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Sulphur cycling in New Zealand hill country pastures. II. The fate of fertilizer sulphur
Author(s) -
SAKADEVAN K.,
MACKAY A. D.,
HEDLEY M. J.
Publication year - 1993
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1993.tb02326.x
Subject(s) - fertilizer , leaching (pedology) , pasture , agronomy , sulfur , chemistry , cycling , environmental science , soil water , zoology , biology , soil science , geography , forestry , organic chemistry
SUMMARY The fate of fertilizer sulphur (S) applied as single superphosphate (SSP) to grazed pasture was examined in a field experiment for a period of 18 months using 35 S‐labelled SSP. Four sites were selected on the basis of contrasting fertilizer history and land slope. The fertilizer histories since 1981 for the sites were 125 (LF) and 375 (HF) kg ha ‐1 a ‐1 SSP and the slope gradients were low (LS, 0‐12°) and medium (MS, 13–26°). The amount of fertilizer S taken up by pasture as a fraction of total applied was greater at the LF (12%) than the HF (6%) site, suggesting that pasture at the LF site depended more on fertilizer than pasture at the HF site. At the LF site, fertilizer application did not significantly increase leaching losses of S (13 and 8.6 kg S ha ‐1 for fertilized and unfertilized plots, respectively). At the HF site, fertilizer application significantly increased leaching losses of S (38 and 21 kg S ha ‐1 for fertilized and unfertilized plots, respectively). The amount of fertilizer S lost by leaching as a fraction of total applied was greater at the HF (20%) than the LF site (7.6%). Most fertilizer S remained as soil organic matter. Plant uptake and leaching losses of fertilizer S were greater in the first year after application. The amount of N lost by leaching was very small in terms of N cycled through soil‐plant system (1 to 6 kg N ha ‐1 ). The majority (> 80%) of the S and N taken up by pasture and lost by leaching was derived from the mineralization of soil organic matter and not from freshly applied fertilizer.