SURVEY OF WEED FLORA AND ASSESSMENT OF CRITICAL PERIOD OF WEED COMPETITION IN SUGARCANE

Abstract

Survey of weed flora of sugarcane crop and a field experiment were carried out during 2014/2015 to identify weed flora of sugarcane and to assess the critical period of weed competition in sugarcane at Kuraz Sugarcane plantation. The experiment was consisted of 12 treatments in which weed infested treatments weeds allowed to compete with sugarcane crop up to 40, 60, 80, 100 and 120 days after planting and weed free treatments, up to 40, 60, 80, 100 and 120 days after planting. These five weed infested treatments and five weed free treatments were tested along with two controls namely weed infested and weed free treatments. The experiment was carried out in RCBD replicated three times. In this experiment, all agronomic practices, except the treatment (weed), were applied uniformly to all plots. As per the treatment, weeds were removed manually at 41, 61, 81, 101, 121 DAP. Data were collected on types of weeds species, weed biomass, sugarcane growth and yield parameters and cane yield. The data were tabulated and analyzed statistically by using SAS statistical software version 9.2 for windows. The results of the survey indicated that weed communities composed of 29 different families were found grown with sugarcane. The species of dominant families in bracket were Poaceae (24) and Asteraceae (11). The most dominant and frequent weed-species were Convolvulus arvensis L., Brachiaria mutica L., Abutilon theoplrast Medicus, Commelina benghalensis L., and Corchorus olitorius L.. Weed dry biomass production was decreased with increasing durations of weed free periods and with decreasing durations of weedy periods. According to the results of the experiment, five percent acceptable cane yield loss level better predicted the actual condition of the location for estimating critical period of weed competition. Thus, the beginning and end of critical periods of weed interference on 5 % acceptable cane yield loss level ranged between 36 to 102 - DAP for NCo 334. This implies to obtain 95 % cane yield of sugarcane, the maximum time allowed to let weeds grow after sett emergence is 36 DAP. The same level of cane yield could be achieved if the crop kept free from weeds until 102 - DAP implying weed control measures should be taken to prevent yield loss in this period. Although different weed competition periods did not affect number of internode and stalk diameter significantly but effect on cane yield, stripped cane weight, cane length and number of millable cane was highly significant. The maximum cane yield loss due to weeds for NCo 334 was 53.3%.