International Research Journal of Applied and Basic Sciences © 2013 Available online at www.irjabs.com ISSN 2251-838X / Vol, 4 (5): 1062-1066 Science Explorer Publications Effect of irrigation disruption and biological phosphorus on nutrient (N,P,K) uptake of canola (Brassica napus L.) Shafie Modarres Motlagh 1 , Alireza Pirzad 2* and Babak Delkhosh 3 1. Student of Department of Agronomy and Plant Breeding, Science and Research Branch, Islamic Azad University, Tehran, Iran. 2. Assistant Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture, Urmia University, Urmia, Iran. 3. Assistant Professor, Department of Agronomy and Plant Breeding, Science and Research Branch, Islamic Azad University, Tehran, Iran. Corresponding Author email: alirezapirzad@yahoo.com ABSTRACT: To evaluate the effect of irrigation (irrigation disruption at beginning of flowering, end of flowering, grain filling and control) and biological phosphorus (0, 50, 100 and 150 g/ha) on the nutrient uptake by Brassica napus L. cv. “Hyola 401”, a split plot experiment was carried out based on randomized complete block design with four replications at the research farm of Shahid Beheshti Agriculture College (latitude 38° 51' N and longitude 41° 44' E and 1313 m above sea level) in 2010. Results of ANOVA showed the significant effect of irrigation disruption on potassium uptake and significant interaction effect between irrigation disruptions and phosphorus on nitrogen and phosphorus uptake. Means comparisons showed that the highest percentage of seed nitrogen (4.52 %) was belonged to irrigation disruption at grain filling stage with 100 g/ha phosphorus and the lowest percent of seed nitrogen (3.3 %) was observed in normal irrigation with 150 g/ha phosphorus. The maximum of percentage of seed phosphorus (1.81 %) was obtained at the beginning of flowering with 150 g/ha phosphorus and the minimum percent of seed phosphorus (1.34 %) at normal irrigation with 150 g/ha biological phosphorus. Keywords: Brassica napus, irrigation disruption, nutrient uptake, phosphorus INTRODUCTION Canola is an important oil crop growing in many part of the world. Canola in Iran is mostly cultivated as a winter annual for oil production and rarely livestock feed. If planted in spring, they can be grown as summer crop but the seed yield would be decreased due to short growing season and lack of enough water at the end of growing season, thus, winter cropping is preferred. Canola cultivars appear to be best adapted to the conditions of Iran, however, some cultivars are less tolerant to environmental conditions (Sharghi et al., 2011). One of the important factors which endanger development of under cultivation and successful production of canola plant is water deficiency, because of limit the growth and production of plant. Some studies in this area indicated that the average annual yield reduction was 17% in the world through the drought which can increase till more than 70% in every year (Edmeades et al., 1994). Water stress had a significant effect on nitrogen and potassium uptake but not on phosphorus uptake (Nahar and Gretzmacher, 2002). Many soil bacteria and fungi have the ability to solubilize phosphate (Pi) minerals and make it available to plants (Oberson et al., 2001; Egamberdiyeva et al., 2003). They are capable of using inorganic and organic forms of phosphorus (Tarafdar and Jungk, 1987; Chen et al., 2002). The application of different levels of phosphorus influenced the nitrogen, phosphorus and potassium uptake significantly (Ranjit et al., 2007). But Islam et al. (2008) reported that levels of phosphorus had a significant effect only on phosphorus uptake and had no effects on N and