Submitted to: Weed Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/1998
Publication Date: N/A
Interpretive Summary: Sometimes, herbicide drift or herbicide residue carry over from one growing season to the next damages crops and reduces yield. Although economic benefits to farmers from using herbicides to control weeds can be estimated for most major field crops, the extent and impact of negative effects, such as crop damage from herbicides, are harder to estimate from crop injury symptoms. One goal of this research was to determine whether crop damage measured early in the growing season soon after herbicide treatment could be used to estimate crop yield loss at harvest. Percent corn ground cover from video photographs was measured using computerized image analysis software. These percent cover measurements were compared with relative corn stunting which was estimated visually. Both types of measurements were made early in the growing season, soon after treatment with a damaging herbicide mixture at various rates. The research shows that percent ground dcover measured with a video camera and computer can better estimate yield loss compared with visually rated stunting. If later research shows that this approach can be easily automated, the information would help farmers improve crop management decisions when herbicide damage occurs.
Technical Abstract: The research goal was to determine whether crop damage from herbicides measured early in the growing season soon after treatment could be used to estimate relative crop yield loss at harvest. Two to four weeks after a sethoxydim-susceptible maize (Zea mays L.) variety was sprayed with sethoxydim at various rates plus crop oil concentrate, visually rated percent stunting and percent crop ground cover for maize from video photographs were determined. Averaged over three years, relative percent maize yields were a negative linear function of relative sethoxydim rate from 0.065x to 0.5x, where the 1x rate was 420 g ai ha**-1. Relative maize yields were positively linearly related to percent crop ground cover and negatively linearly related to rated percent stunting over three years. Linear regression models of a relative maize yield versus percent maize ground cover explained more data variability (r**2=0.86) than did either relative sethoxydim rate (r**2=0.70) or rated stunting (r**2=0.82) over three years.