This study was carried out at Shandaweel Agric. Res. Station (Sohag Governorate), Egypt during 2009 and 2010 seasons. At each season three planting date treatments (March 25, April 10 and April 25) were studied on the Egyption cotton Giza 90 cultivar. The experimental design was Randomized Complete Blocks (R.C.B.) with four replications. Obtained results revealed that plant ages 75, 105 and 135 days late sowing obtained the highest number of heat units and resulted in increasing plant height, number of nodes per plant, dry weight per plant, number of leaves per plant, leaf area and leaf area index while, it had no effect on internode length, leaf area index in age 135 days. Number of sympodia per plant increased in favour early sowing due to lower night temperature which lowered the position of early sympodium and inducing early balance between vegetative and fruiting development. Number of leaves, leaf area and leaf area index of early sowing increased slowly through, early season. Late sowing produced the first flower and open first boll in shorter period as compared to early sowing, but it consumed more number of heat units. The highest yield components and yield per unit area was produced from early sowing, where the cotton plants received the highest number of heat units through the growing season as compared to late sowing. Most of these units were utilized in produced the fruiting organs, while late sowing used most of these units in increasing the vegetative growth. The efficiency use of heat units by cotton plants increased in favour of early sowing rather than in late sowings. Best results were obtained when cotton plants were sown early (25 March). Generally, it is recommended to grow cotton early (25 March) for Giza 90 cotton cultivar gave the highest seed cotton yield per feddan rather than the late sowing (25 April) under the condition of this study.

The present investigation was carried out at Shandaweel Agricultural Research Station during 2005 and 2006 seasons on Egyptian cotton cultivar Giza 90. (Gossypinm barbadense L.) to study the effect of Potassium Sulphate application methods and timing on growth and seed cotton yield as well as yield components. A randomized complete block design with four replicates was used six treatments were as follows: K0: Without Potassium application (control). K1: Potassium Sulphate (48 %K2O) was applied at sowing. K2: Potassium Sulphate (48%K2O) was applied at thinning date. K3: Folair spraying with Potassium Sulphate (48 %K2O) twice at budding and flowering stages. K4: Folair spraying with Potassium Sulphate (48%K2O) three times at budding stage, beginning of flowering and 15 days later. K5: Folair spraying with citrate (Potassium -p 45% citrate) twice at budding and flowering stages. The results of these experiments indicated that plant height at harvest, Number of fruiting branches plant, number of open bolls/plant, boll weight, seed cotton yield/plant and faddan were significantly increased by tested treatments in both seasons. While, height of first fruiting node and number of plants at harvest were not affected by tested treatments.

Two field experiments were carried out at Shandweel Agricultural Research Station in 2009 and 2010 seasons to study the effect of sowing dates and first irrigation(Al-Mohayat) on growth, earliness, seed cotton yield and its components of Giza 90 (Gossypium barbadense L.). A split-plot design with four replications was used. The main plots were assigned to sowing dates (March 25, April 10 and April 25). Al-Mohayat irrigation time i.e., two, three and four weeks after sowing were assigned in the sub-plots. The results indicated that early sowing (March 25) significantly increased days to first flower, days to first open boll, number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. While, plant height at harvest and location of first fruiting node branch were decreased. Meanwhile, number of fruiting branches/plant, boll weight and number of plants at harvest/feddan were not significantly affected by sowing dates in both seasons. Delaying Al-Mohayat irrigation to four weeks after sowing significantly increased plant height at harvest, location of first fruiting node branch and days to first open boll in both seasons. While,delaying Al-Mohayat irrigation to three weeks after sowing significantly increased number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. Meanwhile, number of fruiting branches/plant, days to first flower, boll weight and number of plants at harvest/feddan were not significantly affected by Al-Mohayat irrigation. The interaction between sowing dates and Al-Mohayat irrigation had a significant effect on plant height at harvest, boll weight, number of open bolls/plant, seed cotton yield per plant and per feddan in both seasons. While, number of fruiting branches/plant, days to first open boll and number of plants at harvest/feddan were not affected in both seasons. Generally, best results were obtained when cotton plants were sown early (25 March) and Al-Mohayat irrigation (three weeks).

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The present investigation was carried out at Shandaweel Agriculture Research Station during 2005 and 2006 seasons to study the effect of NPK application levels on growth and seed cotton yield as well as its components of the Egyptian cotton cultivar Giza 90 (Gossypium barb dense L.). A randomized complete blokes design with four replicates was used. Nine treatments were as follows: NPK0 : 45 kg N + 15 kg P2O5 + 0 kg K2O/ fed NPK1 : 45 kg N + 22.5 kg P2O5 + 24 kg K2O/ fed NPK2 : 45 kg N + 30 kg P2O5+ 48 kg K2O/ fed NPK3 : 60 kg N + 15 kg P2O5 + 0 kg K2O/ fed NPK4 : 60 kg N + 22.5 kg P2O5 + 24 kg K2O/ fed NPK5 : 60 kg N + 30 kg P2O5 + 48 kg K2O/ fed NPK6 : 75 kg N + 15 kg P2O5 + 0 kg K2O/ fed NPK7 : 75 kg N + 22.5 kg P2O5 + 24 kg K2O/ fed NPK8 : 75 kg N + 30 kg P2O5 + 48 kg K2O/ fedThe results of these experiments indicated that plant height at harvest, Number of fruiting branches/ plant, height of fruiting nodes, number of open bolls/ plant, boll weight, seed cotton yield/ plant and feddan were significantly increased by tested treatments in both seasons. The greatest values of these traits were obtained from the combined fertilization with 75 kg N + 30 kg P2O5 + 48 kg K2O/fed.