Heterogeneous response of two bedding plants to peat substitution by two green composts

Abstract

The promotion, at local level, of resource recycling chains, with low environmental impact and costs, appears of great interest for the production of green composts to replace peat in ornamental crops. In this work, two green composts, differing for the criterion of raw material selection for composting, were tested for the cultivation of two bedding plants in comparison with 100% peat based substrate. Leaf chlorophyll (SPAD index), biometric and growth parameters, and tissue mineral composition were measured to assess growing media-plant system performances. Both growing media and plants gave heterogeneous responses depending on substrate characteristics and plant requirements and/or tolerance to abiotic stress. Plant biomass was reduced by 63% (on average) in the most sensitive species due to the high Cl concentration detected in one of the two green composts; a similar trend was observed for SPAD index. The results support the shared idea that the selection of raw material is a strategy of primary importance in the composting process to obtain high quality green compost.

Keywords

• impatiens hawkeri
• petunia × hybrida
• growing media
• spad chlorophyll
• chloride toxicity