Effects of cycocel and nitrogen on some physiological traits and grain yield of rice (Oryza sativa L.)

In order to study the effects of nitrogen fertilizer and growth regulator of cycocel on nitrogen use efficiency, some physiological traits and grain yield of rice (Oryza sativa L.), a factorial experiment was conducted based on randomized complete block design with three replications at the farm of Someasaraye from Gilan Provence during 2014-15. Treatments were included nitrogen rates in four levels (without nitrogen application as control (N0) and application 100 (N1), 150 (N2) and 200 (N3) kg N ha-1 as urea) and four cycocel levels (without cycocel as control (C0), application of 0.8 (C1), 1.6 (C2), 2.4 (C3) L ha-1). The results showed that foliar application of 2.4 L ha-1  cycocel and 200 kg N ha-1 increased grain filling rate, grain filling period, effective grain filling period, the number of grains per ear and 1000 grains weight. The highest dry matter remobilization from shoots and stem (114.6 and 57.91 g.m-2  respectively) and the highest dry matter from shoots and stem reserves contribution to grain yield (47.91% and 27.04%, respectively) were obtained  without  nitrogen application and foliar application of 2.4 L ha-1 cycocel. The highest grain yield was obtained in application of 200 kg N ha-1 and the lowest it belongs to no nitrogen application. The highest nitrogen use efficiency was obtained in application of 100 kg N ha-1 and the lowest it belongs to 200 kg N ha-1. The highest nitrogen use efficiency was obtained in application of 2.4 L ha-1 cycocel and the lowest it belongs to no cycocel application. Foliar application of 0.8, 1.6 and 2.4 L ha-1 cycocel increased 12.47%, 21.68% and 32.05% from grain yield respectively in compared with control. It seems that foliar application 2.4 L ha-1 cycocel and application of 200 kg N ha-1 can be as a proper tool for increasing grain yield of rice.