|Torbert, Henry - Allen|
Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/15/2007
Publication Date: 3/15/2007
Citation: Potter, K.N., Velazquez-Garcia, J., Scopel, E., Torbert III, H.A. 2007. Residue removal and climatic effects on soil carbon content of no-till soils. Journal of Soil and Water Conservation. 62(2):110-114. Interpretive Summary: Crop residue is being considered as an alternate source of farm income by marketing it as a fuel source, either by burning or by conversion to ethanol. However the effects of residue removal with no-till on soil quality is not well understood. Residue removal effects soil fertility as nutrients are removed in the residue, but this can usually be compensated for by additional fertilization. Residue removal effects on soil organic carbon, an indicator of soil quality, are not as easily mitigated. Soil organic carbon generally increases after conversion from tillage to no-till management practices if the crop residue is left on the soil surface. In Mexico, crop residues are often utilized as animal food, even with no-till management practices. We conducted a study to determine the effect of removing different amounts of corn residue on soil organic carbon content associated with no-till. No-till practices with all residue removed usually maintained soil organic carbon levels about the same as that which occurred with moldboard plowing. Leaving residue generally increased soil organic carbon content. Climate interacted with residue removal to affect the soil organic carbon. With higher mean annual temperatures, leaving residues on the surface was less effective in increasing soil carbon content than with lower mean annual temperatures. Higher rainfall usually increased soil carbon content with larger amounts of residue remaining on the surface. Leaving crop residues in the field with no-till management can increase soil carbon contents, but with some climatic conditions the residue, in excess of that needed for erosion control, may be better used as animal food or for energy production.
Technical Abstract: While no-till management practices usually result in increased soil organic carbon (SOC) contents, the effect of residue removal with no-till is not well understood, especially in warmer climates. A multi-year study was conducted at six locations having a wide range of climatic conditions in central Mexico to determine the effect of varying rates of residue removal with no-till on SOC. Mean annual temperatures ranged from 16 to 27 °C (61 to 81 °F). Mean annual rainfall ranged from 618 to 1099 mm yr**-1 (24 to 43 in yr**-1). Treatments consisted of annual moldboard plowing under residue and no-till with 100%, 66%, 33%, and no corn (Zea mays L.) residue retained on the no-till surface. At five of the six locations, no-till with all surface residues removed maintained SOC levels above that of moldboard plowing which incorporated all residues. Retaining 100% of the crop residues with no-till always increased or maintained the SOC content. SOC increased in cooler climates, but as mean annual temperature increased, more retained crop residues were needed to increase the SOC. In tropical (mean annual temperature >20 °C) conditions, 100% corn residue retention with no-till only maintained SOC levels. Mean annual temperature had a greater impact on SOC than did annual rainfall. It appears that, in warmer climates, residue in excess of that needed for erosion control may be used for animal fodder or energy production. At the higher temperatures, most of the residue will decompose if left on the soil surface without improving soil carbon contents. [GRACEnet Publication]