Eficiencia de uso del nitrógeno y sus componentes en maíz, en función de la densidad de plantas y dosis de fertilización

VAN OPSTAL, N.V; GREGORUTTI, V.C; CAVIGLIA, O.P.; MELCHIORI; R.J.M.

Congreso; X Congreso Nacional de Maíz; 2014

     Nitrogen use efficiency (NUE) in maize, which has important economic and environmental implications, can be defined as biomass (NUEB) and/or grain yield (NUEg) per unit of available nitrogen (Nav). It can be calculated as the product between an uptake efficiency (efNupt) and a physiological efficiency (efF), which reflects the ability of the crop to capture Nav and to transform the absorbed N in plant material, respectively. Increasing plant density has been proposed as a way to improve NUE through a better efNupt, as a result of a better use of belowground resources than in lower plant density. The aim of this work was to study the interaction between plant density and N rate on NUE and its components, i.e. efNupt and efF. Experiments were carried out at Paraná, Argentina (31º 50?S; 60 º 31? W) during two season (2007-2008 and 2008-2009). Treatments were a combination of two factors: plant density (low, medium and high) and N rate (0, 50, 100 y 200 Kg N ha-1). Initial and residual soil NO3-, biomass, yield, and N concentration in organs were measured. The differences in NUE as affected by N were more associated with efF than with efNupt. Biomass was 9% and 12% greater in the high density than in the low density in the year 1 and 2, respectively. In the other hand, Nupt was a 9% lower and only a 2% higher in the high than in the low plant density in year 1 and 2, respectively. As a result, efF was greater in high than in low density. Similarly, the differences in NUE between the two contrasting season were more associated with efF than with efNupt. Moreover, biomass was proportionally more increased than Nupt in the season with more favorable conditions than in the drier season. Together, these results reflect a higher sensibility of the crop to capture light, i.e. an aboveground resource, than to capture N, i.e. a belowground resource.