Author
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Martens, Dean |
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Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 9/6/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Due to the increasing levels of carbon dioxide in our atmosphere, scientists are beginning to investigate ways of limiting carbon emissions from agriculture. Increasing levels of carbon dioxide have been found in our atmosphere since 1830 and are being connected to our hotter and fluctuating climate patterns. Agriculture has a tremendous potential to reduce carbon present in our atmosphere due to the fixation of atmospheric carbon by growing plants. When the plant residue is returned to the soil after plant growth, this stored carbon can be released to the atmosphere by microbial decomposition processes or remain in the soil as organic matter. It has long been noted that the addition of organic matter to soil will improve many of the soil properties that influence maximum yields. It is now becoming clear that different crops decompose at different speeds and a slower residue decomposition will result in more carbon staying in the soil and not being released to increase the carbon levels in our atmosphere. This study found that the chemical composition of seven crop residues ranged greatly and when added to soil the residues influenced microbial production of carbon dioxide and improvement in soil structure. This work begins to explain how additions of organic residue to soil improves soil structure and will provide new insights for agricultural scientists for reduction of carbon inputs to the atmosphere from agricultural practices. Technical Abstract: Substrate composition is one of the most important factors influencing the decomposition of plant residues in soils. The interaction of organic residue biochemistry with residue decomposition rates, soil aggregation and soil humus composition was determined in a laboratory experiment. Addition of seven different organic residues (2% w/w alfalfa, oat, canola, clover, soybean, corn and prairie) to a Webster soil resulted in a rapid, transient increase in mean aggregate size when incubated for 9 d with residues with low phenolic acid content (alfalfa, canola, and clover) and was inversely correlated with soil carbohydrate content (r= -0.63*). More pronounced improvement in aggregate size was noted upon increased incubation to 84 d with organic residues higher in phenolic acid content (corn, prairie and soybean) and was related to soil phenolic acid (r=0.65*) and carbohydrate content (r=0.70*). Total phenolic acid content of the organic residue was related to mean aggregate size measured after incubation for 84 d by a quadratic response and plateau function (r=0.96***) and the mean aggregate size quadratically increased with an increase in vanillin-vanillic acid concentrations in the plant residues (r=0.997***). Soil organic C after 84 d was related to the mean aggregate size (r=0.82**) and the residue's vanillin-vanillic acid content (r=0.86**), suggesting that C sequestration potential of plant residues is related to the specific phenolic acid content. The results suggest that transient aggregate stability initiated by increased microbial activity is then strengthened by the interaction with phenolic acids such as vanillin or vanillic acid released from residue structural components with long-term soil stability improvement. |
