Fabrizzi, Karina (Kansas State University, 2004 Throckmorton Plant Sciences Center, Manhattan, KS, 66502; Phone: 785-532-7106; 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 affect soil organic C levels, thus having a positive impact in the reduction of atmospheric CO2 levels. Evaluation of these practices with long-term experiments is needed to know the effect of agricultural management on soil C sequestration. The objective of this study was to study the effects of crop rotation, tillage, and fertilization on soil C sequestration in Kansas. Soil organic carbon (SOC) was measured at 0-5, 5-15, and 15-30 cm depth in four long-term experiments with different years and with different 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). Tillage treatments were: conventional tillage (CT), reduced tillage (RT), and no-tillage (NT). Nitrogen rates were 0, 22, 45 and 67 kg N ha-1in Hays (0-N, 22-N, 45-N and 67-N), and 0 and 140 kg N ha-1in Parsons (0-N and 140-N). Crop rotations evaluated at Ashland were: sorghum/sorghum, soybean/sorghum, soybean/soybean, wheat/soybean and wheat/wheat. Data from Hays showed a positive soil C sequestration rate under NT at 0-15 (0.020 Mg C ha-1 yr-1) compared to CT (-0.055 Mg C ha-1> yr-1) and RT (-0.036 Mg C ha-1 yr-1). Rates were affected by the addition of N fertilizer being greater and positive in the 67-N treatment (0.001 Mg C ha-1 yr-1). At Parsons, NT had greater SOC contents at 0-5, 0-15 and 0-30 cm when compared with CT and RT. Soil C sequestration rates at 0-15 cm were 0.229 Mg C ha-1 yr-1 for NT, 0.166 Mg C ha-1 yr-1 for RT, and 0.1398 Mg C ha-1 yr-1 for CT. At Tribune, NT had higher SOC contents (10.5 Mg C ha-1) at 0-5 cm compared with CT (8.7 Mg C ha-1) and RT (9.8 Mg C ha-1). Rates of C sequestration calculated with respect to the native prairie sod at 0-15 cm were negative with the lowest loss of C under NT systems. Data from Ashland showed a significant effect of rotation and tillage on SOC content at 0-15 cm. Wheat/wheat rotation had the greatest SOC of 31.6 Mg C ha-1, with the lowest under soybean/soybean rotation (21.1 Mg C ha-1). Also, NT treatments (28.4 Mg C ha-1) had similar SOC than RT (27.4 Mg C ha-1) but higher than CT (24.4 Mg C ha-1).