New Zealand Journal of Agricultural Research abstracts
Impact of farm-dairy effluent application on the amounts and forms
of phosphorus loss by leaching from irrigated grassland
Gurpal S. Toor1
Leo M. Condron2
Hong J. Di2
Keith C. Cameron2
J. Thomas Sims1
1Department of Plant and Soil Sciences
University of Delaware
Newark, DE 19716, USA
email: gurpal@udel.edu
2Agriculture and Life Sciences
P.O. Box 84
Lincoln University
Canterbury 8150, New Zealand
Abstract Sufficient evidence exists to support the
hypothesis that the eutrophication of surface waters is accelerated by
increased transfer of nutrients (e.g., phosphorus, P) from landscape to
water. The objective of this paper is to combine the results of a
lysimeter experiment that used intact soil monolith lysimeters
(50 cm diameter, 70 cm deep) and a field experiment that used
field plots (10 × 2 m2) of a Lismore stony silt
loam soil (Udic Ustochrept). The soils received mineral P fertiliser
alone at 45 kg P ha–1 yr–1 or in combination
with farm-dairy effluent (FDE) at 200 or 400 kg N ha–1
yr–1. Annual mean total P concentrations and losses were
two- to three-fold higher from the soil amended with both FDE and P
fertiliser than P fertiliser alone. The higher losses as particulate
unreactive P during irrigation seasons are attributed to the regular
inputs of high intensity flood irrigation, which increased the transfer
of soil particles from the soil profile. Greater than 60% of P loss
occurred immediately following FDE application over a 2-year period,
highlighting the importance of preferential flow in this soil.
Phosphorus-31 nuclear magnetic resonance analysis showed that FDE was
rich in inorganic orthophosphate (86%) while leachate contained only
12% of inorganic orthophosphate. This indicated that inorganic P
applied in FDE was sorbed because of the high P fixation capacity of
Lismore subsoil, which is due to higher amounts of Fe and Al. On the
other hand, orthophosphate monoesters and diesters were only 13% of P
in FDE, compared with 88% in leachate suggesting that organic P forms
are mobile in the soil profile, and are selectively transported through
soil. The Olsen P and isotopic exchange parameters (concentration of
inorganic P in the soil solution (CP) and the
quantity of P that is immediately available to plants (E1min))
of Lismore soil increased with increase in P application from mineral P
fertiliser and FDE. This suggests that P fixation sites in soil may be
getting saturated with applied P inputs.
Keywords P leaching; farm-dairy effluent; P
fertiliser; grassland; lysimetry; preferential flow
A04038; Received 28 April 2004; accepted 13 October 2004; Online
publication date 15 December 2004
New Zealand Journal of Agricultural Research, 2004, Vol. 47:
479–490
0028–8233/04/4704–0479 © The Royal Society of New Zealand 2004
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