www.scholarsresearchlibrary.com t Available online a Scholars Research Library Annals of Biological Research, 2012, 3 (6):2575-2578 (http://scholarsresearchlibrary.com/archive.html) ISSN 0976-1233 CODEN (USA): ABRNBW 2575 Scholars Research Library Effect of Potassium Sulfate and water deficit on quantitative and qualitative yield of Rapeseed (Brassica napus L.) Hamidreza Mobasser and Mohsen Sarhadi* Department of Agriculture, Zahedan Branch, Islamic Azad University, Zahedan, Iran ______________________________________________________________________________ ABSTRACT The effects of potassium sulfate application on the quantitative and qualitative yield under water deficiency on Brassica napus Var RGS003 were evaluated in the Research Field of Collage of Agriculture, Zabol University in 2010-2011, on the basis of a split plot with basic design of Completely Randomized Block in three replicates. In this experiment, there were 3 type of irrigation, complete irrigation, halted irrigation at pollination stage, and from start of grain filling as main plot and potassium sulfate treatment included: 0, 50, 100 and 150 Kg/ha which is applied at sowing time as subplot. The results show that the irrigation stoppage had significant effect on grain yield, oil percent, oil yield, and proline content at statistically level (P>0.01). The most of all of these characteristics obtained from complete irrigation. For potassium treatment the most of grain yield, oil yield, and proline obtained from 150 Kg/ha. The final results show that 50-100 Kg/ha potassium sulfate and usually irrigation increase the yield of Brassica napus in Sistan region. Keywords: Irrigation stoppage, Rapeseed (Brassica napus), Potassium sulfate, Yield, Oil percent, Proline. ______________________________________________________________________________ INTRODUCTION Oilseed rape (Brassica napus L.) is an important oil producing species extensively cultivated in Europe, China, North America and Iran. Experiments have shown increases in wheat yields of up to 10% after rapeseed. High seed yield (over two tones per hectare) and high oil content (approximately 40%), in addition to low water needs in dry regions of Iran, have made it one of the most important crop plants that provide the oil needs of the country (Sheidai et al., 2001). The crop can be raised well both under rainfed and irrigated conditions. Being more responsive to fertilizers, it gives better returns under irrigated conditions. About one third of the world lands are classified as arid and semi-arid region and aridity is the most common environmental stress and approximately includes 25% of the world land. Thus, irrigation plays a vital role in growth and yield of this crop in these regions. Sultana et al. (2009) reported that application of three irrigations recorded significant increase in yield of rapeseed. Sharma and Kumar (1992) reported that irrigation not only increased the growth but also enhanced the efficiency of applied nutrients. some evidences have indicated that stress during vegetative phase, flowering or seed filling period causes considerable decrease in yield and oil content of sunflower (Razi, H. and M.T. Asad, 1998). Smis et al. (1993) observed that canola yield in Montana increased with higher availability of water, but had a lower mean oil content. Under dry land conditions, Henry and Macdonald (1978) reported that severe drought decreased oil and increased protein content of rape seed. Thompson (1978) observed little effect of water stress on seed protein content in soybean. Whereas Hobbs and Muendle (1983) reported that drought stress increased protein content. Potassium plays a vital role in: photosynthesis, translocation of photosynthates, protein synthesis, control of ionic balance, regulation of plant stomata and water use, activation of plant enzymes and, many other processes (Reddya