Current Agriculture Research Journal Vol. 4(1), 54-61 (2016) Chlorophyll Meter-Based Dynamic Nitrogen Management in Wheat (Triticum aestivum L.) Under Subtropical Environment M NAZMUL HASAN 1 , QAZI ABDUL KHALIQ 1 , M ABDUL BASET MIA 2 , M NASIMUL BARI 1 and M RAFIQUL ISLAM 1 * 1 Department of Agronomy, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh. 2 Department of Crop Botany, Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur-1706, Bangladesh. http://dx.doi.org/10.12944/CARJ.4.1.05 (Received: April 24, 2016; Accepted: May 17, 2016) ABSTRACT Injudicious use of nitrogen fertilizer is very commonly practice in tropical and subtropical regions. SPAD (Soil-Plant Analysis Development) chlorophyll meter-based nitrogen top-dressing may reduce the risk of under or over application. Considering this, the study was conducted to measure the relative advantage of dynamic methods of nitrogen fertilization over conventional method in wheat field. For this, conventional nitrogen (CN) treatments i.e. CN 60 , CN 90 , CN 120 , CN 150 at 60, 90, 120 and 150 kg ha -1 were compared with four chlorophyll meter-based dynamic nitrogen (DN) treatments i.e. DN 80 , DN 90 , DN 120 , DN 100 at 80, 90, 120 and 100 kg ha -1 nitrogen. Irrespective of treatments, SPAD meter readings remained above 45 (threshold value) beyond 50 days after seeding, but plant performance varied depending on the methods and doses used in nitrogen top-dressing. Treatment CN 150 performed better displaying the highest SPAD values, total dry matter production, leaf area index, crop growth rate and net assimilation rate resulting to the highest grain yield (5.10 t/ha) in wheat. The plant performance in DN 120 , DN 100 , DN 90 and CN 120 treatments were statistically similar to that of CN 150 in respect of all most all plant characters studied. Comparing with CN treatments, DN treatments resulted in better plant growth and grain yield at the same level of nitrogen fertilizer. This is because of maintaining need-based fertilizer at early stage of wheat and application of appropriate amount of nitrogen fertilizer in each time in DN treatments compared to CN treatments. The result suggests that chlorophyll meter can be effectively used for real time nitrogen top-dressing to increase productivity of wheat. Keywords: SPAD, Chlorophyll Meter, Nitrogen, Top-dressing, Wheat. INTRODUCTION Wheat (Triticum aestivum L.) is the third most-produced cereal after maize and rice and staple food of millions of people in the world 1 . Fertilizer nitrogen (N) is the most essential plant nutrient required comparatively a larger amount than other elements in wheat. However, judicious use of this nutrient requires its synchronized application with crop requirement 2 . In absence of synchronization, plants grow vigorously that reduces N fertilizer use efficiency 3,4 . The optimized N fertilization can synchronize N demand of wheat and thus N application rates drastically reduce without any yield losses 5 . Rahman et al 6 . suggested to establish an appropriate N management practice to improve N use efficiency in wheat owing to save our soil from being using over or under doses of fertilizer. The SPAD chlorophyll meter potentially offers a useful nondestructive and handheld system of evaluating plant chlorophyll status 7 . It is evident that much of leaf N is involved in enzymes associated with chlorophyll