Sustainable Olive Culture under Climate Change: The Potential of Biostimulants

Abstract

Climatic extreme events, like droughts, heatwaves, and floods are becoming recurrent and represent a threat to agriculture, lowering plant growth and productivity. The Mediterranean region is a climate-change hotspot, where traditional agricultural systems, like olive groves, are particularly challenged. Both the traditional and intensive systems of olive culture coexist in the Mediterranean. Both systems differ in their demands for water and agrochemicals, but nowadays, the global inputs of agrochemicals and irrigation have increased to achieve high productivity and profitability. Finding sustainable alternatives to maintain high productivity under the ongoing climate change is urgent to meet the EU-Farm to Fork strategy and climate neutrality. Candidate eco-friendly alternatives include biostimulants. These are substances or microorganisms, that activate signaling cascades and metabolic processes, increasing plant yield, quality, and tolerance to stressors. These benefits include a better growth, nutritional status and water availability, leading to a decreased demand for irrigation and agrochemicals. In this review, we aim to present different types of biostimulants (e.g., seaweed, protein hydrolysates, humic substances, microorganisms and nanomaterials), their mode of action and benefits in agriculture. We also explore the current state-of-the-art regarding the use of biostimulants in olive culture, and their potential benefits to increase tolerance to (a)biotic challenges.

Bioactive Compounds from Organic Waste

“…In 2019, olive production was headed by Spain (5,965,080.00 tons), followed by Italy (2,194,110.00 tons), Morocco (1,912,238.00 tons), Turkey (1,525,000.00 tons), and Greece (1,228,130.00 tons) [44]. Olives and olive oil contain different types of lipids (unsaturated, monounsaturated, and polyunsaturated fatty acids) and other compounds, in fewer concentrations, that benefit human health, such as phenols, sterols, squalene, tocopherol, proteins, and pigments [45]. Grapes have the same importance as olives in the Mediterranean, since they are used for producing different types of wine with different varieties of grapes rich in phenolic acids, flavonoids, tannins, and anthocyanins, providing excellent flavor and aromas [46].…”

Climate Change Challenges in Temperate and Sub-Tropical Fruit Tree Cultivation

“…As temperature rises during the growing period, the photosynthetic apparatus is severely affected in multiple ways. There may be stomatal as well as non-stomatal limitations of photosynthesis, leading to a reduced production of assimilates [37]. The most common reaction of plants to increased temperature (above the upper threshold limit), which, in most cases, is accompanied by water shortage as well (due to increased evaporative demand), is the closure of stomata.…”

“…A direct effect of this closure, apart from restriction in water losses, is the reduction of CO 2 entering the sub-stomatal areas. Under a continuous high-temperature exposure, the RuBisCO (Ribulose Bisphosphate Carboxylase Oxygenase) enzyme activity (the enzyme primarily responsible for carbon dioxide fixation and carbohydrate synthesis) declines, so the production of carbohydrates diminishes [37]. At the same time, photosystem II, the key determinant of electron transport during the photochemical reaction of photosynthesis, exhibits severe malfunctions, leading to the formation of reactive oxygen species (ROS) which may severely affect the physiological and metabolic processes by damaging the lipids, proteins, and nucleic acids [16,38].…”

Anomalous Gold Concentrations in Hypersaline Wetland Sediments (Laguna Honda, South Spain) Caused by Nanoparticles Used in Agricultural Practices: Environmental Transformation

“…Mediterranean olive culture is seriously challenged by the effects of climate change, which has motivated an increase in the use of agrochemicals in order to maintain productivity, resulting in potential environmental hazards [ 14 ]. The interest in metal nanoparticles in this sector as a sustainable alternative has grown due to their ability to slowly release nutrients and pesticides in a controlled manner [ 14 , 15 , 16 ].…”

“…Mediterranean olive culture is seriously challenged by the effects of climate change, which has motivated an increase in the use of agrochemicals in order to maintain productivity, resulting in potential environmental hazards [ 14 ]. The interest in metal nanoparticles in this sector as a sustainable alternative has grown due to their ability to slowly release nutrients and pesticides in a controlled manner [ 14 , 15 , 16 ]. Spain is the biggest olive oil manufacturer worldwide [ 17 ], and around 1.6 million ha of land in Andalusia (South of Spain) is dedicated to olive culture, especially in the Guadalquivir River Basin of the Jaén and Cordoba provinces [ 18 ].…”