Editorial: Mineral Nutrition of Fruit Trees

In the era of precision farming, the wise administration of water as well as the correct management of mineral nutrition is of outmost importance to reduce the agricultural inputs. Therefore, the effort to increase the nutrient use efficiency as well as to preserve the environment from redundant minerals, which can pose a serious risk for aquifer contamination, is essential [1]. The best practices aimed at the correct management of the mineral nutrition of fruit trees are also essential to promote fruit yield and quality; the topic deserves particular attention in the context of global change, which may seriously impact fruit tree management [2]. The Special Issue “Mineral Nutrition of Fruit Trees” is therefore timely and offers contributions that may help readers to focus on most recent aspects related to this trivial topic.

The Special Issue includes 19 research papers in which different aspects of fruit mineral nutrition have been investigated, with the help of the most updated technologies available in the sector of tree physiology and arboriculture, including metabolomics, transcriptomic, advanced photosynthesis as well as NMR investigations. Included papers are devoted to: (i) generate knowledge on the uptake, transport, accumulation and utilization of macro- and micro-nutrients by different families and species of widely cultivated fruit trees including: apple [3], peach [4], naranjilla [5], kiwifruit [6], loquat [7], chestnut [8], almond [9] and avocado [10]; (ii) increase the knowledge on how abiotic (i.e., aridity [11,12] and salinity [13,14]) and biotic stress (i.e., Huanglongbing disease in citrus [15]), growing systems and/or cultural techniques (i.e., irrigation [4], soil fertilization [4,9], foliar fertilization [6] and grafting [12,16]) affect fruit trees’ nutritional status and nutrient requirements; (iii) gain insight related to pre- and post-harvest physiological disorders attributable to mineral imbalance (e.g., boron excess in apple trees [17], macronutrient deficiency in fig [18] and bitter pit on apple fruits [19]; and (iv) propose new methods and models to correctly manage the fertilization of fruit tree species in the orchard or in pots [20,21].

In particular, Leitzke Betemps et al. [20] proposed a new Humboldtian diagnosis of peach tree (Prunus persica (L.) Batsch) nutrition using machine-learning and compositional methods in which the authors aimed at customizing nutrient diagnosis of peach trees at local scale. Lanauskas and colleagues [21] proposed the use of cattle horn shaving as a possible alternative of nitrogen for apple cultivation and they highlighted that horn shavings, acting as a nitrogen fertilizer, could be used for the management of apple trees, especially in organic orchards, where the use of synthetic fertilizers is prohibited.

The Special Issue also includes two literature surveys: Doyle and co-workers [22] reviewed the physiology of nitrogen and calcium nutrition in blueberry (Vaccinium sp.) with the attempt to summarize studies dealing with N acquisition, translocation and assimilation in determining N-source preference in blueberry. In addition, modes of Ca acquisition and transport to the fruit, and various approaches to improve Ca concentration in fruit are discussed therein. Kalcsits et al. [23] proposed a literature update related to the recent achievements and new research opportunities for optimizing macronutrient availability, acquisition, and distribution for perennial fruit species.

The Editors of the Special Issue are thankful to all the authors who gave their valuable contribution, which was essential for to the final outcome of the present Special Issue. The Editors are also thankful to the MDPI collaborators for their valuable support.