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Green manure and compost-enriched in phosphorus can promote the sustainability of cropping systems by increasing soil fertility over the long term. They can also be used to manage crop/weed interactions, a key element in guaranteeing an appropriate level of satisfactory crop yields. We studied how green manuring with hairy vetch (Vicia villosaRoth.) and the application of different types of phosphorous-enriched compost affect weed/maize (Zea maysL.) interactions in an organic stockless Mediterranean agroecosystem for two consecutive dry years. Green manure stimulated the expression of maize traits related to a higher competitive ability against weeds, such as early growth, height and leaf area index, while the effect of compost was less clear. Regarding crop/weed competition, both green manuring and a phosphorus-enriched compost application gave a significant advantage to maize. Neither green manure nor compost increased total weed density and biomass compared to the control. Green manuring significantly affected the weed community composition. The relative density of ruderal and competitive-ruderal species (according to Grime's classification) was higher in plots where the green manure was applied. The use of green manure, together with novel composting techniques, significantly affected crop/weed competitive interactions, favoring maize, but also creating favorable conditions for unwanted weed species such as competitive-ruderals. Increasing nitrogen availability in the early growth stages of maize through green manuring can increase crop competitive ability. However, this may not suffice to preserve the system from future weed problems, should potentially detrimental species be selected. Dedicated strategies for the control of emerging weed species may thus be needed.

Soil fertility management in organic farming systems relies on agro-ecological service crops (ASCs, i.e break crops, living mulch) and organic compost application. This study was conducted to determine the effect of tillage, ASC termination, and compost rates on yield and soil N fertility in organic vegetable production in Central Italy. In a long-term organic field, in a strip plot design, barley was cultivated before melon. Two termination strategies of barley (green manure–GM, flattening by the use of a roller crimper–RC) were compared with a control without barley (FA). Three compost application rates (0, 15, and 30 Mg ha⁻¹) were studied. While the compost rates did not show any difference among compared production parameters, the combined tillage–ASC termination strategy significantly increased melon yield in the GM compared with RC treatments, probably due to the lower soil temperature under the thick barley mulch. Soil mineral N (SMN) during the melon cycle was not a limiting factor for plant growth. Mean SMN values ranged from 22 for the 2012 RC and 36 mg kg⁻¹ for the 2012 FA. High C and N inputs in barley treatments and high compost rates indicated an N surplus, which, in the medium–long term, could represent an N storage for subsequent crops in the rotation and potentially determine C sequestration. The results demonstrated that, to assure adequate yield, the ASC mulch based no-tillage approach should follow the redesign of the whole cropping system, taking into account the entire suite of techniques of crop management.

Organic farming relies, for soil fertility management, on proper rotation designs, Agro-ecological Service Crops (ASCs) and a sound use of on- and off-farm organic inputs. The right combination of soil fertility factors in organic farming is essential to enhance soil organic C (SOC) sequestration. A field trial experiment was overlaid on an long term organic farming experiment, in Monsampolo del Tronto (42° 53′ N, 13° 48′ E) in Central Italy, based on a 4-years rotation, with 6 main crops, and 3 different ASCs. The treatments included: i) the alternative termination of the cover crop (barley) with roller crimper technique compared to green manure and ii) the application of compost (not applied before) in different doses. The barley managements were: green manure (GMB); flattened (FB) by the use of a roller crimper; no barley (NB) as control. The compost (Cp) doses were: 0, 15 and 30 Mg C ha−1 to study the effect on soil C dynamics of compost application and ASCs termination techniques. The historic and experiment results were used as input to run a soil C dynamics model (RothC10N) to predict the effect of the factors different combinations in a medium term (20 years). After two years from compost application, the SOC stock increased in all plots, by +1.8, +2.3 and +4.9 Mg C ha−1 for Cp0, Cp15 and Cp30 respectively, compared to the initial stock of 36.8 Mg ha−1. The effect of different ASCs termination and ASC × compost interaction was not statistically significant. The RothC10N model was used to predict the effect of ASCs (NoASCs, FB and GMB) and Cp doses in a 20 years period. Predictions of the calibrated and validated RothC10N model showed that SOC change in 20 years was negative in the scenario with no ASCs-no compost (NoASC Cp0), where the C inputs were not sufficient to offset C losses, whereas positive values were predicted for all the other scenarios. The average values of predicted C stock change in 20 years were 3.8, 13.3 and 19.8 Mg C ha−1 for NoASC, FB, and GMB respectively and 8.2. 12.2 and 16.5 Mg C ha−1. for Cp0, Cp15 and Cp30. Both field experiment and model showed that the green manure of ASC and compost application represent a valid option in terms of carbon sequestration increase. RothC10N model can be used successfully as a tool to compare the C sequestration potential of alternative agronomic practices.

This research focused on the effect of organic production systems on initial quality and postharvest performance of lamb's lettuce leaves stored in air or under modified atmosphere at refrigerated temperature. Different strategies of organic soil fertility management were compared under the same environmental conditions: (i) a simplified organic production system based on organic commercial fertilizers to recover crop uptake (SB); (ii) an organic production system based on organic matter amendment mainly supplied by animal manure (AM); and (iii) an organic production system based on organic matter amendment supplied by green waste compost (AC). Fully developed lamb's lettuce leaves were harvested and then packed into perforated bags (control in AIR) or in modified atmosphere packaging (MAP) and stored at 4 °C.; Results: At harvest, the yield of lamb's lettuce in the AM and AC systems was higher than that in SB. Phenol and dehydroascorbic acid accumulation was observed in the system with the lowest initial supply of organic amendment (SB). Regarding the effect of packaging, AIR conditions maintained the initial quality attributes for a longer period than MAP, which developed off-odours above the threshold of acceptability at 11 days, irrespective of the production system used.; Conclusion: In general, the initial differences among the production systems were minimal during the postharvest storage. As for the tested packaging systems, AIR successfully maintained the initial quality attributes for a longer period than the MAP. © 2018 Society of Chemical Industry.; © 2018 Society of Chemical Industry.

Organic greenhouse production can be a challenge, particularly in terms of selecting agricultural practices that can sustain crop production without creating environmental or economic burdens. This study was designed to assess the economic implications of the integration of agro-ecological practices within a two-year organic greenhouse rotation programme under Mediterranean conditions. Three organic systems were compared; one was a ‘conventionalised’ system based on input substitution (SUBST) and two systems were based on agro-ecological practices associated with cover crops and different soil fertility management regimes using animal manure (AGROMAN) and compost (AGROCOM). The two-year rotation included three crops: strawberry, tomato and green bean. The results revealed better economic performance, for some aspects, of AGROMAN and AGROCOM compared with the ‘conventionalised’ organic system (SUBST) and demonstrated the economic feasibility of introducing agro-ecological practices within a two-yea...

Conventionalization of organic agriculture through input substitution, aimed to fulfill certification requirements, without improvement of natural ecological cycles in agroecosystem, is a relevant concern especially for the organic greenhouse (OGH) sector. Following a holistic approach, more resilient agroecosystems may be designed by taking advantage of Agro-ecological Services Crops (ASC) cultivation during the crops sequence and by using organic matter amendments for the soil fertility management. In this framework, we investigated ecological sustainability of three OGH production systems by studying the soil arthropods taxa. Following systems were under assessment: i) SUBST - bare soil priori to cash crop + organic fertilizer; ii) AGROCOM - ASC as green manure priori to cash crop + compost; and iii) AGROMAN - ASC as dead mulch + animal manure. Monitoring of soil arthropods was performed by using pitfall traps and divided in two phases: the pre-crop period (during cultivation of ASC or bare soil in SUBST) and cash crop (kohlrabi) production. Collembola was the most abundant group during cultivation of ASC, in all tested systems and their activity density (AD) was higher in SUBST compared to other two systems. Isopoda, Araneae and Staphylinidae were significantly more abundant in AGROMAN, where manure was applied before ASC sowing. During kohlrabi cultivation Collembola group was confirmed as the most represented in all systems, with the highest values in AGROMAN. Moreover, significant differences were found among the systems for Opiliones, Myriapoda and Staphylinidae groups; with the highest abundance of all these taxa in the AGROCOM system. Results obtained indicate that an agro-ecological practices (ASC cultivation, compost and manure application) could contribute to ecological sustainability and the development of organic agriculture under protected environment.

In Europe, the lack of specific rules regulating organic vegetable production in protected conditions has led to the implementation of extremely diversified systems of production, at different level of intensification. In this study, we compared three strawberry organic production systems based on the following main criteria of soil fertility management: input substitution (SB), a simplified system of organic production that mimics conventional agricultural practices and two systems characterized by a more complex soil fertility management, based on the introduction, in the rotation of agroecological service crops (ASCs) and compost (AC), and of ASCs and cattle manure (AM). Strawberry yields, in the compared systems, were not significantly different in both years of our research, while, as a whole, the yield in 2013 (30.3 Mg ha−1) was significantly higher than in 2014 (28.9 Mg ha−1). Crop nitrogen (N) needs, during the entire cycle of production, were satisfied according to the same pattern by SB, AC and AM, while green manuring and organic amendments in AM and AC determined a higher soil organic N content, compared with SB. As far as the production quality is concerned, both AM and AC treatments yielded strawberry fruits similar to SB, but with better characteristics in terms of color and phenolic content. AM and AC did not differentiate statistically in the two year period of our research.

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.

In the past decade, the increasing environmental concerns regarding the use of non-renewable resources, such as peat, for growing media production has led to a search for alternative materials as substrate components. Until now, compost represents the most investigated one. Despite the critical aspects related to compost use (i.e., its high pH, salinity, and potential content of toxic elements), partial peat substitution with this material represents an achievable objective. In this study, green compost was evaluated as a component of peat substrates for organic sweet pepper (Capsicum annuum L.) seedling production. Three compost rates (CR) were compared: 0 (peat without compost), 30, and 60% of compost v/v. Two pepper cultivars, one derived from a local (medium-Adriatic) germplasm (L) and a commercial hybrid (H), were tested. Furthermore, organic fertilizers based on hydrolyzed proteins, of animal (A) and vegetal (V) origin, were compared. Substrates were analyzed for characterization (pH, EC, nu...

This work evaluated the response of organic tomato seedlings to locally produced compost-amended growing media and commonly used N liquid fertilizers. Green (GC) and mixed (MC) composts were used in growing media formulation with 70, 45, 20, and 0% (control based on peat) on volume basis for organic tomato seedling growth. Three locally available N liquid fertilizers, hydrolyzed-protein-based fertilizer (HP), blood-meal-based fertilizer (BM), and algae-extract-based fertilizer (AE), were tested. Seedlings were evaluated 34 days after sowing for plant height; stem diameter; shoot weights; sturdiness index; specific leaf area; and N, P, and K contents in the seedlings shoot. The statistical analysis showed that the substrate type, fertilizer, and their interaction significantly (p ≤ 0.05) affected, in most cases, the seedlings growth. The compost, especially with 20 or 45% amended substrate, produced longer seedlings with thicker diameter, greater fresh and dry weights, and greater leaves number com...

International audience; AbstractA transplant can be defined as a seedling or sprouted vegetative propagation material grown in a substrate or in the field, for transfer to the final cropping site. Nurseries use a range of growing media in the production of transplants, and the quality of a substrate may be defined in terms of its feasibility for the intended use and also according to the climatic condition of the production site. Peat is the worldwide standard substrate, but because of its origin and the increasing environmental and ecological concerns, new alternatives have been proposed for organic production. Here, we reviewed these new alternatives, assuming that the proposed growing media will need to respond in a proper way to specific plant requirements while also taking them into consideration to be environmental friendly, at the same time. Appropriate composting management combined with suitable feedstock material can produce substrates with adequate properties to develop transplants. Potential added-value benefits of particularized compost have been highlighted, and these include suppressiveness or capacity for plant pathogen control, biofertilization, and biostimulation. This added value is an important point in relation to the framework of organic agriculture because the use of chemical fertilizers and pesticides is limited. Different permitted fertilizers are proposed by incorporating them by dress fertilization before planting or by foliar fertilization or fertigation during the seedling production phase. In this context, specific beneficial microorganism inoculation demonstrates better and quicker nutrient solubilization. Its inclusion during seedling production not only facilitates plant growth during the germination and seedling stages but also could bring efficient microorganisms or beneficial microorganisms to the field with the transplants. This review will help to bridge the gap between the producers of compost and the seedling plant producers by providing updated literature.

In organic farming, soil application of processed agro-industrial by-products could sustain soil fertility for vegetables, which have short cropping cycles. Therefore, the objectives of this 2-year research on organic spinach crop were to assess the productive performance of different experimental fertilizers, the effects on soil fertility, and investigate the dynamics of some soil properties and the N balance. Two types of olive pomace mixtures, with a different initial C/N ratio, were composted and both stopped at the active phase (A1 and B1) and processed until maturation (A2 and B2). Also an anaerobic digestate (DA), and the B2 applied as amendment (B2A) were studied. The four composts, DA, and B2A were compared with a commercial organic fertilizer (Org), and a control (N0). The Org resulted as not sustainable in maintaining soil fertility in the long-term, mainly due to reduction in the soil of total organic carbon by 32 %, compared to the average of the other treatments. Conversely, choosing stage of maturity and adequate C/N of starting mixtures was among the best practices for compost use in spinach crop. The great content of nutrients (N and K higher by 102 and 86 % than Org, respectively), and N surplus (1431 kg ha−1) in the B2A plots would suggest that they could accumulate after subsequent soil applications, with the risk of losses in the environment. The DA appeared to be the most suitable fertilizer to get a favorable trade-off among yield, quality and N-use efficiency, when applied according to best agronomic practices.

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 c...

This work was supported by the FPU Programme of the Spanish Ministry of Education and the CYCIT AGL2010-21073 project from the Spanish Ministry of Economy and Competitivity. The study was also carried out as part of the Excellence Group, reference 04537/GERM/06, funded by the Seneca Foundation (Murcia, Spain). P.D.V. acknowledges CSIC and the Spanish Ministry of Economy and Competitiveness for his “Ramon y Cajal” research contract, co-financed with FEDER funds.

Stockless systems, where plant and animal production are uncoupled, represent a common condition in Mediterranean areas. In organic systems, soil fertility is mainly managed by green manures, whereas composts of plant origin represent suitable soil conditioners. The low P content of these materials, together with the shortage of animal waste availability, determine potential nutrient depletion overtime and, in calcareous soils, P mining conditions. In a two-year field experiment in Central Italy, the effect of green manure vetch (Vicia villosa) (GM+) was compared with a control left fallow (GM-), combined with P-based fertilizers (F) on organic maize (Zea mays). Yields and N-P dynamics were evaluated by direct measurements, nutrient balance and efficiency index. N balance was higher than in GM+ GM- (+71.8 and -23.6 kg N ha-1, respectively). P enriched compost with RP (rock-phosphate) (EP), showed significant improvement in P use efficiency (meanly +34%) than other treatments (unfertilized control (RP), not P enriched compost (NEP)) and P equilibrium in the short run. On the other hand, P-fertilizers and maize residues soil incorporation determined P surplus in a long perspective (up to +10 kg P ha-1). Results emphasize the possibility of P reintegration in stockless organic systems without animal wastes.

In greenhouses, where intensive systems are widely used for organic production, the differences between &ldquo, conventionalized&rdquo, and agroecological approaches are especially evident. Among the agronomic practices, green manure from agroecological service crops (ASCs) and organic amendments represent the main tools for soil fertility management with respect to the substitution of synthetic fertilizer with organic ones (the input substitution approach). Over a two-year organic rotation, we compared a conventionalized system (SB) and two agroecological systems, characterized by ASC introduction combined with the use of manure (AM) and compost (AC) amendments. A system approach was utilized for the comparison assessment. For this purpose, agronomic performance, soil fertility and the density of soil arthropod activity were monitored for the entire rotation. The comprehensive evaluation of the parameters measured provided evidence that clearly differentiated SB from AM and AC. The drivers of discrimination were soil parameters referring to long term fertility and soil arthropod dynamics. The study confirmed the higher productivity of SB but also no positive impact on soil fertility and soil arthropods, as highlighted by AM and AC. Based on the results, a trade-off between productivity and the promotion of long-term ecosystem diversity and functioning is needed for the assessment of systems of organic production.

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 phyto...

Compost based substrates for producing organic tomato seedlings (Lycopersicum esculentum L. cv. Rio Grande) were evaluated in a peat substitution experiment. Two composts made from olive pomace waste (OWC) and green waste (GWC) were produced and characterized, in comparison with a sphagnum peat moss, for the main physicochemical parameters and for their germination index. Both composts were used as growing media components at four rates (20%, 45%, 70%, 90% on a volume basis) and their performances were compared to peat based control growing media. During plant growth, nitrogen was added as blood meal. Plants were collected 36 days after sowing, plant performance parameters (stem length, leaves, stem and total fresh and dry biomass, leaves number and chlorophyll content values), and NPK shoot contents were measured. Treatments GWC 20%, 45% and OWC 20% showed the best performances, while 70% for green waste compost and 45% for olive pomace compost could be considered as upper limits for producing satisfacto...

To ensure proper use of Trichoderma harzianum in agriculture, accurate data must be obtained in population monitoring. The effectiveness of qRT-PCR to quantify T. harzianum in different growing media was compared to the commonly used techniques of colony counting and qPCR. Results showed that plate counting and qPCR offered similar T. harzianum quantification patterns of an initial rapid increase in fungal population that decreased over time. However, data from qRT-PCR showed a population curve of active T. harzianum with a delayed onset of initial growth which then increased throughout the experiment. Results demonstrated that T. harzianum can successfully grow in these media and that qRT-PCR can offer a more distinct representation of active T. harzianum populations. Additionally, compost amended with T. harzianum exhibited a lower Fusarium oxysporum infection rate (67%) and lower percentage of fresh weight loss (11%) in comparison to amended peat (90% infection rate, 23% fresh weight loss).

A three-year field experiment was conducted in a Mediterranean environment on lettuce to study the production, characteristics and possible use of different amendments as substitution for nitrogen mineral fertilizers. The effects on soil dynamics were also investigated. The following treatments supplying 140 kg N ha−1 were compared: Stabilized anaerobic digestate from wine distillery wastewater (SAD); Non-stabilized organic material from wine distillery wastewater (NSAD); Olive pomace compost (OPC); Mineral N fertilizer (MIN); Commercial organic fertilizer (CORG). These treatments were compared with an unfertilized control (CONTR). No significant reduction occurred with SAD as compared to MIN, but its application significantly increased marketable yield in all experimental years compared to the unfertilized control. Furthermore, SAD treatment reached the highest marketable yield with an increase of 52.9% compared to CONTR in the year characterized by high unevenly rainfall distribution. Even with low abso...

Two citrus composts (C1: composed of 40% citrus wastes, 20% sludge obtained from a citrus industry waste-water treatment facility and 40% green residues; C2: composed of 60% citrus wastes and 40% green residues, and no sludge) and their water extracts amended with Trichoderma harzianum T-78 (T. harzianum T-78) were assayed in order to verify if these composts could act as a partial substitute for peat-based growing media as well as enhance suppressiveness against Fusarium wilt in the production of melon (Cucumis melo L.) seedlings at greenhouse nurseries. Over a 43-day growth cycle of melon seedlings, measurements were taken of the nutriactive effect (the capability of a substrate to express additional and/or synergistic nutritional and biostimulating effects), the pathogen incidence (percentage of fresh weight loss of melon plants grown on treatments infected with Fusarium oxysporum with respect to the same treatment without inoculation of the phytopathogen) and the trend of the T. harzianum T-78 population. A nutriactive effect was observed in the tested citrus compost-based growing media (96% and 112% plant weight increase with respect to peat for C1Th and C2Th, respectively). Pathogen incidence was significantly lower in C2Th than peat (12% compared to 33%), while no difference was observed in C1Th. The T. harzianum T-78 population showed a significant decrease at the first sampling time compared to the initial quantity (from 106 to 105 CFU g−1), but later recovered over time. These results demonstrate that the combination of citrus compost and T. harzianum T-78 can be a viable alternative to peat and can minimise the application of chemicals necessary to control Fusarium wilt in greenhouse nurseries for melon seedling production.

Three composts from citrus-processing industry wastes, sampled at prefixed times during the composting process, were studied with the aim to follow the organic matter evolution by using the isoelectrofocusing (IEF) technique. Results indicated that IEF qualitative analyses allowed evaluation of the organic matter transformation during composting process, showing a decrease of IEF peaks focused at lower values of pH (less stabilized organic matter) and a corresponding increase of peaks focused at higher value of pH (more humified material). The parameter A %, defined as the areas sum of IEF peaks focused at pH>4.7, could be considered particularly effective as a “threshold value” to evaluate the level of organic matter evolution for the considered composts.

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.

Two different types of citrus composts, and their water extracts, were tested with regard to their utilisations as partial substitutes for peat in growing media for melon seedlings in greenhouse nurseries. Both compost showed higher plant growth than peat. Compost composed by citrus waste and green residue (C2) showed greater plant growth than compost obtained from the same organic matrices mentioned above further the addition of sludge obtained from citrus industry (C1). Compost C2 showed a greater auxinic effect than C1 and it was the only one that showed cytokinic effect. Both composts also demonstrated a biocontrol effect against Fusarium oxysporum for melon plants: the effects were also higher in C2 than in C1. Higher number of isolated fungi was active against F. oxysporum in compost C2, than compost C1. No different bacterial biocontrol efficacy was observed between both composts. The water extracts of both composts gave lower plant yields than their solid matrices, their relative effects being similar to those of the solid composts (C2 extract gave higher plant yields than the extract from C1). The biocontrol effects of compost water extracts followed the same trend.

Publisher Summary This chapter describes the quality and agronomic use of compost. The main positive aspect of compost use in agriculture is probably related to the sustainability of this practice. The application of compost to soil is of considerable interest as a means of maintaining a suitable soil structure, as well as a means of adding organic material to soil whose organic matter content has been reduced by the practice of intensive agriculture. The concentration of nitrogen in compost is probably the most interesting from either an environmental or an agronomic point of view and this is the reason for using N content as the basis for calculating the application rates of compost. Soil water and thermal regime influence the redox processes of heavy metals and the more general decomposition processes of compost organic matter. The depth of soil tillage also is important because it determines the nature of the contact and the reactions between metals and soil constituents. The variety and complexity of physico-chemical and biological components in compost and in a soil system affect the possibility of studying the effects of the addition of organic materials into the soil.

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.

Composting of wastes from citrus industrial processing (pastazzo and sludge) was studied in order to evaluate the evolution of organic matter during the process and to individuate chemical and/or biochemical techniques able to set the stability of the final product. Composts from two open-air piles of different composition were sampled every month during the whole period of composting (5 months) and the organic matter of each sample was characterised by chemical and biochemical techniques. Humification rate (HR%) and humification index (HI) were determined. Extracted organic matter of the six samples collected for each compost was investigated by isoelectric-focusing technique (IEF). The biochemical analysis were based on the study of C-mineralisation after the addition of each collected sample to soil. Results obtained clearly demonstrated organic matter evolution during composting processes. Humification rates increased and humification indexes decreased over time, while extracted organic matter showed electrophoretic behaviour typical of stabilised organic compounds. Moreover, mineralisation patterns confirmed the increased level of organic matter stability during the composting process.

A bovine manure compost (BMC) and a green compost (GC) were evaluated as components of substrates in partial substitution of peat for organic melon seedlings production. Treatments, differentiated on the basis of the volume percentage of the two analysed composts, were compared to the control (a mixture of peat, coconut fibre and perlite). In order to respect the guidelines of organic production, all the treatments were fertilised, at the beginning of the trial, with guano. Compost-based substrates were analysed for physical, physicochemical and chemical parameters (bulk density, porosity, pH, EC, nutrients content etc.). Even though significant differences were observed, recorded values were in the range of acceptability for growing media. In terms of performance, seedling growth in treatments containing 30% and 50% of composts was significantly higher than in control.

A 2-year field experiment was carried out in a Mediterranean environment to study the effects of vetch (Vicia sativa L.) residue management strategies incorporating green manure (GM) using a roller-crimper (RC) and different organic fertilizers (municipal solid waste compost, anaerobic digestate, and a commercial organic fertilizer) on organic zucchini (Cucurbita pepo L.) yield and quality. Zucchini yield was influenced positively by the vetch residue management strategy, although the response was significantly different between years. The vetch cover crop increased marketable zucchini yield in the first year by 46.6% compared with the fallow (FA) treatment, indicating that this fertility-building crop could reduce off-farm nitrogen (N) fertilizer input for subsequent crops. Averaging over 2 years of the experiment, marketable zucchini yield increased by 15.2% and 38% with the RC mulch and GM plow-down, respectively, compared with the FA treatment, although differences were significant in the first year only. The application of organic fertilizers in vetch management plots increased marketable zucchini yield by 21.8% in the first year compared with the unfertilized control. This result is particularly relevant, because organic fertilizers were applied at ≈50% of the normal application rate for zucchini after taking into account biological N fixation attributable to the vetch. The concentrations of soil mineral N at harvest were 19, 27, and 28 mg·kg−1 for the RC, FA, and GM treatments, respectively. These mineral N concentrations indicated that a portion of applied organic fertilizer N, and N attributable to vetch (GM and RC), remained in the soil at harvest, suggesting the potential for leaching, which should be taken into account in the overall fertilization program. These research findings suggest that effective vetch cover crop management and the application of organic fertilizers can improve yield and quality of organically managed zucchini.