Field experiments were conducted at Sakha Agricultural Research  Station in  1999 and 2000 seasons. The experimental design was randomized complete blocks design with four replicates. The first experiment was designed to study the effect of first irrigation at five times; 3 , 4 , 5 , 6 and 7 weeks after sowing date WAS using cotton cultivar Giza 70 (extra long staple). The preceding crop was rice (Oryza sativa, L.) in the two seasons. The results of this experiment indicated that delaying the first irrigation significantly decreased plant height, number of internodes of the main stem, leaf area and number of sympodia per plant, while number of monopodia per plant and internode length were insignificantly decreased . Delaying the first irrigation also, significantly delayed the maturity, whereas, delayed the formation of first sympodium and delayed the appearance of the first flower and cracking the first boll as well as reduced the earliness percentage, number of open bolls per plant, boll weight, lint percentage, seed index, seed cotton yield per plant and feddan. The first irrigation at 4 (WAS) gave the best result and highest heavy bolls in the two seasons. The maximum reduction in seed cotton yield per feddan was  20 % when the first irrigation was applied after 7 weeks from the sowing date while, the minimum was 5.4 % when the first irrigation was done after 3 weeks as compared with the first irrigation applied after 4 weeks in both seasons. The second experiment was designed to study the effect of thinning date at four physiological ages; when cotton plant formed the two cotyledon leaves, the second true leaf, the fourth true leaf and the sixth true leaf. The results revealed that thinning date significantly affected the growth traits, earliness parameters, yield and its components in the two seasons. The thinning when cotton plants formed the second true leaf gave the best result in the two seasons. Delaying thinning date significantly increased plant height, the internode length, position of first sympodium, days from sowing date to appearance of the first flower and cracking the first boll while, the reverse was true for number of internodes on the main stem, number of monopodia and sympodia / plant, earliness percentage, number of open bolls / plant, boll weight, lint % and seed cotton yield per plant and feddan in the two season. The maximum reduction in seed cotton yield was 21 % when the cotton plants were thinned after formation the sixth true leaf (about 40 days after sowing ), while the minimum reduction was 6.6 % when the cotton plants were thinned after formation of the two cotyledons (about 20 days after sowing). Generally, Delaying the first irrigation upto 7 weeks and delaying the thinning date until cotton plants formed the sixth true leaf caused a reduction in seed cotton yield about 41 % from the total yield as compared with thinned cotton plants after formation of the second true leaf and giving the first irrigation after 4 weeks in case of the preceding crop was rice.