Residual Effect of Herbicides Used in Pastures on Clover Establishment and Productivity

Abstract

Field experiments in 2013 evaluated residual herbicide effects on ball (Trifolium nigrescens viv.) and white (Trifolium repens L.) clover. For the October planting, averaged across clovers, ground cover for 2,4-D plus aminopyralid and 2,4-D plus picloram averaged 4.4 and was less than for the nontreated (7.0). For the November and March plantings, ground cover for all herbicides was equivalent to the nontreated. Averaged across clover species and planting date, herbicide treatments except 2,4-D plus aminopyralid (4) resulted in ground cover 49/112 days after planting (DAP) equal to the non-treated (5.7). Lowest plant population 4 to 6 wk after Oct/Nov planting was observed for 2,4-D plus aminopyralid (6.3) and 2,4-D plus picloram (7.3). Only 2,4-D plus aminopyralid resulted in yield reduction from the nontreated (29.8%). Field experiments also evaluated simulated residual effects of fluroxypyr plus triclopyr and 2, 4-D plus picloram on ball (Trifolium nigrescens viv.), white (Trifolium repens L.), crimson (Trifolium incarnatum L.) and red (Trifolium pretense L.) clover. For all clovers, when averaged across herbicide rates, plant population 214/217 and ground cover 86/87 DAP was equivalent for fluroxypyr plus triclopyr and the non-treated and greater than 2,4-D plus picloram. Averaged across herbicide rates, clover height was equivalent for fluroxypyr plus triclopyr and the non-treated. 2,4-D plus picloram reduced clover height 67 to 88% from the non-treated. Ground cover 161/196 DAP, when averaged across clovers, for all rates of fluroxypyr plus triclopyr was equivalent to the non-treated. All rates of 2,4-D plus picloram were reduced compared to the non-treated (1.4 to 4.0 vs 7.9). Averaged across clovers, plant height following all rates of fluroxypyr plus triclopyr was equivalent to the non-treated (14.2 to 14.3 vs 15.3 cm) and greater than 2,4-D plus picloram. Compared with the non-treated, 2,4-D plus picloram at 25, 38, and 50% x rates reduced height 58, 76, and 85% respectively. Averaged across clover species, yield for fluroxypyr plus triclopyr at all rates was equivalent to the non-treated (2624.0 to 2839.7 vs 2811.9 kg/ha). Compared with the non-treated, 2,4-D plus picloram at 25, 38, and 50% x rate reduced yield 65,89, and 99%, respectively.