|Wilson, Gail W.|
Submitted to: International Symposium on Soil Organic Matter Dynamics: Land Use, Management and Global Change
Publication Type: Abstract Only
Publication Acceptance Date: 4/20/2009
Publication Date: 7/6/2009
Citation: Mfombep, P., Rice, C.W., Todd, T.C., White Jr, P.M., Wilson, G.T. 2009. Tillage and land-use impacts on soil carbon and nitrogen storage and belowground processes. International Symposium on Soil Organic Matter Dynamics: Land Use, Management and Global Change. Interpretive Summary:
Technical Abstract: Understanding soil carbon (C) and nitrogen (N) storage and cycling in different ecosystems is essential to accurately forecast land-use changes to facilitate GHG abatement. The current study was undertaken in 2004 in a C3 wheat (Triticum aestivum) tillage agriculture system. Three management systems were initiated to assess tillage and land-use effects: 1) RP - Prairie restoration vegetated in warm season grasses; 2) NT - No-tillage grain sorghum (Sorghum bicolor); and 3) CT - Conventional tillage grain sorghum. These plant species exhibit a C4 respiration pathway, and all systems were managed for maximum yield through N addition, pest management, and annual burning. Additionally, in a subset of plots arbuscular mycorrhizal fungi (AMF) colonization was suppressed (by phosphorus (P) or fungicide) to alter the flow of C and N into the soil. Mycorrhizal control plots received equivalent quantities of water. Soil C and N, AMF root colonization, biologic properties, and the addition of new C4-C were assessed yearly. After 5 y, the soil C levels were similar in each system at 0-5 cm, except for a decrease in NT with P addition, and at the 5-15 cm level, with average values of 20.3 and 20.4 Mg ha-1, respectively. Soil N followed similar trends. Percentage AMF colonization was suppressed in RP receiving fungicide, as compared to the control, with levels of 12 and 23, respectively. Soil microbial biomass C was not different after 2 y of treatment, with a mean value of 282 mg C kg-1 soil. Finer resolution measurements provide insight into belowground mechanics. A higher delta 13C value was found in CT (-16‰), as compared to RP (-17‰), indicating greater SOM turnover with disturbance. The soil microbial community structure was affected by management, with increases in fungal phospholipid fatty acid (PLFA) 18:2w6,9c and 18:1w9c and reductions in branched and methylated gram positive PLFA for RP and NT, signaling a change to a fungal-dominated community in plots not annually disturbed. An opposite trend was observed in CT plots, indicating disturbance may increase bacterial abundance in these microbial communities. Nematode abundances in the RP and NT plots exhibited increases in herbivorous species. In this study, management effects on belowground processes were evident after a short time span (2-3 y) but longer time spans are needed to observe management effects on broader soil nutrient dynamics.