Composting of wine industry wastes and their use as a substrate for growing soilless ornamental plants
To study the process of composting of grape marc and test the resulting compost as a substrate for the cultivation of ornamental plants, six composting processes, with mixtures of dealcoholised grapevine marc and grape stalk (DM+GS) in a 1:1 ratio (v:v), were carried out in Seville (Spain) between 2000 and 2006. The duration of the composting ranged between 20 and 24 weeks in the Spring-Summer season. Weekly, temperature, pH, EC, N-NO3- and N-NH4+, were measured. The maximum temperatures reached values of 65-73°C at a depth between 40 and 80 cm. The compost had a slightly alkaline pH, slightly salinity, high organic matter and total nitrogen contents. The final compost chemical composition in total elements showed values in the same range as those corresponding to plant material, except for Fe. The distribution in the size of the particles gives way to a total porous space that is close to the one considered as optimal in a substrate for soilless cropping. Pore size distribution showed a prevalence of big pores that produces unbalance in the water-air ratios, resulting in a material with a good aeration but with low water retention. The composts were tested as substrates for four ornamental species: geranium, petunia, carnation and gerbera. The results suggest that compost has no limiting characteristics for its use as a medium for the cultivation of ornamental plants in container, and can replace conventional substrates, such as peat and coconut fibre.