Respuesta a la fertilización nitrogenada en componentes del rendimiento en plantas de diferente jerarquía.

CAVIGLIA, O.P.; MELCHIORI, R.J.M.

Rosario

Congreso; IX Congreso Nacional de Maíz – Simposio Nacional de Sorgo; 2010

AIANBA

The typical size structuring process that occurs as a consequence of intra-specific competition in maize, promotes the appearance of contrasting plant hierarchies (i.e. dominated and dominant plants). This process can become more intense under low nitrogen (N) availability. The alleviation of plant interference by N addition, improving growing conditions, could reduce plant variability trough a differential response to N in individuals of contrasting hierarchies. The response to N of dominated and dominant plants from stands cropped with contrasting N supply (0 to 140-200 kg N ha-1) was examined on eleven experiments carried out at Paraná, Argentina (31º50’S; 60 º31’ W) in a broad range of growing conditions that included the variation of year, genotype, plant population and sowing date. Our objectives were to: i) evaluate the response to N in contrasting hierarchies of maize plants and, ii) quantify the contribution of dominated and dominant plant to the response to N of the overall stand. At higher grain yield response level (>50-60%), dominant plants had a considerable lower response in comparison with dominated plants, whereas at lower response level the contribution of contrasting plant hierarchies was similar. Difference between plant types in the response to N tended to be negligible in the more equilibrated stands. Restrictions for growing during critical period due to N, and possibly other-resources, shortage generated ample differences between dominated and dominant plant sizes. In this scenario, the higher responses to N at the stand level were recorded, as a result of the increase of yielp per plant more than proportional in dominated plants, mediated trough the response in biomass per plant, harvest index, kernel number per plant and kernel weight.