The present investigation was carried out in the Exper
imental Farm, Faculty of Agriculture at Noshtohor, Zagazig
University during 1990 and 1991 seasons to study the
response of cotton to N, P levels and time of nitrogen
application as well as their interaction. The treatments
were designed split plot with four replications. The results
could be summarized as follows: Seed cotton yield per fed—
dan, yield components and fiber properties were not signifi
cantly affected by phosphours levels in combined analysis.
Plant height and number of unopened boils/plant were
significantly increased by increasing N level up to 90 kg
per f eddari. Number of plants per feddan at harvest and lint
percentage were decreased by increasing N levels.
Applying 30 kg N/fed. gave the highest seed cotton yield
per feddan, lint yield/feddan as well as fiber 1ength. Seed
index was significantly increased by increasing N levels in
both seasons, whereas number of sympodia per plant, number
of open bolls / plant, boll weight, seed cotton yield /
plant and fiber properties were not significantly affected
by N levels.
The best time of N fertilizer application was obtained
by applying 1/2 N after thinning + 1/2 N dose before the
second irrigation. On the other hand, yield components and
fiber properties were not significantly affected by applica
tion time.
The interaction between phosphorus and nitrogen levels
affected significantly number of open boils / plant, boll
weight, seed cotton yield / fed. and lint yield / feddan.
Seed cotton yield / fed. and lint yield / fed were signifi
cantly affected by the interaction between N levels and
* This study is a part of the project NARP ،!oshtohor No, 247
(Econ. Agric., and Ext. Dept. Fac Agric. Moshtohor).