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Immobilization and mineralization of nitrogen in Hawaiian soils
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|Title:||Immobilization and mineralization of nitrogen in Hawaiian soils|
|Authors:||Agarwal, Anand Swaroop|
|Keywords:||Soils -- Hawaii|
Soils -- Nitrogen content
|Abstract:||Immobilization and mineralization of nitrogen was studied in five Hawaiian soils. Of the two energy sources, a readily available source, sucrose, accelerated and increased the magnitude of immobilization of native as well as added nitrogen more than did the slowly available source, sugarcane bagasse. With no energy source added, the Akaka silty clay, a high organic carbon and high C: N ratio soil immobilized the greatest amount of nitrogen. In acid soils maximum immobilization occurred when lime was added at the highest rate. Liming stimulated carbon dioxide production but calcium chloride had a depressing effect. Calcium chloride either decreased or did not influence the immobilization of nitrogen. Without any treatment the Koko and Paaloa soils, the high total nitrogen-containing soils, manifested maximum mineralization of soil nitrogen. The dominantly amorphous soil, Akaka, although highest in total nitrogen content, showed very low mineralization of nitrogen, presumably because of the existence of a nitrogen-containing inorganic-organic complex. This soil consistently displayed the greatest nitrogen and carbon release upon drying and rewetting, and nitrogen release when limed or treated with calcium chloride and when subjected to gamma irradiation. Significant correlation was found between C: N ratio and nitrogen released during drying and rewetting followed by incubation. In the high release soils, namely the Akaka, Koko and Lualualei, the N: C ratio of mineralized elements increased with the temperature of drying. The radiation significantly reduced the nitrate content in the Paaloa and Wahiawa, the reduction being 23.5 and 16.8 percent for Wahiawa and Paaloa, respectively. Liming increased the mineralization in the Wahiawa, Paaloa and Akaka soils, while calcium chloride effected a greater release only in the Akaka. Increasing osmotic pressures obtained by addition of salts resulted in increased mineralization of soil nitrogen In the Akaka. Different salts on the basis of their effectiveness In bringing about nitrogen release are arranged in the following decreasing order: CaCI2.2H2O > KCl > NaCl > K2SO4 > Na2SO4 > CaSO4.2H2O. Immobilization of nitrogen in sucrose-treated and lime-treated soils was related to corresponding carbon dioxide production values. A chemical release of nitrogen from an inorganic-organic complex in Akaka soil was proposed. The release of nitrogen was shown to be affected by the replacing power of cation, kind of anion and solubility of salt. It was postulated that calcium of Ca(OH)2 may act similarly to calcium from CaCl2.2H2O in effecting nitrogen release. Evidence was presented for the direct effect of heat on the chemical breakdown of organic matter, resulting in the release of some nitrogen. It was speculated that the nitrate loss by irradiation in the Wahiawa and Paaloa soils IS influenced by pH of the soil, and by processes such as denitrification and reduction to ammonium.|
Thesis (Ph. D.)--University of Hawaii, 1967.
Bibliography: leaves 124-137.
xiv, 159 l graphs, tables
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|Appears in Collections:||Ph.D. - Soil Science|
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