Resumo

MORA RAVELO, Sandra Grisell et al. Denitrification from a slow release and urea plus monoamonium phosphate fertilizer applied to weat irrigated with waste or well water. Rev. Int. Contam. Ambient [online]. 2007, vol.23, n.1, pp.25-33. ISSN 0188-4999.

The study of N₂O emission originated by the combination of different types of fertilizers and water on rizospheric soil, and non- rizospheric soil along the crop cycle, can contribute to useful knowledge in order to increase fertilizer and manure N recovery efficiency and to reduce the N loss by denitrification. The efficient use of nitrogen fertilizers and non- treated urban waste water for crops is an agronomic, economic and environmental need. The denitrification is an important factor that diminishes the N efficiency in crops. The objective of this investigation was to evaluate the denitrification of a slow release fertilizer using as reference urea plus monoamonium phosphate and an organic fertilizer, applied to wheat irrigated with urban waste water or well water. Analyses were made in the vertisol type soil used in the experiment with both, rizospheric and non-rizospheric soil. The slow release fertilizer used has a matrix enriched with N and P and its patent is currently in progress. Each fertilizer was evaluated alone, as well as the slow release fertilizer plus organic fertilizer. The samples of rhizospheric and non-rhizospheric soils for each treatment were collected at 55, 67 and 97 days after sowing and incubated during 18 days at 25 °C, controlling the soil humidity daily. The results (p < 0.05) showed that the interactions between samplings and types of water, samplings and fertilizers, and types of water and fertilizers affected (p < 0.06) the emission of N₂O, which was increased when urea plus monoamonium phosphate and waste water were applied. On average, there was less N₂O when emissions slow release fertilizer or organic fertilizer were applied and irrigated with well water as compared to irrigation with waste water. As well, use of waste water was, on average, associated with a bigger loss of N. The highest average emission in N₂O was observed 67 days after sowing. The average denitrification was similar in the rhizospheric and non-rhizospheric soil.

Palavras-chave : nitrous oxide; urea-clay; urban waste water.

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