Performance of site-specific nitrogen management for irrigated transplanted rice in northwestern India

Abstract

Leaf colour chart (LCC) guides fertilizer nitrogen (N) application to rice as per requirement of the crop on the basis of a critical leaf colour. We evaluated need-based N management in on-farm experiments at 350 locations in the Indian Punjab during 2002 – 2005. Following LCC-based N management, from 9.4 – 54.2 kg N ha⁻¹, with an average of about 25% less fertilizer N was used, without any reduction in yield as compared to the practice of farmers of applying blanket N at fixed time intervals. Application of fertilizer N when colour of the first fully expanded leaf was less than LCC shade 4, increased nitrogen use efficiency from 48 – 65 kg grain kg N⁻¹. Nitrogen requirement of rice was site-specific both in terms of time and the amount of fertilizer N applied. In 36% of the experiments, a dose of fertilizer N was applied 55 days after transplanting (DAT) of rice. Also there were cases where only one top dressing of N was required. The study reveals that practice of applying N at fixed growth stages of rice may not be adequate and LCC-based N management can result in efficient utilisation of applied N by rice.

Keywords:

• Leaf colour chart
• fertilizer N management
• partial factor productivity of nitrogen
• rice