Evaluation of low-volume herbicide application technology for no-till soybeans

A study performed at The University of Tennessee Milan Experiment Station during 1983 evaluated and compared preemergence and postemergence herbicide application techniques in no-tillage and conventionally-cultivated soybean plots. The equipment utilized for herbicide application included conventional medium-volume hydraulic flat fan nozzles, low-volume flat fan nozzles, controlled droplet applicators (CDA), and an ultra low-volume electrostatic sprayer.

Various application parameters and techniques were compared: low-volume versus medium-volume spray rates, ultra-low versus medium-volume application rates, flat fan nozzles versus controlled droplet applicators (CDA) for low-volume spraying, and water-only carrier versus oil-in-water diluents for low-volume application.

Sprayed plots were evaluated for percentage control of selected weed species and for soybean yields. Results showed that spray application volume (5 gal/acre versus 20 gal/acre) applied either preemergence or postemergence did not affect the level of weed control in no-till soybeans. Moreover, low-volume hydraulic nozzles and controlled droplet applicators (CDA) at 5 gal/acre were equally effective in controlling weeds.

Roundup plus Lorox plus Lasso applied preemergence in wheat stubble gave significantly better control of Pennsylvania smartweed than a tank mix of paraquat plus Lorox plus Lasso. Both full and half-label rates of Basagran plus Blazer applied postemergence in wheat stubble were significantly more effective in controlling cocklebur than Pennsylvania smartweed. Addition of a crop oil concentrate did not increase weed control in the low-volume treatments.

Application of Fusilade in conventionally-cultivated soybeans using an electrostatic spray system at 0.8 pt/acre total spray volume gave similar levels of weed control to applications of the same herbicide rates at 20 gal/acre using conventional hydraulic nozzles.

Soybean yields overall in 1983 were much below normal due to drought conditions during the growing season. Crop yields within a given production practice were not significantly affected by spray application techniques.