Date of Award
Doctor of Philosophy
Agricultural and Biosystems Engineering
James L. Baker
A point-injection system has successfully been designed to inject and incorporate herbicides applied with water into the soil profile in a band. This point-injection cylinder (PIC) can incorporate herbicides in a single pass through the field while leaving the soil surface virtually undisturbed. The PIC functions effectively on both bare soil surfaces and soil surface covered with crop residue;The relative persistence of banded herbicides (alachlor, atrazine, and propachlor) using the PIC and a band sprayer was compared in a field study. A bare soil surface and a soil covered with an average of 79 percent corn residue were used in the comparison. Point injection was found to decrease losses due to a combination of volatilization, photodegradation, and runoff thus increasing persistence for alachlor and propachlor applied to soil. The relative persistence of atrazine applied to soil was found to be about the same for both application methods 21 days after application. Losses were higher for the herbicides sprayed on the corn residue as compared to point-injection into the soil;Weed control with the PIC and broadcast spray with disk incorporation was determined for various herbicides using oats as the test species. There was no significant difference found between these application methods in controlling the oats for the herbicides atrazine, alachlor, butylate, or EPTC. Weed control was significantly higher for trifluralin when disk incorporated versus point-injected. In a full field study, no significant difference in weed control were found between applying atrazine and alachlor with the PIC and band sprayers. Both application methods were effective in controlling the weeds in the banded area when compared to a check treatment;In a rainfall simulation study, band spraying was compared against point-injection to determine if there were differences in the percentages of the atrazine, alachlor, and propachlor lost with runoff and leachate during 10 cm of rain 1 to 6 days after application. Tillages used included no tillage, chisel plow tillage, and ridge tillage. No significant difference was found in the runoff water and sediment, or the leaching water losses for atrazine, alachlor, or propachlor when applied by either the point injector or a band spraying nozzle.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Steven Kent Mickelson
Mickelson, Steven Kent, "Efficient herbicide application to reduce environmental losses " (1991). Retrospective Theses and Dissertations. 9667.