Use of Sensor Based Nitrogen Rates to Improve Maize Nitrogen Use Efficiency in the Northern Argentinean Pampas.
Ricardo J. M. Melchiori1, Octavio P. Caviglia1, Agustin A. Bianchini2, Nelson Faccendini3, and Willium Raun4. (1) INTA Paraná, Paraná, Argentina, (2) AAPRESID, Gob. Garzon 218 Dpto. 3, Villa Carlos Paz, 5152, Argentina, (3) UNER, Paraná, Argentina, (4) Oklahoma State Univ, Ag Hall, Stillwater, OK 74078
Nitrogen use efficiency (NUE) in maize may be improved by using a sensor-based nitrogen rate calculator (SBNRC). The objective of our study was to evaluate the NUE in maize fertilized with fixed or variable rates estimated by using a SBNRC. Four experiments (E) were conducted during the 2004-05 (E1 and E2) and the 2005-06 (E3 and E4) growing seasons in Paraná, Argentina. (31.5ºS). E1 and E3 were timely sowed and treatments included combinations of N rates at planting (0, 70, 140 y 210 kg N ha-1) and two strategies to late N fertilization: a fixed rate (FR = 70 kg N ha-1) and a variable rate (SBNRC). In both strategies, N was broadcasted as urea at V8, V10, V12 and V14 growth stages. E2 and E4 were late planted and treatments included N rates at planting (0, 50, 100 and 200 kg N ha-1 in E2 and 0, 70, 140 and 210 kg N ha-1 in E4) and a late N application at V12 using a fixed rate (50 kg N ha-1 in E2 and 70 kg N ha-1 in E4) or a variable rate (SBNRC). Results in E1 and E2 showed that maize grain yield was similar between strategies and NUE was higher with the SBNRC. In spite of a severe drought in the 2005/06 (E3 and E4) season, that significantly reduced crop yield and N response irrespective of N strategy; NUE was higher in the SBNRC. However, despite of promissory results on NUE increases, more studies to improve yield predictions in late planting dates are needed.