الفهرس 
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Abstract
Objectives:
The main objective of this study was to find out the effect of four mineral NPK fertilizers rates alone or combined with humic acid. The second objective is to test the effect of four humic acid treatments.The third objective is to examine whether the humic acid can reduce the application rate of inorganic NPK fertilizers without risking yield loss of Egyptian cotton Giza 86 under the environmental conditions of El-Gharbia Governorate.
Methods & Results:
Two field experiments were carried out at El-Gemmeiza Agric. Res. Station, El–Gharbia Governorate during two seasons (2010 and 2011) to study the effect of four NPK fertilizers rates i.e. 100% recommended rate, 75%, 50% and 25% recommended rates, and four humic acid treatments i.e. without humic acid (control), seed soaking with 5 cm3/L humic acid for 18 hours before sowing, soil application with humic acid at a rate of 50 cm3/L twice (at sowing and after thinning), foliar spraying with humic acid at a rate of 5 cm3/L three times as well as their interaction on cotton plant growth, seed cotton yield and its components and fiber quality of Giza 86 cotton cultivar. Application of 100% recommended NPK rate significantly increased growth, boll weight, seed index, number of open bolls/plant, seed cotton yield/plant as well as /fed. Application of humic acid as foliar spraying at a rate of 5 cm3/L three times significantly increased growth, boll weight, seed index, number of open bolls/plant, seed cotton yield/plant as well as /fed. NPK rates, humic acid treatments and their interaction gave insignificant effect on most fiber properties under study.
Conclusion:
It is advisible to apply humic acid as foliar spraying in combination with 25% NPK to obtain the best results in growth and consequently high yield for cotton variety Giza 86 at location has similar condition to that of Gemmeiza.