Sulfur Balances and Sulfur-34 Abundance in a Long-Term Fertilizer Experiment
- H. Kirchmann ,
- F. Pichlmayer and
- M. H. Gerzabek
Reduced SO2 emissions, increased use of non-S-containing fertilizers, and higher crop yields may lead to S deficiency in agricultural soils in the future. In a long-term field experiment on a clay loam soil (Typic Eutrochrept) at Uppsala, Sweden, S balances were evaluated for plots under continuous fallow, plots receiving inorganic fertilizers [(NH4)2(SO4 or Ca(NO3)2; 80 kg N ha-1 yr-1], and plots receiving organic amendments (2000 kg C ha-1 yr-1) with the aim of estimating plant uptake, leaching losses, immobilization, and variations of δ34S in soil. Total N was correlated with total S concentrations in soil (R2 = 0.980), but organic C was less well correlated (R2 = 0.741). Total soil S decreased in all treatments where no organic material was added, the largest decrease occurring in the continuous fallow plots with a S mineralization rate of 6 kg ha-1 yr-1. Sulfur added through (NH4)2SO4 and sewage sludge was mainly leached, whereas SO4 leaching was reduced in the Ca(NO3)2-treated plots as a result of increased crop uptake. Of the organic amendments, 26 to 54% of the S remained in the soil with a half-life of 24 to 38 yr. Recoveries of S from organic amendments in soil were correlated with their initial C/S ratios (R2 = 0.999) excluding peat. A significant enrichment of 34S was found only in plots receiving peat. Peat was more highly enriched in 34S than the other organic materials studied and was more resistant to decomposition. The results indicate that shifts in soil δ34S cannot be used as a tool for quantitative determinations of S turnover. Nitrogen transformations were the main cause of acidification in the (NH4)2SO4-treated plots, as opposed to S leaching in the sewage-sludgetreated plots.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
Copyright © .