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Fine-tuning of wheat (Triticum aestivum, L.) variable nitrogen rate by combining crop sensing and management zones approaches in southern Brazil

Schwalbert, R. A., Amado, T. J. C., Reimche, G. B., Gebert, F.
Precision agriculture 2019 v.20 no.1 pp. 56-77
Triticum aestivum, corn, electrical conductivity, fertilizer application, field experimentation, grain yield, nitrogen, nitrogen fertilizers, nutrient use efficiency, remote sensing, soil, topography, wheat, yield mapping, Brazil
The integration of crop sensors and management zones aiming at fine-tuning variable nitrogen rate (VNR) is a technological alternative to increase nitrogen use efficiency (NUE). The main objective of this study was to delimit management zones with different response to nitrogen input and using simulations to compare different wheat fertilization strategies: (a) traditional N management (constant rate), (b) VNR based on crop remote sensing, (c) VNR based on management zones and, (d) integrated approach combining management zones and crop sensing. This study was conducted in three steps: (i) delineation of management by overlapping maize grain yield maps, topographic features and soil apparent electrical conductivity; (ii) field experiments aiming at checking plant N uptake, N use efficiency (NUE) and wheat yield responses to N rates within each MZ—the N rates ranged from 0 to 120 kg ha⁻¹ in field 1 and from 0 to 160 kg ha⁻¹ in field 2- and, (iii) simulations of the four different strategies of wheat N fertilization. Both fields considered in this study were located in Carazinho, southern Brazil. The main outcomes were (1) significant N rates by management zones interactions for plant N uptake (P < 0.05) and for wheat grain yield (P < 0.05); (2) lower N fertilization response and NUE in low yield zone compared to medium and high yield zones and (3) superior performance of the integrated approach combining management zones and remote crop sensing.