Stefano Canali

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.

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.

Effect of roller-crimper technology on weed management in organic zucchini production in a Mediterranean climate zone

Integrating cover crops into vegetable cropping systems can provide a wide range of ecological services, of which weed management is a key component. Cover crop effects on weed control, however, are dependent on termination methods and weed species present in specific cropping seasons. A 2-year weed management experiment with two cultivars of organic zucchini ( Cucurbita pepo L.) in central Italy was carried out to compare the effect of a barley ( Hordeum distichum L.) cover crop terminated with a modified roller-crimper (RC) to incorporated barley as green manure (GM) and a tilled control left fallow (FA) in the off-season. The effects of cover-crop management on crop competitiveness, yields and weed populations were evaluated by direct measurement, visual estimation and competition index methods. Results showed a significant reduction in weed biomass (>80%) and weed abundance with the RC compared to the GM and FA treatments. Moreover, the RC barley mulch maintained weed control in zucchini plots even under high weed pressure, as determined by the agronomic tolerance to competition (ATC) value of 67% in the RC treatment compared to 40 and 34% in the FA and GM treatments, respectively, averaged over both years of the experiment. The competitive balance ( C b ), which quantified the ability of the zucchini crop to compete with weed populations, was also greater (+0.37) in the RC treatment compared to FA (−0.87) and GM (−0.69) treatments over the same period. Zucchini crop biomass was greatest in the RC treatment in 2011. Zucchini fruit yields varied from an average over both years of 1.4 Mg ha −1 in the RC treatment to 0.7 Mg ha −1 in the GM treatment, but yields in the FA treatment, 1.2 Mg ha −1 , did not differ from the RC treatment. No differences in yield between ‘Dietary’ and ‘Every’ zucchini, or any significant interactions between cultivar and cover management related to fruit biomass, were observed. Our findings suggested the viability of the modified RC in creating a barley cover-crop mulch to effectively manage weeds and enhance yields in transplanted zucchini.

Yield, product quality and energy use in organic vegetable living mulch cropping systems: research evidence and farmers’ perception

The effects of living mulch (LM) introduction and management strategies on cash crop yield, product quality and energy use were studied in a wide range of European vegetable cropping systems, climatic and soil conditions, as well as species of LM grown as agro-ecological service crops. Nine field experiments were carried out in research stations and commercial farms located in Denmark, Germany, Italy and Slovenia. Farmers’ perception of the feasibility and applicability of the LM technique was also assessed. The results demonstrated that the LM systems with a substitutive design can be effectively implemented in vegetable production if the value of the ecological services (positive externalities) delivered by LM can counterbalance the yield loss due to the cash crop density reduction. The crop density of the system and the length of the period in which the LM and cash crop coexist are oppositely related both for competition and yield. Moreover, if an additive design is used, the LM should be sown several weeks after the cash crop planting. Overall, different cash crop genotypes (i.e., open pollinated/local cultivars in comparison with the hybrids) performed similarly. Use of human labor (HL) and fossil fuel (FF) energy slightly increased in LM systems (7%), and there was a shift in the proportion of FF and human energy consumption. The farmers’ acceptance of the LM techniques was quite high (75% of the interviewed sample), even though their critical considerations about yield quality and quantity need consideration in future research and practical implementation of LM systems.

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.

Living mulch for weed management in organic vegetable cropping systems under Mediterranean and North European conditions

The aim of this study was to investigate the effect of growing in-season agro-ecological service crops as living mulch (LM) with vegetable crops, exploiting their potential to suppress weeds by filling the ecological niches otherwise occupied by weeds. Two field experiments were carried out in Denmark and Italy to compare different LM introduction strategies in organic vegetable cropping systems. In Denmark, leek ( Allium porrum L.) was grown with dyers woad ( Isatis tinctoria L.) LM strips, while cauliflower ( Brassica oleracea L. var. botrytis ) was intercropped with a broad sowed burr medic ( Medicago polimorpha L., var. a nglona ) in Italy. Two LM times of sowing relative to cash crop transplanting––an early sowing (es LM) and a late sowing (ls LM)––were compared with a control with no LM (no LM). The effects of LM treatment on crop competitiveness, LM smother effect and weed populations were evaluated by direct measurement, visual estimation and competitive index methods. Comparison among hybrid and open pollinated cultivar responses to LM introduction was also performed. Results showed a significant higher cash crop biomass in ls LM than in es LM, with comparable yield to the weeded controls, except for es LM in Italy. Moreover, in the Danish experiment, the LM and weed biomasses were up to 5 times lower in the es LM and ls LM treatments than the weed biomass alone in no LM treatment. Reduction in weed biomass and abundance was observed also in ls LM in the Italian trial. Similarly, the competitive balance (C b ), which quantifies the ability of the cash crop to compete with neighbours, was higher in the es LM (+0.29) and ls LM (+0.72) compared with unweeded no LM control (−0.86) in Denmark. In the Italian experiment, the cauliflower showed more competitive ability against neighbours in ls LM (+0.53) and was a weak competitor in es LM (−1.51). The cash crop had higher competitive ability against LM (C b c-lm) when sowing was more delayed in both experiments, while, in the Italian trial, the LM was more competitive against weeds (C b lm-w) in ls LM (+1.54) than in es LM (−0.41). The slight differences observed for biomass and competitive ability between the tested cultivars, highlighted similar suitability of both hybrid and open-pollinated cultivars to grow with LM. Our findings suggest the viability of the introduced LM in managing weeds and avoiding a smother effect on the crop, with particular effectiveness with delayed LM sowing.

Participatory organic research in the USA and Italy: Across a continuum of farmer–researcher partnerships

Organic agriculture continues to expand in the USA and in the European Union (EU), particularly in Italy, which had 48,650 organic farms in 2014 compared with 19,474 in the USA. Additionally, EU support for organic research is nearly double than that of the USA. Along with increased support for organic research, the EU organic community has achieved recognition at the European Commission policy level for a dedicated innovation platform, advocating the practice of farmer-first models for participatory research. The US land-grant universities have a long history of on-farm research, primarily through the Extension Service, but the need exists for more inclusive, second-loop, co-research with organic farmers. A survey was conducted of organic farmers and researchers in Italy and in the USA to ascertain the extent of participatory organic research activities and experiences, and explore the vision each group had for the future of co-innovation between organic farmers and researchers. Results indicated that, despite the higher level of organic research support in the EU, the percentage of researchers involved in on-farm/participatory organic research was equivalent in Italy and the USA, presumably due to the more recent emphasis in Italian/EU agricultural research agendas on the importance of farmer knowledge and participation in organic research. Overall, 60% of surveyed organic researchers in both countries cited involvement in on-farm/participatory organic research, with ‘farming systems’ and ‘nutrient/pest management’ the main research focus in the USA, compared with ‘farming systems’ and ‘equipment’ in Italy. Both countries’ researchers expressed their vision of participatory research as helping to improve communication between researchers and farmers, to enable work on relevant research, and to allow farmers to adapt technologies to their own conditions. Organic farmers in Italy completed survey questionnaires as part of a field day activity, leading to more Italian farmers responding to the survey, compared with USA counterparts who were queried via e-mail. Organic farmers in Italy identified ‘knowledge-sharing’ as a critical value of participatory research, and were conducting on-farm research with less compensation than US farmers. The ‘lack of time’ was cited as the most important constraint limiting participatory research by Italian and US farmers, although the ‘lack of common language’ also was rated as potentially impairing full participation. Lessons shared between EU and US organic researchers as a result of this project included methods to institute policies aimed at increasing support for organic research and co-innovations with organic farming communities, and connecting experienced on-farm researchers in the US with Italian colleagues to enhance collaborative activities with organic farmers.