Determination of Nitrogen Requirement of Rice (Oryza sativa L. cv Guilaneh) Using Nitrogen Nutrition Index and Chlorophyll Meter

In order to determine the nitrogen requirement of rice (cv. Guilaneh) using the nitrogen nutrition index and chlorophyll meter, an experiment was conducted as a randomized complete block design with three replications in the research field of the Faculty of Agricultural Sciences, University of Guilan, Rasht, Iran in 2016. Experimental treatments consisted of six nitrogen fertilizer levels (0, 60, 120, 180, 240, and 300 kg N. ha-1; Urea source). Evaluation of the relationship between nitrogen nutrition index and chlorophyll-meter readings at three stages of plant growth (maximum tillering, booting, and heading) to predict grain yield in response to nitrogen fertilizer showed that the equation of the critical nitrogen concentration in Guilaneh was Nc = 3.99W -0.36. The correlation between chlorophyll-meter readings and nitrogen nutrition index was positive and significant at each plant growth stage. The results showed that the mature lower leaves were more sensitive than the younger higher leaves in response to nitrogen fertilizer and were more suitable for detecting plant nitrogen status, especially during the booting and heading stages. The highest correlation was found between the nitrogen nutrition index and chlorophyll-meter (r=0.95*) and relative chlorophyll-meter (the ratio of chlorophyll-meter readings in each treatment to nitrogen saturated treatment) (r=0.96**) in the third leaf and booting stage. The overall results of this experiment showed that the nitrogen nutrition index and chlorophyll meter may consider reliable indicators for evaluating the nitrogen status of rice (cv. Guilaneh) during the growing season.