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Accueil du site → Doctorat → États-Unis → 1995 → Weed interference and control in sugarbeet (Beta vulgaris L.) in the Gharb region of Morocco

University of Minnesota (1995)

Weed interference and control in sugarbeet (Beta vulgaris L.) in the Gharb region of Morocco

Rzozi, Si Bennasseur

Titre : Weed interference and control in sugarbeet (Beta vulgaris L.) in the Gharb region of Morocco

Auteur : Rzozi, Si Bennasseur

Université de soutenance : University of Minnesota

Grade : Doctor of Philosophy (PhD) 1995

Résumé
Field experiments were conducted in the Gharb region of Morocco to determine : the minimum weed free period for sugarbeet necessary to limit yield loss to 5%, the maximum weed interference duration beyond which sugarbeet yield loss will be greater than 5%, comparisons of preemergence and postemergence herbicides and their combination with hand-weeding were made. Also, comparisons were made of the effect of nitrogen application timing, irrigation and hand-weeding on sugarbeet root and extractable sucrose yields. The minimum weed-free period necessary to limit sugarbeet root yield loss to no more than 5% from late-emerging weeds was 17 weeks after sugarbeet emergence (wae) in 1990 and 15 wae in 1991. Sugarbeet root yield was reduced by 5% if weeds were allowed to interfere with sugarbeet for 2 wae in 1990 and for 2.5 wae in 1991. TCA (trichloroacetic acid) plus chloridazon (5-amino-4-chloro-2-phenyl-3(2H)-pyridazinone), lenacil (3-cyclohexyl-6,7-dihydro-1 H-cyclopentapyrimidine-2,4(3H,5H)-dione) plus ethofumesate ((+/$-$)-2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulfonate) applied preemergence, and phenmedipham (3- ((methoxycarbonyl)amino) phenyl(3-methylphenyl)carbamate) plus sethoxydim (2- (1-(ethoxyimino)butyl) 5- (2-(ethylthio)propyl) -3-hydroxy-2-cyclohexen-1-one) applied postemergence were ineffective in preventing yield loss from competition. Three hand-weedings at 4, 7 and 11 wae, and the combination of one hand-weeding at 15 wae with phenmedipham plus sethoxydim postemergence seem the best strategies to be adopted for weed control in polygerm sugarbeet given current hand-labor and herbicide costs in Morocco. Weed development was increased by both early and late-applied nitrogen. Nitrogen benefitted weeds at the expense of sugarbeet if weed control was inadequate during early growth stages. Sugarbeet quality tended to decrease following late irrigation, and following late application of nitrogen, compared to early nitrogen application. Supplementary irrigation at the beginning of the growing season was not always beneficial in the Gharb. Irrigation harmed the crop directly by causing excessively wet growing conditions during the sugarbeet canopy establishment phase, or through stimulation of weed growth. Three hand-weedings were required to achieve entire-season weed control under irrigation, but only two hand-weedings were required in the absence of irrigation.

Présentation (PROQUEST)

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