الفهرس 
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Abstract
The experiments were carried out at the Farm of the Faculty of Agriculture, El Fayoum University, in the summer seasons of 2010 and 2011 in a split plot design with five replicates, to investigate the effects of different sowing times, as indication of different climatic environments i.e. micro-environments on earliness, yield and its components as well as fiber properties in some Egyptian genotypes (varieties). br The obtained results indicated that the studied plant characters were significantly affected by micro-environments. However, its effect was not observed in some earliness measurements i.e. node number of first sympodium, the period between first bud and first flower appearance, the period between first flower appearance and first boll opening, mean maturity date as will as fiber attributes i.e. microniare reading, fiber strength and fiber length, in both seasons of the study. Early sowing (M1) recorded the highest values of the characters. While, delaying sowing to 1st April (M3) significantly decreased the values of the characters. This trend of the previous results was manifested in both studied seasons. br Significant differences among varieties were found in all studied traits in both seasons over the three environments expect the period between first bud initiation and first flower appearance and the period between first flower appearance and first boll opening. Giza 90 gave the highest seed and lint cotton yields. While, Giza 88 gave the highest values of fiber properties. br The results obtained clearly indicated that the treatment combination comprising early time on the first of March (M1) with cotton Giza 90 proved to gave the highest seed and lint cotton yields. While, Giza 88 gave the highest values of fiber properties. br It could be concluded that earliness traits were able to result in a linear regression model for all the five tested genotypes. At least two of these traits were included in the yield per feddan model of the five varieties. Consequently, this way of estimating earliness could be favored over the other methods used regardless of the variety studied.