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United States Department of Agriculture

Agricultural Research Service

Title: Soil Organic Matter Assessments in a Long-Term Cropping System Study

Authors
item Varvel, Gary
item Liebig, Mark
item Doran, John

Submitted to: Communications in Soil Science and Plant Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2001
Publication Date: February 2, 2002
Citation: VARVEL, G.E., LIEBIG, M.A., DORAN, J.W. SOIL ORGANIC MATTER ASSESSMENTS IN A LONG-TERM CROPPING SYSTEM STUDY. COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS 33(13&14):2119-2130. 2002.

Interpretive Summary: Accurate projections regarding sequestration and emission of CO2 by agricultural soils requires measurements of cropping systems effects on soil organic matter (soil C) changes. This process requires substantial annual management inputs and large outlays for soil sampling and analyses. Our objectives were: (1) to evaluate and test an alternative method for soil organic matter determination, (2) to determine if crop rotation and N fertilizer management significantly affected soil organic matter at the beginning (1986) or after 12 yrs (1998), and (3) to determine if total soil organic matter levels have changed after 12 years in a long-term cropping system study. Soil samples were taken in 1986 and 1998 to a depth of 150 cm in 30 cm increments. Total soil organic C and organic matter by weight loss on ignition concentrations determined for the soil samples taken in 1998 were highly correlated. Crop rotation and N fertilizer rate had no significant effect on soil organic matter by weight loss on ignition or total soil organic C concentrations for either sampling date, soil organic matter changes between 1986 and 1998, or total soil C in the profile (0 to 150 cm) in 1998. In spite of the lack of soil organic matter differences between treatments in the study, the excellent relationship we obtained between results from the two methods of organic matter analyses demonstrated that the less expensive and easier to use weight loss on ignition method can be used to make these types of assessments.

Technical Abstract: Assessing effects of cropping systems on soil organic matter (soil C) changes are necessary to make accurate projections regarding sequestration and emission of CO2 by agricultural soils. This process requires substantial annual management inputs and large outlays for soil sampling and analyses. Our objectives were: (1) to evaluate and test an alternative method for soil organic matter determination, (2) to determine if crop rotation and N fertilizer management significantly affected soil organic matter at the beginning (1986) or after 12 yrs (1998), and (3) to determine if total soil organic matter levels have changed after 12 years in a long-term cropping system study. Soil samples were taken in 1986 and 1998 to a depth of 150 cm in 30 cm increments. Total soil organic C and organic matter by weight loss on ignition concentrations were determined for the soil samples taken in 1998. Results from both methods of analyses for the 1998 samples were highly correlated. No significant differences in soil organic matter by weight loss on ignition or total soil organic C concentrations between crop rotations or N fertilizer rates were obtained for either sampling date, in the change in soil organic matter concentrations between dates, or total soil C amounts in the profile (0 to 150 cm) after 12 yrs (1998). Although no differences in soil organic matter (soil C) were obtained in the study, the excellent correlation between results of the two methods of organic matter analyses demonstrates that the less expensive and easier to use weight loss on ignition method can be used to make these types of assessments.

Last Modified: 9/3/2014
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