Honors Theses and Capstones

Date of Award

Spring 2024

Project Type

Senior Honors Thesis

College or School

COLSA

Department

Agriculture, Nutrition, and Food Systems

Program or Major

Sustainable Agriculture and Food Systems

Degree Name

Bachelor of Science

First Advisor

Richard Smith

Second Advisor

Natalie Lounsbury

Abstract

Climate change is expected to yield warmer winters that have the potential to place additional stress on our already stressed agricultural systems. Understanding how agricultural systems may respond to these changes is essential to creating crop and land management plans that ensure food security for future generations. To better understand how warming winters can/will affect air and soil temperatures and cover crop performance, open top chambers (OTCs) were deployed post cover crop seeding in a field experiment at the UNH Kingman Research Farm in Madbury, NH. The experiment consisted of four cover crop treatments sown into or after corn: an interseeded mixture of clover, tillage radish, and annual ryegrass; interseeded winter rye; winter rye seeded post corn harvest; and a weedy control. Only the two interseeded treatments and the control were included in the present study. Cover crops were replicated across four blocks, and each replicate was split into two subplots. OTCs were randomly assigned to one subplot within each replicate and the other subplot served as an ambient control (no OTC). Temperature sensors were placed at three depths within the OTCs and outside the OTCs– aboveground, 3 cm belowground, and 10 cm belowground. Temperature data were recorded hourly from November 2023 to April 2024 while percent ground cover was measured twice in March and once in April 2024. A literature review examining the relationship between OTC height to top-diameter ratio and warming effect was also conducted to understand the viability of OTCs as a passive warming device in climate warming experiments. On average OTCs were found to cause a soil and air warming effect of 1ºC, with a max warming effect of 2ºC. OTCs were also associated with a higher percent ground cover across all three cover crop treatments. The literature review revealed a positive correlation between OTC height to top-diameter ratio and the magnitude of the reported warming effect. These results suggest that OTCs are an effective method for passively generating air and soil warming in climate change experiments, as the OTCs used in this experiment caused a significant winter warming effect that was correlated with enhanced plant cover.

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