In order to study of potassium sulphate and irrigation intervals on some growth and yield characteristics of cowpea (Vigna unguiculata), an experiment was carried out in 2013 in field of Elbaji village of Ahvaz. Experimental design was split plot within randomized complete block with four replications. The factors were irrigation intervals (6, 11 and 16 days) and potassium sulphate (0, 60, 100 and 140 kg/ha-1) in main and subplot, respectively. The effects of irrigation intervals and potassium

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... ulphate were significant on all traits. The interaction effects of potassium sulphate and irrigation intervals, was statistically significant on weight of 1000 seeds and seeds in pod. Among irrigation levels, 6 days irrigation has higher grain (1764.18 kg/ha-1). Irrigation levels of 6 days, have been to 26.81 and 40.93% yield increase compared to 11 and 16 days irrigation. Between potassium sulphate levels, the maximum level (140 kg/ha-1) significantly higher in grain yields for 18.39% and improve growth. Based on the results of this experiment and according to water shortages in most parts of the country, potassium application is recommended for drought effect reduction. INTRODUCTION Vigna unguiculata (Blackeyed peas) is one of the annual legumes with fast growing that its growth period has been reported 90 to 120 days (Doorenbas and Kasam, 1979). Bean plant is so sensitive to water and soil conditions and their qualities and its performance is also hurt from the short periods of water shortage, in a way that the damage resulting from the dryness and water shortage is increased with plant age (Maoor et al., 1969). Irrigation time is one of the important factors in plant water stress and it has an effect on performance. When the water shortage is occurred in flowering and pod packaging stage, the performance is reduced more from other stage (Mckey and Ivans; Maoor et al., 1969; Millar and Gardener, 1972). Proper nutrition under stress conditions can somewhat help the plant enduring various stresses (Abedi et al., 2011). Potassium has a direct and indirect impact on the plant growth. Using potassium directly causes the reduced transpiration, increasing water absorption or creating internal conditions in order to endure the dryness. The indirect effects take place when using potassium has no value in the plant water relations but based on feeding grounds, it causes the growth increasing. Therefore, the amount that is needed for producing each dry material is being reduced (Salaridni, 2005). Studiest show that potassium ion gathering in plants before the stresses likes water shortage, coldness, and salinity is insurance for plant survival (Loid, 1992). (Mahammadi et al., 2014) studied the potassium sulphate fertilizer effect on potassium gathering in flowering stage and black eyed peas function under the water shortage in Ahvaz weather conditions and they reported that in total caring watering period was 70 mlm evaporation and 100 kilogram in a hectare of potassium sulphate fertilizer was the best caring step. Fooladiv et al., (2014) studied the dryness effect with 120 mlm (without stress), 180 (average stress) and 240 (server stress) of evaporation washbasin and potassium fertilizer (0,90,180 kilo in hectare) on qualitative features of (Vigna radiata) in Dezful Agricultural Research Center and reported that dryness and potassium fertilizer had a meaningful effect on the study and using 180 kilo potassium fertilizer was yielded. They also stated that total dry weight, pod numbers and seed function had a logical difference between two numbers.