Ammonia sorption by peat and N fractionation in some peat-ammonia systems
1993
Abbes, C. | Parent, L.E. | Karam, A.
Ammonia sorption is an important peat property for making composts and peat-mineral fertilizers. In this study, we investigated the influence of moisture content of fibric, hemic and sapric peat materials on ammonia sorption capacity, and we determined the N forms and the amount of solubilized humic substances following peat ammoniation. Ammonia sorption capacity increased curvilinearly with degree of decomposition from the fibric to the sapric peats, and increased with peat moisture content up to 600 g H2O [kg wet peat]-1 in the range of 400 to 700 g H2O [kg wet peat]-1. The amount of chemically sorbed ammonia was highest in the sapric peat containing [600 g H2O][kg wet peat]-1. On a dry weight basis, maximum sorption capacity was 24 g NH3-N kg for the fibric peat, 29 g NH3-N kg-1 for the hemic peat and 49 g NH3-N kg-1 for the sapric peat. Ammonia loss of physically retained ammonia was greatest at the highest moisture content and for the least decomposed peat. At ammoniation rates exceeding 30 g NH3 [kg dry peat]-1, exchangeable ammonium and acid-hydrolyzable N were the dominant N fractions in ammoniated peats. Peat ammoniation increased significantly (p < 0.001) the amounts of water-soluble carbon in all peat materials, of fulvic acid in the fibric peat and of both humic and fulvic acids in the hemic and the sapric peats. At maximum ammonia sorption capacity, the total amount of water-soluble and alkali-extractable organic matter reached 338 g kg-1 in fibric peat, 683 g kg-1 in the hemic peat and 848 g kg-1 in the sapric peat. The hemic and sapric peats appeared more appropriate than the fibric eat for making peat-base fertilizers.
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