الفهرس 
INTRODUCTION
Effect of planting datesOnly 14 pages are availabe for public view
 |  | from | 116 |  |  |
| | | from | 116 | | |
Abstract
The present research was concerned with studying the effect of some cultural practices and heat units on physiological response of cotton in upper Egypt. The variety studied was Giza 90 (Gossypium barbadense L.) which is one of the long staple cultivars and developed from the cross between Giza 83 x Dandara. The variables studied were planting date, hill spacing and different rates of NPK. This work was carried out in the experimental farm of Shandaweel, of A.R.C., Ministry of Agriculture through 2010 and 2011 seasons. The planting dates were on the first of March, 1st April and 1st May. Each planting date contained two variables, hill spacing and NPK fertilizer rates. The variables were designed in a split plot design in which hill spacing was in the main plots, whereas the fertilizers rates were in the sub-plots. Hill spacings were 15, 20 and 25 cm between hills. The NPK rates were 75%, 100% and 125% of the recommended doses which were 60, 22.5 and 24.0 kg/fed. of N, P, K respectively. The combined analysis was carried out between planting through each season.
Here too, the temperature-degrees above zero point of growth scored by cotton plants for a period of 45 days from planting were calculated for each planting.
The results obtained from this study could be summarized as follows:-
A- Vegetative characters:
A.1- Plant height at harvest in cm. plant height tended to be increased as planting date was delayed. Hill spacing affected significantly plant height at harvest in favour of narrow spacing. An significant increase in plant height was detected as the rates of NPK were increased. The interactions of planting date x hill spacing, planting date x fertilization and the second order of planting date x hill spacing x fertilization were significant in the two seasons.
A.2- Number of fruiting branches/plant was decreased as planting date was delayed. Here too, this trait was increased as hill spacing was increased and rates of NPK were increased.
A.3- The total soluble carbohydrates in the stem of cotton seedling were reacted significantly to planting date in favour of early sowing. This trend could be ascribed to the lower scored temperature-degrees above zero point of growth during seedling stage of early sown plants. This trait was increased as hill spacing and NPK rates were increased.
B- Earliness traits:
B.1&2- Days to the first flower appearance as well as first boll opening were decreased as planting date was delayed. Here too, the days to first flower and first boll tended to be increased as hill spacing was increased. Little increase in number of days to both first flower appearance and first open boll as NPK rates were increased.
B.3- Location of first fruiting node tended to be lowered for early sown plants as compared by late ones. Wide hill spacing as well as fertilized cotton by the highest rates of NPK, i.e. equal to 125% of the recommended doses lowered the location of first fruiting node.
C – Lint and seed characters:
C.1- Lint percentage was reacted significantly to planting date in favour of late planting date. As to hill spacing, lint percentage tended to be decreased as h ill spacing was increased. Here too, the lowest rates of NPK gave the highest lint percentage.
C.2- Seed index was reacted significantly to planting date. Early planting favoured seed index as compared to late one. Seed index tended to be heavier as hill spacing was increased. Here too, seed index tended to be increased as the rates of NPK were increased.
D- Yield of seed cotton and its components:
D.1- Average number of open bolls/plant was affected significantly by planting date in favour of early plantings. Here too, consistent and significant increases were found as hill spacing as well as NPK rates were increased.
D.2- Boll weight was reacted significantly to planting date in favour of early planting. Here too, boll weight was increased significantly as hill spacing as well as NPK fertilizers were increased.
D.3- Yield of seed cotton/fed. was reacted significantly to planting dates studied in favour of early sowings. The maximum yield of seed cotton was obtained from the wider spacing and higher rates of NPK fertilizers. Here too, the interaction of planting date x fertilization with NPK was significant in the two growing seasons. The interaction revealed that early sown plants had a great response to NPK fertilizers as compared to late ones. Here too, the second order interaction of planting date x hill spacing x NPK fertilizers turned to significant. It revealed that the maximum yields of seed cotton/fed. were obtained from planting on the first of March, sowing at 25 cm between hills and fertilized with 125% of the recommended doses of N, P, K, i.e., 75, 28 and 30 kg/fed. of nitrogen, phosphorus and potassium nutrients, respectively.
E- Fiber properties:
E.1- Micronaire reading tended to be increased as cotton sown early. That means the increase in fiber maturity. Here too, micronaire reading tended to be increased as hill spacing as well as NPK rates were increased.
E.2- Fiber strength was reacted significantly to planting date in favour of early sowing. Fiber strength tended to be increased as hill spacing was increased. The NPK rates failed to show significant effect on fiber strength. However, little increase in this respect was noted as NPK rates were increased.
E.3- Fiber length (U.H.M) was affected by planting date in favour of early planting. The fiber length tended to be increased as hill spacing and NPK rates were increased.
F- The relations between total soluble carbohydrates in stem seedling and the vegetative, yield and yield components were strong and significant. The correlation values (r) ranged from 0.782 to 0.946 in 2010 season. The corresponding range in 2011 was from 0.669 to 0.966.