Tracking Casing Water Dynamics to Support Peat-Alternative Mushroom Production

Peat-based casing is widely used in Agaricus bisporus production because it provides a stable structure and a reliable water reservoir for fruitbody development. As the sector moves toward peat-reduced and peat-free casing materials, the way water is stored and released within the casing layer can change substantially, making irrigation decisions less straightforward. We show how embedded sensors make casing water dynamics measurable and interpretable, relate these dynamics to yield and quality outcomes in peat-reduced casings, and are extending the same framework to peat-free systems at industry-representative scale.

The water status of casing treatments, comprising peat diluted in volume proportions with wood-fibre, composted and uncomposted bark, was monitored in real time, using embedded solid-state tensiometers measuring matric potential (Ψm), i.e. how tightly water is held in the casing (more negative Ψm indicates lower water availability). Rather than relying on single-point Ψm values, we focus on time-resolved Ψm behaviour (e.g., the duration of sustained low Ψm and rate of recovery following irrigation). In two repeated peat-reduced casing trials, wood-fibre amendments closely matched peat controls in in-crop Ψm evolution (a similar rate of decline during each flush; not exceeding −34.4 kPa) and produced mushroom yield and quality (colour) that was statistically indistinguishable from peat across both trials. By contrast, bark-amended casings diverged from peat controls: Ψm dynamics were more sensitive to changes in crop management, and yields were significantly lower than peat in the first trial, with uncomposted bark remaining significantly below peat across both trials. Importantly, high pin-set, more common in the looser-structured bark treatments, increased water demand early in the crop cycle and reduced water availability for subsequent flushes, highlighting the need to avoid or control over-pinning to protect against casing structural degradation and related losses in potential yield.

To link in-crop sensor signals to casing hydraulic behaviour, water-release characteristic curves were measured independently (Hyprop 2) for all peat-reduced materials. These curves describe each material’s inherent water-release response, independent of irrigation regime and uptake by developing mushroom, providing a physical basis for interpreting in-crop Ψm patterns and separating material-driven responses from management and demand effects.

We are extending this approach to peat-free casings at 1 m² scale using a balanced blocked design (16 trays per run, two runs) comparing standard irrigation with a sensor-guided watering strategy that applies small in-flush top-ups only when Ψm indicates a persistent deficit. Continuous Ψm monitoring across all trays (24 sensors; one per tray plus dual-sensor subsets) and irrigation event logging will link Ψm time-metrics to yield, grade and mushroom dry matter.

Overall, combining water-release characteristics with in-crop, multi-point Ψm monitoring offers a practical route to understand and manage water availability in peat-alternative and peat-free casings, supporting peat reduction while maintaining yield and quality.