EFFECT OF FIRST AND LAST IRRIGATION CONSIDERING IRRIGATION INTERVALS ON YIELD, YIELD COMPONENTS AND SOME CHEMICAL CONSTITUENTS OF GIZA 89 X 86 HYBRID COTTON

Four experiments were carried out at Sakha Agric. Res. Station, AgriculturalResearchCenter. These experiments were divided into two series, each contained two experiments. One experiment of each series was conducted in 2004 and the second one in 2005 growing season. The experiments of the first series were performed to investigate the effect of the first irrigation (after 14, 21 and 28 days after sowing) and irrigation intervals (15 and 21 days after the first irrigation) on yield and its components of hybrid cotton Giza 89 x 86. The experiments of the second series were conduced to study the optimum flowering stage for applying the last irrigation (termination irrigation at the end of 7th, 9^th and 11^th week of starting of flowering) on yield and its components of hybrid cotton Giza 89 x 86.
The results could be summarized as follows:
1.   When the first irrigation was applied 28 days after sowing it gave the highest number of final plant height and number of nodes per plant, however, highest number of sympodia, number of open bolls per plant, boll weight and seed cotton yield per plant and feddan were obtained when the first irrigation was applied 21 days after sowing, while earliness percentage was reduced by delaying the first irrigation.
2.   The irrigation every two weeks gave the tallest plants and more number of node on the main stem, number of sympodia per plant, number of open bolls per plant, boll weight, seed cotton yield per plant and feddan and earliness percentage than the irrigation every three weeks.
3.   Seed index, lint percentage, all fibre properties and chemical constituents in leaves except carbohydrate content were not significantly affected by the date of the first irrigation but all these traits were significantly increased by close irrigation intervals. On the other hand, most of chemical constituents under study were significantly increased as irrigation intervals increased in 2005 season but oil and protein % in seed were reduced.
4.   There was a tendency of increase for growth characters, yield, yield components, seed index, lint percentage, fibre properties and chlorophyll contents while the reverse trend was detected with respect to carbohydrates, oil and protein %.
5.   The interaction between the days of the first irrigation and irrigation intervals did not affect all characters studied herein.