Site-specific weed management in maize (Zea mays)

Site-specific weed management can increase crop production efficiency by minimizing herbicide input costs without compromising crop yields. A reduction in herbicide inputs resulting from site-specific weed management may also decrease the probability level of nonpoint pollution compared with conventional herbicide applications. A 4.5-ha field was selected to compare site- specific and conventional weed management techniques in a field location at Knoxville, TN. Variable rate applications (VRAs) of atrazine pre-emergence (PRE) followed by dicamba post-emergence (POST) were investigated for the reduction of herbicide inputs and their resulting impact on weed control and corn yield. VRAs of atrazine were on the basis of weed density data collected in Year 1. VRAs of dicamba were according to common cocklebur density evaluations within the field. Com- pared with conventional applications, atrazine usage was decreased by 43 and 32% in the site-specific application treatments in Year 2 and Year 3, respectively. VRAs of dicamba reduced herbicide inputs by greater than 45% for Year 2 and Year 3. Corn yields were similar for the conventional and site­ specific treatments in both years. On the basis of these data, site-specific herbicide applications have the greatest potential and least risk for managing weeds when POST or PRE + POST variable rate herbicide applications are used.