Shifts in Soil C Cycling Following Lime Additions to an Oxisol Under Varied Managements.

Management of soil pH by liming has strong potential to improve productivity of acid soils, but its effects on soil carbon cycling are not fully understood. Although short-term declines in soil organic carbon (SOC) have been observed following liming, it is not known how lime may affect enzymatic drivers of SOC. To this end, we evaluated the response of soil respiration, labile C, and C-cycling enzymes to liming in a Typic Kandiudox under three differing long-term (11 yr) managements. In addition to an unlimed control, five rates of Ca(OH)₂ were used to established a pH gradient of 4.5 – 6.6 during a 34 day incubation. Soil respiration initially increased for high liming rates, but converged after three weeks. At the end of incubation, potential activities for β-glucosidase and cellobiohydrolase decreased with increasing pH but increased for β-glucosaminidase, and were unchanged for β-galactosidase. With increasing pH, permanganate-oxidizable C (POXC) increased for all soils. However, in the unfertilized soil there were only minor increases in POXC at the highest liming rates. In fertilized soils, increases in POXC occurred only at higher rates in P-fertilized soils, whereas any lime addition increased labile C in the manured soil. Relative increases in POXC were greatest for manured soil (18%), followed by P-fertilized soil (4%) and unfertilized soil (2%). Results identify shifts in soil C cycling that may explain observed short-term decreases in SOC following liming, and may be modulated by previous fertility inputs.