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The objective of this study was to investigate the role of S impurity in zerovalent iron (ZVI) on the chemical speciation and solubility of Cd in the reduced soils. Two types of ZVI with contrastingly different S levels (0.009 and 1.08%) were used to find how the solubility and speciation of Cd would be influenced by the S impurity in ZVIs. Synchrotron-based X-ray absorption fine structure (XAFS) spectroscopy was used to determine the relative proportion of CdS and other species in the Cd-spiked soils amended with ZVIs with different S levels (hereafter low- and high-S ZVIs). Microscale distribution and speciation of Cd at the interface between ZVI and soil particles were investigated using micro-X-ray fluorescence (μ-XRF) and micro-XAFS (μ-XAFS) spectroscopy. The difference in S contents in ZVIs did not affect the soil solution Cd concentrations, but a significant decrease in exchangeable Cd was found in the soil with added high-S ZVI. Linear combination fitting (LCF) on Cd K-edge XAFS spectra of bulk soils determined up to 16% CdS in the reduced soils amended with ZVIs. The μ-XRF map of the soil amended with high-S ZVI showed that the spots with S accumulation were discretely distributed on the ZVI, and some S accumulating areas corresponded to Cd localization. The LCF on Cd K-edge μ-XAFS spectra for selected soil particles revealed that the proportion of CdS ranged from 20 to 87% (avg. 53 ± 22%) in the soil with low-S ZVI and from 64 to 98% (avg. 84 ± 14%) in the soil with high-S ZVI. A higher S content in ZVI, and probably in other amendments, decreases labile Cd fractions and enhances CdS formation in reduced soils. [ABSTRACT FROM AUTHOR]

Understanding soil sulfur pools and associated aggregates S fractions can provide a platform for monitoring S dynamics in soils. A long-term experiment established in 1922 on an Aquic Eutrocryepts in South-eastern Norway was chosen to investigate the effects of long-term fertilization on S fractions in bulk soil and those associated with aggregates. Chloroform fumigation-extraction was used to determine Microbial biomass S (MBS) and the wet chemical analysis method was used to fractionate soil S into ester S (hydriodic acid reducible S), carbon-bonded S (Raney nickel reducible 5) and residual S (Raney nickel non-reducible S). High farmyard manure (FYM) application resulted in higher MBS in bulk soil than nitrogen + potassium (NK) application, but it did not differ significantly from the control. Application of FYM at 60 Mg ha-1 resulted into accumulation of total S, total organic S and carbon- bonded S in bulk soils, while mineral fertilizer (nitrogen+phosphorus+potassium+sulfur [NPKS] and NK) and the medium rate of FYM did not increase the accumulation of total S and organic S fractions. The macroaggregate sizes (>2 and 1-2 mm) and the finest aggregate size (<0.106 mm) showed significantly greater total S concentration than other aggregate sizes. Ester S and residual S were predominant organic S fractions and they accounted for 39 to 52% and 38 to 51% of the organic 5, respectively. The macroaggregate sizes (>2 and 1-2 mm) contained the highest ester 5, but microaggregates (<0.106 mm) exhibited higher carbon-bonded S and residual S than other aggregates. In conclusion, the accumulation of S was dependent on fertilizer type, the rate of FYM application and aggregate sizes. [ABSTRACT FROM AUTHOR]

Reduction in soil disturbance associated with conservation tillage planting systems suggests that it is important to evaluate management practices for use of S for corn (Zea mays L.) grown in these planting situations. Evaluation of source, placement, and rate of S applied has not been the focus of past research. In this study, two S fertilizers [21-0-0-24 (ammonium sulfate), 12-0-0-26 (ammonium thiosuifate)] were applied at rates to supply 0, 6.7, 13.4, and 20.1 kg S ha-1 either in contact with the seed at planting or in a band near the seed at planting. Soil texture varied from loamy fine sand to silty day loam at the experimental sites. Corn emergence was reduced when 12-0-0-26 was placed in contact with the seed at sites with a loamy fine sand and sandy loam texture and soil was dry at time of planting. Stand reduction was most severe when 12-0-0-26 fluid material was used at rates to supply 13.4 and 20.1 kg S ha-1. Placement maintaining soil between seed and fertilizer had no negative effect on emergence. When placed in a band near the seed, both S sources had an equal effect on yield. Reduction in emergence due to 12-0-0-26 in contact with the seed had a negative effect on grain yield. Application of fertilizer S increased yield at all sites except where the texture was a silty clay loam. Optimum rate of fertilizer S was either 6.7 or 13.4 kg S ha-1 and varied with site. The response to fertilizer S on the silt loam soil suggests that inadequate S is released from soil organic matter via mineralization in conservation tillage planting systems. [ABSTRACT FROM AUTHOR]

The objectives of this study were to obtain a reliable index for the evaluation of the S nutrition status in soybean [Glycine Max (L.) Merr.] and to identify the critical S level in relation to seed yield and quality. Two Oxisols were used: A-horizon soil from Serra dos Gerais, and A- and B-horizon soils from Sambaiba in Maranhão State, Brazil. Soybean plants in pots were grown in a greenhouse with the supply of 0 to 80 mg S kg-1 soil. The seed S concentration was a more reliable index of seed yield because of the higher correlation between S concentration and yield. In the plants with visible symptoms of S deficiency, the seeds contained 1.5 g S kg-1, and the seed yield was 60% of the control. Electrophoresis analysis indicated that the critical seed S concentration for deficiency of protein components was 2.0 g kg-1 when the yield was 80% of the control. The S concentration was 2.3 g kg-1 or higher for >90% yield when the composition of the protein components was identical with that in the original seeds obtained under sufficient S fertilization. We classified the S concentration in the seeds as: deficient (S < 1.5 g kg-1), very Iow (1.5 ≤ S < 2.0 g kg-1), low (2.0 ≤ S < 2.3 g kg-1), and normal (2.3 g kg-1 ≤ S). Because of stable S concentration, easy sampling, and sufficient time for planning of fertilizer application for the subsequent cropping, seed analysis is preferable to leaf analysis. [ABSTRACT FROM AUTHOR]

Determines if nitrogen and phosphorus availability change in a predictable manner across an ombrothropic-minerotrophic gradient in 16 wetlands in northern Minnesota. Laboratory and field indices of soil nutrient availability in a diverse group of organic soils; Importance of nutrient availability in determining ecosystem structure and function.

Discusses the derivation of predictive models for organic and pyrite sulfur in coastal marsh soils from Dorchester County, Maryland. Determination of the rates of organic sulfur accumulation for the last 150 years; Factors that affect the rate of pyrite sequestration in organic horizons.

Investigates the influence of parent material on sulfate sorption in forest soils from northwestern Spain. Counteracting effects of organic matter on sulfate sorption; Low sorption in surface horizons of soils derived from acidic materials.