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Coupled Water and Light Use and Efficiency in Four Row Crops under Optimal Growth Conditions

Meetpal S Kukal, University of Nebraska - Lincoln


Quantitative estimates of growth and resource use for regionally dominant cropping systems are imperative for various agricultural applications. Crop selection in irrigated conditions entails characterization of crop water use and efficiency dynamics under the limited freshwater availability in a changing environment. Similarly, accurate estimates of light (Photosynthetically Active Radiation or PAR) absorption, in addition to other interactions is crucial to quantify canopy growth, productivity, energy and water balance and other physiological and biophysical processes for any vegetative surface. Currently, a fair comparative assessment of light interaction patterns across row crops as well as water use is lacking, especially under current levels of productivity achieved under optimal growth conditions in the U.S. High Plains. Field research was conducted in semi-arid South-Central Nebraska during 2016-2019 to comprehensively characterize crop growth, water and light use and efficiency dynamics in four major C3 (soybean and winter wheat) and C4 (maize and sorghum) crops under consistent and well-managed conditions. Via these investigations, we benchmarked quantities such as canopy height (CH), leaf area index (LAI), and aboveground biomass (AGB), crop growth rate (GR), relative growth rate (RGR) and their normalized (LAI per plant, LAI per canopy height, AGB per plant, AGB per canopy height) and integrative forms [net assimilation rate (NAR) and leaf area ratio (LAR)], total soil water, soil water depletion, crop evapotranspiration (ETc), single (Kc) and basal crop coefficients (Kcb), water use efficiency (WUE), canopy light transmittance (R), reflectance (R), fraction of intercepted PAR (fIPAR), fraction of absorbed PAR (fAPAR), light extinction coefficients (k), and light use efficiency (LUE). Crop-specific signatures were highlighted and were modeled using transferrable indices. It was also demonstrated that conventional estimation methods for resource use efficiency (RUE) are largely subject to arithmetic weakness, and tend to oversimplify the complex interactions among carbon assimilation and resource use in agroecosystems, which are accurately represented when independent methods are employed. The data measured, modeled and interpreted here is unprecedented for these major crops grown under uniform conditions in the U.S. Midwest, and are valuable for applications in effective estimation and understanding of crop growth and resource use, and their interactions.

Subject Area

Agronomy|Agricultural engineering

Recommended Citation

Kukal, Meetpal S, "Coupled Water and Light Use and Efficiency in Four Row Crops under Optimal Growth Conditions" (2019). ETD collection for University of Nebraska - Lincoln. AAI13861925.