This investigation was conducted in the Faculty of Agriculture, University of Khartoum, at Shambat demonstration farm, during the growing seasons 1997/98 and 1998/99 to evaluate the efficacy of three pre-emergence herbicides in weed control in sorghum (Sorghum bicolor L), supported by one hand-weeding, (4WAA).
Herbicides used were Triazines, namely,Sorgoprim, Gesaprim and Gesapax, at 1 kg/ha, 1.5 kg//ha and 2 kg/ha for the three herbicides
The herbicides used showed insignificant effect on some growth parameters such as plant height, number of leaves per plant and number of tillers per plant, whereas, a reduction in number of plant per plot was observed, with the medium and high rates of Gesaprim and Gesapax in both seasons.
The rates used proved insignificant effect on some sorghum yield components such as number of heads per plant and 1000s seed weight in (g). However, Some herbicides at the rates used had increased grain number per plant, and grains weight per plot in (g) as compared to un-weeded control and the hand weeded check
Within the three herbicides, Gesaprim at its high rate gave the highest number of seeds per plant in the first season, whereas the highest number of seeds per plant was obtained with Sorgoprim at its low rate in the second season. Gesapax at its low rate gave the highest yield per plant in the first season, whereas the highest yield per plant was obtained with Gesapax at its high rate in the second season. However, Sorgoprim at its all used rates resulted in the best consistent final yield calculated in tons per feddan, in both seasons.
Almost all herbicides at their used rates significantly decreased the number of weeds per m2. Also decreased weed biomass in both seasons except Sorgoprim in the first season. Gesaprim at its medium and high rates gave the highest control percentage (91%-94%) in the second season, whereas it ranked second after Gesapax in the first season (60%-61%), while Gesapax at its medium and high rates gave a significant consistent control percentage in both seasons from (81%-82%) in the first season to (86%-87%) in the second season. Therefore the effect of these herbicides at their used rates on weed control resulted in good to excellent weed control.