Resumo

MARTINEZ, Juan Manuel et al. Fertilización nitrogenada en trigo de la región subhúmeda: eficiencia del uso del agua y nitrógeno. Cienc. suelo [online]. 2016, vol.34, n.1, pp.81-92. ISSN 1850-2067.

Water and nitrogen (N) are typically the main wheat crop production factors in regions with water constraints. For this reason, it is of great importance to increase the N use efficiency (EUN) -when applying fertilizers- and the water use efficiency (EUA) in sub-humid environments. The objectives of this study were i) to analyze wheat response to different N rates, ii) to evaluate the EUN and EUA of total aboveground biomass (MST) and grain yield, and iii) to predict these efficiencies with models using principal components (CP) related to MST and grain yield as variables for five years in a sub-humid environment. During the 2008-2012 years, nitrogen fertilization trials were conducted in wheat using four rates (0-25-50-100 kg ha^-1) applied at sowing. At physiological maturity, MST and grain yield were measured, and EUN and EUA were calculated for both parameters. The CP analysis was performed using available N and soil moisture at planting, and rainfall in function of MST and grain yield. Three CP were made for each parameter, with a full explanation of 90% and 96% of the MST and grain yield total variance. The NUE predictions used three CP with a high fit (R² = 0.78 - 0.81) for MST and grain yield. However, the EUA predictions of MST and yield were low (R² = 0.38 to 0.45), excluding from the model the CP highly influenced by the available N. The high variability in water availability did not allow a significant increase in the EUA by N application, showing that water is the most limiting factor in this environment. The use of CP as regressor variables allowed accurate models for EUN prediction of MST and grain yield.

Palavras-chave : Triticum aestivum L; Erratic rainfalls; Principal components.

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