Resumo

MACHADO, Daniel  e  SARMIENTO, Lina. Response of potato crop to the combination of different sources of nitrogen fertilization: an evaluation of the synchronization hypothesis. Bioagro [online]. 2012, vol.24, n.2, pp.83-92. ISSN 1316-3361.

It has been proposed that the combination of organic amendments of different quality with mineral fertilizer can improve nitrogen use by crops, synchronizing their N requirements with soil availability. The aim was to evaluate if using this approach it is possible to improve potato production with the same amount of N fertilization in the Venezuelan Andes. The effect of different sources of N on the accumulation and deficit of this element, and on several growth parameters was analyzed. An experiment was carried out using a random block design, with three replicates and four fertilization treatments, applying different sources of N but the same dose of 250 kg·ha^-1: FM: mineral fertilizer; G+F poultry manure and mineral fertilizer; P+F rice hulls and mineral fertilizer, and G+P+F: poultry manure, rice hulls and mineral fertilizer. The P+F treatment, followed by the G+P+F, produced a significant increase in N accumulation, leaf area index and duration, intercepted  radiation (IPAR), total dry matter and tuber yield, with a decrease of N deficiency, compared to the FM and G+F treatments. Leaf N concentration and radiation use efficiency (RUE) did not vary significantly among treatments. In conclusion, potato crop responded to the type of nitrogen source, experimenting a lower nitrogen deficit when the labile sources (mineral fertilizer and poultry manure) were combined with less labile sources (rice hulls), showing the potential  of combining appropriately different N sources for increasing N uptake.

Palavras-chave : Nitrogen; nitrogen nutrition index; poultry manure; rice hulls; radiation use efficiency.