Effects of 2,4-D and nitrogen on incidence of witchweed (Striga hermonthica (Del.) Benth.) and sorghum (S.bicolor (L.)Moench) growth

Awadallah B. Dafaallah, Abdalla M. Hamdoun, Abd Elgabar T. Babiker

Abstract


A greenhouse experiment was conducted during the period November 2005 to April 2006 in Wad Medani, Sudan. It aimed to study the effects of 2,4-D at 0.32 kg a.i /fed applied 3 or 4 weeks after sorghum seedling emergence, nitrogen at 18 or 36 kg/fed at planting and their combination applied 3 or 4 weeks after emergence on witchweed incidence, sorghum growth, total dry weight and root: shoot ratio. Witchweed parameters measured included emergence, underground shoots, number of capsules and dry weight. The results revealed that witchweed incidence significantly reduced sorghum growth by up to 67%, total dry weight by up to 80% but increased root : shoot ratio from 0.39 to 0.72. 2,4-D applied 3 or 4 weeks after emergence, nitrogen at 18 or 36 kg/fed at planting and their combination displayed a respective promotion in sorghum growth by up to 100, 33 and 179% and total dry weight by up to 225, 80.3 and 347.6%. 2,4-D applied at 3 or 4 weeks after emergence effected a respective increment in root : shoot ratio from 0.72 to 0.92 and 1.09. Nitrogen at 18 or 36 kg/fed at planting changed root : shoot ratio from 0.72 to 0.7 and 1.0, respectively, while combinations of 2,4-D and nitrogen displayed a change from 0.72 to 0.7 and 1.4 at harvest. 2,4-D alone and in combination with nitrogen applied 4 weeks after emergence suppressed witchweed emergence by up to 100% early in the season. However, nitrogen alone increased the number of emerged witchweed by 43% and 309%. 2,4-D, nitrogen and their combinations displayed a respective suppression in underground witchweed shoots by up to 14.6%, 56.9% and 78.5%, number of capsules by up to 98.9%, 68.97 and 80% and witchweed dry weight by up to 82%, 84.75 and 91.3% at harvest. Generally, 2,4-D applied at 4 weeks after emergence in combination with nitrogen at 36 kg/fed exhibited the best performance.


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