Organic Matter Fractions from Organically and Conventionally Managed Soils: I. Carbon and Nitrogen Distribution
1996
Wander, M. M. | Traina, S. J.
Chemical and physical fractionation techniques were used to study the effects of organic and conventional management practices on soil organic matter (SOM) characteristics. We isolated SOM from: (i) organic animal-based, manure-amended (ORG-AN), (ii) organic cash-grain-based, cover cropped (ORG-CC), and (iii) conventional, cash-grain-based (CONV) rotations. We quantified the total C and N contents of humin (HN) and humic substances (HS), and light (LF), heavy (HF), fine organo-clay, and organo-sand fractions. Management changed the quantity and distribution of C and N in physically and chemically isolated fractions. The ORG-CC soil had significantly greater quantities of C in its HN, HS, LF, and HF fractions than the CONV soil. Management impacted the distribution of C and N only in the LF fraction. The ORG-CC had a larger percentage and proportion of C and N in its LF than the other soils. The percentage of soil N in HS was higher in the ORG-AN and ORG-CC than in the CONV soil. Even though the quantity of N in the CONV's HN equaled the other soils, it had the highest percentage and proportion of N allocated to this fraction. Farming systems did not significantly alter the C and N contents of HS or the quantity of C associated with selected particle-size fractions; however, the C content of fine clay isolated from aggregated soil was significantly greater than the C content of clay isolated from loose soil. By isolating macroorganic matter (LF) in concert with HS and HN fractions, we were able to assess management practice impacts on SOM characteristics.
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