Two field experiments were carried out at Sakha Agriculture Research
Station Farm during two successive summer seasons of 2002 and 2003 using
soybean (Glycine max L.) variety Giza 111. Split plot design was used. The main
plots were assigned to three nitrogen application times: 1- applicating of nitrogen
fertilizer with the first irrigation (T,), 2- applicating of nitrogen fertilizer with the second
irrigation (T2), 3- applicating of nitrogen fertilizer with the third irrigation (T3). The sub
plots were allotted for four nitrogen levels i.e., 0 (No), 20 (N20), 40 (N40) and 60 (Nso)
kg N fed:' to investigate the effect of nitrogen apptication times and levels on
soybean seed, straw, protein and oil y:ields kg fed:' as well as residual available N
and P in the soil. The plot area was 15 m². The obtained results show that nitrogen application times high significantly
affected seed, straw, oil and protein yields. T, treatment gave the highest straw yield
in both seasons. While T2 treatment gave the highest seed yield (996 and 965 kg fed-
\ oil yield (231 and 287 kg fed-') and protein yield (356 and 346 kg fed") in the first
and second s. sons, respectively. Nitrogen levels high significantly affected seed,
straw, oil and protein yields. The highest values were obtained with Nee treatment. Applicating of nitrogen fertilizer with the second irrigation T2 increased
nitrogen use effici.,..,t;y. On the other hand, increasing nitrogen fertilizer levelled to
clear decree _ . in nitrogen use efficiency values.
T3 treatment gave the highest nodules number, nodules dry weight and the residual
N, P in the soil. Neo treatment had the highest nodules number and nodules dry
weight.