Author(s): P. SINGHA AND B. MITRA

Abstract: A field experiment was conducted under sub-Himalayan plains of West Bengal during rabi, 2017-18 and 2018-19 to assess the crop response to normalized difference vegetation index (NDVI) sensor in optimizing the dose of fertilizer N in wheat. The experiment was laid out in a Randomised Block Design (RBD) with ten N scheduling treatments[T1-Absolute Control i.e. no NPK, T2-75 kg N basal +37.5 kg N ha-1 at crown root initiation (CRI ) and tillering (T), T3-60 kg N basal +30 kg N ha-1 at CRI and T, T4-75 kg N basal + 75 kg N ha-1 at CRI, T5-60 kg N basal + 60 kg N ha-1 at CRI, T6-30 kg basal+30 kg N ha-1 at CRI +Green Seeker (GS) at 40-45and 60-65 DAS, T7-30 kg basal+60 kg N ha-1 at CRI +GS at 40-45 and 60-65 DAS, T8-60 kg basal+60 kg N ha-1 at CRI + GS at 40-45 and 60-65 DAS, T9-60 kg basal+30 kg N ha-1 at CRI +GS at 40-45 and 60-65 DAS and T10- Rich N with 112.5 kg basal+112.5 N ha-1 at CRI ], each replicated thrice. It was revealed that all the major growth parameters, viz., plant height, tiller number, leaf area index (LAI) as well as total biomass production of wheat varied significantly with respect to various N scheduling treatments, maximum being under N-rich plots where 225 kg ha-1 of N was applied in two equal splits. Excess N application under N-rich plot altered the source-sink relationships for which we got lesser number of filled grains spike-1 in N-rich plots despite production of higher tiller vis-à-vis spike number m-2. In both the years, the maximum grain yield (4.957 and 5.068 t ha-1 during 2017-18 and 2018-19, respectively) was achieved with the treatment in which 60 kg N was applied as basal+60 kg N at CRI followed by GS based N application twice at 40-45 and 60-65 days after sowing (DAS). This treatment resulted in 5-7.4% increase in yields over the recommended doses of N application with only 2-5 kg ha-1 of additional N. However, with increasing rates of nitrogen application; there was gradual decline in partial factor productivity of N (PFPN) as well as agronomic nitrogen use efficiency (NUE). In N-rich plots where excess N (225 kg ha-1) was applied, it resulted in very poor values of PFPN and agronomic NUE as compared to NDVI based N application. N application @ 120 kg ha-1 recorded maximum PFPN (34.15-35.80 kg grain kg-1 of N application) and agronomic NUE whether it was applied in 2 or 3 splits. The study revealed that the application of N based on NDVI sensor was more efficient as indicated by increased grain yield with higher values of PFPN and agronomic NUE as compared to recommended doses.

DOI: 10.22271/09746315.2020.v16.i3.1364

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