non chemical management of weeds effects on forage sorghum production

to assess the effect of non chemical management of weed control on forage sorghum (sorghum bicolor) a field study was conducted in varamin, iran during 2010 crop year in a three- replicated- split factorial experiment laid out in randomized complete block design with four weeding levels (w1= one time cultivation at 3-leaf stage using a duck foot cultivator, w2= two times cultivation at 3 and 5-leaf stages using a duck foot cultivator, w3= hand weeding throughout growing season and w4= without weeding) as main plots, and two plant density levels (d1= 190000, and d2= 266000 plant ha-1) and two plant pattern levels (p1= one-row and p2= two-row) as sub plots. weed density, weed biomass, number of leaves (nl), stem diameter (sd), number of tillers (nt), plant height (ph), leaf area index (lai), dry matter yield (dm yield), dry matter digestibility (dmd), water soluble carbohydrates (wsc), crude protein (cp), acid detergent fiber (adf), total ash (ash), and crude fiber (cf) where measured. the results revealed that the highest weed density and biomass observed in not weeding treatment. there was not significant difference among one time cultivation at 3-leaf stage and two times cultivation at 3 and 5-leaf stages from the weed density and biomass point of view. the lowest nl, sd, and nt observed in not weeding treatment. increasing plant density decreased dm yield, ph, sd and nl of sorghum. two-row plant pattern showed a significant preference in comparison to one-row plant pattern from the dm yield point of view although the highest cp obtained in one-row plant pattern. the highest dmd obtained in p2d2. the highest ash obtained in w2d2 and w2p2