Resumen

HERRERO, M. A. et al. Nutrient transference from paddocks to milking area in grazing dairy farms in Buenos Aires, Argentina. InVet [online]. 2006, vol.8, n.1, pp.23-30. ISSN 1668-3498.

In grazing dairy farm systems, nutrients present in excreta return to the system with irregular distributions, with great accumulation in the milking area. The objective of this study was to quantify excess Nitrogen and Phosphorus (N&P) transferred annually to the milking area according to permanency time (PT) in this area, in bovine milk production systems in the Buenos Aires Province. Nutrient excess was quantified in 17 farms, based on the N&P balances estimated by the difference between inputs (nutrients provided by the total ration for milking cows) and outputs (milk production). To establish the real excess of the balance that is transferred to the milking area, the real daily PT of the animals (milking and feeding) was considered. An optimum PT was established in 4 hours/day to define the minimum transferred excess. The 88% of the farms evaluated presented a PT over the optimum. The Wilcoxon test showed significant differences (p<0.05) between the central values in both distributions (real excess-optimum excess), showing the persistence of more N&P excess than the optimums. As a consequence, there will be loss of field fertility and a nutrient concentration in areas that become potential sources of surface and groundwater contamination.

Palabras clave : Nutrient transference; Nitrogen; Phosphorus; Dairy production.

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