Tuesday, 8 November 2005 - 8:45 AM
179-2

Nitrogen Loss Pathways from Urine Patches in Relation to Stocking Schedules.

Christy L. van Beek1, Wim J. Corré2, Eduard W. J. Hummelink1, Gerwin F. Koopmans3, and Jan Willem Van Groenigen1. (1) Alterra, Wageningen UR, PO Box 47, 6700 AA, Wageningen, Netherlands, (2) Plant Research International, Wageningen UR, PO Box 16, 6700 AA, Wageningen, Netherlands, (3) Department of Soil Quality, Wageningen UR, PO Box 8005, 6700 AA, Wageningen, Netherlands

Urine patches from cattle in pastures represent high local applications of nitrogen (N), of which a substantial part is lost to the environment by emissions of NOx, N2O and NH4 and leached as organic N (DON), NO3 and NH4. Cattle stocking schedules provide an important tool for farmers in controlling the amount and distribution of urine patches, and potentially mitigating losses. In a lysimeter study we applied artificial urine (400 kg N ha-1) with 15N labeled urea (1.480% excess 15N) to undisturbed soil cores (Ĝ =18 cm, h = 60 cm) taken from two pastures on sandy soils. Simultaneously, a replicated field study was initiated on one of the pastures, receiving a similar urine application with 0.493% excess 15N. In both studies, 3 treatments were implemented: urine application in the beginning of September, October and November 2004. At the end of the leaching season (October-March) leaching, soil storage and crop uptake averaged approximately 20%, 40% and 30% of the 15N recovery, respectively. The total N-recovery from the urine patches was >90%. Initially, mineral nitrogen (NO3) accounted for the majority of the soil storage (>80%), especially for the November treatment, but in March 60% of the total 15N recovered in the soil was in the form of organic N. Both N2O emissions and N leaching were significantly different in the respective treatments. Therefore, stocking schedules can be used to mitigate various types of nitrogenous emissions from urine patches.

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