Weather, Soil and 2,4-D Effects on Tallgrass Prairie in Oklahoma

Abstract

A study was conducted from 1971 through 1975 in a north central Oklahoma tallgrass prairie to determine effects of (1) different rates of 2,4-D on grass production in fair to good condition areas where forb production was low, (2) repeated applications of 2,4-D on grass and forb production, and (3) species composition and range site growing conditions on grass and forb production responses to 2,4-D application. Five rates 2,4-D (0.00, 0.28, 0.56, 0.84, and 1.68 kg/ha) were applied in 1971 to determine their effects on grass production where forbs had been removed manually prior to spraying. Grass production increases equalled forb production decreases, regardless of whether forbs were reduced by 2,4-D or hand-weeding prior to 2,4-D application. From 1972 through 1975, the same 5 rates of 2,4-D were applied annually on four tallgrass prairie sites differing in range condition, past use, and soil factors. Site and annual growing conditions had more effect on grass production than did 2,4-D applications. There was no evidence of a stimulative growth effect by 2,4-D on grass production. All increases in grass production were accompanied by decreases in forb competition.