Desempenho fisiológico das forrageiras cornichão e trevo vermelho em função do controle químico

Abstract

The objective of this research was to evaluate viability, seed vigor and growth of birdsfoot trefoil and red clover, plants from Embrapa Pecuária Sul, was submitted to different doses of pre and post emergent herbicides (diclosulam, bentazon and iodosulfuron-methyl), with purpose to identify herbicides selective to these forages. In the first stage of the experiment the effect of the pre-emergent herbicide diclosulam in physiological potential of seeds and initial growth of seedlings was evaluated. The seeds of this forages were sown on a substrate previously moistened with diclosulam solution at concentrations 0; 0,5; 1,0 and 1,5 times the dose registred by manufacturer. In second stage, after the cultivation in the greenhouse for 107 days, the postemergence application was carried out by a costal sprayer with constant pressure at atmospheric conditions of 23 ºC and 71% relative humidity). Herbicide concentrations used were zero; 0,5; 1,0 and 1,5 times the dose registred by manufacturer. The results of the first stage showed that the variables shoot length, root length and total dry mass were negatively altered by exposure to different doses of diclosulam, while germination potential and emergence capacity were not impaired in both species studied. In the second stage, the results obtained showed greater sensitivity of birdsfoot trefoil plants to herbicide bentazon and the red clover plants to iodosulfuron-methyl herbicide. Therefore, it is possible to conclude that, different doses of diclosulam do not compromise germination potential, neither ability to emerge from birdsfoot trefoil and red clover seeds, but negatively interfere in its development. With the post-emergence application, the birdsfoot trefoil showed sensitivity to herbicide bentazon and characteristics of tolerance to herbicide iodosulfuron-methyl, while the red clover responded in a contrary way, being more sensitive the application of the herbicide iodosulfuron-methyl and tolerant to bentazon, activating mechanisms of adaptation and allowing plant development.