New Zealand Journal of Agricultural Research abstracts
Effects of land application of farm dairy effluent on soil properties: a literature review
R. M. Hawke
S. A. Summers
School of Earth Sciences
Victoria University of Wellington
Wellington, New Zealand
Abstract Land application of wastes is becoming an
increasingly popular practice. The application of farm dairy effluent
(FDE) to land, as opposed to direct discharge to waterways, is the
preferred mechanism for disposal in New Zealand as regulatory
authorities move to protect and enhance water quality and meet Maori
spiritual and cultural values. For example, in the Waikato the
percentage of dairy farmers who apply FDE to land has risen from 35% in
1993 to effectively 100% in 2004. Land application recognises the
nutrient value of FDE; however, it is not without risks. At present the
management of land application of FDE is primarily concerned with
potential nitrate contamination of groundwater. There are other,
considerable, potential risks such as microbial contamination and
impacts on soil properties. Despite soil properties being spatially
extremely variable and the effects of land application of FDE being
long-term, the majority of studies on the impacts of FDE to soil
properties are limited in their temporal and spatial extent. The
evidence of effects of FDE on soil properties is limited; however, it
is reviewed and linked to the effects of land application of other
effluents in general and their effect on specific soil properties. The
effects of FDE application on soil physical properties are highly
variable (e.g., both increases and decreases in soil hydraulic
conductivity have been observed). This is in part because of
measurement issues and the difficulty in separating out the effects of
the FDE application from the effects of stock management. Overall, most
changes due to FDE application appear to improve the soil’s
long-term fertility, i.e., increased concentrations of total nitrogen,
total phosphorus, and plant available nutrients. FDE application has
been observed to result in a greater and more diverse microbial
biomass. However, optimal environmental management and the continued
use of the soil for FDE management require ongoing monitoring.
Keywords farm dairy effluent; soil properties; pasture; land application; nitrogen; phosphorus
A04045; Received 5 May 2004; accepted 31 March 2006; Online publication date 13 July 2006
New Zealand Journal of Agricultural Research, 2006, Vol. 49: 307–320
0028–8233/06/4903–0307 © The Royal Society of New Zealand 2006
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