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Abstract Three field expriments were carried out at the Research and Experimental Station of the Faculty of Agriculture at MoshtohoT, Zagazig University, Kalubia, Egypt, during 1981, 1982 and 1983 seasons. The intention was to study the effect of delaying sowing dates and the absence of some irrigations during the different stages of plant growth on yield, earliness and fiber and yarn properties . A split-plot design with four replications was used. Th e t h ree sow i n g d ate 5 i _e ., Mar chI!!..!..,ApT’ill st. and ”1ay 1s t. were applied in the main plots . The sub-plots were devoted to 8 irrigation treatments as follows B L- Control: It is worth mentioning that the control treatments were 10,9 and 8 irrigations, for the first, the second and .the third’ planting dates, respectively- B2- Without the first irrigation . B3- Without an irrigation at the beginning of flowering stage. B4- Without an irrigation at the beginning of fruiting stage. B5- Without the first irrigation and an irrigation at the beginning of flowering stage. B6- Without the first irrigation and an irrigation at the beginning .d fruiting stage. B7- Without an irrigation at the beginning of flowering stage and an irrigation at the beginning of fruiting stage B8- Without the first irrigation~ an irrigation at the beginning of flowering stage and an irrigation at the beginning of fruiting stage . It is rather interesting to note that the first irrigation was given after 30 days from sowing date. The other irrigations were applied at IS-day intervals. Other cultural practices were done according to the system usually followed in Kalubia district. The sub-plot area waS 10.5 m 2 .( 1/400 fed.) with 5 rows; each row was 3.5 m. long~ 60 em. apart and hills were spaced at ZO em. apart. The plants were thinned to two plants per hill after 45 days from sowing time . ~alcium super phosphate ( 16% PZOS ) at a rate of 24 kg. P205 per feddan was applied immediatly before the first irrigation . The nitrogen fertilizer ( ammonium nitrat~ 33.5 X) was applied at a rate of 50 kg. N/fed. just”before the second irrigation. The Egyptian ” . long staple variety Giza 75 ( £.barbadense ) was used as a material in the present study . This variety was derived from a cr0&S between the two Egyptian varieties Giza 67 and Giza 69. Giza 75 is a high yielding variety baving higher yarn strength as compared withit8”parent~ . It is also characterized by high lint percentage which is slightly lower than Giza 69 variety. The plots were picked twice. the first picking was done 40 days after the first boll opening and the second one was done 20 days. after the first picking . Studied Characters : The growth attribu~es~ earliness, yield~ yield components and fiber and yarn properties, were studied in the present investigation. The results, obtained could be summarized as follows : (A) Growth Characters 1. There was a tendency of increase in germination i. as a result of delayi~g sowing date. This trend was the same in all the three seasons involved in the s t u dy • 2. The plant height tended to decrease significantly when the sowing date was delayed in all the three seasons under study. It was also found that there was a tendency of decrease in plant height as a result of reducing the numbe~ of irrigations, given to the plants • 3. The delayed date of sowing resulted in decreasing the number of fruiting branches per plant. This trend could be seen during the three seasons. The irrigation treatments showed an insignificant effect on the number of fruiting branches per plant 4. ~he number of vegetat~ve branches per plant tended to decrease significan~ly when the planting date was delayed in two seasons out of three . The effect of irrigation treatments on the number of vegetative branches per plant was not significant in all seasons. (B) Earliness:. 1. The delaying in planting date caused a marked reduction in the number of days to the first flower appearance and th~ first boll opening . There was a general trend of decrease in the days to the first flower and the first boll opening whenever the number of irrigations decreased . 2. The height of first fruiting branch tended to increase significantly as the planting date was delayed . The decrease in the number of irrigations did not affect significantly the height of first fruiting branch. (C) Yield and Yield Components : 1. The number of open bolls per plant tended to decrease materially when the plants were grown late in April or in May. The absence of the first irrigation did not significantly affect the number of open bolls per plant • However, the absence of an irrigation either before the flowering stage or the fruiting stage res~lted in decreasing the number of open bolls per plant . whereas ~he absence o£ two irrigation$ obviously reduced this character . In fact the lowest number of open bolls per plant. was obtained when three irrigations were absent . 2. The earlier sowings resulted in a higher boll weight • It was clear that the absence of the first irrigation did not result in a significant differences among the averages of boll weight as compared with the control. However. whe~ an irrigation was not given eithet before flowering stage or fruiting stage, .the boll weight si gnifieant 1y dec rea sed . The absence of two irrigations, distinctly reduced the boll weight. However, the lowest boll weight was observed when th~ee irrigations, were not given. 3. The plant stand evidently increased when the seeds were sown late. Irrigstion treatments did not reveal any significan~ effect on plant stand 4. SeeJ cotton yield per plant was substant~ally reduced as a result of late planting. Irrigation treatments proved to have a pronounced effect on seed cotton yield per plant a8 indicated by the fact that the absence of anyone irrigation tended to significantly decrease seed catton iield per plant compared with the control . This tendency was more evident as the number of absent irrigations was increased . The latesow~ng dates tended to decrease the seed inde~. It is clear, however that the plants grown in April and May did not differ significantly regarding their seed index, but they w~re generally of lower seed index values than those grown earlier in March. When the first irrigation was not given the seed index was not significantly affected . On .th. other hand, the absence of an irrigation either before the flowering stage Of th~ fruiting stage slightly reduced the seed index. This pattern was true when two or three irrigations were not given. ’However. the differences between the irri~ gation treatments were generally small . 6. ’The lint percentage was found to be significantly reduced wh~n the sowin~ date was delayed . Irrigation treatments had no significant influence upon the lint percentage 7. There was no sign~ficant difference between the averages of seed cotton yield/feddan when the plants were grown· in March or April On the co~trary. a ~arked reduction Ln yield was registered when the plants were grown late in May. The same pattern was true regarding lint yield per feddan. The absence of anyone irrigation resulted in a significant decrease in both seed cotton yield and lint yield per feddan . However. when two irrigations were absent this tendency of dec~ease was more pron6unced • In fact. the lowest seed cotton yield and lint y~eld per feddan were obtained when three irTigations were not given . 8. There was no significant differences between the averages of seed yield per feddan when the plants were grown in March or April. However. the planting date did not appear to have any significant effect on oil percentage • whereas the oil yield per feddan significantly increased when the plants were grown in April as compared with those grown in March. On the other hand when the planting date was delayed till Maya quite size.able reduction in seed yield and oil yield per feddan was found . Irrigation treatments, had no evident. effect on oil percentage. When an irrigation was not given, a significant decrease in seed yield per feddan was found. However. the magnitude of reduction in seed yield was dependent on the time at which that irrigation was not given. It is obvious that the tendency of decrease in seed yield was clearer as the number of absent irrigations increased . In regard to the effect of irrigation treatments on oil yield per feddan, it was found that when the first irrigation was not given, no significant difference 1n oil yield was observed, while the absence of an irrigation either before flowering stage or fruiting stage caused a significant reduction in oil yield. ltis clear, however that the oil yield tended to decrease progressively as the number o~ absent irrigations increased. This. was indicated by the lowest oil yield obtai~ed when three irrigations were not given . (D) Fiber and Yarn Properties : 1. Fiber 2.5% S.L., 50% S.L. and length uniformity ratio, were not found to be significantly affected by planting date. Irrigation treatments did not reveal any dlstincteffect upon fiber length characteristics. 2. Fiber tensile properties i.e. tenacity, elongation , toughness and stiffness did not .appear tQ be significantly influenced by planting date. Also irrigation treatments proved to have an insignificant effect on fiber tensile properties . 3. Planting date exhibited insignificant effects on both percent reflectance ( Rd % ) and degree of yellowness ( + b ) in 1981 and 1982 seasons.. Howev~r, in 1983 season, it was found that percent reflectance tended to decrea~e significantly when planting date was ,.’ := ~ -. ”-’; - 86 - delayed. The reversed pattern was true regarding . -’;”’, the degree of yellowness ( +b ). ~here i~ was observed that ( +b ) values significantly increased with delaying planting date in 1982 season • Irrigation treatments had no significant effect on cotton colour measurements . 4. There waB a general tendency of decrease in Micronaire reading in the two seasons 1981 and 1982 as planting date was delayed. However, planting date showed an insignificant effect on Micronaire’reading in the third season 1983. Irrigation treatments did not show any significant influence upon Micronaire read ing . 5. Lint cotton grade was not found to be significantly affected by planting date during two seasons .However in 1982’ season, cotton grade declined gradually when the sowing date was delayed . Irrigation treatments did not exhibit any significant effect on lint cotton grade . 6. Planting date had no significant effect on yarn strength expressed in terms of lea product in two seasons. However, during 1982 season, yarn strength ..... ’ tended to diminish progressively when the planting date was delayed. Irrig~tion treatments. did·not show ”,:’. any significant effect on yarn strength except in 1982 season. 7. Yarn appearance grade was not significantly affected by planting date during 1981 and 1983 seasons . The reversed pattern was true in 1982 season. but there was no definite trend related to planting date . In fact the highest yarn appearance grade was obtained when the plants were grown in April during that season . ”~’,. Irrigation treatments did not show any significant effect on yarn appearance grade . |