Nitrogen mineralization rates in salinevs. salt-amended soils |
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Authors: | G. McClung W. T. Frankenberger Jr. |
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Affiliation: | (1) Department of Soil and Environmental Sciences, University of California, 92521 Riverside, CA, USA |
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Abstract: | Studies were conducted to compare N mineralization rates in salt-amended nonsaline soils to naturally-occurring saline soils. NaCl, CaCl2, and Na2SO4 were added to nonsaline soils at rates that produced electrical conductivities of the saturation extracts (ECe) of 5, 10, 15, and 20 dS m−1. Saline soils with similar properties were leached to the same ECc levels. N mineralization in the Chino soil was inhibited by salt addition, particularly with sodium and calcium chlorides. In the Domino soil there was some inhibition of N mineralization with the chloride salts, but enhancement with Na2SO4 was observed. Nitrification in both soils was more sensitive to salt addition than ammonification. N mineralization occurred more slowly in both leached saline soils compared to the salt-amended soils. Leached saline soils often accumulated greater amounts of inorganic N compared to their native saline counterparts, particularly with the 5 dS m−1 Chino soil (native, 44 dS m−1) and with the 5, 10, 15 and 20 dS m−1 Domino soils (native, 32 dS m−1). Kinetic parameters were estimated by the linear least squares (LLS) and the nonlinear least squares (NLLS) methods. Generally, the LLS transformation estimated greater values of potentially mineralizable N (No) and lower rate constants (k). With the NLLS equation, No values for the leached saline soils were usually lower, and k values usually higher than in the salt-amended soils. The nonsaline controls generally had the highest No and lowest k estimates. Average LLS rate constants for the salt-amended and leached saline soils were 0.055 and 0.083 for the Chino, and 0.104 and 0.137 week−1, respectively, for the Domino soils. With the NLLS equation, average k values for the salt-amended and leached saline soils were 0.087 and 0.089 for the Chino, and 0.181 and 0.387 week−1, respectively, for the Domino soils. These results suggest that N mineralization rates obtained in salt-amended nonsaline soils may not be representative of those in naturally-occurring saline soils. |
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Keywords: | ammonification kinetics nitrification osmotic potentials soluble salts |
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