Corn water productivity assessments with aerial camera onboard drone by modelling surface and aerodynamic resistances

Abstract Aerial images taken from a camera onboard a drone were used for corn water productivity (WP) assessments in Northeast Brazil, by using a Mapir camera together with weather, biomass and productivity (Pr) data, modelling actual evapotranspiration (ETa) and biomass production (BIO). The effects of different nitrogen (N) fertilization cover levels were analyzed showing that there were significant differences on WP components from the emergency (E) to physiological maturation (PM) crop stages (CS), however, stabilizing at N at 200 kg ha⁻ ¹. Above this level, farmers should lose money increasing risks of negative environmental impacts with more N leaching to the water table. The evaporative fraction (ETf), i.e., the ratio of ETa to reference evapotranspiration (ET₀), taken as a root-zone moisture indicator, presented the best correlation with BIO and Pr, but the fraction of the absorbed photosynthetically active radiation (fp), representing soil cover by the canopies, is also important through photosynthetic activity. Comparing Pr and the BIO, the highest determination coefficient at V6 (pant with six leaves), confirming that the potential of corn yield is already defined at this CS. The models applied showed potential for monitoring vegetation and water conditions in corn crops, allowing rational fertilization practices while maintained yield at sustainable water use, with the possibility for replication of the methods in other environmental conditions.