Substitution of Peat in Horticultural Seedlings: Suitability of Digestate-Derived Compost from Cattle Manure and Maize Silage Codigestion

Abstract

The increasing demand for soilless media for horticultural crop production and the rising environmental concerns about the use of non-renewable resources such as peat as substrate has led to the search for alternative materials as constituents of growing media, such as waste organic by-products. Also, biogas production through the anaerobic digestion of organic wastes generates a potential fertilizer, the digested substrate (digestate). The aim of this work was to study the feasibility of using the composted solid fraction of a digestate obtained after the codigestion of cattle manure and maize–oat silage as a component in the formulation of growing media for the commercial seedling production of three species: tomato (Lycopersicon esculentum Mill.), muskmelon (Cucumis melo L.), and pepper (Capsicum annuum L.). Four substrates were compared: pure peat (control) and three mixtures containing 25%, 50%, and 75% by volume of compost with the corresponding amount of peat. Physical, physicochemical, and chemical analyses of the different growing media were carried out and the effects of the different mixtures of peat/compost on seed germination and on the nutritional status of the seedlings were also studied. In general, compost addition neither influenced negatively the physical and physicochemical properties nor produced any reduction in the germination rate in the species studied, but it did enhance the seedlings’ nutritional status.

Keywords:

• Anaerobic digestate
• compost
• growing media
• seedling production

Acknowledgments

This work has been financed by the Spanish Ministry of Science and Innovation and European Regional Development Funds (ERDF) through “Proyecto Singular Estratégico Probiogas.” The contract of Dr. Bustamante has been supported by “Juan de la Cierva” (MCINN, Spain) in collaboration with the European Social Funds. The authors also thank Semilleros El Raal-Cox S.L. for its help in the practical development of this experiment.