Effect of Irrigation Methods and Nitrogen Application Rates on Yield and Yield Components of Onion (Allium Cepa L.) Grown under Russian Environmental Conditions

Field experiments were conducted to study the influence of three irrigation methods and nitrogen fertilization rates on yield and yield components of onion (Allium Cepa L., cv. Creole Red) grown under Russian environmental conditions during the growing seasons of 2012 and 2013. The three applied irrigation methods were the rain fed (RF), surface drip irrigation (SDI) and subsurface drip irrigation (SSDI) in which placement depths of drip laterals were 10 cm. Nitrogen fertilizer , as ammonium sulfate, was applied at three rates of 0 , 90 and 180 kg N.ha^-1. The experiment was implemented in a randomized complete block design with three replicates. Plant height, number of leaves/plant, Bulb dry matter, bulb diameter and bulb weight of onion (yield components) were measured and consequently crop yield and water use efficiency (WUE) were determined for all treatments. The obtained results indicated that surface drip irrigation or subsurface drip irrigation with 90 kg N/ha resulted in higher yield and yield components. The highest values of plant height, number of leaves/plant, and neck diameter were obtained by SDI + 90 kg N/ha treatment while the lowest values belonged to RF treatment with zero (0.0) rate of Nitrogen. The fresh crop yield was the highest (38.0 t ha^-1) with SDI + 90 kg N/ha treatment, while RF treatment with 0.0 nitrogen produced the lowest value of crop yields (20.5 t. ha^-1). The highest WUE (0.89 t. ha^-1 cm^-1) was obtained by the SDI + 90 kg N.ha^-1 treatment while the lowest value of WUE was obtained through RF treatment with 0.0 nitrogen. It can be concluded that SDI + 90 kg N.ha^-1 treatment was found to be the most effective irrigation method and nitrogen application rate in improving WUE and increasing the yield and yield components of onion grown under Russian environmental conditions.