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Fate of 35S-labelled urine sulphate in urine affected areas of pasture soil under field conditions
Published online by Cambridge University Press: 27 March 2009
Summary
The fate of 35S-labelled sheep urine sulphate in the soil and its plant uptake were measured in field experiments over a 12 month period in 1990/91 in Canterbury, New Zealand. Urine was applied in either summer or winter. After the summer application, there was a marked increase in pasture growth and S uptake which lasted for a period of c. 90 days. Plant uptake of applied 35S was very rapid and c. 11% was recovered in the pasture herbage within 65 days of application. By the end of the experiment, c. 80% had been recovered in the herbage. A portion of applied 35S was incorporated into soil organic forms mainly as C-bonded S. After 86 days, 30% of the applied 35S was in the C-bonded form but during the rest of the experiment this declined to 17% as the 35S was remineralized and absorbed by the growing pasture plants.
Following the winter urine application, the increase in pasture dry matter production and 32S uptake was much less marked than that for the summer application. Twenty five percent of the applied 35S was recovered in pasture herbage within 65 days and this increased to 70% by the end of the experiment. Some of the applied S was incorporated into soil organic forms and, by 83 days, 20% of the applied 35S was present in C-bonded form. Through mineralization this declined to 7% by the end of the experiment. Over the initial 41 days of the experiment, c. 25% of the 35S was lost due to leaching.
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- Crops and Soils
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- Copyright © Cambridge University Press 1993
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