Canopy Indices: a Model to Estimate the Nitrogen Rate for Barley and Wheat

REUSSI CALVO, NAHUEL I.; WYNGAARD, NICOLÁS; QUEIROLO, IGNACIO; PRYSTUPA, PABLO; SAINZ ROZAS, HERNÁN R.

Journal of Soil Science and Plant Nutrition

Springer

Año: 2020

0718-9508

PurposeThe objectives were to calibrate the Soil Plant Analysis Development (SPAD) and Green Seeker (GS) as tools to determine the economic optimum nitrogen rate (dEONR) at different growth stages of barley, and to evaluate if a single SPAD or GS calibration model can be used for two cereal crops: barley and spring wheat.MethodsFourteen field experiments were conducted (2016-2018) evaluating 5 N rates. Relative canopy indices were determined using a SPAD-502 meter (rSPAD) and a GS sensor (rNDVI) at Z24, Z31, and Z39 growth stages. The relationship between sensor indices and dEONR was evaluated by fitting quadratic-plateau (QP) regression models. Data from a previous study was used to evaluate if a unique QP model could predict dEONR from canopy indices for barley and wheat. ResultsStatistically significant QP models were determined for rSPAD and rNDVI at all evaluated growth stages. The sensitivity of these models was greater for rSPAD (0.0006 on average) than for rNDVI (0.0004 on average). A single QP model was developed to predict dEONR from rSPAD at Z31 and Z39 barley growth stages (r2=0.68). Also, a unique model was developed to predict dEONR from rSPAD at Z31 and Z39, but not only for barley but for wheat (r2=0.64). ConclusionA single model could be used to determine variable in-season N rates for barley and wheat, increasing the N use efficiency and limiting possible negative economic and environmental impacts of fertilization over the agroecosystems.