
TY  - JOUR
A1  - Phillips, I. R. 
T1  - Phosphorus sorption and nitrogen transformation in two soils treated with piggery wastewater
JF  - Soil Research
JO  - Soil Res.
Y1  - 2002
VL  - 40
IS  - 2
SP  - 335
EP  - 349
KW  - sorption kinetics, nitrification, ammonium, nitrate.
UR  - https://doi.org/10.1071/SR01040 
N2  - Land application of piggery wastewater has the potential to contaminate receiving water bodies due to the presence of elevated concentrations of nitrogen (N) and phosphorus (P). This paper investigates P sorption and N transformation using soil from 2 wastewater disposal sites in south-east Queensland. Soil from Site 1 was classified as a clay (Vertosol) and soil from Site 2 was classified as a sandy loam (Sodosol). Soil was collected from wastewater disposal (irrigated) and non-disposal (non-irrigated) areas of each site. Nutrient sorption kinetics and transformation were studied by reacting each soil with either wastewater or an inorganic salt solution over a period of 21 days. Solution P concentrations decreased with time for all soils. These changes were greatest during the early stage of the study (<10 days), after which time solution P concentrations remained relatively stable. Concentrations of solution P tended to remain higher in irrigated than non-irrigated soils. This was attributed to a loss of high-affinity sorption sites due to past wastewater additions. Cation exchange (for times <3 days) and nitrification (for times >3 days) were found to be the primary mechanisms responsible for decreases in solution ammonium (NH4-N) over the 21-day period. Phosphorus and NH4-N sorption isotherms were determined using a leaching procedure, and the data were adequately described (r2 >0.95) by the Freundlich equation. Irrigated samples generally sorbed less P than non-irrigated soils. This was attributed to the loss of high-affinity P sorption sites due to previous wastewater additions. Cation exchange and competition between added and resident cations for the exchange sites was found to govern NH4-N sorption by these soils. Results from this study suggest that long-term land application of piggery wastewater may encourage leaching of N and P from the plant root-zone in soils with limited capacity to retain these nutrients. Appropriate management strategies to minimise these losses need to be developed to avoid degradation of the receiving soil and&sol;or water environments. sorption kinetics, nitrification, ammonium, nitrate. 
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