Need-based fertilizer nitrogen management using leaf colour chart in hybrid rice (Oryza sativa)

Abstract

Field experiments were conducted during 2006–08 to study the response of hybrid rice cultivar PHB 71 to fertilizer N and to study the possibility of improving N-use efficiency by affecting fertilizer N as per need of the crop as guided by leaf colour chart (LCC). Treatments included six rates of N application (0, 60, 90, 120,150 and 180 kg/ha) applied in three equal splits at fixed growth stages. The two need-based N management treatments comprised of application of 20 kg N / ha as basal dose and application of 30 kg N /ha whenever greenness first fully opened leaf from the top was less than shade 4 or 5 on the LCC. Hybrid rice PHB 71 showed significant response to application of N up to 120 kg N /ha applied in three equal split doses. Beyond this level fertilizer N-use efficiency was significantly reduced. The LCC shade 4 proved better than LCC shade 5 for guiding real time N management and achieving higher N-use efficiency. Application of 80–110 kg N /ha using threshold LCC shade 4 inclusive of 20 kg N /ha as basal dose produced grain yield of rice which was at par with the application of 120 kg N /ha applied in three equal split doses.