Abstract

A Field experiment was carried out at the experimental farm of El-kod Agricultural Research Station - Southern Coastal Plain of Abyan - during 2010 and 2011 seasons. The study aimed at determining the influencing of four levels of nitrogen fertilizer (N0, N30, N60 and N90 kg/ha) in the form of urea 46% N. On yield and its components of long-staple cotton cv. (Muallem 2000), the experiment included 4 treatment. The design of each experiment was RCBD ,with four replications, was used. The area of each  plot was 12 m2.
The results could be summarized as follows:
The results indicated that the values ​​of the number of open boll/plant and seed cotton yield/plant were affected significantly by nitrogen fertilizer in both seasons, where the percentage increase were 25.6% and 17.3% for first character and 24.8 and 17.0 for second character in both seasons, respectively, compared to the treatment of the control.
Different yield per hectare of cotton seed significant depending on the different rates of nitrogen fertilization,   achieving the highest yield at the treatment (N60), were 5345.00 and 3311.67 kg / ha for both seasons respectively, where the percentage increase were 31.2% and 19.8% for the two seasons, respectively, compared to the treatment of the control.
Nitrogen fertilizer: no significant effect on weight of one boll and lint percentage in both seasons.
Nitrogen fertilizer reflected significantly linear regression correlation to increase yield per hectare of cotton seed in both seasons, an addition to positive significant correlation with yield per hectare of cotton seed.