Abstract

The high and inefficient use of Nitrogen (N) fertilizer continues to be a problem in rice (Oryza sativaL.) cultivation sites in Northern Iran. The leaf color chart (LCC) based N management can be used to optimize N application with crop demand or to improve existing fixed split N recommendations. We conducted a field experiment in 2008 at Amol region of Northern Iran, to determine the LCC critical value for N application in different rice genotypes. Treatments included 12 LCC based N management contained the combination of three critical levels of LCC (3, 4 and 5) with four levels of N application (20, 25, 30 and 35 kg ha^-1) for two rice genotypes which consist of Tarom-Hashemi and GRH-1 were compared with the zero N control and a recommended fixed time N splitting. Nitrogen was applied in form of urea as per treatment schedule and the LCCs assessed at 10 days intervals from 12 days after transplanting. Result showed a considerable opportunity to increase farmers yield and N use efficiency (NUE) levels through improved N management with the LCC. The critical LCC value of 4 with 25 kg N ha^-1 for Tarom-Hashemi and critical LCC value of 4 with 35 kg N ha^-1 for GRH-1 were found to be suitable for guiding N application to achieve the highest grain yield for the Amol region of Northern Iran.

Key words: Oryza sativa L., N management, LCC, N use efficiency.