The use of spent coffee grounds in growing media for the production of Brassica seedlings in nurseries.

Large quantities of spent coffee grounds (SCG) are generated the last decades, and their recycling is of research interest challenge. In the present study, SCG was tested to substitute peat (P) in substrate mixtures for the production of Brassica seedlings. Seeds of cauliflower, broccoli, and cabbage were placed in substrate mixtures containing 0-2.5-5-10% SCG. The mixture of SCG with peat affected several physicochemical characteristics of the growing media, providing also considerable amount of mineral elements for the seedling growth needs. Seed emergence was stimulated in 2.5-5% of SCG for cauliflower and at 2.5% of SCG for cabbage, while 10% of SCG decreased the percentage and increased the mean emergence time of the examined species. Plant biomass and leaf number were increased at 2.5% SCG for broccoli and cabbage but maintained at cauliflower when compared with control. The SCG at 10% decreased stomatal conductance of broccoli and cabbage (including 2.5-5% SCG in cauliflower) while chlorophyll content was increased at 10% of SCG media. The incorporation of SCG impacted the mineral content accumulated in plants with increases in nitrogen, potassium, and phosphorus and decreases in magnesium and iron content. Total phenolics and antioxidant activity (DPPH, FRAP) decreased at ≥ 5% SCG at cauliflower and cabbage or unchanged for broccoli when compared with the control. The cabbage seedlings grown in 10% SCG media subjected to stress with increases in the production of hydrogen peroxides and lipid peroxidation, and reflected changes in the antioxidant enzymatic metabolism (catalase, superoxide dismutase). The present study demonstrates that SCG (up to 5%) can be used for seed germination biostimulants and/or partially substitute the peat for Brassica seedling production.

Deployment of olive-stone waste as a substitute growing medium component for Brassica seedling production in nurseries.

In the Mediterranean region, olive-stone waste (OSW) is accumulated and considered of environmental and human health constraints. In this study, OSW was used for peat (P) replacement in growing media for Brassica seedling production. Cauliflower, broccoli, and cabbage were seeded in growing media consisted of 0-20-40-60% OSW. The mixture of OSW with peat increased growing media bulk density and reduced the total pore space and available water and air at root system. A Considerable amount of minerals were provided into the growing media with the OSW, while their availability was increased with the raised pH values. Seed emergence percentage decreased with high ratio of OSW which also increased mean emergence time. The addition of OSW decreased plant height, leaf number, and fresh weight in all three examined species. The OSW decreased stomatal conductance (in cauliflower and cabbage) and chlorophylls content (including broccoli). The insertion of OSW affected the mineral accumulation in plants with decreases in nitrogen and sodium content and increases in potassium and calcium. OSW increased to some extent for cauliflower and broccoli or unchanged for cabbage polyphenolic content and antioxidant activity (ABTS, FRAP). Cellular damage was caused by the addition of OSW by increasing the lipid peroxidation and the production of hydrogen peroxide, and as a consequence, the plant antioxidative (catalase, superoxide dismutase) enzyme metabolism increased. The current study demonstrates that up to 20% of OSW can substitute peat for cauliflower, broccoli, and cabbage seedling production while cabbage was performed better under the increased OSW-caused stress.

Alternative soilless media using olive-mill and paper waste for growing ornamental plants.

Peat-based growing media are not ecologically sustainable and peat extraction threatens sensitive peatland ecosystem. In this study, olive-stone waste (OSW) and paper waste (PW) were used in different ratios-as growing media-for ornamental crop production, as peat (P) substitutes. Marigold (Calendula officinalis L.), petunia (Petunia x hybrita L.) and matthiola (Matthiola incana L.) plants were grown in (1) P (100%), (2) P:OSW (90%:10%), (3) P:OSW (70%:30%), and (4) P:OSW:PW (60%:20%:20%). The physicochemical properties of these substrates and the effects on plant growth were determined. The addition of 10-30% OSW into the substrate increased marigold height compared to plants grown in 100% peat. No differences in plant size, plant biomass (leaves and flowers), and dry matter content were found. Adding PW, in combination with OSW, maintained marigold height and total number of flowers produced to similar levels as in plants grown in 100% peat. In matthiola, adding 30% OSW into the substrate reduced plant size and fresh weight, but not plant height. No differences were observed when plants grew in lower OSW (i.e., 10%) content. Petunia's height, its total number of flowers and flower earliness (flower opening) were increased in the presence of OSW compared to the plants grown in 100% peat. The addition of OSW did not affect petunia's size and fresh weight among treatments. The addition of PW suppressed several plant growth-related parameters for both matthiola and petunia. The insertion of OSW did not change leaf chlorophyll content whereas the presence of PW decreased chlorophylls for marigold, petunia, and matthiola. Both OSW and PW altered the content of total phenolics and antioxidant capacity of 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) in leaves and flowers for marigold and petunia. Both 30% OSW and PW increased antioxidative enzyme metabolism due to the increased damage index and lipid peroxidation observed in plants. Leaf N and P content decreased in PW-based media, while matthiola displayed visual phytotoxicity symptoms when PW was added into the substrate. The present work indicates that up to 30% of OSW can replace peat for marigold and petunia growing and only up to 10% of OSW for matthiola, while the addition of PW on top of OSW is not recommended, so further research is needed.