Behaviour and effects of organic hydromulches on soil biological aspects in nursery crops

Common practices for weed control in horticultural and fruit crops often rely on herbicides, petrochemical plastics and intensive tillage. However, the environmental impact of these techniques has encouraged researchers worldwide to explore more sustainable alternatives aligned with circular economy principles. These eco‑friendly approaches could also be applied to other production systems, such as seedbeds or nursery plants. Within this context, biopolymers and paper-based materials show promising performance, although their shorter lifespan makes them more suitable for annual herbaceous crops. Based on preliminary laboratory tests, we therefore established a field trial in a forest tree nursery in Central Spain, applying hydromulches of different compositions and characteristics to newly transplanted seedlings grown in open-field conditions.

The hydromulches were formulated using agricultural and agri‑food by‑products—wheat straw, camelina pellet, almond pruning wood, elm + walnut, and a mixture of elm, walnut and camelina. These materials were combined with a binder and recycled paper pulp, and applied in liquid form to the soil, where they subsequently solidified. In addition, two unmulched treatments were included as controls (manual weeding and no weeding) within a randomized complete block design with three replications.

In order to evaluate the possible effect of the different hydromulches on soil respiration, the CO₂ flux was measured using an EGM‑4 portable soil respiration system (non‑dispersive infrared gas analyzer) equipped with an SRC‑1 chamber (PP Systems). Measurements were taken between 12:00 and 14:00 (solar time) at the same point in each treatment. Throughout the trial, the degradation dynamics of the hydromulches (thickness, puncture resistance, soil cover, etc.) were also monitored, together with their influence on soil biological activity and mesofauna abundance. Clear differences were observed among treatments, with the camelina‑based hydromulch showing the fastest and most pronounced degradation. While this behavior could limit its effectiveness as a persistent weed control layer, it was associated with higher soil biological activity and supported a greater quantity of mesofauna.

 

Keywords: hydromulch, soil respiration, biological activity, mesofauna.

Acknowledgements: PID2020-113865RR-C43 (HMulchCircle)/AEI/10.13039 / 501100011033 (Spanish Ministry of Science and Innovation) / 2024-TRAN-36705 (University of Castilla-La Mancha).