Abstract
The most common substrate for potted ornamental plants is prepared with Sphagnum peat; however, the cost and declining availability of high-quality peat, due to environmental constraints, make it necessary to investigate for alternative organic materials. The present study aimed to determine the effects of partial compost replacement with peat and the optimum electrical conductivity (EC) level of the nutrient solution in potted weeping lantana [L. montevidensis (Spreng.) Briq.] under a recirculating soilless system. Three compost-based substrates were prepared by mixing peat (Pe) with sewage sludge-based compost (Co.) at a rate of 0% (Pe90Co0Pu10, control), 30% (Pe60Co30Pu10), or 60% (Pe30Co60Pu10), respectively. The soilless recirculated closed system was equipped with two different EC levels (high and low) of nutrient solution. Growing media main characteristics and plant bio-morphometric parameters were evaluated. Our first evidence clearly demonstrates that the replacement of peat with compost at doses of 30% and 60% gave the poorest results for plant diameter, shoots, leaves, flowers, and fresh and dry mass, probably indicating that the physical characteristics of the compost based substrates may be the major factor governing plant growth rate. Compost media pH and EC values, too, showed negative effects on plant growth. Considering the effect of EC level, all morphological traits were significantly improved by high EC compared to low EC in weeping lantana. Thus, based on first evidence, further research is needed on organic materials for the establishment of ecological substrates with optimal physicochemical characteristics for the growth of weeping lantana.
Highlights
Ornamental greenhouse production has increased in the last decades and is an intensive form of agriculture
According to Abad et al [18], an acceptable electrical conductivity (EC) value should be lower than 0.5 dSm−1 ; and in our trial the Pe60Co30Pu10 and Pe30Co60Pu10 EC values were strongly affected by the addition of compost
Weeping lantana plants in our experiment showed high rusticity and adaptability, demonstrating their viability for recycling soilless cultivation
Summary
Ornamental greenhouse production has increased in the last decades and is an intensive form of agriculture. Great amounts of both organic and mineral growing media, mineral fertilizers, water and pesticides are needed to obtain high-quality product in a short cultivation cycle [1]. Rapid growth and flowering in potted plants are mainly correlated to nutrient availability both in the growing media and in fertilizer solutions [2,3]. Previous studies have investigated peat replacement with organic wastes originating from composting [6,7]. The compost is principally produced by urban and agro-industrial sludge and can be reused in soil as nutrient-rich fertilizers [8] and as soilless growing media, growing seedlings, plant propagation and ornamental pot production [9]. The proportion of compost in the final substrate is very important in order to minimize potential hazards, especially high salinity and heavy metal contents [10]
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