Limited rainfall makes irrigation critical for plant growth and optimal yield. In this context, soil moisture management plays a key role in optimizing irrigation practices, improving plant performance, and enhancing fruit quality. However, conventional monitoring systems, based on single or multiple sensors installed along the soil profile, often fail to deliver accurate and representative information on water availability within the root zone. The aim of this research was to evaluate the effectiveness of a real time system made of in situ probes, able to predict the moisture in the soil unit explored by root, for the development of an irrigation recommendation. In a two-year (2024-2025) research experiment carried out in northern Italy, on mature pear fruit trees cv. ‘Abbé Fétel’, grafted on seedlings and planted at a distance of 4 x 2,4 m apart, to evaluate the effectiveness of a smart irrigation system (SMARTER) compared to a traditional one (CONTROL). The main goal of the study was to use a probe system to detect the total amount of water in the first 100 cm of soil depth and wisely select the amount of water to irrigate the crop. Water management in the CONTROL treatment followed the advisory service guidelines, based on daily evapotranspiration, soil texture, and crop phenological stage. In contrast, the SMARTER system applied irrigation according to soil water content measured by potentiometric probes located according to the grid of nine sensors (placed ad different distance and depth from the emitters). Irrigation started when soil matric potential dropped below -0.1 MPa in more than 50% of the volume of soil explored by the root system and was aimed at replacing the optimal water level for the phenological stage. The first year (2024), two treatments were applied: SMARTER vs CONTROL, with an irrigation system made of a single pipeline. While in the second year (2025), a new treatment was added, consisting of the same irrigation system, however water application rate was reduced to maintain only 40% of the volume of soil at a matric potential > -0.1 MPa (SMARTER 2). During the growing season, stem water potential was evaluated as a measure of the plant water status and at harvest the total yield was compared to the control. In comparison to CONTROL, the SMARTER system decreased the volume of water used for irrigation of 36% and 19%, in 2024 and 2025, respectively; while in 2025 the SMARTER 2 showed a 52% of water saved compared to the CONTROL. Total yield and fruit quality were not affected by the treatments during the two-year trial. However, in 2025 growing season, fruit size was increased by SMARTER and SMARTER 2 compared to CONTROL. In conclusion, the real time, in situ smart system used in this experiment, showed an important potential to decrease the volume of water commonly used in the traditional irrigation system, without affecting the total production and fruit quality.Keywords: soil moisture, water potential, soil matric potential, Pyrus communis, drip irrigation, evapotranspiration rate

Fertilization management is crucial mainly during the walnut training phase in order to obtain good plant formation, which is essential for guaranteeing future optimal yield. The aim of the present experiment was to evaluate the effect of different organic amendments on plant nutritional status and soil fertility in young bearing walnut trees. The experiment was conducted in 2023 and 2024 on walnut trees of the cultivar Chandler grafted on Juglans regia, planted in 2021. Since 2023, plants were yearly treated as follows: 1. non-fertilized control; 2. mineral fertilization; 3. application of municipal solid waste compost; and 4. application of compost from agri-food chain scraps. Soil amendments were supplied at the same rate as mineral fertilizer (120 kg N ha-1) in spring on the tree row on a 1.5 m wide strip, while mineral fertilizer was split in two applications (50% in spring and 50% in summer). Plant growth, measured with trunk diameter and pruning wood weight, was enhanced by mineral fertilization, followed by compost, in comparison to the control. Soil mineral N was too high in relation to plant needs, with a consequent increase in the risk of nitrate leaching. Organic amendments increased soil nutrient availability, microbial activity, and carbon concentration, which, in the long term, could provide a positive environmental effect related to its sequestration into the soil.

Understanding how P availability affects root turnover and P redistribution within plants is essential for optimizing fertilization strategies and sustaining forest growth under low-P soils. This study evaluated the effects of P fertilization on root system dynamics, plant growth, and P nutrition of Handroanthus heptaphyllus, a flowering landscape tree, cultivated in a subtropical climate. Plants were grown under two soil P levels (low and high). Plant height, stem diameter, leaf P concentration, soil P availability, total numbers of living and dead fine roots, total fine root surface area, and fine root production rate were measured at 18, 24, 30, and 36 months after planting. Phosphate fertilization increased soil P availability during the first 24 months and resulted in significant gains in plant height, stem diameter, fine root production, total surface area, and the ratio between living and dead fine roots, indicating a higher proportion of living roots relative to dead ones. Under high P availability, the greatest fine root production and surface area of living fine roots occurred in the 0-20 cm soil layer, reflecting localized P application near the plants. High P availability enhanced root system development, promoted greater soil exploration, and improved P uptake. These results indicate that under P supplementation, plants strategically invest in root growth, improving nutrient acquisition efficiency and reducing dependence on external inputs. Increased phosphorus availability enhances root growth and increases fine root production and turnover. Minirhizotron monitoring effectively captured shifts in root system dynamics driven by P availability, including enhanced root growth, increased fine root production and turnover, and improved nutrient uptake under high P, as well as limited root activity under low P conditions, indicating a more conservative strategy with reduced investment in root production.

Vermicomposting is an environmentally sustainable, economically viable, and agronomically valuable method for converting organic waste into nutrient-rich soil amendments, thereby supporting sustainable development. However, the fertilization efficiency of vermicompost can vary significantly depending on the physicochemical properties of the feedstock used. This study aims to compare different feedstocks on vermicompost and evaluate their performance on soil fertility and plant nutritional status. Organic matter (OM), pH, salinity (EC), total Kjeldahl nitrogen (TKN), total phosphorus (TP) and total potassium (TK) of various vermicompost samples were taken into consideration to evaluate their fertilization efficiency as performance determinants in terms of plant growth, plant nutritional status, yield, crop quality and cost with the aim of determining the weights of the specific parameters in the total performance using multi-criteria decision-making (MCDM) methods. The integrated ENTROPY-TOPSIS method was used. Twenty-one different vermicompost feedstock analyses were collected from the literature and compared in order to create an agronomic performance ranking based on the selected criteria. The ENTROPY method revealed that the TP was the most influential factor (21.6%), followed by the EC (20.7%) and the TK (18.5%), while the OM had the lowest impact (11.3%). Based on the TOPSIS ranking, vermicompost from brewer’s spent grain achieved the highest performance, followed by cow manure plus rice straw and olive pruning waste, whereas paper waste ranked at the bottom. A comparative analysis with other objective MCDM weighting methods proved strong correlations, particularly with WENSLO, MPSI and LODECI methods, confirming the robustness of the ENTROPY method.

Reliable tools for assessing soil nutrient availability are essential for the accurate determination of fertilizer application rates. The aim of this study was to evaluate the reliability of commercially available electrochemical sensors for the real-time determination of water-soluble N, P, and K in soil as indicators of nutrient supply to crops. The experiment was conducted under both greenhouse and field conditions using seven probe models. Four probes (designated 1–4) were equipped with three sensors for the measurement of N, P, and K. Probes 5, 6, and 7 were equipped with sensors for N, P, K, electrical conductivity (EC), pH, soil temperature, and soil moisture, although probe 7 was manufactured by a different company. Each probe was inserted into 4 L pots filled first with a clay-loam soil and subsequently with a sandy soil. The soils were irrigated with nutrient solutions containing different concentrations of N, P, and K in order to modify nutrient concentrations in the soil solution and compare sensor readings with values obtained through standard chemical analyses. The results showed no significant correlation between probe readings and soil N, P, or K concentrations in either clay-loam or sandy soils. At the same time, all probes exhibited a constant relationship among N, P, and K readings regardless of soil texture or nutrient concentration. This finding suggests that the probe algorithms rely on a single measured variable that is subsequently converted into multiple output variables using fixed conversion coefficients. In conclusion, the NPK probes tested in this study were unable to provide reliable real-time measurements of soil N, P, and K concentrations.

The necessity for nutritional standards to evaluate the nutritional status of grapevines is a critical concern for viticulturists worldwide. This study addressed the lack of multinutrient standards that consider specific genetic and environmental factors by proposing regional standards based on data collected under different growing conditions. Using the compositional nutrient diagnosis (CND) method and multivariate analyses, leaf samples from 585 commercial vineyards in Emilia-Romagna, Italy, and the states of São Paulo and Rio Grande do Sul, Brazil, were evaluated. The results confirmed significant variations in nutritional standards among regions and cultivars, emphasizing the need for regional adjustments in fertilization recommendations. This work proposes critical levels, sufficiency ranges, and nutritional standards that can improve grapevine nutritional assessments, promoting greater precision in fertilization management. The findings reinforce the importance of regional standards, avoiding the use of unsuitable universal recommendations.

Little information is available on the yellow-fleshed Zespri Zesy002 kiwifruit dynamic of mineral nutrient uptake and partitioning within organs. The aim of the present experiment was to find nutrient requirements and supply data for a specific nutrient management plan for Zesy002. The trial was conducted, for three years, in northern Italy, on a six-year-old kiwifruit orchard of the variety Zespri Zesy002. During the experiment organs were periodically sampled and analyzed for macro- and micronutrient concentration. A yearly nutrient uptake of 175 g N plant−1, 16 g P plant−1, 138 g K plant−1, 235 g Ca plant−1, 48 g Mg plant−1, 17 g S plant−1, 247 mg B plant−1, 673 mg Cu plant−1, 5.20 g Fe plant−1, 473 mg Mn plant−1, and 263 mg Zn plant−1 was calculated, confirming that kiwifruit is a high-nutrient-demanding species. The nutrients found in the tree organs were divided in two factions: removed (not returned into the soil) and recycled (returned into the soil during and at the end of the growing cycle). The two fractions were similar for N, P, K, S, and Mn. The fraction recycled of Ca, Mg, Cu, and Zn was higher than the fraction removed, and the reverse was observed for Fe. These data created the basis for the determination of the correct nutritional plans that take into consideration not only nutrient requirements but also the dynamics of uptake during the season.

The control of soil moisture is fundamental for optimizing water supply, plant performances and fruit quality. Traditional monitoring systems rely on a single sensor, or several sensors positioned along the soil profile not giving reliable information on soil water availability in the soil volume occupied by roots. In a 3-years field experiment we tested the effectiveness of PLUTO, an original approach able to define soil moisture profiles thanks to a bi- and tri-dimensional grid of sensors. The study was carried out, from 2021 to 2023, in northern Italy, on kiwifruit Zezy002 (A. chinensis var. chinensis) grafted, in 2012, onto micro-propagated Hayward (A. chinensis var. deliciosa) planted at a distance of 4.5 m x 2 m apart. During the experiment a traditional irrigation system (CONTROL) was compared to smart irrigation (PLUTO). Water management in the control treatment was carried out according to the advisory service, only based on daily evapotranspiration. On the other side, according to PLUTO water was applied taking into consideration the soil water content measured by potentiometric probes located according to the grid of sensors. Irrigation started when soil matric potential dropped below -0.1 MPa in more than 50% of the volume of soil explored by the root system and was aimed at returning the same amount of water lost the day before and estimated by evapotranspiration. During the experiment, compared to the CONTROL, PLUTO reduced the volume of water without impairing plant water status and yield. Fruit juice soluble solid concentration and fruit dry matter at harvest was increased by the smart irrigation system with a similar response also after 2 and 4 months of cold storage. PLUTO water management also induced a lower fruit firmness and yellow pulp color (defined by H angle) at harvest. In conclusion, the definition of irrigation volumes and timing according to smart irrigation system were able to reduce water consumption and increase fruit quality. Taking into consideration that the cost of sensors is progressively decreasing, PLUTO provides a cost-effective, operative, and precise solution to monitor soil water availability.

In the last years commercial walnut orchards plantation is increasing in Emilia-Romagna, an Italian region renowned for its excellence in fruits cultivation. Despite the expansion of walnut plantations in this region, there is scarcity of studies focusing on the water demand of this crop. This research aims to assess the response of an adult walnut orchard (cv. 'Chandler') to three distinct irrigation treatments (100% ETc, 75% ETc, and 50% ETc). Water supply was managed according to the IRRIFRAME water balance model. Plant water status (stem water potential, SWP), leaf gas exchanges (leaf photosynthesis, A; stomatal conductance, gs), yield, nut quality (e.g., nut weight, shelled yield, kernel colour) and water use efficiency (WUE) were measured for four consecutive seasons (2018-2021). Differences in plant water status were detected only in half of the performed measurements and trees irrigated at 100% ETc generally showed more positive SWP values compared to 75% and 50% ETc trees. Gs and A were less sensitive than SWP to the different water regimes, showing limited differences among treatments only in the first two years. Yield and main nut quality parameters were slightly affected by irrigation treatments mainly in 2018 and 2019, with the 50% ETc showing a reduced productivity compared to 100% and 75% ETc. No differences where registered for shelled yield and kernel colour for all the four consecutive years. On the contrary, irrigation treatments highly affected WUE in all the considered years, with 100% ETc being the less efficient treatment, followed by 75% and 50% ETc.

Calcium (Ca2+) plays a fundamental role in metabolic processes, and it is involved in several structural functions at the cell level, such as vacuole osmotic regulation, cell wall strengthening, and plasma membrane stability, as well as acting as a secondary messenger for several different signals. The role of Ca2+ in signal transduction and cell wall organization is crucial for stress responses, cell activity, and plant tissue development. In addition, Ca2+ is essential in modulating enzymatic activities, hormonal control, water, and ion transport across the plasma membrane. Although calcium’s role in fruit trees is well studied, many of its specific functions in kiwifruit remain unclear, including the optimal amount of Ca2+ in fruit and its distribution in fruit cells for the best pre- and post-harvest fruit quality. Calcium transport to the fruit is mainly regulated by the xylem sap flow; however, the contribution of fruit transpiration and the requirements of fruit cells are not clear. Understanding the kinetics of Ca2+ accumulation in fruit under different environmental conditions can help establish correct nutrient management. This review addresses the current knowledge on Ca2+ involvement in plant physiology, metabolic processes, structural functions, and fruit growth, quality, and storage, with particular emphasis on Actinidia chinensis. In addition, the different analytical techniques used for the quantification and definition of Ca2+ in different plant organs, including stain technology, X-rays, and advanced imaging methods, are here explored.

The intensification of agricultural practices and the consequent dramatic decrease in soil organic matter has increased the use of organic fertilizer to recover soil fertility and plant productivity. The aim of this study was to compare the effect of three amendments obtained from the recycling of urban and agri-food wastes on rhizosphere microbial community, soil, and plant nutrient status. The experiment was carried out on rhizobox-grown, 1-year-old vines of Sangiovese (Vitis vinifera L.), grafted onto 110 Richter (V. berlandieri × V. rupestris) planted in April 2023. Twenty-four rhizoboxes were filled with soil collected from a field trial in which three types of amendments had been applied since 2019. In detail, the complete randomized experimental design (with four replications) compared the following treatments: (1) municipal organic waste compost (ACM), (2) agri-food organic waste compost (ACF), (3) defecation gypsum (GDD), and (4) a control that received 60 kg of N ha−1 year−1 (CK). The application of the amendments increased the soil concentration of total C, total N, and pH. The application of ACM increases soil K and Zn and the concentration of N and K in plant roots. The application of all the amendments increased leaf N concentration in comparison with CK, but only ACF increased leaf P. ACM was the most effective in promoting microbial biodiversity, increasing phyla like Bacillota, Pseudomonata, and Bacteroidota, including genra like Bacillus, Neobacillus, Paenibacillus, and Pseudomonas. ACF promoted Nitrosospherota and Chitinophaga, and GDD promoted Chloroflexota and Agrobacterium.

Calcium (Ca) is one of the most important nutrients involved in fruit quality and storability; therefore, its application in fruit trees is often used in pre- and post-harvest. The aims of this study were to manipulate soil Ca, K, and N availability, photosynthetic active radiation, and fruit transpiration rate to understand their implication on fruit Ca accumulation on green-flesh kiwifruit grown in calcareous soil. Our results show that Ca partitioning into the fruit is not affected by the applications of Ca, K, and N, as well as the increase of photosynthetic active radiation. However, the presence of reflective films reduced fruit firmness and increased soluble solid content at harvest and during cold storage, thus enhancing fruit quality. Fruit calcium accumulation is decreased by the reduction of fruit transpiration rate; however, it has the possibility to recover, even close to fruit harvest, when the fruit transpiration is restored. The presence of bags reduced fruit weight from 84 to 63 g even though bags were removed. Our data provide evidence of the inefficiency of calcium fertilization in kiwifruit in calcareous soils and demonstrate the extension of calcium transportation into the fruit, which seems to occur during the entire growing season.

In recent years, reduced summer precipitation frequencies related to climate change have raised the probability of water scarcity, even in the Po Valley of Italy, thus requiring an optimization of the irrigation management for walnut cultivation which has become very present in the area. The aim of the present study was to evaluate, during four consecutive seasons (2018–2021), the physiological (stem water potential Ψw, leaf photosynthesis A and stomatal conductance gs), yield (nut weight, shelled yield, kernel colour) and water use efficiency (WUE) responses of walnut trees to different irrigation levels (100

High copper (Cu) concentration in soils used for vegetable production is an agricultural, social and environmental issue. The excess of Cu in soil can cause toxicity in plants, reducing growth and yields. Moreover, Cu can also be absorbed and accumulated in edible organs, increasing risks for human health. This study aimed to compare Cu fractions in soils: (1) non-cultivated, natural soil (NC), (2) soils cultivated with open field crops (FCs) and (3) soils cultivated in controlled environments (CEs). The survey was carried out on 25 sites in Rio Grande do Sul (Southern Brazil), with each site containing the three types of soils described above. From these sites, the four with the highest soil Cu concentrations were selected to compare soluble (Cu-CaCl2), available (Cu-EDTA) and total (Cu-EPA) Cu. Both total and available soil Cu concentration in soil solution, in CE and FC areas were higher than in NC. At sites 23R1 (Oxisol) and 11R1 (Molisol) the soluble and available Cu content was higher in the FC environment than in CEs, and the same was observed for the total Cu content at sites 23R1 (Oxisol) and 9R1 (Molisol). Some FC soils showed total Cu concentrations higher than the limits established by Brazilian environmental legislation, being, as a consequence, potentially contaminated. Soil monitoring and cropping practices must be adopted to reduce the Cu content in soils of vegetable crops in this region.

Soil fertility is mainly related to soil total organic carbon (C) that should be preserved in order to optimize soil quality and functionality. Consequently, the use of organic amendments could be a possible strategy to increase soil C and nitrogen (N) storage particularly in orchard systems where the disturbance of soil is reduced thus making favorable conditions for C and N stabilization. The aim of this study was to evaluate the distribution and stabilization of organic C and total N in aggregate fractions after a 14-years-period of compost application to a peach orchard. The trial was conducted in the southeastern Po valley, on a commercial nectarine orchard and the following treatments were compared in a complete randomized block design with four replicates: 1. unfertilized control; 2. mineral fertilization; 3. compost at a rate of 10 Mg dry weight ha(-1) yr(- 1). At the end of orchard lifetime, soil was sampled from the row at four depths (0-0.15, 0.16-0.25, 0.26-0.45, and 0.46-0.65 m) and physically fractionated to separate macroaggregates (> 250 mu m), microaggregates (250-50 mu m) and silt and clay (< 50 mu m) that were analyzed for organic C, total N, delta C-13 ,and delta N-15. Compost addition induced a significant increase of macroaggregates (66%), no changes in microaggregates and a decrease of silt and clay (22%) compared to control and mineral fertilization. With compost the accumulation of organic C and total N content in the macroaggregates was four-five times higher than the other two treatments in all the depths, therefore almost 50% of the soil organic C was in this fraction, compared to 20-24% in the control and mineral. In the micro-aggregates more C and N accumulated only in the two top layers, while no effect was observed in the silt and clay fraction. From macro-to microaggregates to the silt and clay fraction, the C/N ratio shifted from 9 to 7.5 to 6 on average indicating that the C and N stabilized in the finer fractions is mainly of microbial origin. The enrichment in C and N isotopic composition from macro-to micro to silt and clay is also indicative of the isotopic fractionation due to microbial metabolism and the consequent stabilization of microbial residues in the finer fractions. In the control and mineral, only receiving orchard litter, this change was observed in all the layers, on the contrary, with compost similar delta C-13 and delta N-15 values characterized the fractions in the top soil layer suggesting the occlusion of compost in all the fraction. With depth the macroaggregates maintained the same delta C-13 and delta N-15 values indicating consistent redistribution of compost in deep soil layers, while the finest fractions showed a progressive enrichment of delta C-13 due to the presence of C fractionated during microbial metabolism and progressively stabilized. In conclusion, compost supply leads to positive effects on C and N accumulation and stabilization also in the deeper layers favoring the increase of long-term soil fertility and C storage.

Correct water management of golden kiwifruit vines, besides being essential for reaching high yield and fruit quality, is also fundamental to keep plants healthy and avoid useless water loss. The objectives of this trial were to: 1) assess the water retention curve in typical soils for the kiwifruit production in Italy; 2) evaluate the response of potted Zezy002 plants to the variation of soil moisture, in term of leaf gas exchange and stem water potential. Plants grown on each soil were divided into two groups: 3 plants were irrigated maintaining soil water at field capacity (control); 4 plants were subjected to water stress as follows: irrigation rate was reduced 50 % of the evapotranspiration rate for one week, then irrigation was suspended. Two days after water suspension, 2 of the 4 stressed plants were irrigated as for the control plants (recovery), the other 2 vines were not irrigated (stress). Each pot was provided with a chalk potentiometric probe so that soil matric potential was constantly monitored. During the experiment leaf gas exchange and stem water potential were daily measured. After irrigation stop, a decrease of net photosynthesis, transpiration and stomatal conductance were observed, on the other hand, intercellular CO2 concentration showed the opposite trend. Specific behavior has been detected for the two loam soils tested (here labelled as "sand-clay-silt" and "silt" soils). At wilting point, established when plant photosynthetic activity stopped, soil matric potential, measured by chalk probes, ranged between -1.8 and -2.0 MPa in all soils with the exception of "sandy-clay-silt", where it was -0.49 MPa. Soil matric potential at field water capacity ranged between -20 and -50 kPa in all soils with the exception of "silt" soil (-140 kPa). This peculiar behavior will be likely due to specific pore size distribution or poor-connected pores, however further investigations are needed.

Environmental extremes, such as drought and flooding, are becoming increasingly common, resulting in significant crop losses. The aim of the present study was to understand the molecular response induced by drought and waterlogging conditions, and to link these responses to the physiological adaptation of plants. For this purpose, leaf RNA expression was analyzed in potted kiwifruit plants by Illumina Next Generation Sequences. Stressed plants showed an impairment of all physiological parameters (leaf-gas exchange and stem-water potential) with a more evident effect in waterlogging condition than in drought condition. However, the impact on the transcriptome in waterlogged plants was less intense than in drought stress. Drought affected several metabolic pathways, among which “plant hormone signal transduction”, “protein processing in endoplasmic reticulum”, and “mitogen-activated protein kinase signaling pathway” were the most representative in terms of number of genes involved. The genes involved in the biosynthesis of phenylpropanoids were positively influenced by both drought and waterlogging. Finally, waterlogging stimulated secondary metabolisms by upregulating the genes responsible for the biosynthesis of terpenoids and flavonoids, such as stilbenoids. The obtained results show that the two contrasting stress conditions share several common physiological responses and molecular mechanisms.

Fruit crops under soil conservational management might sequester carbon (C) in soils and mitigate greenhouse gases emissions. Using grape pomace residues as soil amendment holds promise for sustainable viticulture. However, its actual capability to increase soil organic carbon (SOC) and nitrogen (N) is unknown, especially in subtropical climates. This research aims to investigate whether grape pomace compost and vermicompost can increase SOC, total N (TN), and C and N stocks in subtropical vineyards. Two vineyards located in Veranópolis, in South Brazil, one cultivated with ‘Isabella’ and the other with ‘Chardonnay’ varieties, were annually amended with these residues for three years. We quantified SOC and TN in each condition in different soil layers, as well as C and N content in two different granulometric fractions: mineral-associated organic matter (MAOM) and particulate organic matter (POM). C and N stocks were also calculated. Despite potential benefits, neither treatment enhanced SOC, its fractions, or C stocks. In fact, vermicompost was rapidly mineralized and depleted SOC and its fractions in the 0.0 to 0.05 m layers of the ‘Isabella’ vineyard. Our findings indicate that the tested grape pomace residues were unable to promote C sequestration in subtropical vineyards after a three-year period.

Nitrogen (N) derived from the decomposition of litter from cover crops can contribute to the mineral nutrition of citrus trees. This study aimed to assess the prior contribution of N derived from the decomposition of forage radish (Raphanus sativus) and black oats (Avena strigosa) to Satsuma mandarin tree N demand. Forage radish and black oats were grown and enriched with 15N stable isotope. Two studies were conducted on (1) non-bearing, potted satsuma mandarin seedlings for 120 days in the greenhouse (Experiment 1) and (2) bearing field-growing Satsuma mandarin trees for 270 days (Experiment 2). Tree growth and total N and 15N concentrations were determined in annual and perennial organs of citrus and soil. The highest value of N derived from the decomposition of cover crop root residues was observed in the leaves and roots of non-bearing trees, while the highest amount of N derived from shoot residue decomposition was observed in the leaves of bearing trees. The results showed little contribution of the decomposition of residues of forage radish and black oats on the total N budget of annual and perennial organs of both bearing and non-bearing Satsuma mandarin trees, probably because the climatic conditions promoted a fast N mineralization and possible losses through volatilization and leaching.

Persimmon is a typical fruit crop of the Mediterranean region and, since it is considered a minor species, little information is available on its nutrients need. In the present experiment, it was estimated the quantity of removed and recycled nutrients by Kaki Tipo and Rojo Brillante, the two main varieties of persimmon grown in Emilia-Romagna region (Po Valley, Italy). Plants from ten mature orchards were selected and harvested; organs (leaves in summer, fruits at harvest, abscissed leaves, roots and skeleton) biomass and mineral composition were determined. The yearly uptake of macronutrients was similar for the 2 varieties, accounting for (kg ha−1): N 89-91, P 10-11, K 79-91, Ca 132-162, Mg 22-26 and S 9. While K was mostly found in fruits, Ca and Mg were mainly partitioned to leaves. Among micronutrients, Mn and Fe showed the highest values (1.1–1.3 and 1.2–2.1 kg ha−1, respectively), followed by B (370 g ha−1), while Cu and Zn showed the smallest amounts (less 100 g ha−1). Nitrogen, Ca, Mg and S were those more recycled than removed, while K showed an opposite trend; among the microelements, the annual recycled fractions of B and Mn were higher than that removed.