Evaluation of different amount of potassium sulphat on yield and yield components of Hulless Barley (Hordeum vulgare L.) under different irrigation regims

Introduction Drought stress is one of the most important abiotic stress that leads to decreasing yield of crops, particular cereals, not only in Iran but also around the world. Accessing to sufficient nutrients like potassium is one of the ways that increase crop resistance. Potassium is an essential element to growing plants. This element is a multitasking nutrient in plants that use in activation of enzymes, osmotic control, carbohydrate production and partitioning and anion cation balance. So because of Hulless Barley importance for human, animals and birds feed,  drought expansion in Iran and around the world, importance of potassium element to decrease drought stress effects, metabolic process improvement and plant photosynthesis, an experiment to find out the effects of drought stress and potassium on yield and yield components of Hulless Barley conducted.   Materials and methods To find out effects of different irrigation regimes and different amounts of potassium on yield and yield components of Hulless Barley, a split plot experiment based on randomized complete block design with three replicates was conducted at the Research Farm of Islamic Azad University, Meybod Branch in 2012. Each block was consist of 3 main plots and 4 sub plots in each main plot. Main plot was consist of irrigation cycles: 7 days irrigation (control), 14 days irrigation (moderate stress) and 21 days irrigation (extreme stress). Sub plot was consist of 4 levels nutrient elements: 0, 100, 200 and 300 kg.ha-1 potassium sulphate. Different potassium levels were applied before sowing. At the end of growing season, grain yield, straw yield, biological yield measured. Also Fertile tiller number, grain number per spike and 1000 grain weight of Hulless Barley measured as yield components.   Results and discussion Results showed that most yeild(3147.5 kg.h-1) and yield components achieved in 7 days irrigation cycle. Yield components decreased 12 and 43 percentage by increasing irrigation cycle to 14 and 21 days. Seed yield was 2761 and 1792 kg.h-1 at 14 and 21 irrigation cycle. Also potassium sulfate application improved agricultural characteristics and decreased negative effects of drought stress. Result showed that increase potassium sulphate application from 0 upto 300 kg.h-1 had significant effect on seed yield, but there was no significant difference between 200 and 300 kg.h-1 application. Maximum harvest index (36.1%) achieved at 200 kg.h-1 potassium sulphate applications. Minimum harvest index (32%) achieved at 0 kg.h-1 potassium sulphate applications. Maximum fertile tillers (1.2) was in 7 days irrigation cycle + 200 kg.h-1 potassium sulphate applications and minimum fertile tiller was in 21 days irrigation cycle + 200 kg.h-1 potassium sulphate applications. In 7 days irrigation cycle and 14 days irrigation cycle, 100 kg.h-1 potassium sulphate applications caused to increasing fertile tiller number. More potassium sulphate application had no significant effect on fertile tiller number. Also results showed that increase potassium sulphate application from 0 upto 100 kg.h-1 lead to increasing grain number per spike from 26.6 to 31. Among different amounts of potassium suphate application, no potassium sulphate application treatment had the lowest (30.9 gr) 1000 grain weight and 300 kg.h-1 potassium sulphate applications had highest (34 gr) 1000 grain weight.   Conclusion Results showed in no water limitation condition recommended 7 days irrigation cycle for maximum yield. Results showed Hulless Barley can tolerate moderate water stress, so in water limitation condition 14 days irrigation cycle application can suggest for achievement acceptable biological yield of Hulless Barley. According to this experiment results, potassium nutrition can improve yield characteristics in water limitation. There was no significant difference between 200 or 300 kg.h-1 potassium sulphate application, so for reduce negative enviromental effects, 200 kg.h-1 potassium sulphate application can suggest for achievement acceptable yield of Hulless Barley.