Effects Of Sowing Date And Chemical Control Of Broad – Leaved Weeds On Yield And Yield Components Of Wheat (Triticum Aestivum L. ) In The River Nile State (Sudan)

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Ahmed, Khalid Mohammed Ali
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A field trial was carried during the winter season in 2003 at Hudeiba Research Station Farm as to study the effects of sowing date and control of broad-leaved weeds by the systemic herbicide 2,4-D on wheat production. The variety Condor was sown at three dates, namely, 1, 15 and 31/ December. The herbicide was applied at the rate of 0.6 kg a.i /feddan at three weeks after sowing at each date. Results indicated that the yield and yield components of this variety were significantly lower when the crop was sown at the end or in the middle of the month. It appeared that the reductions were greatly due to the effect of competition of broad-leaved weeds with the crop. According to the results these weeds became more abundant in number and highly infested the crop when it was sown on 31/ December. The average grain yield of the crop grown under conditions of unchecked weed growth decreased from 2393kg/ha to 671 kg/ha when sowing date was delayed from 1/ December to 31/ December. The crop showed a relatively slight reduction in the grain yield when it was sown on 15th of December. Reductions in the straw yield, the number of seeds / spike, the 1000- seed weight and the plant height were almost in the same trend of the reduction in the grain yield. The systemic herbicide 2,4- D gave highly efficient control of the broad- leaved weeds. Data on percent weed control collected at 6 and 9 weeks after sowing showed that 86% to 98% of the plants of seven annual species of the broadleaf weeds were killed by the herbicide when applied after the first and the second sowing dates. Complete control of the weeds was achieved when the herbicide was used in the last sowing. Effectiveness of the herbicide was also reflected in significant reductions in the dry weight of the total weeds at all sowing dates. No clear effect of the herbicide on the grassy weeds could be detected in this study. Killing of the broadleaf weeds had increased the grain yield of the crop sown on 31/December by 52% and the straw yield by 35%. The respective percent increases in the grain yield for the first and the second sowing dates were 43 and 26 and the straw yields were 31 and 25. Results indicated that the use of the herbicide had resulted in an increment of about 5 seeds/spike at each of the three sowing dates whereas it gave only slight increase in the 1000-seed weight. Both the average height of the main stem of the plant and the straw yield were also significantly increased as a consequence of the herbicide treatment.
July 2005
Wheat (Triticum Aestivum L. )