Shafie Modarres Motlagh - Student of Department of Agronomy and Plant Breeding, Science and Research Branch, Islamic Azad University, Tehran, Iran
Alireza Pirzad - Assistant Professor, Department of Agronomy and Plant Breeding, Faculty of Agriculture, Urmia University, Urmia, Iran
Babak Delkhosh - Assistant Professor of Agronomy and Plant Breeding, Science and Research Branch, Islamic Azad University, Tehran, Iran

Results of evaluation 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 yield of 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 interaction effect between irrigation disruptions and phosphorus on yield components like percentage of infertile pods, number of incomplete pods, number of complete pods. Means comparisons indicated that the maximum number of complete pods (17.38) was observed in 150 g/ha of biological phosphorus usage at normal irrigation and The lowest number of complete pods (5.49) belonged to no phosphorus application in irrigation interrupted at the beginning of flowering stage. The maximum number of incomplete pods (0.99) belonged to irrigation disruption at the end of flowering stage with no phosphorus and The minimum number of incomplete pods (0.73) was observed in normal irrigation (without disruption). The highest percent of infertile pods (55.29%) was obtained from no phosphorus application and at the beginning of flowering. The minimum percent of infertile pods (20.67%) belonged to 150 g/ha biological phosphorus application at normal irrigation.

Brassica napus, irrigation disruption, biological phosphorus, yield components