Fabrizzi, Karina (Kansas State University, 2004 Throckmorton Plant Sciences Center, Manhattan, KS, 66502; Phone: 785-395-6018; Email: firstname.lastname@example.org)
K.P. Fabrizzi *, C.W. Rice, A. Schlegel, D. Sweeney, D. Peterson, C. Thompson
Management practices such as crop rotation, tillage, and fertilization can influence soil biological activities through their effects on the quantity, structure, and distribution of soil organic matter (SOM). The effects of these management practices on soil C fractions were evaluated in this study. Soil samples were taken from four long-term experiments with different years under tillage systems, at four locations in Kansas: Tribune (16 yr, tillage effects)(Aridic Argiustolls), Hays (37 yr, tillage and N effects) (Typic Argiustolls), Ashland (23 yr, crop rotation and tillage effects) (Cumulic Haplustolls), and Parsons (20 yr, tillage and N effects) (Mollic Albaqualfs). Soil organic carbon (SOC), microbial biomass (SMB-C) and mineralizable C (MinC) were measured at 0-5 and 5-15 cm depth. Tillage treatments considered during the study were: conventional tillage (CT), reduced tillage (RT), and no-tillage (NT). N rates were 0, and 67 kg N ha-1 in Hays (0-N and 67-N), and 0 and 140 kg N ha-1 in Parsons (0-N and 140-N). Crop rotations evaluated at Ashland were wheat/soybean and wheat/wheat. In Hays, CT and RT treatments had greater SMB-C fractions than NT at 0-N treatment at 0-15 cm. MinC was greater under NT than the other tillage systems at 67-N treatment. Tribune data showed a greater proportion of C in the labile pools (SMB-C and MinC) under NT and native prairie treatments at 0-15 cm. In Ashland, SMB-C represented between 2.2 and 2.8%, and MinC between 25-30% of the soil organic carbon in the wheat/soybean rotation. Values for wheat/wheat rotation were 1.0 to 1.3 % for SMB and 28 to 34% for wheat/ wheat rotation.