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Title: SOIL ORGANIC CARBON CONTENT AND COMPOSITION OF 130-YEAR CROP, PASTURE AND FOREST LAND-USE MANAGEMENTS 1492

Author
item Martens, Dean
item REEDY, T. - NRCS LINCOLN NEBRASKA
item LEWIS, D. - UNIV OF NEBRASKA RETIRED

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/8/2003
Publication Date: 12/17/2003
Citation: Martens, D.A., Reedy, T.E., Lewis, D.T. 2003. Soil organic carbon content and composition of 130-year crop, pasture and forest land-use managements Global Change Biology. 10:65-78.

Interpretive Summary: Agricultural management of the large expanses of native Midwest prairie has led to significant decreases in the fertility and organic carbon content of these soils. Agriculture sequesters a tremendous amount of carbon in living biomass during the growing season, but this carbon can quickly cycle back to the atmosphere under certain management practices. If mechanisms for carbon retention in soils can be better understood, then properly managed agricultural soils may have a greater capacity to increase the soil organic carbon content. This study evaluated a native prairie soil, the same native prairie soil that had been converted into a deciduous forest and the same native prairie soil that had been converted to agricultural crops about 130 years ago. The conversion of native prairie to an agricultural soil decreased soil organic carbon 46% compared to the conversion of prairie to a forest-prairie mix and decreased organic carbon 25% compared to the remaining native prairie. The main mechanism for increasing soil organic carbon in this soil was the lack of tillage in the forest and native prairie soils, as tillage quickly returns the carbon-sequestered by the plant back to the atmosphere and limits the potential soil storage. This work shows that combination of lack of tillage and the growth of a mix of trees and prairie vegetation can increase soil organic carbon contents to levels greater than were found in the prairie soils when first cultivated.

Technical Abstract: Management of former agricultural land as grasslands and forests to increase long-term biomass production is a suggested management option for mitigation of atmospheric CO2 increases. The changes in soil organic C composition in a Sharpsburg prairie loess soil (fine, smectitic, mesic Typic Argiudoll) with three land uses, a native tall grass prairie remnant, a 130 year-old mixed deciduous forest and a 130 year-old cultivated field, both established on the native prairie soil provided treatments to study the impact of long-term land-use on soil organic C. The conversion of the prairie to forest land use increased soil C content (m2 by 33 cm depth) by 29% compared to the original prairie and the combination of tillage and agricultural crops significantly reduced the cropped soil C content by 25% as compared with the prairie soil. Soil organic C was composed of carbohydrates (59%, 34% and 40%), amino acids (17%, 14% and 15%), phenolic acids (4.5%, 16.6% and 1.2%), lipids (2.3%, 2.3% and 2.9%) and unidentified C (17%, 32% and 41%) for the prairie, forest and crop soils, respectively. Regression analysis found that soil organic C content in the prairie (r = 0.95; P > 0.001) and forest soils (r = 0.98; P > 0.001) was significantly related to ester-linked phenolic acids of vascular plant origin. The results suggested that a large portion of the soil C sequestered in long-term prairie and forest soils is present within stable soil aggregates and the majority of extractable C can be identified as plant residue C through the use of CH and PA biomarkers.