The intensification of highly specialized viticulture has led to a dramatic decrease of soil fertility that can be restored by increasing soil organic matter using organic fertilizers. The aim of the present experiment was to evaluate the effect of different organic amendments on vine vegetative growth and nutritional status, soil N availability and microbial biomass, as well as on yield and grape quality. The experiment was carried out in 2020 and 2021, on cv. Sangiovese (Vitis vinifera L.) vines grafted on 110 Richter (V. berlandieri × V. rupestris) planted in February 2019. Plants were fertilized yearly in spring with (1) mineral fertilization (MIN), (2) municipal organic waste compost (MOW), and (3) sewage sludge compost (SS). The application of SS increased nitrate availability in both years, while the supply of organic matter (no matter the source) enhanced soil microbial biomass content. Plant nutritional status was in the optimal range for all treatments, with an increase of N in SS and K in MOW. Fruit yield in 2020 was not influenced by treatments, while in 2021 it was enhanced by MIN and MOW, which also induced a higher berry quality. Plant vegetative growth was stimulated by the application of SS. In conclusion, from these preliminary results we observed a higher N availability as a consequence of SS supply that resulted in a higher plant biomass, but reduced yield and berry quality, supporting the theory that for vineyards, N should be carefully managed to reach an equilibrium between vegetative and reproductive activity.

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.

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.