Wheat Yield and Protein Estimation with Handheld and Unmanned Aerial Vehicle-Mounted Sensors.

Wheat Yield and Protein Estimation with Handheld and Unmanned Aerial Vehicle-Mounted Sensors

by 

Olga S. Walsh

 1,*,

Juliet M. Marshall

 2,

Eva Nambi

 1,

Chad A. Jackson

 3,

Emmanuella Owusu Ansah

 1,

Ritika Lamichhane

 1,

Jordan McClintick-Chess

 4 and

Francisco Bautista

 1

1

Parma R&E Center, University of Idaho, Parma, ID 83660, USA

2

Idaho Falls R&E Center, University of Idaho, Idaho Falls, ID 83402, USA

3

Aberdeen R&E Center, University of Idaho, Aberdeen, ID 83210, USA

4

AG Idaho Consulting LLC, Wilder, ID 83676, USA

*

Author to whom correspondence should be addressed.

Agronomy 2023, 13(1), 207; https://doi.org/10.3390/agronomy13010207 (registering DOI)

Received: 11 November 2022 / Revised: 29 December 2022 / Accepted: 2 January 2023 / Published: 10 January 2023

Abstract

Accurate sensor-based prediction of crop yield and grain quality in-season would enable growers to adjust nitrogen (N) fertilizer management for optimized production. This study assessed the feasibility (and compared the accuracy) of wheat (Triticum aestivum L.) yield, grain N uptake, and protein content prediction with in-season crop spectral reflectance measurements (Normalized Difference Vegetative Index, NDVI) obtained with a handheld GreenSeeker (GS) sensor and an Unmanned Aerial Vehicle (UAV)-mounted sensor. A strong positive correlation was observed between GS NDVI and UAV NDVI at Feekes 5 (R2 = 0.78) and Feekes 10 (R2 = 0.70). At Feekes 5, GS NDVI and UAV NDVI explained 42% and 43% of wheat yield, respectively. The correlation was weaker at Feekes 10 (R2 of 0.34 and 0.25 for GS NDVI and UAV NDVI, respectively). The accuracy of wheat grain N uptake prediction was comparable to that of yield: the R2 values for GS NDVI and UAV NDVI were 0.53 and 0.37 at Feekes 5 and 0.13 and 0.20 at Feekes 10. We found that neither GS NDVI nor UAV NDVI in-season data were useful in prediction of wheat grain protein content. In conclusion, wheat yield and grain N uptake can be estimated at Feekes 5 using either handheld or aerial based NDVI with comparable accuracy.

Keywords: 

normalized difference vegetative index; handheld sensor; unmanned aerial vehicle; wheat; grain yield; grain protein; grain N uptake

We hypothesized that the in-season NDVI from handheld (GS) and aerial (UAV) sensors can be used to accurately estimate wheat yield, grain N uptake, and protein content. Our results have confirmed that wheat yield and grain N uptake can be estimated with GS NDVI and UAV NDVI. We observed a strong linear relationship between GS NDVI and UAV NDVI (0.78), especially at tillering. The GS NDVI and UAV NDVI relationship with wheat yield and N uptake was stronger at tillering compared to flowering. This makes sense because at tillering the plant vigor is high and most of N uptake is channeled towards biomass production. In contrast, at the flowering stage, the N uptake direction is shifted towards grain production. The GS NDVI and UAV NDVI correlation with wheat yield and grain N uptake were comparable. We found that neither GS NDVI nor UAV NDVI in-season data were particularly useful in the prediction of wheat grain protein content.

Author Contributions: Conceptualization, O.S.W. and J.M.M.; Methodology, O.S.W. and J.M.-C.; Investigation, J.M.-C. and C.A.J.; Data curation, O.S.W., E.N., R.L., E.O.A. and F.B.; Writing—original draft, E.N.; Writing—review and editing, O.S.W. and E.N.; Visualization, O.S.W.; Supervision, O.S.W. and J.M.-C.; Project administration, O.S.W. and J.M.M.; Funding acquisition, O.S.W. and J.M.M. All authors have read and agreed to the published version of the manuscript.

Funding: This work was funded in part by the Idaho Wheat Commission and the Idaho wheat producers.