『Abstract
Long-term application of phosphorus (P) to soils as fertilizer
or manure can increase the potential for P loss to ground and
surface waters. Vertical P transport was investigated in a sandy
soil material receiving seven different P fertilizer sources:
poultry compost, poultry litter, triple superphosphate[Ca(H2PO4)2・H2O], dairy lagoon liquid, swine lagoon liquid,
swine lagoon sludge, and dissolved potassium dihydrogen phosphate
(KH2PO4). The P sources
were surface-applied to soil columns (6.35-cm diameter, 10-cm
long) at two rates equivalent to 75 and 150 kg total P ha-1,
and columns were intermittently leached with deionized (DI) water.
Column effluents were collected for up to 23 pore volumes and
analyzed for dissolved reactive phosphorus (DRP) and dissolved
organic carbon (DOC). In addition, a P retardation factor was
determined for the soil from a P adsorption isotherm. Transport
of P through soil columns receiving liquid P sources was simulated
by a one-dimensional equilibrium convective-dispersive equation
(CDE) based on water-extractable P (WEP) concentrations. Cumulative
amounts f DRP leached were linearly related to the amounts of
WEP in P source materials (r2=0.87***).
The recovery of DRP in the column effluents relative to WEP in
the applied materials was 126±15％ (mean±standard error) for organic
P sources and 66±2％ for inorganic P sources. The use of WEP in
the CDE model underpredicted P transport in the columns amended
with lagoon liquids compared with dissolved KH2PO4. Results indicated that leaching losses of P
from land-applied manures exceed the amounts of WER in source
materials because of organic P mineralization and competitive
sorption of DOC.
Keywords: Adsorption; Leaching; Organic carbon; Phosphorus; Water
quality』
1. Introduction
2. Materials and methods
2.1. Soil column preparation
2.2. Bromide tracer test
2.3. Phosphorus leaching
2.4. Phosphorus transport simulation
2.5. Statistical analysis
3. Results and discussion
3.1. Bromide tracer test
3.2. Properties of phosphorus input mixtures
3.3. Cumulative amounts of phosphorus leached
3.4. Concurrent transport of P and DOC
3.5. Simulation of phosphorus transport
4. Conclusions
Acknowledgements
References