SHUKLA AK, SINGH VK, DWIVEDI BS, SHARMA SK, SINGH Y. Nitrogen use efficiencies using leaf colour chart in rice (Oryza sativa)-wheat (Triticum aestivum) cropping system. Indian J Agri Sci. 2011;76(11). Accessed October 27, 2025. https://epubs.icar.org.in/index.php/IJAgS/article/view/3259