Biswas S.K.,Khair A.,Sarker P.K.
Abstract
This study investigated the level of leaf purple blotch incidence by different levels of irrigation and its
effect on the bulb yield of onion (Allium cepa L.). Four irrigation levels comprised of: irrigation at 10- (I1),
15- (I2), 20- (I3) and 30-day (I4) intervals along with a non-irrigated control (Io) treatment were tested.
A small difference in the score of leaf purple blotch disease in onion was found between the irrigated and
non-irrigated plots. The highest level of disease infection (score: 1.96) was recorded in Io, and the lowest
score (1.45) was found in I1. There was a trend to decrease the disease incidence with increasing number of
irrigations. However, irrigation had insignificant effects on the disease incidence of onion. Irrigation
significantly increased the yield of onion; the highest yields were obtained from treatments I1 and I2
associated with higher percentage of bulbs having size greater than 30 g. The lowest yield was recorded in
non-irrigated treatment, Io. The total water use was 248 mm in treatment I1. The incremental benefit-cost ratio
was the highest (28.36) in treatment I2.
Key words:
onion, bulb yield, yield components, irrigation, water use efficiency, disease infection, incremental benefit-cost ratio