Solubilization of Soil Organic Matter by Liquid Anhydrous Ammonia1
- R. J. Norman,
- L. T. Kurtz and
- F. J. Stevenson2
A laboratory study on the solubilization of organic matter in three soils (Drummer, Typic Haplaquoll; Blount, Aeric Ochraqualf; Cisne, Mollic Albaqualf), by application of liquid anhydrous ammonia (LAA) revealed a six- to sevenfold increase in water-soluble organic C in the center radial zone (0-1.5 cm radius) around the point of application of 44 kg N ha−1 and a seven- to ninefold increase where 206 kg N ha−1 had been applied. Initially, a three- to fourfold increase in water-soluble organic C was measured as far as 3.0 cm from the application point at the 44 kg N ha−1 rate and as far as 6.0 cm at the 206 kg N ha−1 rate. Maximum concentrations of water-soluble organic C (700 mg C kg−1) decreased with time after LAA applications and with distance from the point of application. When pH levels were above 6.5 to 7.0, water-soluble organic C was linearly related to both exchangeable NH+4-N concentration and pH. As the concentration of exchangeable NH+4-N and soil pH declined with time due to nitrification and its acidifying effects, the concentration of water-soluble organic C also declined. After periods of 28 to 112 d, depending on application rate and soil properties, amounts of water-soluble organic C, on a whole soil basis, declined almost to their original levels although elevated concentrations were still present in the center of the application zones. Estimates were not made of losses of solubilized organic C via microbial conversion to CO2. However, since the maximum increases in solubilized organic C were always <1% of the total organic C (calculated on a total surface soil basis), drastic declines in soil organic matter content would appear unlikely as a result of LAA applications to these soils.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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