Yield Assessment and Water Use Efficiency in Economical Tea Production Affected by Nitrogen Fertilizer and Supplemental Irrigation Treatments

Sustainable economical production of tea depends on the proper use of water and fertilizer. For this purpose, the role of supplemental irrigation and nitrogen fertilizer on economical production of tea plantations was studied by assessment of yield, production function, water use efficiency, and benefit/cost ratio, and final return in a field experiment at Feshalam Tea Research Station in Fouman, Guilan, during 2008-10. The experiment was conducted by line-source technique of irrigation and the strip plot experiment with randomized complete block design with four replications. Six levels of zero, 100, 200, 300, 400, and 500 kg N ha^-1 were mixed with the soil (source urea) in the main plots and five irrigation levels consisting of full irrigation (I₄), deficit irrigation (I₁, I₂, I₃) and no-irrigation (I₀), were applied as sub-plots. The full irrigation (342 mm) by sprinkler method and application of 320 kg N ha^-1 in mature tea bushes produced 3928 kg yield (made tea) ha^-1 and water use efficiency of 7.2 kg ha^-1 (made tea) for each mm of water used. The highest yield in rain-fed condition (1403 kg ha^-1) and water use efficiency (6.1 kg ha^-1 for each mm of rain water) were obtained with application of 200 kg N ha^-1. The mean benefit/cost ratio for full irrigation and no irrigation were 1.75 and 1.17, respectively. According to this, although costs increased in full irrigation, but profit increased due to higher production and better quality of green leaf (first grade), compensating the costs.