Abstract
Previous high N surplus levels on Dutch dairy farms have
stimulated investigations into more efficient ways of farming.
Increases in N efficiencies are especially relevant for the
Pleistocene sandy soils where nitrate concentrations in the
upper groundwater have exceeded the EU 50 mg/l threshold in
the past. On the northern fringe of the Dutch coversand area,
several farmers have reduced N surpluses from over 300 kg per
ha per year to about 120 kg per ha per year over a period of 10
years. Reduced surplus levels were especially reached through
reduced use of fertilizer N. A field survey into soil nitrate levels
was performed in spring 2007 on 29 dairy farms on sandy soil.
This followed a previous survey in 2006 focusing on soil mineral
N levels in autumn. On the farms, land use was dominantly
grassland with a small percentage of silage maize.
During the survey of 2007 measurements were done on 300
locations selected by stratified random sampling with
combinations of soil type, groundwater level and land use as
strata. During the 20 days sampling period, continuous
monitoring was performed on two locations.
It was found that almost 70% of the observations were below the
detection threshold of 1.5 mg/l Nitrate-N although locally much higher concentrations were observed. For further analysis we
preferred to use 90th percentile points and areal proportion
where a specified threshold is exceeded. When distinguishing
between two contrasting types of N-management among the
farms we found that the relative area where the NO3-standard is
exceeded was 6.3% for high N-input farms and 8.7% for low Ninput
farms. Our results confirm some national forecasts where
regional average nitrate concentrations in the upper groundwater
in the northern sandy regions are expected to stay below the
established EU threshold.
Original language | English |
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Title of host publication | Eurosoil 2008: Soil - Society - Environment; Book of Abstracts, Vienna, Austria, 25-29 August 2008 |
Editors | W.E.H. Blum, M.H. Gerzabek, M. Vodrazka |
Place of Publication | Vienna, Austria |
Publisher | University of Natural Resources and Applied Life Sciences (BOKU) |
Pages | 149-150 |
ISBN (Print) | 9783902382054 |
Publication status | Published - 2008 |
Event | Eurosoil 2008: Soil - Society - Environment, Vienna, Austria - Duration: 25 Aug 2008 → 29 Aug 2008 |
Conference/symposium
Conference/symposium | Eurosoil 2008: Soil - Society - Environment, Vienna, Austria |
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Period | 25/08/08 → 29/08/08 |