Barbara De Lucia

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.

Composted Amendment Affects Soil Quality and Hedges Performance in the Mediterranean Urban Landscape

ABSTRACT The influence of increasing rates (0, 15, 30, and 45%) of composted sewage sludge (CSS) in the plantation hole on both urban soil properties and three native Mediterranean woody hedge growth was monitored over a two-year period after establishment. The results indicate that the urban soil physical characteristics were positively influenced by the compost: the highest CSS rate showed an increase in both moisture and infiltration values. The chemical properties of the amended soils were also directly affected by the CSS rate, but the compost effect on organic matter, N and K contents decreased over time. At the end of the trial, the hedge grown on the 30% CSS rate showed significantly higher dry weight values compared to the 45% CSS. The growth response to the compost rates of the three species was not similar: mock privet presented hedges with higher dry weight value than the Mediterranean buckthorn mean value, whereas the lowest ones were found in Tarentum myrtle. Phillyrea, in our experimental conditions, developed regularly not being stressed by the presence of high pH values (45% compost rate); it encourages, in the the Mediterranea basin, sustainable landscaping and xerogardening. The results proved that, compared to urban non amended soils, the amended ones are more suitable to the hedge growth; therefore, a plan of hedge establishment based on the use of composted sludge as amendment for sclerophyllous could be feasible and, what is more, helpful to mitigate the environmental impact of organic waste disposal.

Organic and Mineral Soil Fertilisation in Gladiolus

Research was undertaken for the purpose of assessing, from a bioagronomic point of view, the effect of some organic fertilisers, obtained from purified urban wastewater sludge and of biodegradable mulch on the growth and yield of gladiolus cut flowers, with a view to promoting the development of a sustainable floriculture in Mediterranean environments. The use of sludge + straw-derived compost induced the earliest on the mean flowering period, even through mulching; in any case, the soil supplementation with organic matter only, or added with mineral fertilisers, increased the yield of cut flowers, as compared to mineral fertilisation only. The highest value was obtained by applying sludge + stalk-derived compost; the stem quality, notably the total length and spike length and the number of flowers, was positively influenced by the use of both mineral and organic matter fertilisations, in particular the sludge + stalk-derived compost, either single or mixed with mineral fertilisers. The results obtained seem to prove the effectiveness of the use of purified urban wastewater sludge composted with different organic matrices in floriculture.

Effects of an Animal-Derived Biostimulant on the Growth and Physiological Parameters of Potted Snapdragon (Antirrhinum majus L.)

To assess the effect a new animal-derived biostimulant on the growth, root morphology, nitrogen content, leaf gas exchange of greenhouse potted snapdragon, three treatments were compared: (a) three doses of biostimulant (D): 0 (D0 or control), 0.1 (D0.1), and 0.2 g L−1 (D0.2); (b) two biostimulant application methods (M): foliar spray and root drenching; (c) two F1 Antirrhinum majus L. hybrids (CV): “Yellow floral showers” and “Red sonnet.” The treatments were arranged in a randomized complete-block design with four replicates, with a total of 48 experimental units. Plant height (+11%), number of shoots (+20%), total shoot length (+10%), number of leaves (+33%), total leaf area (+29%), and number of flowers (+59%) and total aboveground dry weight (+13%) were significantly increased by the biostimulant application compared to the control, regardless of the dose. The lowest dose resulted in the best effect on the ground plant dry weight (+38%) and, in order to the root system, on total length (+55%), average diameter (+36%), volume (+66%), tips (+49%), crossings (+88%), forks (+68%), projected (+62%), and total surface area (+28%). Compared to the control, plants treated with the biostimulant significantly enhanced leaf (+16%) and root (+8%) nitrogen content, photosynthetic rate (+52%), transpiration rate (+55%), and stomatal conductance (+81%), although there were no changes in dark-adapted chlorophyll fluorescence. Differences in the application method were not evident in the aboveground morphological traits, except in the plant shoot number (root drenching: +10%). The foliar spray compared to root drenching had a significant effect only on flower dry weight (3.8 vs. 3.0 g plant−1). On the other hand, root drenching had a positive effect on ground dry weight (2.7 vs. 2.3 g plant−1), root morphology, leaf-N and root-N content (+3%), transpiration rate (+21%), stomatal conductance (+40%), concentration of CO2 in intracellular spaces (+11%), as well as on the efficiency of Photosystem II (+11%). A higher pot quality was obtained in “Red sonnet” compared to “Yellow floral shower.” Based on our findings, applying the biostimulant to potted snapdragon at the lowest dose, as part of a fertilizing regime, improves the crop quality in an agro-environmental sustainable way.

Response of Weeping Lantana (Lantana montevidensis) to Compost-Based Growing Media and Electrical Conductivity Level in Soilless Culture: First Evidence

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.