Extractability and adsorption of sulphate in soils

Abstract

upon Tyne NEI 7RU. U K S U M M A R YVirtually all of the indigenous sulphate (SO,) in a range of UK soils with moderately high pH values (> 6) was found to be present in the soil solution and, as a consequence, was highly susceptible to leaching. For acid soils containing adsorbed SO,, the extractability of SO, in NaCl and CaCI, solutions was dependent on both the ionic strength and cation species. Addition of small amounts (< -1 0 -2~) of either NaCl or CaCI, actually decreased the amount of SO, extracted, but SO, extractability increased sharply with concentrations of NaCl or CaCI, higher than about 0.1 M. At a similar ionic strength, more SO, was extracted by NaCl than CaCI,. Sequential extraction with 1 M NaCl removed essentially all of the absorbed SO,. The release characteristics of SO, were very different to those of phosphate and this difference in behaviour is not easily reconciled with the view that SO, is chemisorbed, as is phosphate. Except for a few acid soils with high oxide contents, the capacity of the soils to adsorb added SO, was quite small. None of the soils with pH values higher than 6 adsorbed a significant amount SO,. The results raise questions regarding the efficiency of SO,-containing fertilizers in correcting and preventing S deficiency in situations where leaching is important. *Present address: Agriculture Canada Research Station, PO Box 1030, Swift Current, Saskatchewan S9H 3x2. Canada.

Glucosinolates inBrassicavegetables: The influence of the food supply chain on intake, bioavailability and human health

“…rapa) is largely dependent on S content. Changes in (i) S availability in soil [97], (ii) S uptake by roots at different stages of growth [98,99], and (iii) high-affinity S transporter gene expression that is primarily regulated by S supply [100] as triggered by varied water supply all might contribute to differences in S content, and hence in higher GLS contents under reduced water supply.…”

FeSO₄/lime mixtures - an alternative to mineral sulfur and lime fertilizer for summer rape

“…The capacity of adsorption is increased with a decreasing pH of soil and the concentration of oxides and hydroxides (Schinner and Sonnleiter 2013). The strongest sulfate adsorption was observed at pH of 3.0 (Scott 1976), whereas no specific sulfate adsorption was analysed at pH of 6.5 (Curtin and Syers 1990). In this study, soil pH of 6.4 was recorded in the control treatment and 6.7-7.0 in the FeSO 4 × 7 H 2 O/lime mixtures ( Table 1).…”

Sulfur fractions in particle-size separates as influenced by long-term application of mineral and organic fertilizers

“…It should be further pointed out that adsorption of SO 4 2-is pH dependent and gets stronger at low soil pH. At pH > 6.5, adsorption is negligible and most SO 4 2-is in soil solution (Curtin and Syers 1990). Therefore generally little SO 4 2-adsorption is expected in the pH range of our soil samples (Table 2), because maximum is reached at pH 3 and falls rapidly as the pH rises to levels normally prevailing in limed soils.…”