CROP rotation is thought to reduce weed density, hence preventing the domination of some weeds problem. Variance in weed population between cropping systems may be the direct result of crop rotation. Two rotation experiments in a long - term study were carried out at Shandaweel Res. St., Sohag Governorate in Upper Egypt from 2014/15, 2015/16 and 2016/17 winter seasons. The area used for agriculture has not changed over the three seasons. Plots were not changed in every treatment in the sense that all experimental pieces received the same treatment in the three seasons of summer and winter.
Results showed that of crop rotation system (Faba bean/maize/faba bean/maize) gave the height effect in decreased on number and weight of grassy, broad-leaved and total weeds and increased weight of pods, weight of seeds/plant, 100-seed weight and seed yield (arad/fad) compared with (Faba bean/peanut/faba bean/peanut) in seasons 2014/15,2015/16 and 2016/17, respectively. Gradually increased the weight of pods and seeds/plant, 100-seed weight and seed yield (arad/fad) from season to season using of herbicide or hand hoeing compared with control.
Significant positive correlation values were detected between the number and weight of all weeds spices in both seasons. A correlation value was negative between the number and weight of weeds and seed yield (ard/fad) and 100-seed weight but a correlation value was positive between yield and it's components.
Economic evaluation of the results indicated that using crop rotation system (Faba bean/maize/faba bean/maize) gave the highest economic values in the average of three seasons for all economic evaluation.