『Abstract
Phosphorus (P) losses from intensively farmed dairy pastures
can impair surface water quality. One of the first steps in mitigating
this loss is to determine where in a field the potential for P
loss is greatest. This study compared P export in overland flow
from grazed pasture with areas that receive elevated P inputs
and stock traffic (e.g. gateway, water trough, stream crossing
and cattle lane). Intact soil blocks were removed, simulated rainfall
applied and overland flow analysed for P fractions and suspended
sediment (SS). Soil bulk density, hydraulic conductivity, porosity,
Olsen P and water soluble P were also measured. P loss from the
sites was in the order: trough>crossing>gateway>pasture. Total
P losses from the trough averaged 4.20 mg P/m2 while
the pasture exported 0.78 mg P/m2. In addition, runoff
from lane soil was measured with total P averaging 5.98 mg P/m2,
however the method used as different from the other soils. Using
stepwise linear regression, Olsen P or H2O-P,
% bare ground and % saturation were the most commonly occurring
variables to predict P loss among the sites. This suggests that
locating and minimizing the size of these areas in fields has
the potential to significantly decrease P loss to surface waters.
Keywords: source areas; dairy; pasture; phosphorus; export; water
quality』
Introduction
Materials and methods
Study area
Rainfall simulation
Surface runoff and soil analysis
Results and discussion
Soil properties
Loss of P and SS in surface runoff
Predicting P loss for sites
Conclusions
Acknowledgements
References