An insight into productivity,profitability,and sustainable energy use in maize under precision nitrogen management using a smartphone appOA

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)(N0PK),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+GSTM and N_(75)PK+GSTM).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(PFPN)and apparent recovery efficiency(AREN)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 N2O 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 GSTM,while simultaneously promoting N and energy use efficiency thereby,minimising GHG emission.