Residue removal and climatic effects on soil carbon content of no-till soils

摘要

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 wanner 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℃ (61℉ to 81℉). 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℃) 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.