Abstract
A method for determining total sulphur in plant material and soil samples using the induction furnace technique and subsequent turbidimetric determination of sulphate sulphur was discussed. A procedure for extracting sulphur from soil samples with ammonium acetate (pH 4.65), the interference of the organic matter being reduced by oxidation of the extract with H2O2, was proposed. Sulphur balance in Finnish cultivated soils was estimated by taking into account the average amounts of emitted (8 kg S/ha/yr.), precipitated (8 kg S/ha/yr.) and leached (8 kg S/ha/yr.) sulphur. The actual situation in the cultivated soils seems thus to be depending, on an average, on the uptake by plants and the sulphur applied (12 kg S/ha/yr. in the early 1970s). In 104 samples of cultivated soil, the content of total sulphur showed a slight correlation with the content of organic carbon. The amounts of sulphur extracted in various ways were not predictable by means of the soil characteristics used (pHCaCl2, org. C and texture). Extracted sulphur did not correlate sufficiently with the development and sulphur uptake of plants. Under field conditions in northern Finland, sulphur application produced a relatively distinct result in respect both to the ley yields on Carex peat, and their sulphur content. On mineral soils in southern Finland the yields were unaffected by supplementary fertilization with sulphur. In the pot experiments performed a fairly close relationship between sulphur and nitrogen was demonstrated.
Highlights
The other characteristics of the plant material and soil samples were generally determined in accordance with instructions in the literature and are described in main outline only
The sulphur fertilizer consisted of industrial-grade sodium sulphate (Na 2SO 4) with a sulphur content of a good 22 per cent
In the three experiments comprising sulphur fertilization in combination with supplementary nitrogen, both the sodium sulphate and the ammonium nitrate limestone were spread by hand over the soil surface about one week after sowing, i.e. about May 20
Summary
The sulphur supply situation of cultivated plants in Finland is examined in the present work. The reported methods are of a provisional character insofar as they concern the sulphur in cultivated soil available to plants, and further investigations are required in order that the methods may provide results that are reliable and more interpreted. Sufficient information about the sulphur contents of cultivated soils in Finland did not exist, and an inventory was made in the present study with the intention of providing a preliminary notion of the sulphur contents of these soils and the solubility of the sulphur. The importance to cultivated plants of this solubility is investigated by comparing the results of the chemical analysis with sulphur uptakes in pot experiments. The uptake of sulphur in ley and cereal was investigated in a few field experiments
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