Abstract
Land application of piggery effluent (containing urine, faeces, water, and
wasted feed) is under close scrutiny as a potential source of water resource
contamination with phosphorus (P). This paper investigates 2 case studies of
the impact of long-term piggery effluent-P application to soil.
A Natrustalf (Sodosol) at P1 has received a net load of 3700 kg effluent
P/ha over 19 years. The Haplustalf (Dermosol) selected (P2) has received a
net load of 310 000 kg P/ha over 30 years. Total, bicarbonate-extractable,
and soluble P forms were determined throughout the soil profiles for paired
(irrigated and unirrigated) sites at P1 and P2, as well as P sorption and
desorption characteristics.
Surface bicarbonate (P B , 0–0.05 m depth) and
dilute CaCl 2 -extractable molybdate-reactive P (P
C ) have been significantly elevated by effluent
irrigation (P1: P B unirrigated 231, irrigated 2906; P
C unirrigated 0.030.00, irrigated 23.90.2; P2: P
B unirrigated 7248, irrigated 39501960; P
C unirrigated 0.70.0, irrigated 443287 mg P/kg;
means.d.). Phosphorus enrichment to 1.5 m, detected as P
B , was observed at P2. Elevated concentrations of CaCl
2 -extractable organic P forms (P
OC ; estimated by non-molybdate reactive P in
centrifuged supernatants) were observed from the soil surface of P1 to a depth
of 0.4 m. Despite the extent of effluent application at both of these sites,
only P1 displayed evidence of significant accumulation of P
OC .
The increase in surface soil total P (0–0.05 m depth) due to effluent
irrigation was much greater than laboratory P sorption (>25 times for P1;
>57 times for P2) for a comparable range of final solution concentrations
(desorption extracts range 1–5 mg P/L for P1 and 50–80 mg
P/L for P2). Precipitation of sparingly soluble P phases was evidenced in
the soils of the P2 effluent application area.
Subject
Earth-Surface Processes,Soil Science,Environmental Science (miscellaneous)
Cited by
16 articles.
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