Nitrogen management in boro rice using chlorophyll meter (SPAD) under sub-tropical condition

Abstract

Nitrogen deficiency in rice has so far received limited attention in Bangladesh. Balanced fertilization is a pre-requisite for better rice production and it is necessary to determine optimum combination of fertilizer dose and varieties. The field experiment was carried out during the period from November 2020 to May 2021 at the Agronomy Field Laboratory, Bangladesh Agricultural University (BAU), Mymensingh to study the SPAD value and yield performance of boro rice varieties at different nitrogen levels. The experiment comprised of four boro rice varieties viz., BRRI dhan28, BRRI dhan58, BRRI dhan74, BRRI dhan81 and four level of nitrogenous fertilizers viz. 50 kg N ha-1, 100 kg N ha-1, 150 kg N ha-1 and 200kg N ha-1. The experiment was laid out in a randomized complete block design with three replications. SPAD value ranged from 34.01 to 42.12 for variety and 37.81 to 42.15 for nitrogen application, while leaf nitrogen ranged from 2.98 to 3.67 % for variety and 2.94 to 3.48%. The yield contributing parameter varied significantly with variety and nitrogen rate. The highest grain yield (6.13 t ha-1) was found in BRRI dhan58 and the lowest (3.89 t ha-1) was observed in BRRI dhan28. In terms of fertilizer management, the highest grain yield (5.35 t ha-1) was obtained due to the application of 150 kg N ha-1 and the lowest grain yield (4.72 t ha-1) was recorded from50 kg N ha-1. The interactive effect of variety and fertilizer application exerted that the yield of BRRI dhan58 with 150 kg N ha-1 was the highest (6.59 tha-1) and the lowest performance (3.42 tha-1) in grain yield was found in BRRI dhan28 with 50 kg N ha-1. Thus, the variety BRRI dhan58 with 150 kg N ha-1 was superior for attaining the highest yield.