Sustainability of High-Density Olive Orchards: Hints for Irrigation Management and Agroecological Approaches

Abstract

The production of olive oil in Portugal and other countries of the Mediterranean region has greatly increased in recent years. Intensification efforts have focused on the growth of the planted area, but also on the increase of the orchards density and the implementation of irrigation systems. Concerns about possible negative impacts of modern olive orchard production have arisen in the last years, questioning the trade-offs between the production benefits and the environmental costs. Therefore, it is of great importance to review the research progress made regarding agronomic options that preserve ecosystem services in high-density irrigated olive orchards. In this literature review, a keywords-based search of academic databases was performed using, as primary keywords, irrigated olive orchards, high density/intensive/hedgerow olive orchards/groves, irrigation strategies, and soil management. Aside from 42 general databases, disseminated research, and concept-framing publications, 112 specific studies were retrieved. The olive orchards were classified as either traditional (TD) (50–200 trees ha−1), medium-density (MD) (201–400 trees ha−1), high-density (HD) (401–1500 trees ha−1), or super-high-density (SHD) orchards (1501–2500 trees ha−1). For olive crops, the ETc ranged from 0.65 to 0.70, and could fall as low as 0.45 in the summer without a significant decrease in oil productivity. Several studies have reported that intermediate irrigation levels linked with the adoption of deficit irrigation strategies, like regulated deficit irrigation (RDI) or partial rootzone drying (PRD), can be effective options. With irrigation, it is possible to implement agroecosystems with cover crops, non-tillage, and recycling of pruning residues. These practices reduce the soil erosion and nutrient leaching and improve the soil organic carbon by 2 to 3 t C ha−1 year−1. In this situation, in general, the biodiversity of plants and animals also increases. We expect that this work will provide a reference for research works and resource planning focused on the improvement of the productive and environmental performance of dense irrigated olive orchards, thereby contributing to the overall enhancement of the sustainability of these expanding agroecosystems.

Hedgerow Olive Orchards versus Traditional Olive Orchards: Impact on Selected Soil Chemical Properties

“…It is important to note that, when we go from traditional rainfed olive groves to irrigated olive groves, many factors affecting soil organic matter content must be considered besides the introduction of irrigation and fertilizers, such as the type of tillage carried out, the existence or lack of cover crops between the rows, and the incorporation or absence of pruning residues [43]. In fact, Sobreiro et al (2023) [44] said that, with the combined utilization of cover crops, non-tillage, and pruning residue recycling, it is possible to reduce soil erosion and nutrient leaching and improve the soil organic carbon by 2 to 3 Mg C ha −1 year −1 .…”

“…The introduction in soil of ions by irrigation water and fertilization would lead to the assumption that EC values would be bigger in olive groves managed in hedgerows, where these inputs are used to a greater extent, compared with the traditional ones [44]. In fact, irrigation, even with good-quality water, introduces appreciable quantities of salts into the soil.…”

“…In addition to this, olive groves grown under hedges, with greater growth and production potential, inevitably have a greater uptake of ions when compared to traditional rainfed olive groves [44], and therefore, the ion concentration in the top layer of the soil in the first system can be lower. Nevertheless, the registered values, in both cases, are very low and without any possibility of negatively affecting the development of this crop.…”

Planting density: Key strategy for optimizing soil health and fruit antioxidant activity in a calafate orchard

“…This is achieved by optimizing resource distribution and minimizing interplant competition, thereby amplifying the performance of each individual plant. However, the appropriateness of density requires tailored evaluation for each fruit species, as exemplified in olive orchards, where, higher densities (401-1500 plants ha -1 ) have demonstrated an increase in soil biodiversity and an enhancement of N balance compared to lower densities (201-400 plants ha -1 ) (Sobreiro et al, 2023). Furthermore, a high-density of 1850 plants ha -1 resulted in a remarkable 29% increase in soil organic C (SOC) and root biomass compared to a lower density of 300 plants ha -1 (Gómez et al, 2022).…”

Advancing tree genomics to future proof next generation orchard production

“…However, some tree crops like avocado (Persea americana) and macadamia (Macadamia integrifolia, Macadamia tetraphylla, and hybrids) lack available varieties or rootstocks with these traits, and many horticultural industries have not made substantive use of available varieties and/or rootstocks. Planting at higher densities gives the potential for higher yield per land as seen in olive orchards (Sobreiro et al, 2023), however, this may not be applicable to all tree crops (Haque and Sakimin, 2022). The benefits of higher density plantings are increased if trees flower and produce high yield at a younger age as this improves the return on investment and allows for faster turn-around of plantings and quicker introduction of newer, improved varieties.…”