The preservation unaltered,of mineral nitrogen in tropical soils and soil extracts

Summary Experiments have been conducted on different methods of storing soils and soil extracts to preserve the mineral-N status unaltered. Neither the addition of chemicals at the rates used nor storage at sub-zero temperatures were found to preserve the mineral-N status of the soils completely unaltered over short periods of time. Furthermore, evidence was found to show that storage at sub-zero temperatures can effect subsequent mineralization of nitrogen during incubation.The mineral-N content of soil extracts prepared with an acidified K₂SO₄ reagent was not preserved over short periods by the addition of chemicals, by storing the extracts at sub-zero temperatures or by the addition of copper ions to the extracting solution. The mineral-N content of soil extracts prepared with a neutral KCl reagent could be preserved during storage at subzero temperatures but the addition of copper ions to the extracting reagent was not effective.Changes in the mineral-N content of both soils and soil extracts during storage were not consistent and in the soils appeared to be related to biological activity and the concentration of mineral N present. In soil extracts changes appeared to be related to the concentration of mineral-N present and to some other factor(s).Part of a thesis submitted for the degree of Ph. D in the University of East Africa.