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Title: SOIL CARBON AND NITROGEN MINERALIZATION: INFLUENCE OF DRYING TEMPERATURE

Author
item Haney, Richard
item Franzluebbers, Alan
item PORTER, E - TEXAS A&M UNIV
item HONS, F - TEXAS A&M UNIV
item ZUBERER, D - TEXAS A&M UNIV

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/20/2003
Publication Date: 3/20/2004
Citation: Haney, R.L., Franzluebbers, A.J., Porter, E.B., Hons, F.M., Zuberer, D.A. 2004. Soil carbon and nitrogen mineralization. Soil Science Society of America Journal. 68(2):489-492.

Interpretive Summary: Soil microbes are responsible for releasing nutrients from soil organic matter which is then available to plants such as nitrogen and phosphorus. This nutrient cycling is a natural response to drying and wetting the soil from periodic rain. This research shows that soil microbial activity is highest quickly after soil wetting and continues for roughly three days, after which it returns to normal. For many years scientists have avoided using the this ¿flush¿ of nutrients from microbial activity suggesting that it is an artifact of soil drying and rewetting even though soil drying and rewetting is a naturally occurring system. Our research shows that soils need not be kept in a moist state but can be oven-dried prior to experimental analysis.

Technical Abstract: Controversy exists concerning the quantification of microbial activity (C and N mineralization) in dried and rewetted compared to field-moist soils. Soils kept continuously moist may represent optimum laboratory conditions for C and N mineralization but may not truly represent routine drying cycles that occur in the field. The objective of this study was to compare C and N mineralization from eight soils that were maintained in a moist condition with that from the same soils dried at 40 degrees, 60 degrees, or 100 degrees C and rewetted. Coefficients of determination (r**2) for the linear relationships between C mineralized in 24 d from moist soils vs. C mineralized in 24 h from soils dried at 40 degrees, 60 degrees, and 100 degrees C and rewetted were 0.99, 0.98, and 0.30 respectively. Carbon mineralization values for 24 d vs. 3 d resulted in r**2 values of 0.99, 0.98, and 0.97 respectively. Coefficients of determination for N mineralization in 24 d from moist vs. dried and rewetted soils at 40 degrees, 60 degrees and 100 degrees C were 0.99, 0.86, and 0.63 respectively. These results indicate that short term mineralization following drying and rewetting soil may be a useful indicator of potential microbial activity without the need for keeping soil in a continuously ¿field moist¿ state.