Saffron is traditionally cultivated in soil as a semi-perennial crop, although the feasibility of crop production is today constrained in Europe due to both agronomic and socioeconomic factors. Accordingly, interest has been increasing concerning its possible cultivation within protected environments through adoption of soilless cultivation technologies. The aim of the present study was to optimize nutrient solution features in the soilless cultivation of saffron corms. The trial was conducted in a greenhouse at Almeria University. Saffron was grown in 15-L pots filled with perlite. Three fertigation treatments were used, obtained by a linear increase of all nutrients of one standard in order to reach an electrical conductivity (EC) of 2.0 (control, EC2.0), 2.5 (EC2.5) and 3.0 (EC3.0) dS·m−1. Measurements included determinations of shoot length, corm yield, as well as nutrient uptake from the nutrient solution and concentrations within plant tissues. The nutrient solution with the highest EC (EC3.0) allowed obtaining three to five times more corms above 25-mm diameter. The increasing EC had a significant effect on the increase of macronutrient uptake, except for NO3− and NH4+ and resulted in a general increase of nutrient concentrations in tissues, such as corms and roots. Both macronutrient uptake and accumulation in plant tissues were highest under EC3.0. Nutrient uptake was significantly correlated with production of larger corms due to higher horizontal diameter.

The valorisation of vegetal waste as a source of crop nutrients constitutes a circular strategy to improve the sustainability of intensive horticultural production systems. The main goal of this study was to evaluate the effects of organic amendments derived from vegetal residues on the yield and quality of tomato. The following fertilisation treatments were carried out: fresh vegetal residues (4 kg m−1), compost (3 kg m−1), and vermicompost at two different doses (3 and 9 kg m−1), all derived from previous tomato crop vegetal residues, an organic treatment with goat manure (3 kg m−1), and a control mineral fertigation treatment. The highest yield was obtained with conventional mineral fertigation management, followed by vermicompost treatments at two different doses (3 and 9 kg m−1), with no statistical differences. The organic treatments with fresh crop residues, compost and goat manure resulted in lower yield. Regarding quality parameters, the lycopene content was higher in the mineral fertilisation and vermicompost at 3 kg m−1 treatment, while the other antioxidants measured were more concentrated in tomatoes fertilised with vermicompost treatment at 9 kg m−1 and goat manure. The plant nutrient management with vermicompost is the best circular solution, as it allows to reintegrate the residues generated in previous crop cycles into the soil, obtaining a yield equal to chemical input management and tomatoes with high nutritional quality.

The invasion of the macroalgae Rugulopteryx okamurae is causing several environmental and economic problems along Spanish Mediterranean coasts. The use of composts based on R. okamurae as a peat alternative in nursery production could be a valid alternative for the exploitation of this organic material. The present study evaluated three different composts as peat substitutes in potting media to grow tomato seedlings: compost of R. okamurae, compost of green horticultural residues (two-thirds) and R. okamurae (one-third), compost of garden pruning residues (two-thirds) and R. okamurae (one-third). Each compost was used to formulate two different substrates to reduce the use of peat (40% compost, 40% peat, 20% perlite) or entirely substitute it (80% compost, 20% perlite), using a control treatment with 80% peat and 20% perlite. Only the control treatment received mineral fertigation during the trial. The results showed that the high initial electrical conductivity and ion concentration were remarkably reduced thanks to the fast leaching of salt that occurred with customary irrigation. Generally, compost-based treatments allowed us to obtain tomato seedlings with satisfactory morphological parameters. The substrates that contained 40% compost of R. okamurae or a compost of garden pruning residues and R. okamurae led to the best results in term of seedling parameters. It is therefore concluded that composts based on R. okamuare could be used as a seedling growing medium for the valorization of algae.

The inadequate management of agro-waste in intensive agriculture has a severe negative impact on the environment. The valorization of crop residue as a source of crop nutrients is a valid alternative to close the nutrient cycle and reduce the use of external input. In this study, plant material was incorporated into the soil as fresh crop residue, after either composting and vermicomposting processes, to evaluate their effects on tomato yield and nutritional status (petiole sap analysis: NO3 and K+ concentration) over three crop cycles. A control treatment with mineral fertigation and an organic control treatment with goat manure were also included. Enzymatic activity and microbial population in the soil were evaluated. Although no differences between treatments were observed in the first cycle, in the second and third cycles, the yield obtained with the application of organic amendments derived from agro-waste was comparable to the yield obtained with mineral fertilizers. Overall, the sap analysis did not reveal a clear relationship with yield performances. The compost treatment resulted in higher microorganism presence in the soil. Soil dehydrogenase activity (DHA), acid phosphatase activity (ACP), and β-glucosidase activity (β-GLU) were generally more stimulated when organic amendments were used. The study confirms the applicability of soil fertilizers derived from agro-waste as a good alternative to mineral fertilizers.