratio of fruit yield to crop water use (Angus &amp; Van Herwaarden, 2001). More specifically, water use efficiency is calculated as fruit yield (kg/ m<sup>2</sup>) divided by seasonal evapotranspiration (m<sup>3</sup> m<sup>-2</sup>). Consequently, WUE is expressed as kg m<sup>-3</sup>. Evapotranspiration is the water evaporated from the soil and/or transpired by the plants in the field during the whole cropping period (Sinclair <em>et al</em>., 1984). WUE indicates how much yield can be harvested from a crop per unit volume of water consumed by this crop. As a ratio, WUE is not an indicator of crop productivity or water consumption but only indicates if a particular yield level was achieved by saving water, consuming standard amounts of water, or wasting water. A high WUE in a crop can be achieved either by increasing the yield, or by decreasing the water consumption, or by a combination of both. Similarly, a low WUE in a crop may be either due to impairment of yield, or to waste of water, or to a synergistic effect of both. Different variations of this method include the ratio of fruit yield to crop water use or the ratio of plant fresh biomass accumulation to crop water use or the evapotranspiration when plants are cultivated for the shoot or the root consumption but not for the fruit production (Kang <em>et al.</em>, 2002) Water use efficiency can also be calculated using data obtained from gas exchange measurements, as the ratio of net photosynthetic rate (μmol CO<sub>2 </sub>m<sup>-2 </sup>s<sup>-1</sup>) to transpiration rate (mmol H<sub>2</sub>O m<sup>-2 </sup>s<sup>-1</sup>). <strong>Nutrient Use Efficiency based on yield biomass</strong> The growth and yield of a plant under normal (non-stress) environmental conditions is determined by the availability of light, CO2, water, and all mineral nutrients that are absolutely essential for the completion of their life cycle (Marshner, 1995). However, of all essential plant nutrients, commonly only N, P, and K are available in limited quantities in the root environment and can quickly be depleted in arable lands due to an appreciable part of the plant biomass being regularly harvested. That is why, the application of these essential nutrients (especially nitrogen, phosphorus and potassium) to plants in the form of chemical fertilizers is part of intensive agricultural practices. Root system and architecture are also very important parameters for plant productivity and nutrient use efficiency as roots explore the soil for uptake of essential nutrients and water. Therefore, an efficient and extensive root system and optimal soil conditions for root growth are considered as prerequisites for optimal plant growth, yield, and consequently for a high-water use efficiency.
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