Sulphur mineralization and release of soluble organic sulphur from camp and non-camp soils of grazed pastures receiving long-term superphosphate applications

✍ Scribed by M. L. Nguyen; K. M. Goh

• Publisher: Springer
• Year: 1992
• Tongue: English
• Weight: 731 KB
• Volume: 14
• Category: Article
• ISSN: 0178-2762
• DOI: 10.1007/bf00395463

✦ Synopsis

Topsoils (0-75 mm) from four soil types with different sulphate retention capacities were collected from stock camp and non-camp (main grazing area) sites of grazed pastures in New Zealand which had been annually fertilized with superphosphate for more than 15 years. These soils were analysed for different S fractions and incubated at 30 ~ for 10 weeks using an open incubation technique in order to assess the extent of S mineralization and the release of soluble soil organic S from camp and non-camp soils during incubation. The soils were preleached with 0.01MKC1, followed by 0.04M Ca(H2PO4) 2 before being incubated. Pre-incubation leachates and weekly 0.01 MKC1 leachates were analysed for mineralized S (i.e., hydriodic acid-reducible S) and total S. Soluble organic S was estimated as the difference between these two S fractions. Results obtained show higher cumulative amounts of all three S fractions in leachates over a 10-week incubation period in camp than in non-camp soils, suggesting that higher mineralization occurred in camp soils. Cumulative amounts of mineralized S from camp and non-camp soils showed a linear relationship with duration of incubation (R2___0.985"**), while the cumulative release of soluble organic S followed a quadratic relationship (R 2_> 0.975"**). A significant proportion (14.6~ of total S release in KC1 leachates was soluble organic S, indicating that organic S should be taken into account when assessing S mineralization. Mineralized S and soluble organic S were best correlated with 0.01 M CaC12-extractable soil inorganic S (R2= 0.767***) and 0.04MCa(H2POa)2-extractable soil inorganic S(R 2= 0.823"**), respectively. Soil sulphate retention capacity was found to influence amounts of mineralized S and soluble organic S, and thus periodic leaching with KC1 to remove mineralized S from soils may not adequately reflect the extent of soil S mineralization in high sulphate-retentive soils. In low (< 10~ sulphate-