Abstract

DIAZ VALDEZ, Santiago T.; GARCIA, Fernando O.  and  CAVIGLIA, Octavio P.. Calibration of critical thresholds of soil available nitrogen for late-sown maize in Entre Rios province, Argentina. Cienc. suelo [online]. 2020, vol.38, n.1, pp.106-120. ISSN 1850-2067.

Since 2010, late-sown maize (MT) area in Entre Rios Province, Argentina has noticeably increased, in order to stabilize grain yields avoiding the coincidence of flowering with water deficit periods, which are typical in early sowings. We aimed to develop a methodology to recommend N fertilization in MT for the Entre Ríos Province, considering available N (soil N + fertilizer) (N_av). Twelve experiments of N fertilization were carried-out during two growing seasons. Owing wide yield variability among locations, no association between yield and N_av was detected, when all the locations were pooled. To deal with this variability, models considering Relative Yield (RR) can be alternatively used. Models considering soil sampling at pre-sowing (PS) have a better fit than those with soil sampling at V6. In PS, the fit of the model did not change across soil depth sampling (0-20, 0-40 or 0-60 cm). Using RR, fit of the model was improved and it allowed obtain a unique threshold of N_av (0-60 cm) of 165 kg N_av ha^-1. However, since there are no single thresholds for all the environments, models considering yield-environment level could be more adequate. We defined yield-environments of: less than 6000 kg ha^-1, 6000 to 9000 kg ha^-1 and more than 9000 kg ha^-1, with N_av (0-20 cm) thresholds of 93; 102 y 108 kg N ha^-1 and N use efficency of 13; 21 y 26 kg grain kg N_av ^-1, respectively.

Keywords : Nitrogen Fertilization; Soil test; Diagnosis.

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