Abstract
Glyphosate is the most widely used herbicide in crop production due to the widespread adoption of glyphosate-resistant (GR) crops. However, the spray of glyphosate onto non-target crops from ground or aerial applications can cause severe injury to non-GR corn plants. To evaluate the crop damage of the non-GR corn plants from glyphosate and the recoverability of the damaged plants, we used the hyperspectral imaging (HSI) technique in field experiments with different glyphosate application rates. This study investigated the spectral characteristic of corn plants and assessed the corn plant damage from glyphosate. Based on HSI image analysis, a spectral variation pattern was observed at 1 week after treatment (WAT), 2 WAT, and 3 WAT from the glyphosate-treated non-GR corn plants. It was further found that the corn plants treated with glyphosate rates equal to or higher than 0.5X (X = 0.866 kilograms acid equivalents/hectare (kg ae/ha) represents the recommended spray rate for GR corn) would suffer unrecoverable damage. Using the Jeffries–Matusita distance as the spectral sensitivity criterion, three sensitive bands from the measured spectra were selected to create two spectral indices for crop recoverability differentiation in band ratio and normalization forms, respectively. With the two spectral indices, the corn plants recoverable and unrecoverable from damage were classified with an overall accuracy greater than 95%. Then, three machine learning algorithms (k-nearest neighbors, random forest, and support vector machine) were respectively combined with the successive projections algorithm to create models to relate selected feature spectral bands to glyphosate spray rates. The results indicated that the models achieved reasonable accuracy, especially in the group of recoverable plants. This study illustrated the potential of the hyperspectral imaging technique for evaluating crop damage from herbicides and recoverability of the injured plants using different data analysis and machine learning modeling approaches for practical weed management in crop fields.
Highlights
Herbicides have played an important role in weed control and crop production.Since the discovery of its herbicidal properties in 1971 and commercialization in 1974, glyphosate has been used extensively on both crop and non-crop lands
Corn plants sprayed at glyphosate rates lower than 0.5X are recoverable, whereas those sprayed at glyphosate rates higher than or equal to 0.5X are unrecoverable
This study evaluated the ability of hyperspectral imaging (HSI) to assess the severity of GR corn plant damage from glyphosate and the recoverability of the damaged GR corn plant
Summary
Herbicides have played an important role in weed control and crop production.Since the discovery of its herbicidal properties in 1971 and commercialization in 1974, glyphosate has been used extensively on both crop and non-crop lands. Herbicides have played an important role in weed control and crop production. Glyphosate is the most commonly applied herbicide either alone or with other herbicides to manage a broad spectrum of weeds [1]. Glyphosate is applied multiple times in a year using either ground or aerial equipment for different purposes. Glyphosate has been more frequently used in agriculture, forestry, and orchards because of its effectiveness in controlling weeds and improving agricultural economic benefits. Glyphosate spray onto non-GR crops from ground or aerial applications is a major concern for farmers. The use of glyphosate, is important because it is a non-selective herbicide and highly active on sensitive, non-GR plant species even at low doses [2]. Evaluation of off-target crop damage by glyphosate is critical for effective weed management
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