Location: Application Technology Research
Project Number: 5082-21000-001-109-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2024
End Date: Aug 31, 2027
Objective:
(1) Create or identify robust methods to measure total carbon emissions from soilless substrate components and their mixtures and (2) create or identify robust reliable methods to measure hysteresis in soilless substrates. Collective information will be used to (3) validate use of methods to design and modify substrates based on associated cultural practices including irrigation scheduling.
Approach:
Objective 1: Total carbon emissions. Researchers will conduct a greenhouse study using four substrates: pine bark (=12.7 mm), Sphagnum peat, coir, and extruded wood fiber. The latter three will be mixed with 70% pine bark and 30% of each substrate (by volume). Forsythia liners ( will be planted with these substrates (and given urea ammonium nitrate (UAN) controlled release fertilizer (6.3 g nitrogen/container). Plants will be irrigated daily, and water use, temperature, and humidity will be monitored. On three occasions (initial planting, 30 days, and 90 days), we will measure carbon dioxide (CO2), carbon monoxide (CO), and methane CH4 fluxes using a FTIR analyzer). One pot per substrate will be destructively sampled to analyze root length, diameter, surface area, and volume.
Additionally, we will evaluate low-cost near-infrared (NIR) CO2 sensors for the measurements.
Objective 2: Water retention hysteresis. Alongside the carbon emissions study, researchers will grow another set of forsythia in the same four substrates On days 30 and 90, we will collect intact core samples using a 7.5 cm diameter by 5 cm tall metal cylinder to analyze water retention, researchers will adapt a hanging water column system Measurements of water content and potential at each step will help us assess hysteresis under different root growth conditions. These results will be compared with those from an automated systems.
Objective 3: Substrate Design. In this step, researchers will use the same four substrates but may adjust blends and size fractions. Initially, substrates will be fallow, but plants might be added as needed. We will measure hysteretic water retention and unsaturated hydraulic conductivity. These data will be input into one- and three-dimensional models to simulate wetting and draining dynamics at various irrigation rates. Optimal irrigation will be identified. This effort will help refine substrate blends and irrigation scheduling.
