Evaluation of nitrogen status in a wheat crop using unmanned aerial vehicle images

Víctor Manuel Gordillo-Salinas1*, Héctor Flores-Magdaleno2, Carlos Alberto Ortiz-Solorio2, and Ramón Arteaga-Ramírez3
The excessive use of N in agriculture has created various environmental and economic problems. Remote sensing and unmanned aerial vehicles (UAV) are feasible solutions to infer the status of a crop and enable a better management during the growing season. The objective of this study was to correlate experimental N content and wheat (Triticum aestivumL.) crop aboveground biomass data with vegetation indices estimated using UAV images. In this study, the N nutritionindex and N dilution curve were used as indicators of the state of plant N; input variables to estimate these indicators were the N content and aboveground biomass. Four flight campaigns were conducted at different phenological stages of a wheat crop and seven N doses were evaluated. A linear relationship of blue normalized difference vegetation index (BNDVI) and green normalized difference vegetation index (GNDVI) with aboveground biomass and N content was identified. BNDVI and biomass demonstrated high R2 during boots swollen and end of anthesis growth stages (0.62 and0.68, respectively), while GNDVI showed the highest R2 during the ear half emerged and beginning of anthesis growth stages(0.84 and 0.79, respectively). For N content estimation, GNDVI showed a higher correlation than BNDVI, and the adjustment curve showed an R2 up to 0.81 only for the last flight (end of anthesis), BNDVI showed an R2 of 0.78. Remote sensing and vegetation indices estimated from UAV images can be reliably used to estimate N content and wheat biomass, contributing to knowing the crop N status.
Keywords: Blue normalized difference vegetation index, critical nitrogen dilution curve, green normalized difference vegetation index, nitrogen nutrition index, Triticum aestivum.
1Instituto Mexicano de Tecnología del Agua, Coordinación de Riego y Drenaje, Paseo Cuauhnáhuac No. 8532, Jiutepec, Morelos 62550, México.*Corresponding author (manuel_gordillo@tlaloc.imta.mx).
2Colegio de Postgraduados, Campus Montecillo, Carretera México-Texcoco, km 36.5 Montecillo, Texcoco 56230, México.
3Universidad Autónoma Chapingo, Departamento de Irrigación, km 38.5 Carr. México-Texcoco, Chapingo, Texcoco 56230, México.