Fabio Tittarelli

The Challenge of Peat Substitution in Organic Seedling Production: Optimization of Growing Media Formulation through Mixture Design and Response Surface Analysis

Peat replacement is an increasing demand in containerized and transplant production, due to the environmental constraints associated to peat use. However, despite the wide information concerning the use of alternative materials as substrates, it is very complex to establish the best materials and mixtures. This work evaluates the use of mixture design and surface response methodology in a peat substitution experiment using two alternative materials (green compost and palm fibre trunk waste) for transplant production of tomato (Lycopersicon esculentum Mill.); melon, (Cucumis melo L.); and lettuce (Lactuca sativa L.) in organic farming conditions. In general, the substrates showed suitable properties for their use in seedling production, showing the best plant response the mixture of 20% green compost, 39% palm fibre and 31% peat. The mixture design and applied response surface methodology has shown to be an useful approach to optimize substrate formulations in peat substitution experiments to standardize plant responses.

Phosphorus availability from rock phosphate: Combined effect of green waste composting and sulfur addition.

Rock phosphate constitutes a natural phosphorus (P) source for organic farming systems, but with a limiting direct agricultural use due to its poor inherent reactivity. Thus, this work studies the effect of the co-composting of rock phosphate with green wastes and elemental sulfur on phosphorus availability. Six composts were prepared combining different green wastes and rock phosphate in three different proportions (0%, 0.27% and 0.54% P fresh mass basis) and elemental sulfur in two proportions (0% and 0.5% S fresh mass basis). During composting, the temperature of the mixtures was monitored, as were physico-chemical and chemical parameters, especially those related to phosphorus. The co-composting of green wastes with rock phosphate improved phosphorus mobilization and also constituted a viable method to manage green wastes, obtaining P-enriched compost for organic farming systems. Sulfur addition favored the composting process and also phosphorus solubilization, especially in the mixture with the lowest proportion of rock phosphate.

Rock phosphate enriched compost as a growth media component for organic tomato (Solanum lycopersicum L.) seedlings production

Peat substitution in growth media with renewable organic components such as compost is one of the main challenges for organic nursery production. Two greenhouse experiments were carried out to investigate the performance of tomato seedlings grown on different compost-based growing media. The factors investigated were: (1) dose of compost, (2) level of phosphorus (P) enrichment and, only in the experiment 2, (3) source of P enrichment (rock phosphate enriched compost or rock phosphate amended growing media). Tomato seedling length, diameter, leaf area, leaf dry weight, shoot dry weight and seedling N, P and K concentrations were determined. Growth substrates with 30% compost showed the best seedling growth regardless of the source and level of P enrichment. Furthermore, at higher compost doses (60%) in the growth media, rock phosphate enriched compost (0.59 g P kg− 1 compost) produced seedlings that were comparable to the rock phosphate amended substrates (1.18 g P kg− 1 substrate). This demonstrates the capacity of the rock phosphate enriched compost in the growing media to supply more P to seedlings than the rock phosphate amended substrate. Moreover, growth media with 60% compost and peat-based growing media with standard rock phosphate application produced similar seedling growth confirming the potential of compost to substitute 60% of the peat in the growth media.

Soil Fertility Management in Organic Potato: The Role of Green Manure and Amendment Applications

During the last decade in the European Union, the organic food and farming (OFF) sector has grown considerably. The potato (Solanum tuberosum L.) crop plays an important role in organic farming systems, being one of the most highly demanded products on the market for organic produce. In this chapter, the role of green manure and organic amendments application for soil fertility management in agro-ecosystems based on organically managed potato crop is discussed in the light of the most relevant scientific literature. Moreover, as a case study, the results of a field experiment designed to evaluate the combined effects of green manure and organic amendment applications on organic potato yield, nitrogen (N) use efficiency and soil mineral N dynamic are presented. Our results indicated that legume green manure management and the recycling of organic materials may provide a valid alternative to the conventional synthetic fertilizer-based management system to sustain potato yield without enhancing potential environmental risks due to N leaching. Our study demonstrated that ecofunctional intensification of potato-based organically managed cropping systems is achievable through the exploitation of the combined effect of legume green manure with organic amendments application.

Bioassays and application of olive pomace compost on emmer: effects on yield and soil properties in organic farming

Abstract Composting olive oil pomace could solve the problem of disposal, by recycling this organic waste for agricultural purposes. Furthermore, application of composted organic waste could be a way to sustain both soil fertility and production, especially in organic farming. Therefore, the aim of this research was to evaluate the phytotoxicity and the effects of application of olive pomace composts on emmer performance and soil properties. Two types of olive pomace composts, with a different initial C/N ratio, were stopped at the active phase and processed until maturation. The obtained four olive pomace composts were compared with a commercial fertilizer in a two-year field experiment. Before the field trial, a bioassay was performed to assess phytotoxicity both for the raw pomace and the not-stabilized composts. Growing and yielding data for emmer were determined during the two-year period and soil characteristics were measured at the start and at the end of the experiment. The composts were not phytotoxic (germination index was higher than 90%) and their total organic carbon content was always higher than the minimum values established by the Italian fertilizers legislation. The emmer protein content was significantly higher in the matured compost treatment with low C/N, than in the other compost treatments. Its value was comparable with that of the commercial fertilizer, suggesting a good performance on crop yield quality. Although not significant, this compost showed an increase of 9.8% in grain yield compared with commercial fertilizer treatment. On the whole, it can be suggested that repeated compost application might preserve the soil organic carbon content and supply macronutrients to a crop.

Can living mulches in intercropping systems reduce the potential nitrate leaching? Studies of organic cauliflower (Brassica oleracea L. var. botrytis) and leek (Allium porrum L.) production across European conditions

The effect of introduction strategy for living mulches (LMs) to reduce the potential nitrate leaching was investigated when grown with vegetables with high nitrogen (N) demand and low use efficiency in four European countries: Italy, Slovenia, Germany and Denmark over 2 yr. The plant N uptake and soil nitrate N content at harvest, in the autumn, and in the following spring were measured below open-pollinated and hybrid cultivars of cauliflower and leek crops. The cultivars performed differently over the 2 yr. In Italy and Slovenia, when LM of burr medic or white clover was broad sown (addition design ADD) at the same time as crop transplanting, the N uptake of crops was hampered without increasing the total aboveground N accumulation. Delaying LM sowing by 2.5–4 weeks maintained the N uptake of crops. In Germany, delaying white clover sowing for a month in cauliflower reduced soil nitrate at the start of leaching by 17–33 kg N ha−1 in the ADD design and 25 kg N ha−1 in the substitution design (SUB), where rows of cash crops were replaced by rows of LM. An overwintering LM of grass–clover incorporated in strips and root pruned decreased soil nitrate at the start of the leaching period by 35 kg N ha−1 in cauliflower, and in leek, an LM of dyers woad decreased the soil nitrate by 55 kg N ha−1 at harvest and 30 kg N ha−1 at the start of leaching. The effect of delayed LM sowing depended on the LM species and system design. Overall, the SUB and ADD designs showed potential to reduce nitrate leaching, whereas the ADD design had stronger competition against either cash crop or LM. The key to reduce soil nitrate N without jeopardizing crop yields may be to identify suitable growing periods, sometimes combined with root pruning, for each LM species and system design. The LM introduction strategy can be used to control competition and reduce the potential leaching, but the performance depends on the intensity of the interspecific competition and the local conditions.

Effectiveness of living mulch strategies for winter organic cauliflower (Brassica oleracea L. var. botrytis) production in Central and Southern Italy

In crop rotations, cover crops planted either before or concurrent with a main crop and maintained as a living ground cover (living mulch, LM) may provide many beneficial ecosystem services, and can be defined as ‘agro-ecological service crops’ (ASC). The objective of this research was to study the suitability of burr medic ( Medicago polymorpha L. var. anglona ) as an LM for organic cauliflower ( Brassica oleracea L. var. botrytis ) production in a Mediterranean environment. Two LM sowing times (early sowing – sowing concurrent with cauliflower transplanting versus late sowing – 3 weeks later) compared with a no living mulch control (LM-CT) were investigated in central Italy (Experiment 1), along with a comparison between two local cauliflower cultivars and a hybrid. In Southern Italy (Experiment 2), crop performance under two LM sowing times [20 days before cauliflower transplanting versus concurrent sowing (CS)] compared with a no LM-CT , with organic fertilizers and amendments allowed in organic farming as subplots, was assessed. In Experiment 1, no competition was observed between the late-sown ASC and the cash crop. An increase in crop nitrogen (N) uptake and weed mitigation was also determined in this treatment. There was a mixed response when comparing cultivar and LM interactions, with the hybrid cultivar in the late-sown LM producing the greatest yield. In Experiment 2, weather conditions had the greatest effect on crop response. However, an inverse trend between growth of the cash crop and the LM crop was observed in the CS treatment. A positive effect of LM introduction was found, particularly in altering the competitive relationship for N between the cash crop and weeds. In addition, yield results showed that, in LM systems, commercial organic fertilizers could be replaced with locally available organic fertilizers and amendments without any yield penalty. The effectiveness of LM strategies will thus depend on several factors: type of LM, cultivar of vegetable, weather, soils, length of growing season and ability to plant the cash crop into the LM. Initial research suggests the potential for burr medic as a LM for Mediterranean winter vegetable systems, but additional research is needed to ensure the viability of LM systems for longer periods of time.

Organic Citrus: Soil Fertility and Plant Nutrition Management

During the last decade, the organic food and farming (OFF) sector has grown considerably worldwide. Citrus play an important role in organic farming systems, being one of the most highly demanded products on the market for organic produce. In this chapter, the criteria for citrus orchards fertility management and plant nutrition in the organically managed agroecosystems are discussed in the light of the most relevant scientific literature. Moreover, two case studies carried out in Southern Italy and aimed at comparing conventional and organic orange management in terms of yield, yield quality and long-term impact on soil fertility are reported. The body of knowledge available and the results presented demonstrate that organic citrus management is a technically feasible option for citrus growers. In addition, the shift to organic farming could contribute to enhance the environmental sustainability of citrus productions in the long term.