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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.

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.

Organic greenhouse (OGH) production is characterized by different systems and agricultural practices with diverse environmental impact. Soil arthropods are widely used as bioindicators of ecological sustainability in open field studies, while there is a lack of research on organic production for protected systems. This study assessed the soil arthropod abundance and diversity over a 2-year crop rotation in three systems of OGH production in the Mediterranean. The systems under assessment differed in soil fertility management: SUBST – a simplified system of organic production, based on an input substitution approach (use of guano and organic liquid fertilizers), AGROCOM – soil fertility mainly based on compost application and agroecological services crops (ASC) cultivation (tailored use of cover crops) as part of crop rotation, and AGROMAN – animal manure and ASC cultivation as part of crop rotation. Monitoring of soil fauna was performed by using pitfall traps and seven taxa were considered: Carabidae, Staphylinidae, Araneae, Opiliones, Isopoda, Myriapoda, and Collembola. Results demonstrated high potential of ASC cultivation as a technique for beneficial soil arthropod conservation in OGH conditions. SUBST system was dominated by Collembola in all crops, while AGROMAN and AGROCOM had more balanced relative abundance of Isopoda, Staphylinidae, and Aranea. Opiliones and Myriapoda were more affected by season, while Carabidae were poorly represented in the whole monitoring period. Despite the fact that all three production systems are in accordance with the European Union regulation on organic farming, findings of this study displayed significant differences among them and confirmed the suitability of soil arthropods as bioindicators in protected systems of organic farming.

Soil fertility management systems in organic greenhouses are quite diversified within Europe. The challenge is to identify and implement strategies which are in agreement with the organic principles stated by (EC) Reg. 834/2007 and (EC) Reg. 889/2008 as well as environmentally, socially and economically sustainable. In this paper, written by a group of scientists of different geographical origin and with different background, the state of the art of the sector and the main characteristics of the European greenhouse cropping systems are described. The main bottlenecks and constraints are discussed with a particular reference to the regulatory framework in force. The more relevant issues that may influence the enforcement and future development of the sector have been identified as specific knowledge gaps. For each of them, the appropriate research needs were elaborated in a multidisciplinary perspective as forthcoming challenges for the whole sector. Far to be exhaustive, given the wide heterogeneity of the implemented systems, this paper is able, for the first time, to give a structured outlook, on soil fertility in protected organic condition at an European scale.

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−1in the ADD design and 25 kg N ha−1in 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−1in cauliflower, and in leek, an LM of dyer's woad decreased the soil nitrate by 55 kg N ha−1at harvest and 30 kg N ha−1at 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.

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.

Soil arthropods have been recognized as indicators of habitat quality and diversity in open field organic systems, while in organic greenhouses (OG) research is still rather limited. Conservation and promotion of arthropods diversity are often unrelated to the identity of the components that provide it like cover crops (CC). CC may enhance arthropods diversity and provide wide range of ecological services (e.g. shelter, soil temperature moderation). However, the use of the CC in OG is not a widespread practice because farmers aim to produce cash crops for the market during the whole year. The present study aims to investigate the soil arthropods dynamics during CC growth cycle and following cucumber cultivation within a rotation plan in OG under Mediterranean conditions. Three organic farming systems were evaluated in term of soil arthropods dynamics and abundance: i) a simplified organic production system based on organic commercial fertilizers (SUBST); ii) organic production system based on animal manure amendment and cover crops (AGROMAN), and iii) organic production system based on green manuring of cover crops and on-farm compost amendment (AGROCOM). Assessment was based on pitfall traps monitoring and classification of individuals in macrogroups. Spiders, rove beetles and isopods were more abundant in CC treatments, while other groups did not differ significantly among systems. Cucumber cultivation revealed different patterns, with more uniform results among the systems, except for AGROMAN. Results show that cover crops influenced soil arthropod diversity and their suitability to be used as bioindicators of ecological sustainability.

Soil quality in Mediterranean conventional and organic stockless arable systems was assessed by a multidisciplinary approach. At the end of the first cycle of a 5-year crop rotation (2002–2006) in the Mediterranean Arable Systems Comparison Trial (MASCOT) long-term experiment, the effects of organic and conventional management systems were evaluated by using soil chemical, biochemical and biological parameters. Chemical and biochemical parameters linked to soil C cycle, arbuscular mycorrhizal fungi (AMF) and microarthropod communities were analysed according to a comparative approach. Results suggested a higher soil carbon sequestration in the organic respect to the conventional system, as shown by the values of total organic C (9.5 and 7.8 g kg −1 , for organic and conventional system, respectively) and potentially mineralisable C (277 and 254 mg kg −1 , for organic and conventional system, respectively). AMF population, AMF root colonisation and diversity of microarthropod population were slightly influenced by management system. On the other hand, mites/collembolans ratio was higher in conventionally than in organically managed soil (2.67 and 1.30, respectively), indicating as organic managed soils were more disturbed than conventional ones, probably as the consequence of the more frequent soil tillage performed for mechanical weeds control. The overall results demonstrated that, even in the short-term, the implementation of organically managed stockless systems in Mediterranean areas determined significant changes of some attributes for soil quality evaluation.