Int.J.Curr.Microbiol.App.Sci (2017) 6(11): 1030-1036 1030 Original Research Article https://doi.org/10.20546/ijcmas.2017.611.120 Calibrating the Leaf Colour Chart for Nitrogen Management in Maize (Zea mays L.) under Irrigated Condition Shivakumar 1 , M.A. Basavanneppa 2* , B.G. Koppalkar 1 , M.R. Umesh 1 and Ashok Kumar Gaddi 2 1 Department of Agronomy, University of Agricultural Sciences, Raichur, Karnataka, India 2 Agricultural Research Station, Siruguppa- 583 121, Karnataka, India *Corresponding author ABSTRACT Introduction Nutrient management has played a crucial role in achieving self-sufficiency in food grain production. The need for precise and responsive management of N fertilizer in Maize is compelling for both economic and environmental reasons. Static fertilizer recommendations based on average response lead to excessive fertilization in some years and inadequate fertilizers in years with high N losses. The uncertainty in optimum N rate poses risks for profit loses which is exacerbating by the asymmetric profit response of maize to N rates. The associated higher cost of under fertilization relative to over fertilization drives farmers to apply imbalanced rates. This uncertainty can be addressed by providing more accurate location and time specific recommendations that increase accuracy and reduce uncertainty. The farmers generally use leaf colour as a visual and subjective indicator for N fertilizer need (Furuya, 1987). Since farmers generally prefer to keep leaves of the crop dark green, it leads to over application of fertilizers N resulting in low recovery efficiency. Thus, the spectral properties of leaves should be used in a more rational manner to guide need based International Journal of Current Microbiology and Applied Sciences ISSN: 2319-7706 Volume 6 Number 11 (2017) pp. 1030-1036 Journal homepage: http://www.ijcmas.com The field experimentwas conducted at Agricultural Research Station, Siruguppa, University of Agriculture Sciences, Raichur, Karnataka, during kharif 2016 to study the “Calibrating the leaf colour chart for maize (Zea mays L.) nitrogen management under irrigated condition” and to evaluate and establish LCC threshold values for saving fertilizer N and achieve higher grain yield. The experimental site was medium deep black soil. The experiment consists of ten treatments viz., T 1 : N application at LCC threshold ≤ 1, T 2: N application at LCC threshold ≤ 2, T 3: N application at LCC threshold ≤ 3, T 4 : N application at LCC threshold ≤ 4, T 5 : N application at LCC threshold ≤ 4.5, T 6 : N application at LCC threshold ≤ 5, T 7 : N application at LCC threshold ≤ 5.5, T 8 : N application at LCC threshold ≤ 6, T 9 : RDN (190 kg ha -1 ) and T 10 : Absolute control. These treatments were replicated thrice in Randomized Complete Block Design (RCBD). Application of nitrogen fertilizer based on LCC threshold ≤ 5 recorded higher grain yield (8339 kg ha -1 ), stover yield (10424 kg ha -1 ) and harvest index (44.4%). Net returns (Rs. 80650) and B:C ratio (2.88) were recorded in N application at LCC threshold ≤ 5. Keywords Grain yield, Nitrogen management, Leaf colour chart and economics. Accepted: 10 September 2017 Available Online: 10 November 2017 Article Info