Herbicide Screening For Four Grain Legumes in Puerto Rico

Abstract

The performance of 19 herbicides in 50 treatments was evaluated in terms of their selectivity to soybean, pigeon pea, cowpea and field beans, and of their effect upon the weed populations of three localities in Puerto Rico represented by three of the substations of the Agricultural Experiment Station. Although the majority of the products tested were selective to the four crops at the three sites, some were more toxic to certain crops or in given localities. Fluchloralin was more toxic to soybeans and field beans at Lajas and to pigeon pea in lsabela and Fortuna. Cowpeas and field beans were very sensitive to metribuzin, while soybeans and pigeon peas were more tolerant. Toxicity of metribuzin to soybeans and pigeon peas was more pronounced at higher rates and in the lightest soil. Oryzalin was more toxic to pigeon pea in lsabela and to cowpea in Fortuna. Profluralin was more toxic in Lajas and prometryn in Fortuna than in the other sites. U 27267 was more toxic when incorporated than when applied to the surface. There were differences in the degree of weed control among products, rates and localities. The differences among localities were related to variations in soil characteristics and weed populations. The results strongly support the importance of simultaneously considering the crop, the weed population and soil characteristics before recommending herbicides.