Sustainable Substrates and Capsaicinoid Expression in Hydroponic Pepper Production ​

Commodities

Practices

Greenhouse pepper production depends heavily on imported substrates such as rockwool and coco coir. These materials increase costs, energy use, and waste, and they are not always practical for growers in the Southwest who also face limited water availability and rising input prices. This project asks whether locally available materials, including Tucson soil amended with mesquite pods, can perform as well as conventional substrates for green chile production in controlled environment agriculture.

Eighty Anaheim Charger green chile plants will be grown in the Teaching Greenhouse at the Controlled Environment Agriculture Center at the University of Arizona using four substrates: rockwool, coco coir, Tucson native soil, and mesquite-amended soil. Plant growth, yield, fruit quality, water retention, substrate pH, and capsaicin levels will be measured to compare substrate performance. Using mesquite pods, which are abundant in Arizona, provides a creative approach to testing a locally available and low-cost material that could reduce reliance on imported greenhouse media.

Results will be shared with agricultural stakeholders through greenhouse demonstration events, producer factsheets, classroom presentations, and submission of a peer-reviewed journal manuscript. Expected outcomes include data comparing conventional and bio-circular substrates, recommendations for greenhouse pepper growers in the Southwest, improved understanding of water retention and fruit quality across substrates, and educational materials that support training in controlled environment agriculture.

Research:

1. Evaluate how four substrate treatments (rockwool, coco coir, Tucson native soil, and Tucson native soil amended with mesquite pods) affect green chile plant growth, yield, and fruit quality under controlled greenhouse conditions over a single growing season
2. Quantify how substrate type influences water retention, substrate pH, and overall plant performance through weekly moisture and growth measurements.
3. Determine whether substrate treatment influences capsaicin concentration in harvested green chiles using laboratory extraction and photospectrometry analysis.

Education:

1. Share practical substrate findings with producers.
2. Develop educational materials for students and agricultural professionals.
3. Disseminate findings through scholarly channels.