ABSTRACT:
Accrately predicting the amount of nitrogen (N) made available for crop use by N mineralization (Nmin) of native soil organic matter (SOM) is complicated by different soils, climate, and management, all highly variable from one location to the next. In this paper, we have compiled seasonal estimates of Nmin from eleven field studies. We only include data for native SOM and do not include organically-amended soils. Initially, the data sets were graphed and regression was performed on the data as is. To further analyze the data, and because different incubation times were used for the different studies, we normalized reported Nmin to a twenty-week incubation period. Values of Nmin for a season range between 0.4 and 152 kg N ha−1 (0.3 and 136 lb N ac−1). The average amount of Nmin for all of these studies was 49.3 kg N ha−1 (44 lb N ac−1). A graph of Nmin for all of the data against SOM shows a negative relationship. A simple linear fit on that data results in a non significant R2 of 0.0008. A similar fit of all of the data against total N was also of little value. Eliminating the data collected from short incubations (less than fifteen weeks long) improved the fit; 42% of the variability in normalized twenty-week Nmin could be explained by total N. Regression analyses of the total soil N and of SOM content on the seasonal Nmin indicated that neither SOM nor total N is a good predictor for the seasonal Nmin amount. Soil type, management, and climate at the various locations obviously influence the magnitude of the estimates. More importantly, this review supports the push for an accurate predictive simulation model for seasonal Nmin that is non site-specific.
Footnotes
Merle F. Vigil is a soil scientist at the U.S. Department of Agriculture-Agricultural Research Service, Central Great Plains Research Station in Akron, Colorado; Bahman Eghball is a soil scientist in the Department of Agronomy at the University of Nebraska-Lincoln in Lincoln, Nebraska; Miguel L. Cabrera is a professor of soil science in the Department of Crop and Soil Sciences at the University of Georgia-Athens in Athens, Georgia; and Brad R. Jakubowski is a graduate research assistant and Jessica G. Davis is a soil scientist in the Department of Soil and Crop Sciences at Colorado State University in Fort Collins, Colorado.
- Copyright 2002 by the Soil and Water Conservation Society
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