Abstract
Radiation Use Efficiency (RUE) defines the productivity with which absorbed photosynthetically active radiation (APAR) is converted to plant biomass. Readily used in crop growth models to predict dry matter accumulation, RUE is commonly determined by elaborate static sensor measurements in the field. Different definitions are used, based on total absorbed PAR (RUEtotal) or PAR absorbed by the photosynthetically active leaf tissue only (RUEgreen). Previous studies have shown that the fraction of PAR absorbed (fAPAR), which supports the assessment of RUE, can be reliably estimated via remote sensing (RS), but unfortunately at spatial resolutions too coarse for experimental agriculture. UAV-based RS offers the possibility to cover plant reflectance at very high spatial and temporal resolution, possibly covering several experimental plots in little time. We investigated if (a) UAV-based low-cost camera imagery allowed estimating RUEs in different experimental plots where maize was cultivated in the growing season of 2016, (b) those values were different from the ones previously reported in literature and (c) there was a difference between RUEtotal and RUEgreen. We determined fractional cover and canopy reflectance based on the RS imagery. Our study found that RUEtotal ranges between 4.05 and 4.59, and RUEgreen between 4.11 and 4.65. These values are higher than those published in other research articles, but not outside the range of plausibility. The difference between RUEtotal and RUEgreen was minimal, possibly due to prolonged canopy greenness induced by the stay-green trait of the cultivar grown. The procedure presented here makes time-consuming APAR measurements for determining RUE especially in large experiments superfluous.
Highlights
In agronomy, radiation-use efficiency (RUE, referred to as light use efficiency LUE) is defined as crop biomass produced per unit of total solar radiation or photosynthetically active radiation (PAR)intercepted by the canopy [1]
We investigated if (a) UAV-based low-cost camera imagery allowed estimating Radiation Use Efficiency (RUE) in different experimental plots where maize was cultivated in the growing season of 2016, (b) those values were different from the ones previously reported in literature and (c) there was a difference between
It follows the concept introduced decades ago [2], where the amount of photosynthates or dry biomass production (DM in g m−2 ) is expressed as the product of the fraction of absorbed photosynthetically active radiation and the efficiency (ε) with which the absorbed light is converted into fixed carbon (Equation (1))
Summary
Intercepted by the canopy [1] It follows the concept introduced decades ago [2], where the amount of photosynthates or dry biomass production (DM in g m−2 ) is expressed as the product of the fraction of absorbed photosynthetically active radiation (fAPAR, with APAR defined as absorbed solar radiation between 400 and 700 nm wavelength in MJ m−2 ) and the efficiency (ε) with which the absorbed light is converted into fixed carbon (Equation (1)). This concept is widely used in dynamic crop growth modelling [1], where daily biomass production is estimated as the product of the amount of radiation intercepted and the RUE for forecasting crop growth and yield.
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