In 2018, 23.2 Mt of pears were produced in the world across 1.3 million hectares (ha) of cultivated land. This review analyzes different training systems and management styles that have been adopted worldwide, emphasizing the European pear’s economic and environmental sustainability for the Mediterranean area of cultivation. Despite a reduced number of cultivars utilized around the world, pear presents a plethora of innovative training systems. In Europe, dwarfing rootstocks have led to reduced planting distances and a subsequent increase in planting density. Still, the economic sustainability of these systems is now questionable. Many of the quince rootstocks have made it possible to considerably reduce the size of the tree and introduce the concept of continuous row planting, with the management of orchards from the ground (i.e., pedestrian orchard). The planting distance must be chosen according to the soil fertility, the vigor of the grafting combination, and the training system. The planting distance dramatically affects the pruning and the management of soil, fertilization, and irrigation. The reduction of tree size also lowers the volume of spray necessary when applying pesticides. The variability in yield worldwide results from the interaction amongst cultivar/rootstock/training system/climate/management.

The increase in the demand for almonds, the development of novel self-fertile and late-flowering varieties, and the establishment of plantations in new irrigated areas have led to significant progress in the productive techniques of almond tree cultivation. One of the most important has been the increase in planting density, due to the development of dwarfing rootstocks. This paper presents a comparison between two training systems with ‘Soleta’ almond cultivar: a super high density (SHD) system using Rootpac-20 dwarfing rootstock versus an open-center training system using GF-677 rootstock. To this end, several parameters related to chlorophyll content (fluorescence and SPAD) and light interception (from photosynthetically active radiation (PAR) measurements) were monitored throughout two vegetative cycles, and other productive conditions (flowering, fruit set and production) were tracked at specific times of the cycle. The open-center system resulted in higher PAR interception than the SHD system, but also in the presence of poorly illuminated fractions of the canopy. Differences were observed between both systems in terms of average fruit weight and yield per canopy volume. Lower yields were obtained in SHD system than in open-center, which may be significantly increased by adapting the inter-row spacing. However, the degree of efficiency in the use of resources or productive inputs, such as irrigation, was favorable to the new SHD training system, so its potential to become a reference system in modern plantations (using over-the-row harvesters similar to those used for vine and olive trees) seems promising.

Modern almond growing travels on the tracks of super-high density (SHD). Born in 2010, it has already reached 6700 ha planted all over the world. This new cultivation system needs to define efficient agronomic techniques in order to identify it as a “Super-Efficient System”. Among these, the choice of cultivar is a crucial technique and a key factor for sustainability. The purpose of this study was to compare different cultivars in terms of vegetative, productive, and efficiencies parameters in order to gain applicable relevant knowledge about the SHD almond cultivation technique. For this, 3 years of research was carried out during 2017–2019, on a young almond grove made in 2014 with row spacing of 3.80 m × 1.20 m (2190 trees/ha), to evaluate the agronomic behavior of the two most planted cultivars in Italy, Guara-Tuono and Lauranne^® Avijor, grafted on the Rootpac^®20 dwarfing rootstock. The main biometric, productive, yield, mechanical harvesting efficiencies, and almond quality parameters were evaluated. Cv Lauranne^® showed greater vigor, greater fruit yield, and damaged axes by mechanical harvesting, while higher values of yield efficiencies were observed for cv Tuono. Harvesting efficiency was related to canopy size and tree age. On the contrary, almonds quality parameters were strongly related to the cultivar, confirming the good performance of Tuono as varietal characters. Then, this cultivar seems to be the most suitable for an efficient SHD planting system, in line with the objectives of modern sustainable fruit growing. The better performance of cv Tuono could be related to the positive influence of the terroir as well.

Two trials were conducted under Mediterranean conditions to monitor several physiological indicators before harvest (leaf chlorophyll concentration, quantum yield of photosystem II electron transport, stem water potential, and stomatal conductance) and some agronomic performance parameters before and at harvest (vigor, fruit growth, fruit size, fruit weight, and yield), of ‘Vairo’ almond and ‘Big Top’ nectarine cultivars grafted onto eight Prunus rootstocks, six of which are common in both cultivars. For both ‘Vairo’ almond and ‘Big Top’ nectarine cultivars, factors including rootstock, date, and the interaction between rootstock and date, from fruit set to harvest were evaluated. Significantly affected were certain physiological and agronomical traits which were evaluated before harvest, with stem water potential being the parameter affected by interaction in both cultivars. In fact, the stem water potential presented low levels in Rootpac-20 and high levels in Rootpac-40 for both cultivars. With regard to the other physiological traits evaluated during the growing period, changes in stomatal conductance were observed in ‘Vairo’, but not in ‘Big Top’. Comparing rootstocks throughout the season, Rootpac-40 and IRTA-1 exhibited the highest stomatal conductance values, whereas the lowest was observed in Rootpac-R; Rootpac-20 and Ishtara also presented low values. Regarding agronomical traits at harvest, GF-677 and IRTA-1 produced high yields for ‘Vairo’ almond cultivar, whereas Rootpac-40 and Ishtara performed better with ‘Big Top’ nectarine cultivar.

By 2022, the total area of super high-density (SHD) almond orchards worldwide had spread to 14,622 ha. As well as factors such as spacing, and tree architecture, proper row orientation should ensure a more efficient sun exposure, yield and harvesting. This research was conducted in an irrigated SHD almond orchard of cv. Lauranne^® Avijor in Andria, Italy, in 2021 and 2022 (at 4th and 5th year from planting, respectively) to gain a deeper understanding on the effects of two row orientations on available Photosynthetic Active Radiation (PAR), Leaf Area Index (LAI), canopy growth, yield and harvesting efficiencies in this new planting system. The east-west row orientation in a SHD almond orchard negatively impacted LAI, canopy growth, yield, fruit quality and yield efficiencies, especially in the second year. The north-south row orientation allowed a better PAR distribution inside the whole canopy than east-west row orientation. This unevenness in PAR distribution inside the whole east-west oriented canopies could represent the driving engine of the effect on growth and yield parameters. Although some quality parameters differed between exposures, they all remained within the standard range of the cultivar. The results provide a scientific basis for improved SHD orchard management, helping to keep them as Sustainable and Efficient Systems (SES).

Super-high density (SHD) is the latest innovation in almond growing. This new cropping system needs to be studied in different climates, soils, latitudes and cultivars in order to promote more efficient and sustainable orchard management. This study shows the effects of two row orientations and different canopy positions on leaf area index (LAI), photosynthetically active radiation (PAR) and biological, phenological and agronomical parameters of a SHD almond orchard. Total bud number and flower bud number were higher for N-S row orientation and more wood buds were detected in top layers. LAI was strongly influenced by layer, but not by row orientation. Row orientation did not affect blooming or ripening phenology. Fruit number per layer was higher for North–South (N-S) row orientation and in middle layers; fruit set showed the opposite trend to flower bud and fruit numbers, achieving higher values for East–West (E-W) row orientation. Hulled fruit yield was not affected by row orientation but by canopy height. N-S oriented rows showed a greater number of empty nuts than E-W, but no differences were found between layers. We concluded that in SHD almond orchards, row orientation is determinant for sustainable crop management.