Clopyralid Influences Rotational Crops

Abstract

Field research was conducted at Fargo, Langdon, and Prosper, ND to determine carryover of clopyralid applied at 70 to 560 g ae ha^-1 in soil as indicated by response of crops planted 1 yr after application. Flax, potato, and safflower growth at Fargo were not affected by clopyralid residues. At Fargo, soybean height, stand, and yield were reduced by residues from clopyralid at 560 g ha^-1, and sunflower heads ha^-1 and yield were reduced by residues from clopyralid at 280 and 560 g ha^-1 and 560 g ha^-1, respectively. Potato and sunflower at Langdon and Prosper and lentil at Langdon were not affected by clopyralid residues. Soybean yield at Prosper was not affected by clopyralid residues, but plant height was reduced by residues from clopyralid at 280 and 560 g ha^-1. These results indicate that residues from clopyralid applied at labeled cropland rates, of 280 g ha^-1 or less, in silty clay, clay loam, and silty clay loam soils in North Dakota probably will not adversely affect the dicot crops tested in these experiments planted 11 mo or more after application.