An insight into productivity, profitability, and sustainable energy use in maize under precision nitrogen management using a smartphone app
• Pusa N Doctor app enhances real-time N prescription in maize, ensuring yield parity. • N50PK + App shows optimal yields, high N uptake, and reduced energy consumption. • N50PK + App boosts N and energy use efficiency while minimizing GHG emissions. • N50PK + App outperforms RDF with higher N recovery and lower nitrate leaching. • Balanced N application with Pusa N Doctor reduces CO2 and N2O emissions effectively. During previous implementation of dark green colour index (DGCI), conventional tools were found inadequate for providing accurate nitrogen (N) recommendations in maize. In contrast, camera-based DGCI methods demonstrated greater effectiveness in predicting the in-season N requirements. To address this incongruity, maize leaf images were captured; resized; white balance corrected; followed by selection of region of interest; normalization; red, green, blue channel extraction; conversion into hue, saturation, brightness spectrum and calculation of DGCI. Simultaneously, NDVI, SPAD, LCC and leaf N% data were collected; and correlated with DGCI; followed by performance analysis; DGCI-based N prescription algorithm development; and its incorporation in “Pusa N Doctor” app developed using Android studio with JNI and Android NDK. The app validation was carried out using basal N dose of 0 kg ha −1 (N 0 PK), 50 kg ha −1 (N 50 PK), & 75 kg ha −1 (N 75 PK) including 2 split applications of N at 35 & 45 days after sowing (DAS) as per Pusa N Doctor & GreenSeeker™ recommendation. The treatments directed by the mobile application (app-guided) (N 50 PK + App and N 75 PK + App) were evaluated with reference to standard RDF as well as those managed using GreenSeeker™ (N 50 PK + GS TM and N 75 PK + GS TM ). The N 50 PK + App showed at par yield attributes, stover yield (9.34 t ha −1 ), total biomass yield (17.17 t ha −1 ), grain protein yield (646.17 kg ha −1 ), total N uptake (145.96 kg ha −1 ) and remobilized vegetative N (89.8 kg ha −1 ) into grain with the RDF. Partial factor productivity (PFP N ) and apparent recovery efficiency (ARE N ) of N in N 50 PK + App was 23% and 22.1% higher than RDF respectively. The B:C in N 50 PK + App (2.43) was at par with N 75 PK + App (2.44). N 50 PK + App had the lowest energy consumption (9.72% lower than RDF), highest N energy use efficiency (24.3% higher than RDF) along with the maximum energy profitability, productivity and use efficiency. N 50 PK + App treatment resulted in marked reductions in GHG emission compared to RDF, with 11.1% lower CO2-eq. emission ha −1 , 29.4% lower N 2 O emission ha −1 , and 11.14% lower CO2-eq. emission t −1 . Thus, basal application of 50 kg ha −1 N with two splits of N (35 & 45 DAS) as per Pusa N Doctor can provide at par yield with RDF and GS TM , while simultaneously promoting N and energy use efficiency thereby, minimising GHG emission.
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