Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2006
Publication Date: 7/22/2007
Citation: Wienhold, B.J. 2007. Comparison of laboratory methods and an in situ method for estimating N-mineralization in an irrigated silt-loam soil. Communications in Soil Science and Plant Analysis 38:1721-1732. Interpretive Summary: Inappropriate application of N fertilizer has environmental, economic, and agronomic implications. Insufficient N application results in low yields and lost income. Application of excessive N results in excessive production costs and potential environmental contamination. Crop residue and soil organic matter contribute to crop available N as they mineralize. Understanding the magnitude of this contribution is essential to efficient N fertilizer management. A number of laboratory and field methods have been devised to estimate mineralization rates and to study the effect of management practices on mineralization. This study compared a number of field and laboratory methods. Results using laboratory methods were poor likely due to differences in temperature and moisture between those used in the laboratory and those encountered in the field. The in field method, while labor intensive, provided realistic estimates and is a useful tool for studying management effects on mineralization.
Technical Abstract: Nitrogen mineralization makes a considerable contribution to crop available N and is difficult to estimate. Reliable methods for measuring N mineralization are needed to produce data sets for developing N-mineralization models, as a component in fertilizer recommendation algorithms, and to assess the effect of management practices on N mineralization. Numerous methods are available for estimating N mineralization. Laboratory methods are relatively easy but may not reflect conditions in the field and field methods are usually labor intensive. A study was conducted to compare N mineralization estimates using anaerobic and aerobic laboratory methods and an in situ field method for the 0- to 15-cm depth of a silt loam soil under irrigated corn (Zea mays L.). Mineralization estimates were also compared to N mineralization based on crop N content. Estimates of N-mineralization were 101 kg ha-1 for the anaerobic laboratory method, 284 kg ha-1 for the aerobic laboratory method, and 134 kg ha-1 for the in situ field method. The in situ field method provided a reasonable estimate of N-mineralization (0- to 15-cm) when compared to the estimate of mineralized N (root zone) based on crop N content (215 kg ha-1). The in situ field method can be used to measure N-mineralization during the growing season and for comparing N-mineralization among management practices.