Weed competition in garlic (Allium sativumL.)

Abstract

ummaryThree field experiments at two locations studied the effect of weed competition on garlic (Allium sativum L.) in 1991,1992 and 1993. Treatments included plots hand weeded for various periods after crop emergence or left weed-infested for the same periods before weeds were removed. Results showed that the shorter the initial weed-free period, or the longer weeds remained in plots before removal, the greater the reduction in garlic yield and quality. Average reduction in bulb yield of the three years was up to 85%. None of the weed-free periods gave a total fresh weight of garlic comparable with the weed-free control. In 1991, weeds present for 28 d or more after crop emergence, or keeping plots weed-free for 42 d or fewer after crop emergence, significantly lowered bulb yield compared with the weed-free treatment, while none of the weed-free periods was sufficient to increase yield to the level of the weed-free control in 1992 and 1993. Weed competition for only 14 d of crop emergence was enough to reduce yield significantly in 1991, while weed-free periods of 35 or 28 d from crop emergence failed to produce bulb yield higher than the weed-infested plots in 1991 and 1992, respectively. Weeds emerged at 42 d of crop emergence significantly reduced clove number per plant to the level of unweeded control in the three years. The minimum weed-free period required to produce a bulb size similar to the weed-free control was 21, 28 and 49 d of crop emergence for the three years, respectively. Based on bulb yield data, the critical period of weed competition under irrigation in the Jordan Valley (mainly broadleaved weeds) occurred at 21–28 d in 1991 and 42 to 49 d in 1992, depending on the competing weed species and their densities. Under rainfed conditions at the Al-Jubeiha location (where Avena sterilis was dominant weed) this period was at 49 d from crop emergence. Weeds emerged before or after these periods had no significant effect on garlic yield provided they were removed at this time.