EFFECT OF WEED CONTROL METHODS ON THE PRODUCTIVITY AND QUALITY OF STAR GRASS (Cynodon plectostachyus (K. Schum.) Pilg.)

Abstract

From August 2005 to February 2007 an experiment was carried out at the Municipality of Cotaxtla, Veracruz, Mexico, in order to determine the effect of different treatments to control Sida rhombifolia and other 10 broadleaf weed species in production and quality of Star grass [Cynodon plectostachyus (K. Schum.) Pilg.], during two years in the rainy season. The complete randomized block design with four replications was used. The treatments were: i.- Aminopyralid + 2,4-D (40 + 320 g/100 L water), ii.- Picloram + 2,4-D (64 + 240 g/100 L water) iii.- Mowing with machete and iv.- Weedy check. The treatments were applied in the same experimental plots on August 24, 2005 and July 25, 2006. Weed population density was determined before treatment application, whereas weed control, forage production and quality were evaluated at 36, 98, 155 and 224 days after treatment application (DAA) during the first rainy season and at 30, 79, 140 and 197 DAA during the second one. Aminopyralid + 2,4-D and picloram + 2,4-D controlled Sida rhombifolia between 86 and 99%, whereas the control with the mowing treatment, varied between 35 and 68%. On the other hand, the control of the other weed species ranged between 95 and 99% with both herbicide treatments and between 26 and 59% with the mowing treatment. The plots in which the weeds were mowed produced from 27.6 to 58% and from 33.9 to 47% less forage than the average of those which were applied with aminopyralid + 2,4-D and picloram + 2,4-D, in the first and second period, respectively. The protein content of the forage was similar for all treatments during the rainy season; however, under low temperature and moisture conditions, the nutritive value of the forage obtained with the chemical control treatments was significantly higher than that obtained with the mowing treatment or in the weedy check plots.