Wednesday, November 15, 2006 - 10:30 AM
282-6

Nitrogen Losses from Urine Patches; the Effects of Soil Type and Application Time.

Christy van Beek1, Jan-Willem van Groenigen1, Eduard Hummelink1, Oene Oenema1, and Wim Corr�2. (1) Alterra, PO Box 47, Wageningen, 6700 AA, Netherlands, (2) Plant Research International, PO Box 16, Wageningen, 6700 AA, Netherlands

 

Urine patches are a known �hot-spot' of N losses to the environment. Prior research has shown a seasonal trade-off of urinary-N between plant uptake in spring and leaching in fall, and therefore grazing regimes may be an important tool for farmers to prevent unwanted N losses. On� smaller time-scales, i.e. within seasons, dynamics of N loss pathways from urine patches are unclear. In this paper the results of two experiments are presented to unravel urinary N loss pathways applied at different moments. A lysimeter experiment with two sandy soils and a replicated field experiment to relate observations of the lysimeter experiment to the field-scale was performed. Urine containing 1.4669% (lysimeter) and 0.5280% (field) atomic excess 15N was applied in triplicate in September 2004, October 2004, November 2004, July 2005, September 2005, October 2005 and in November 2005. Measurements (N-difference and 15N) included N2O emission, NH3 volatilization, grass uptake, soil storage and leaching (only in lysimeters). In total more than 90% of the urinary-N was retrieved, of which 28-31% in grass uptake, 35-65% in soil storage, 18-32% in leaching, 1.5% in N2O emission and 0.2% in NH3 volatilization. Leaching and crop-uptake showed some significant effects, but we were unable to derive clear seasonal trade-off mechanisms. However, gaseous emissions were lowest for the November treatment and our results demonstrate the possibilities to direct the fate of urinary-N, e.g. minimizing N2O emission by prohibiting late-autumn grazing.