In-situ plant hyperspectral sensing for early detection of soybean injury from dicamba

Authors: Huang, Yanbo; YUAN, LIN - Zhejiang University; Reddy, Krishna; ZHANG, JINGCHENG - Hangzhou Normal University

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/23/2016
Publication Date: 7/1/2016
Citation: Huang, Y., Yuan, L., Reddy, K.N., Zhang, J. 2016. In-situ plant hyperspectral sensing for early detection of soybean injury from dicamba. Biosystems Engineering. 149:51-59.

Interpretive Summary: Crop injury from off-target dicamba spray is becoming a major concern. Dicamba is highly active on susceptible crops even at low doses. Early detection of crop injury is critical in crop management. Scientists in USDA-ARS Crop Production Systems Research Unit, Stoneville, Mississippi, Zhejiang University of Water Resources and Electric Power and Hangzhou Dianzi University collaboratively developed the data analysis method for soybean response to dicamba doses through in-situ hyperspectral plant sensing in a soybean field. The results indicated that it was difficult to clearly differentiate the dose response of soybean to different dicamba spray rates within 72 HAT (hours after dicamba treatment). However, it was found that regardless of spray rates the soybean treated with dicamba could be clearly differentiated from untreated soybean from 24 to 72 HAT. This study illustrates the capability and limitation of the hyperspectral remote sensing method for early detection of soybean injury from exposure to off-target dicamba drift in the field.

Technical Abstract: Dicamba (3, 6-dichloro-2-methoxybenzoic acid) drift onto non-target crops is a major concern because dicamba is highly active on susceptible crops even at low doses. Early detection of crop injury is critical in crop management. A field study was conducted to determine spectral characteristics of soybean (Progeny P4819LL) treated with dicamba. Dicamba drift was simulated by direct application at 0.05 to 1.0X of the recommended label rate (X = 0.56 kg ae/ha) to soybean at the 5- to 6-trifloliolate leaf stage, approximately 6 weeks after planting. The canopy spectral measurements were taken at 24, 48, and 72 hours after treatment (HAT) using a portable spectroradiometer in 325 to 1075 nm spectral range on 3 randomly selected plants within each plot with device optimization and data calibration. The results of the study indicated that it was difficult to clearly differentiate the dose response of soybean to different dicamba spray rates within 72 HAT. It was found that regardless of spray rates the soybean treated with dicamba could be clearly differentiated from untreated soybean from 24 to 72 HAT through spectral vegetation index analysis with ARI (Anthocyanin Reflectance Index) and PRI (Photochemical reflectance Index) with an accuracy ranging from 76 to 86% with 24, 48, and 72 HAT. Simulated dicamba drift injured soybean and reduced soybean yield by 71 and 90% at 0.05 and 0.1X rate, respectively. This study demonstrated that hyperspectral remote sensing has a potential in early detection of soybean injury from exposure to off-target dicamba drift at sub lethal rates in the field.