. Properties of tree barks in relation to their agricultural utilization. Bark Utilization. readily added 4 percent nitrogen in experi- ments conducted by Aspitarte7 and Bollen and Glennie (1963). In a much simpler proc- ess, anhydrous ammonia gas is admitted through perforated pipes at the bottom of a 5-foot-deep bark pile covered with poly- ethylene sheets (fig. 1). Ammoniated bark is much darker than raw bark (fig. 1). Bark must be wet for ammoniation to be effective. Portions of the pile near the points of gas admission become darker and more highly ammoniated. For a uniform product, the p
. Properties of tree barks in relation to their agricultural utilization. Bark Utilization. readily added 4 percent nitrogen in experi- ments conducted by Aspitarte7 and Bollen and Glennie (1963). In a much simpler proc- ess, anhydrous ammonia gas is admitted through perforated pipes at the bottom of a 5-foot-deep bark pile covered with poly- ethylene sheets (fig. 1). Ammoniated bark is much darker than raw bark (fig. 1). Bark must be wet for ammoniation to be effective. Portions of the pile near the points of gas admission become darker and more highly ammoniated. For a uniform product, the pile must be turned and allowed to cure after treatment, permitting equal distribution of the added nitrogen and escape of any free ammonia which might otherwise volatilize from the product when used as a mulch. An excess of ammonia could also cause too high a pH in the mulch or soil which could injure some plants. A total nitrogen content of about 2 per- cent is obtained by ammoniation. Bark so treated, sometimes called stabilized or com- posted bark, has a pleasing dark color. Bol- lerslev (1968) describes a successful com- mercial operation wherein the best product is produced by composting ammoniated bark at 135° to 150° F. for approximately 90 days. Ammoniation also softens the needlelike bast fibers of Douglas-fir so that they lose much of their objectionable handling prop- erties. Ammoniated or otherwise fortified bark products should be positively labeled; otherwise, users may add nitrogen fertilizer and cause undesirable growth effects on plants. Cork and fine bark fractions absorb more ammonia with longer exposure, but they ab- sorb it differentially. Ricard8 found that Douglas-fir bark fibers treated with anhydrous ammonia at room temperature and atmos- pheric pressure had a nitrogen content of about 3 percent. For the cork fraction, the value was percent and for fines, 7 percent. Half of the nitrogen introduced into Douglas-fir bark by ammoniation is not readil
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