EFFECT OF PRECEDING CROPS IN THREE-YEAR CROP ROTATIONS AND N RATES ON YIELD AND YIELD COMPONENTS OF EGYPTIAN COTTON

Four types of cotton rotations have been started since 1995/ 1996 season at Shandaweel Agric. Res. St. (Upper Egypt) to evaluate the effect on cotton production of different crop sequences and N rates on yield and yield components of cotton. Four preceding crop sequences viz., wheat/maize (P1), wheat/soybean (P2), faba bean/maize (P3) and faba bean/soybean (P4) were studied as main plots. Three nitrogen lev­els, i.e. 45,60 and 75 Kg N/fed. were applied to the cotton crop in the sub-plots. Results in 1999 and 2000 seasons Indicated that preceding crops significantly affected plant height, number of fruiting branches/ plant, total open bolls/plant, average bolls weight and weight of seeds/ boll. In both seasons seed cotton yield was 11.4 and 15.7% higher when cotton followed soybean than cotton grown after the cereal crops. All studied cotton characters were increased by increasing N lev­els up to 75 Kg N/fed. Seed cotton yield from 75Kg N/fed. Was higher than at 60 and 45 Kg N/fed. by 8.5, 15.9%, 6.73 and 16.88% in first and second seasons, respectively. The highest performance of cotton was observed when cotton was grown after legume crops and fertilized with 75 Kg N/fed., while the lowest performance was obtained following cereal crops and the lowest N level in both seasons.