Today, we congratulate RegenPGC Graduate Education Community member Malcolm Yusuf St Cyr for his successful thesis defense and completion of his Master’s studies at Iowa State University under the mentorship of RegenPGC CoPd Dr. Marshall McDaniel. Learn more about Malcolm’s thesis, Perennial ground covers: A mitigation strategy to nitrous oxide (N₂O) emissions for maize cropping systems, at www.regenpgc.org/wp-content/uploads/2026/05/2026-05-19-StCyr-OFFICIAL-THESIS.pdf
ABSTRACT
Agricultural intensification in the U.S. Midwest has led to widespread of nitrogen (N) losses through nitrate (NO₃⁻) leaching and nitrous oxide (N₂O) emissions, two processes that threaten water and atmospheric quality. Traditional winter cover crops (WCCs) have proven to be effective in reducing NO₃⁻ leaching but remain limited in adoption due to economic and management challenges. Perennial ground cover (PGC) systems integrate non-leguminous perennial grasses in between annual row crops offering a potentially optimized alternative that maintains continuous soil cover without requiring annual replanting. However, their influence on soil nitrous oxide emissions and soil nitrogen and carbon pools remain poorly explored. In this study we used three PGC treatments: 1) Zea mays L. without PGC (Maize Control), 2) maize with Poa bulbosa, a summer-dormant grass commonly called bulbous bluegrass (Maize+BBG), and 3) maize with Poa pratensis, or Kentucky bluegrass (Maize+KBG) to analyze the impact of PGC on N₂O emissions and soil N and C pools. Both PGC treatments reduced interrow cumulative N₂O emissions by 38–81% relative to the control in both years (p < 0.01), although row-position emissions were more variable and influenced by fertilizer placement. Despite these consistent interrow reductions, field-level cumulative N₂O emissions were not significantly different among treatments in either year. Overall, our results indicate that PGC does not affect field-level soil N₂O emissions, while maintaining similar levels of plant-available N, and had no effect on maize yield.









