Soil Redox Potential and Carbon Fractions in Manured and Cover-Cropped Soils Under Reduced Tillage.

Reduced tillage and cover cropping have become more widespread management practices in the past 30 years. In addition to increasing soil carbon (C) content and water-holding capacity, these practices could create lower redox potentials and affect microbial respiratory processes in surface soils. The objective of this study is to assess relationships between specific soil properties and redox potential (4- and 10-cm depths) in experimental plots under contrasting management in the Sustainable Dairy Cropping Systems project at Penn State’s Agronomy Research Farm, Rock Springs, PA. These plots have been managed with reduced tillage in the same rotational systems for the last six years. Preliminary data from the 2017 growing season will be presented, with a focus on assessing the effect of a single tillage event in manured and cover-cropped soils. Our hypothesis is that soil redox potentials are lower in soils with higher levels of labile carbon. The rationale for a focus on redox potential and carbon availability is the need to understand how these soil properties influence nitrogen cycling and other microbial respiratory pathways. By affecting microbial use of electron acceptors, redox potentials could exert important controls on nitrification, denitrification, and dissimilatory nitrate reduction to ammonium. Reducing disturbance and increasing mineralizable C pools may therefore lead to increased nitrogen use efficiency in cropping systems.