Canopy Indices: a Model to Estimate the Nitrogen Rate for Barley and Wheat
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ORIGINAL PAPER
Canopy Indices: a Model to Estimate the Nitrogen Rate for Barley and Wheat Nahuel I. Reussi Calvo 1,2,3 & Nicolás Wyngaard 1,2
&
Ignacio Queirolo 1 & Pablo Prystupa 4 & Hernán R. Sainz Rozas 1,2,5
Received: 13 May 2020 / Accepted: 22 July 2020 # Sociedad Chilena de la Ciencia del Suelo 2020
Abstract The objectives were to calibrate the Soil Plant Analysis Development (SPAD) and Green Seeker (GS) as tools to determine the differential of 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. Fourteen field experiments were conducted (2016–2018) evaluating five N rates. Relative canopy indices were determined using a SPAD-502 (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. Statistically 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 also for wheat (R2 = 0.64). A 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. Keywords Canopy indices . Chlorophyll meter . Barley . Wheat . Diagnose . Nitrogen
1 Introduction Nitrogen (N) is the most important macronutrient limiting the agricultural production of diverse crops (Prystupa et al. 2018; Rahimikhoob et al. 2020; Rasool et al. 2020). Among these * Nahuel I. Reussi Calvo [email protected] * Nicolás Wyngaard [email protected] 1
Facultad de Ciencias Agrarias, Universidad Nacional de Mar del Plata, Ruta 226 km 73.5, Balcarce, Buenos Aires, Argentina
2
Consejo Nacional de Investigaciones Científicas y Técnicas, Mar del Plata, Buenos Aires, Argentina
3
Laboratorio de suelos FERTILAB, Moreno 4524, (7600) Mar del Plata, Buenos Aires, Argentina
4
Facultad de Agronomía, Universidad de Buenos Aires, INBA-CONICET, Av. San Martín 4453, C1417DSE Buenos Aires, Argentina
5
Instituto Nacional de Tecnología Agropecuaria Balcarce, Ruta 226 km 73.5 (C 7620), Buenos Aires, Argentina
crops, barley (Hordeum vulgare L.) and wheat (Triticum aestivum L.) are two of the most widely grown cereals throughout the world (Zhou 2009). The rate of nitrogen (N) fertilizer application is important for these crops, since N availability affects its grain yield and quality (Prystupa et al. 2018). However, it has been reporte
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