Factors regulating fine-root growth are poorly understood, particularly in fruit tree species. In this context, the effects of N addition on the temporal and spatial distribution of fine-root growth and on the fine-root turnover were assessed in irrigated sweet cherry trees. The influence of other exogenous and endogenous factors was also examined. The rhizotron technique was used to measure the length-based fine-root growth in trees fertilized at two N rates (0 and 60 kg ha⁻¹), and the above-ground growth, leaf net assimilation, and air and soil variables were simultaneously monitored. N fertilization exerted a basal effect throughout the season, changing the magnitude, temporal patterns and spatial distribution of fine-root production and mortality. Specifically, N addition enhanced the total fine-root production by increasing rates and extending the production period. On average, N-fertilized trees had a length-based production that was 110–180% higher than in control trees, depending on growing season. Mortality was proportional to production, but turnover rates were inconsistently affected. Root production and mortality was homogeneously distributed in the soil profile of N-fertilized trees while control trees had 70–80% of the total fine-root production and mortality concentrated below 50 cm depth. Root mortality rates were associated with soil temperature and water content. In contrast, root production rates were primarily under endogenous control, specifically through source–sink relationships, which in turn were affected by N supply through changes in leaf photosynthetic level. Therefore, exogenous and endogenous factors interacted to control the fine-root dynamics of irrigated sweet cherry trees.

Calcium (Ca) and Boron (B) are structural components of the cell wall with limited phloem mobility. The absorption, movement, and distribution of these two nutrients have a greater effect on leaves than on fruits since their transport is dependent on transpiration flow. This research aimed to study the absorption and movement of ⁴⁵Ca applied to the soil and the fruit of sweet cherry trees under B-deficient and B-adequate soil conditions. In the first experiment, ⁴⁵Ca was applied to the soil surface before the occurrence of leaf senescence. Soil and tree components were sampled and analyzed 6 months after ⁴⁵Ca application. The second experiment involved a ⁴⁵Ca application to the surface of small fruits with 5 mm diameters, which were analyzed after 45 days. The tree Ca allocation in the B-deficient soil condition was significantly fewer in shoots and higher in roots, contrary to the B-adequate soil. On the other hand, the fruit evidenced significant differences in Ca levels in the edible portion of the fruit (i.e., the flesh and peel), which was higher in the B-adequate soil condition. Therefore, under B-deficient soil, Ca was ‘retained’ in the root system and in the fruit pit, suggesting a synergistic mechanism between Ca and B. This mechanism might indicate a survival ecological function where B triggers biological signals to restore Ca homeostasis.

Annual top-dressing application of agricultural lime is a common practice in fruit orchards on acidic soils in southern Chile, which could result in surface over-liming and base imbalances. A trial was performed in a cherry orchard with an 8-year history of surface liming to evaluate the effectiveness of lime materials in neutralizing acidity in the soil profile and the effect on the tree nutritional status. No-lime (NL), calcitic (AgL), hydrated (HL), and liquid (LL) lime treatments were applied on soil surface at commercial rates, and soil acidity variables were measured at depths of 0–5, 5–10, and 10–20 cm in samples collected at 0, 15, 30, 60, and 225 days after application. Tree nutritional status was evaluated through foliar analysis. Top-dressing application of AgL was ineffective in ameliorating subsoil acidity at depths >5 cm, even in high-rainfall conditions. HL did not exhibit greater alkalinity mobility compared to AgL, although it had a faster but shorter-lived reaction. At the manufacturer-recommended rates, LL application was ineffective. After 8 years of top-dressing liming with AgL, a significant stratification of soil pH, Al, and Ca was observed. However, foliar concentration of bases did not reflect the surface Ca accumulation in soil, discarding an antagonistic cation competition for tree uptake.

Aluminum (Al) toxicity constrains plant performance in acidic volcanic soils, yet nitrogen (N) fertilization may influence Al availability and plant responses. This study evaluated the effects of N source and rate under contrasting soil liming conditions on vegetative growth, mineral nutrition, and physiological performance of non-bearing northern highbush blueberry (Vaccinium corymbosum L. cv. Blue Ribbon^®) plants. A split–split-plot experiment was conducted in southern Chile using urea or potassium nitrate applied at 0, 20, or 40 kg N ha⁻¹ to plants grown in unlimed soil or soil amended with calcium carbonate or magnesium oxide. Vegetative growth, tissue mineral composition, stomatal conductance, chlorophyll fluorescence, and leaf chlorophyll were monitored during the first season. Growth responded primarily to soil liming rather than N supply, indicating low N demand and substantial soil N mineralization under the experimental conditions. Foliar N increased from 1.36 to 1.70% with increasing N rates. Urea nutrition reduced foliar Al concentration by 12% compared with nitrate. Under unlimed conditions, representing maximal soil Al availability, urea fertilization was associated with 70% higher Al retention in roots relative to nitrate. Chlorophyll content was consistently higher under urea supply, while the maximum photochemical efficiency of photosystem II remained unaffected. These findings indicate that N form influences plant Al partitioning independently of growth responses. Although the underlying mechanisms were not directly assessed, the observed patterns suggest that urea fertilization may reduce Al translocation to shoots under conditions of high Al availability.