Estimating Soybean Radiation Use Efficiency Using a UAV in Iowa

Xavier A Phillips,Mark A Licht,Daren S Mueller,Yuba R Kandel

doi:10.3390/agronomy10122002

Abstract

Radiation use efficiency (RUE) is difficult to estimate and unreasonable to perform on a small plot scale using traditional techniques. However, the increased availability of Unmanned Aerial Vehicles (UAVs) provides the ability to collect spatial and temporal data at high resolution and frequency, which has made a potential workaround. An experiment was completed in Iowa to (i) demonstrate RUE estimation of soybean [Glycine max (L.) Merr.] from reflectance data derived from consumer-grade UAV imagery and (ii) investigate the impact of foliar fungicides on RUE in Iowa. Some fungicides are promoted to have plant health benefits beyond disease protection, and changes in RUE may capture their effect. Frogeye leaf spot severity did not exceed 2%. RUE values ranged from 0.98 to 1.07 and 0.96 to 1.12 across the entire season and the period post-fungicide application, respectively, and fell within the range of previously published soybean RUE values. Plots treated with fluxapyroxad + pyraclostrobin had more canopy cover (p = 0.078) compared to the non-treated control 133 days after planting (DAP), but yields did not differ. A “greening effect” was detected at the end of the sample collection. RUE estimation using UAV imagery can be considered a viable option for the evaluation of management techniques on a small plot scale. Since it is directly related to yield, RUE could be an appropriate parameter to elucidate the impact of plant diseases and other stresses on yield.

Highlights

Radiation use efficiency (RUE), known as light use efficiency (LUE), is defined as the plant’s ability to convert photosynthetically active radiation (PAR) into biomass on a per unit basis [1]
The objectives of this study were to: (i) demonstrate RUE estimation of soybean from reflectance data derived from consumer-grade Unmanned Aerial Vehicles (UAVs) imagery and (ii) investigate the impact of foliar fungicides on RUE in Iowa
The RUE values of the non-treated control and the flutriafol + fluoxastrobin treatment were slightly less for the post-fungicide application timeframe beginning at R3, while the RUE

Summary

Introduction

Radiation use efficiency (RUE), known as light use efficiency (LUE), is defined as the plant’s ability to convert photosynthetically active radiation (PAR) into biomass on a per unit basis [1]. This measurement of photosynthetic performance is important for crop growth modeling [2]. Of the three commonly used methods to estimate RUE (i) from incoming radiation (RUEinc ), (ii) total absorbed light (RUEtotal ), and (iii) radiation absorbed by photosynthetically active vegetation (RUEgreen ) [4], Tewes and Schellberg [5] made the case to have RUEgreen (Equation (1)) be the standard method. By only considering the photosynthetically active vegetation to determine the fraction of absorbed photosynthetically active radiation (fAPARgreen )

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Discussion

Conclusion