L. Vecchietti

Nursery growing media: agronomic and environmental quality assessment of sewage sludge-based compost

There is a stringent need to reduce the environmental impact of peat in the plant nursery production chain. In this experiment, the use of different rates of sewage sludge compost in the preparation of growing media for potted Bougainvillea was evaluated to assess its efficiency for the replacement of peat and to quantify the environmental impact of such alternative substrates by the life cycle assessment (LCA) method. Five substrates containing increasing proportion of composted sewage sludge to peat (0%, 25%, 40%, 55%, and 70% v/v) were used, and their physicochemical properties were measured. Bougainvillea plant growth, biomass production, and macro- and micronutrient absorption were also determined. The main results were that compost addition improved the plant nutrient and increased the substrate pH, electrical conductivity (EC), and dry bulk density values. Globally, the results showed that compost could be used at up to 55% by volume with no negative effects on plant growth. The LCA showed that use of compost reduced the environmental loads of the growth media, except the Global Warming Potential value (GWP100). Environmental implications of the use of compost in the plant nursery chain are discussed.

EFFECT OF PEAT-REDUCED AND PEAT-FREE SUBSTRATES ON ROSEMARY GROWTH

The objective of this work was to study the use of four composts, obtained by agro-industrial, urban and green wastes, as growing media components on Rosmarinus officinalis L. Substrates were obtained by mixing each compost with peat in different proportions. Main physical and chemical characteristics of prepared substrates have been compared and, at the end of growing cycle, the biometric survey on main growing parameters and plant nutritional status was performed. The obtained results showed that substrates with 30% compost have main physical and chemical parameters comparable with those of the control. Best quality plants have been obtained substituting peat with 30% of compost, except with the olive mill compost. At the end, the green pruning compost can be recommended as growing media component (up to 50%) for the growth of Rosmarinus officinalis L., being able to determine high quality plants, together with an implemented plant nutrient efficiency.