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Title: EVALUATION OF LONG-TERM MANAGEMENT EFFECTS ON SOIL ORGANIC NITROGEN DISTRIBUTION IN THE MORROW PLOTS 1729

Author
item BERMEO, E. - UNIVERSITY OF ILLINOIS
item <I;VAMEY, R. - UNIVERSITY OF ILLINOIS
item KHAN, S. - UNIVERSITY OF ILLINOIS
item Martens, Dean

Submitted to: American Society of Agronomy Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2005
Publication Date: 8/1/2005
Citation: Bermeo, E., <I;Vamey, R.J., Khan, S.A., Martens, D.A. 2005. Evaluation of long-term management effects on soil organic nitrogen distribution in the morrow plots. {abstract}. Agronomy Abstracts CD-ROM.

Interpretive Summary: Soil management practices and crop rotations are generally recognized to affect soil N availability, and should be reflected in the chemical distribution of soil organic N. Yet such effects have been difficult to detect by soil N fractionation, which can be attributed, at least in part, to defective methodology. Using acid hydrolysis in conjunction with new diffusion methods that permit quantitative determinations of amino sugar-N and amino acid-N, a study was conducted to compare the distribution of hydrolyzable N in Morrow Plots selected to represent a wide range of management and cropping practices employed since 1876. The results showed a consistent increase in total hydrolyzable-N, hydrolyzable NH4-N, amino acid-N, and amino sugar-N in the order: unfertilized continuous corn followed by continuous corn with N-P-K, corn-soybean with N-P-K, manured corn-oats-hay. The same trend was observed for the Illinois soil N test (ISNT), which estimates potentially mineralizable N as an alkali-labile fraction that is highly correlated with hydrolyzable amino sugar-N. In either case, values for the manured and unfertilized plots differed by more than 50%. Corn yields for these plots varied by almost 300%.

Technical Abstract: Soil management practices and crop rotations are generally recognized to affect soil N availability, and should be reflected in the chemical distribution of soil organic N. Yet such effects have been difficult to detect by soil N fractionation, which can be attributed, at least in part, to defective methodology. Using acid hydrolysis in conjunction with new diffusion methods that permit quantitative determinations of amino sugar-N and amino acid-N, a study was conducted to compare the distribution of hydrolyzable N in Morrow Plots selected to represent a wide range of management and cropping practices employed since 1876. The results showed a consistent increase in total hydrolyzable-N, hydrolyzable NH4-N, amino acid-N, and amino sugar-N in the order: unfertilized continuous corn followed by continuous corn with N-P-K, corn-soybean with N-P-K, manured corn-oats-hay. The same trend was observed for the Illinois soil N test (ISNT), which estimates potentially mineralizable N as an alkali-labile fraction that is highly correlated with hydrolyzable amino sugar-N. In either case, values for the manured and unfertilized plots differed by more than 50%. Corn yields for these plots varied by almost 300%.