The principal goal of the organic farming system (OFS) is to develop enterprises that are sustainable and harmonious with the environment. Unfortunately, the OFS yields fewer products per land than the non-organic farming system in many agricultural products. The objective of our study was to assess the effects of digestate and biochar fertilizers on yield and fruit quality of processing tomato produced under the OFS. The experiment was carried out in Po Valley, during the 2017 and 2018 growing seasons. Liquid digestate (LD), LD + biochar (LD + BC) and pelleted digestate (PD) were evaluated and compared to biochar (BC) application and unfertilized control. The results showed that plants fertilized with LD + BC recorded the maximum marketable yield (72 t ha⁻¹), followed by BC (67 t ha⁻¹), PD (64 t ha⁻¹) and LD (59 t ha⁻¹); while the lowest production (47 t ha⁻¹) was recorded in unfertilized plants. Over the two cropping seasons, LD + BC, BC, PD, and LD, increased fruit number per plant (+15%), fruit weight (+24%), Brix t ha⁻¹ (+41%) and reduced Bostwick index (−16%), if compared to the untreated control. Considering the overall agronomic performances, digestate and biochar can be useful options for increasing yield and quality of processing tomato production in the OFS. Hence, these fertilizers can be assessed in future research both on other crops and farming systems.

The enhancement of the actual low yields is the most important challenge regarding organic farming management. In this view, a valid tool may arise by the improvement of fertilization management and efficiency. In this regard, arbuscular mycorrhizal fungi (AMF) can play an important role, especially in low fertility soils such as calcareous ones, through a better nutrient uptake and by alleviating abiotic stresses. A replicated-space experiment was carried out to investigate the role of mycorrhizal-based inoculants combined with full or halved fertilizer doses on yield and physiological traits of three early potato cultivars organically grown in highly calcareous and alkaline soils. The results indicate that AMF symbiosis ameliorated, in comparison to the not-inoculated plants, the potato tolerance to limestone stress by enhancing the potential quantum efficiency of photosystem II (F_v/F₀) and plant gas-exchange parameters (photosynthesis rate and stomatal conductance). Moreover, a significant improvement of marketable yield (+25%) was observed, mainly due to an increase of the number of tubers plant⁻¹ (+21%) and, to a lesser extent, of average tuber weight (+10%). The AMF efficiency was higher applying halved fertilizer doses and in the location where soil conditions were unfavourable for potato growth. Moreover, the qRT-PCR highlighted that AMF colonization was similar in each location, demonstrating their tolerance to limestone, alkalinity and P stresses. These findings outlined that AMF are good candidate to bio-ameliorate calcareous soils and are very useful for improving potato yields under organic farming, limiting external fertilizers supply and environmental pollution.

Recently, on the EU market, phosphonic acid residues were detected in many organic goods, although fosetyl-derivates and phosphite salts are not allowed by Reg. EC n. 889/2009. The BIOFOSF project “Solving phosphite issue in organic fruit and horticultural crops” aimed at verifying whether the phosphonic acid contamination could be due to unproper use of fertilizers/plant protection products by organic farmers, or to the plant’s ability to self-produce it spontaneously. Applying a participative approach, field case-studies on potato, rocket lettuce, and pears were carried out (organic vs. integrated systems). The ethyl-phosphonic acid and phosphonic acid were determined in soil, tubers, leaves, fruits, tree woody organs, used fertilizers, and plant protection products to correlate them to the applied farming management. Tested crops were not able to self-synthetize phosphonic acid, being its detection due to: (i) external inputs not allowed in organic farming; (ii) fertilizers/plant protection products allowed in organic farming, contaminated by fosetyl or phosphite. In addition, it was found that tree crops can stock the phosphite in their woody organs, then translocate it from branches to leaves and fruits over time. Regression models applied to field data showed that fruit trees decontamination could take more than 5 years, depending on the starting value of phosphonic acid contamination, useful to define the phosphite maximum residue limit in organic fruit crops.

Soil mycorrhization can play an important role for the qualitative improvement of organically grown “early” potato tubers especially in low fertility soils (such as calcareous ones), by ameliorating plant uptake of limiting mineral nutrients in the soil. Hence, the objective of the present research was to elucidate the impact of soil mycorrhization on the tuber minerals content of three potato cultivars organically grown in two locations with different soil characteristics. Our data revealed the keyrole of soil mycorrhization on the tuber accumulation of Na, Cu, Mn, and P and on reducing the Na/K ratio, although the effects of soil mycorrhization were cultivar- and location-dependent. Accordingly, soil mycorrhization was able to enhance the levels of K and Ca in ‘Arizona’ and that of Mn in ‘Universa’, while it increased the Zn amount in all the cultivars under study. Additionally, soil mycorrhization significantly improved the levels of Cu and Mn in tubers in the location characterized by an initial higher soil level of these micro-minerals. This work highlighted the possibility to fortify organic early potato tubers, in terms of macro- and micro-mineral elements, by applying an eco-sustainable tool such as soil mycorrhization, provided that specific consideration is given to cultivar choice and soil characteristics.

Understanding the nature of the perceived quality advantage of organically-grown early crop potatoes over conventionally-grown ones is of relevance given the expansion in demand for foodstuffs produced by environmentally friendly agricultural practices. The effect of the cultivation system (organic vs. conventional) on physicochemical (skin color, firmness, skin thickness, pH, titratable acidity), nutritional (dry matter, ascorbic acid, total phenolics content, antioxidant activity), and sensorial (for boiled and fried tubers) traits of early potatoes were explored in a field trial conducted during two-seasons in Sicily (Southern Italy) and involving five yellow-fleshed genotypes. The organic cultivation system, averaged across seasons and genotypes, produced tubers displaying a more attractive skin color, with higher skin thickness and firmness, higher dry matter content (19.0 vs. 17.9%), and total phenolics content (350 vs. 232 mg GAE 100 g⁻¹ dry weight) but lower ascorbic acid content (76 vs. 103 mg 100 g⁻¹ dry weight) and antioxidant activity (42 vs. 56% DPPH reduction). The organic cultivation did not affect attributes after boiling but improved all sensory attributes (crispness, typical taste, and browning degree) after frying, highlighting that the superiority of the organic potatoes does not cover all aspects of quality. The positive effects of organic cultivation on physicochemical, nutritional, and sensorial quality were particularly evident in Arinda, Ditta, and ISCI 4F88. Even if the response of organic cultivation on overall quality also depended upon seasonal conditions, cultivar choice plays a key role in optimizing this production system, highlighting the importance of breeding programs.

Wireworms (Agriotes spp., Coleoptera, Elateridae) are a major threat to potatoes, as are the current commercial standards for assessing potato damage. To reduce wireworm impacts on potato crops and comply with IPM legislation, we started research to assess the potential for new Italian 4x-breeding clones to reduce wireworm feeding on daughter tubers. Two sets of trials were carried out over a six-year period (2018–2023): in-field and in semi-natural conditions, with pots used to introduce a set number of reared wireworms. In the field trials, the varieties were planted in 4.8 × 9–12 m plots in a randomized-block layout with at least three replications. The same wireworm damage assessment was used for both sets of trials. The assessment involved counting all the erosions/scars caused by wireworm feeding activity. The prevalent wireworm species studied was Agriotes sordidus. Both sets of trials showed that some 4x-breeding clones were tolerant to wireworm attacks. The percentages of tubers damaged (any symptom) or with at least one ordinary/large hole was up to five times lower than in the commercial varieties. Glycoalkaloids and the caffeic acid content in tubers are considered to be the main cause of lower appetibility to wireworms.