This study was conducted during 2000 and 2001 seasons on Thompson
Seedless grapevine grown in clay loam soil to examine the effect of spraying Dorcy
(49% hydrogen cyanamide) at 2%,4% or 5% on two dates (10^th of Jan. and t" of
Feb). These treatments were carried out to study the effect of Dorcy on bud behavior,
yield and fruit quality. Results showed that spraying Dorcy on the io" of Jan gave earliness in the
beginning of bud burst by about 21 and 24 days compared with the control during the
two seasons. Bud burst percentage reached about 50% as a result of Dorcy spraying
on 10th of Jan by about 1824 days than the control and by about 6,7 days than the
Dorcy treatments on the 1 sl of Feb. during the two seasons of study respectively. All
applications hastened bud burst, fertility and leaf area. Number of bunches per vine,
bunch weight and length were increased and lead to increase yield per vine by about
34.2 and 33.7% over the control during the two seasons of study respectively when
vines were sprayed with Dorcy at 5% on 1^st of Feb. Fruit quality (berry weight,size,T.S.S,T.S.S acid ratio and total sugar) and total
carbohydrates were increased by all treatments while the acidity was decreased.