Graduate Thesis Or Dissertation
 

Influence of anhydrous ammonia on the solubility of soil organic matter

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vt150n35b

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  • Four surface and three subsurface horizons of agriculturally important Oregon soils were exposed to excessive volumes of anhydrous ammonia and reequilibrated with the atmosphere for several time periods prior to extraction with water. The carbon solubilized was determined by a modified wet combustion technique. Nitrogen in the soils, extracts, and residues was determined by a micro-Kjeldahl procedure. About three to ten % of the indigenous carbon was extracted. The actual amount of carbon solubilized was proportional to the original soil carbon contents, This amount of carbon approximated that solubilized during extraction of soils with 0.15 N NH₄OH. The soil moisture content at ammoniation time appeared to have little influence on the quantity of carbon solubilized. With an increase in reequilibration time with the atmosphere there was only a slight decrease in the amount of carbon extracted. Anhydrous ammonia application and subsequent aeration increased nitrogen contents over the indigenous values about twice as much in the C horizons as in the A horizons. Within three days 20 to 50% of the initially retained nitrogen was lost to the atmosphere. The pH values of the soils and extracts corresponded to the nitrogen values and decreased with the length of time elapsing prior to extraction, Assuming that the laboratory treatments and extracting methods were much more severe and effective in solubilizing organic matter than would be expected under field conditions, it is suggested that soil structural changes due to organic matter solubilization after anhydrous ammonia application would be minor. Changes in structural stability may be more related to phenomena accompanying large pH changes than to dissolution and redistribution of the organic fraction.
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