Degree Type

Dissertation

Date of Award

2014

Degree Name

Doctor of Philosophy

Department

Agronomy

Major

Sustainable Agriculture

First Advisor

Matt Liebman

Abstract

Increasing carbon (C) in the soil is important both for removing harmful C from the atmosphere and improving the health of the soil. In this dissertation, I set out to examine how planting and harvesting prairies on soils suitable for corn affected soil C storage potential when compared to corn-based systems. I addressed three questions designed to a) improve our understanding of the fundamental differences between how prairies and corn grow throughout the year, b) test how prairies and corn add C to the soil after establishment, and c) use our current understanding of prairie and corn growth and C and N dynamics to predict how SOC will change over the next 50 years. Measurements of fundamental differences showed corn produced more aboveground and overall biomass with faster growth rates that peaked later in the season than prairie. Duration of growth was shorter in corn than prairie. Corn allocated a much smaller proportion of its biomass belowground than prairie and produced much less root biomass than prairie. Corn biomass had higher N concentrations, but less efficient growth relative to these concentrations. Six years after establishment of the experiment, I found prairies had more root mass that was more recalcitrant and located at depths unfavorable to decomposition, but did not have greater amounts of labile C (POXC) or total SOC than corn-based treatments, nor greater amounts of total SOC than in the establishment year. However, it was important to note that prairies placed ~5 times more C belowground as root C than corn-based treatments. Simulations made over 50 years using the APSIM model showed that prairies had much larger increases in root C, fresh organic matter, and microbial biomass pools, while a corn-based system with a winter cover crop maintained these pools, and continuous corn and corn-soybean rotations lost C in these pools. However, all treatments lost C from the more stable C pool, resulting in an overall loss of SOC after 50 years. The lack of gain in soil C was attributed to a combination of C-saturated soils and rhizosphere-induced priming. However, the validity of these mechanisms needs more investigation.

DOI

https://doi.org/10.31274/etd-180810-3221

Copyright Owner

Ranae Dietzel

Language

en

File Format

application/pdf

File Size

131 pages

Share

COinS