Using 13C isotopic analysis to assess soil carbon pools associated with tile drainage management during drier and wetter growing seasons

Abstract

Controlled tile drainage (CTD) is an agricultural management practice with well-documented water quality and agronomic benefits. However, due to field water drainage abatement effects, the practice could potentially impact soil respiration. The δ13C of soil gas samples were analyzed from silt loam CTD and uncontrolled tile drained (UTD) fields cropped with corn, soybean, and forage to test whether CTD affects total soil respiration (RT) through altering residue decomposition and/or gas transport. We also examined whether CTD imparted an over tile (OT) and between tile (BT) locational effect on RT. All gas samples are from bulk rhizosphere and microbial sources; except for the forage crop measurements which included plants growing inside the sampling chamber collars. The mean values of δ13C for RT were not statistically different (p>0.05) between four of the five CTD and UTD field pairs. Neither were the means of δ13C of RT different (p>0.05) between OT and BT locations in four of the five CTD fields. The generalized lack of statistical differences in δ13C of RT observed, may have resulted from the drier and wetter seasonal conditions muting drainage management effects on surface soil water contents. The results could be used to help refine the carbon footprint of tile drainage management practices.