Cowpeat as a Substitute for Peat in Container Substrates for Foliage Plant Propagation

Abstract

This study evaluated the potential for using cowpeat, a composted dairy manure, as a component of container substrates for foliage plant propagation. Using a commercial formulation (20% perlite and 20% vermiculite with 60% Canadian or Florida peat based on volume) as controls, peat was replaced by cowpeat at 10% increments up to 60%, which resulted in a total of 14 substrates. Physical and chemical properties such as air space, bulk density, container capacity, total porosity, pH, carbon-to-nitrogen ratio, and cation exchange capacity of the cowpeat-substituted substrates were largely similar to those of the respective control. However, the electrical conductivity (EC) increased with the increased volume of cowpeat. The 14 substrates were used for rooting single-node cuttings of golden pothos (Epipremnum aureum) and heartleaf philodendron (Philodendron scandens ssp. oxycardium) and three-node cuttings of ‘Florida Spire’ fig (Ficus benjamina) and germinating seeds of sprenger asparagus (Asparagus densiflorus) in a shaded greenhouse. All cuttings rooted in the 14 substrates, and the resultant shoot and root dry weights of golden pothos and ‘Florida Spire’ fig 2 months after rooting did not significantly vary across seven Canadian peat- or Florida peat-based substrates. Shoot dry weights of heartleaf philodendron were also similar across substrates, but the root dry weight produced in the Canadian peat-based control substrate was much greater than that produced in the substrate containing 60% cowpeat. Root dry weight and root length produced in the Florida peat-based control substrate were also significantly greater than those produced in substrates substituted by 60% cowpeat. These results may indicate that cuttings of golden pothos and ‘Florida Spire’ fig are more tolerant of higher EC than those of heartleaf philodendron, as the substrate with 60% cowpeat had EC ≥ 4.16 dS·m−1. Seed germination rates of sprenger asparagus from cowpeat-substituted Canadian peat-based substrates were greater than or comparable to those of the control substrate. Seed germination rates were similar across the seven Florida peat-based substrates. The root-to-shoot ratios of seedlings germinated from both control substrates were significantly greater than those germinated from substrates substituted by cowpeat. This difference could be partially explained by the higher nutrient content in cowpeat-substituted substrates where shoot growth was favored over root growth. Propagation is a critical stage in commercial production of containerized plants. The success in using up to 60% cowpeat in rooting and seed germination substrates may suggest that cowpeat could be an alternative to peat for foliage plant propagation.