Effect of supplemental irrigation on yield and yield components of flue-cured tobacco

In order to study the effect of supplemental irrigation on yield and yield components of tobacco, an experiment was conducted at Guilan Tobacco Research Station in 2004 and 2005 croping seasons. A randomized complete block design with four treatments and three replications was conducted. Treatments were: no supplemented irrigation (SI0), supplemental irrigation till the end of flower bud forming stage (SI1), supplemental irrigation till the end of flowering stage (SI2) and supplemental irrigation till the end of growth stage or full irrigation (SI3) as control in each cropping season. The required water for each treatment was determined based on water holding capacity and maximum allowable deficiency (MAD). The soil water holding capacity was measured by using Pressure Plate. The time of irrigation was determined by using Tensiometer and soil was irrigated to the field capacity level. Leaves were harvested at six times. At flowering stage; leaf length, leaf width, plant height, number of leaf and leaf area index were recorded and after harvesting of leaves; fresh leaf yield, dried leaf yield, unit price, gross income per unit area, quality traits such as sugar and nicotine percentage were also measured. The combined analysis of variance showed that all of the traits except number of leaves per plant were affected by irrigation and a positive correlation was observed between increasing amount of water and the traits. The effect of year was not significant on the traits except for dried leaf yield as the mean of dried leaf yield decreased in the first year of study, due to the non optimum distribution of precipitation immediately after transplantation. The dried leaf yield increased in the second year of experimental. The mean dried leaf yield of (SI0), (SI1), (SI2) and (SI3) treatments were 2096.80, 2170.00, 1974.00 and 1302.00 kg/ha, respectively. Irrigation until flower bud forming stage had the highest water productivity index based on dried leaf yield and gross income in comparison to other irrigation treatments in this study. Therefore, application of supplemental irrigation and optimum usage of available water resources are essential in tobacco production.