Smooth Bromegrass Response to Herbicides as Affected by Time of Application in Relation to Nitrogen Fertilization

Abstract

Smooth bromegrass (Bromus inermis Leyss.) treated in the fall tended to be more damaged than that treated in the spring, regardless of herbicide. Nitrogen fertilizer reduced the loss in yield resulting from herbicides but was least effective with 1 lb/A of 4-amino-3,4,6-trichloropicolinic acid (picloram). Laboratory studies showed that roots of smooth bromegrass were the primary site of picloram uptake. Root uptake explained the severe damage in curred from applications of picloram made in the fall. The order of increasing phytotoxicity of herbicides to smooth bromegrass studied in these experiments was 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4-dichlorophenoxyacetic acid (2,4-D)<2-methoxy-3,6-dichlorobenzoic acid (dicamba) < picloram.