Nitrogen Management Effects on Soil Carbon
Dynamics and Microbial Biomass in Continuous Corn and Corn-Soybean Rotation. (3615)
Authors:
H. Wilson - Iowa State Univ.
M.M. Al-Kaisi* - Iowa State Univ.
Abstract:
Nitrogen fertilization has been shown to have significant effect on soil organic carbon (SOC) and impact microbial populations. The objective of this study was to investigate the effects of three nitrogen rates (0, 145, and 290 kg ha-1) on soil carbon dynamics and microbial biomass in a continuous corn and a corn-soybean rotation. The study was conducted on a Clarion loam soil west of Ames, Iowa utilizing a chisel plow tillage system. Soil samples were taken at soil depth increments of 0-5, 5-10, 10-15, 15-30, and 30-60 cm every 2 years beginning in 1998. Soil samples were analyzed for total C and total N using a LECO CHN analyzer. Carbon dioxide emissions were measured every 7 to 10 days during the growing season in 2003 and 2004 using a Li-Cor 6400 gas analyzer equipped with a soil emissions chamber. Microbial biomass was determined using a chloroform fumigation method. Preliminary results show N fertilization did not significantly increase SOC after 2 years. The CO2 emission was not significantly different between all N rates. However, CO2 emission rate with high nitrogen rate (290 kg ha-1) was much lower than the other 2 rates, especially in the middle of the growing season. This may be attributed to the impact of high N rate on microbial activities.
Speaker Information: Mahdi Al-Kaisi, Iowa State Univ., Department of Agronomy 2104 Agronomy Hall, Ames, IA 50011-1010; Phone: 515/294-8304; E-mail:
Session Information: Wednesday, November 3, 2004, 10:00 AM-12:00 PM Presentation Start: 10:00 AM (Poster Board Number: 2539)
