In rainfed olive groves, regularity is not a matter of chance, but of balance. When the soil works properly and nutrition is well managed, the olive tree responds with stability and continuity. Organomineral fertilization fits into this approach as a tool capable of combining soil improvement with efficient nutrition, helping the tree to better manage its reserves, cope with heavy crop years and move towards more regular production season after season.

Production irregularity in rainfed olive groves is one of the most persistent characteristics of the crop and results from the difficulty of the tree in maintaining a stable balance between production and the replenishment of reserves in an environment conditioned by scarce and irregular water availability. Alternate bearing is not an occasional failure or an anomaly, but the consequence of a physiological system working at its limit, in which the fruit load of one year directly conditions the olive tree’s ability to prepare the following harvest. Under rainfed conditions this phenomenon is intensified because water stress limits photosynthesis, nutrient uptake and the replenishment of reserves, especially during summer and autumn, which are key periods for the tree’s balance.

When the olive tree enters a year of heavy crop load, a significant part of the photoassimilates and available nutrients is allocated to maintaining and developing the fruit over a prolonged period. This effort reduces vegetative growth and limits the formation of new shoots, which are the structures that will bear flowers in the following season. At the same time, fruit load conditions floral induction and the internal allocation of resources, so that if the tree reaches the end of summer with accumulated stress and without the capacity to replenish reserves, flowering in the following year will be reduced even if subsequent climatic conditions are favorable. In rainfed olive groves, alternate bearing develops throughout the entire cycle and cannot be explained solely by what happens in spring.

Olive tree reserves play a central role in this process, but they must be correctly understood. Leaves are essential as photosynthetic organs and as a short-term reserve of mobile compounds while they remain active, but most structural reserves are stored in the wood and in the root system. These reserves support early bud break and the first stages of growth, when photosynthetic activity is still limited. In rainfed conditions, any factor that reduces functional leaf area, such as defoliation, severe water stress or nutritional imbalances, compromises the production of assimilates and therefore the tree’s ability to replenish reserves at the end of the cycle, increasing the likelihood of alternation.

From a nutritional point of view, alternate bearing cannot be attributed to the deficiency of a single element, but there is a clear relationship between the nutritional balance of the tree and its production regularity. Nitrogen influences vigor and the ability to produce new shoots, but under rainfed conditions its management must be particularly careful, since both deficiency and excess can worsen imbalance. Potassium plays a relevant role in the transport of assimilates and in the physiological regulation of the tree, and in years of heavy crop load its demand increases significantly. Boron influences flowering and fruit set, and under rainfed conditions its availability may be limited by low soil moisture. Phosphorus is rarely the determining factor, but in calcareous soils its low availability can reduce overall root system efficiency and contribute to a less balanced tree. Overall, regularity is not achieved by increasing doses, but by ensuring continuity and coherence in nutrition.

The soil is the element that integrates and conditions all these processes, and in rainfed olive groves its role is even more decisive. Organic matter improves soil structure, promotes infiltration and water retention, and sustains biological activity that regulates nutrient availability, especially nitrogen. In soils poor in organic matter, nutrient supply is more irregular and the tree is more exposed to periods of deficiency following episodes of stress or high demand. High-quality organic matter does not eliminate the inherent limitations of rainfed systems, but it does buffer the system and reduces dependence on very precisely timed nutrient applications.

In this context, organomineral fertilization is presented as a management tool aimed at improving the stability of the soil–plant system. By combining an organic fraction that helps improve soil properties with a mineral fraction that supplies nutrients in defined proportions, organomineral fertilizers allow for a more continuous and predictable supply than highly soluble mineral fertilizers applied sporadically. This greater stability does not imply the absence of losses, but it does mean less dependence on applying nutrients at an exact moment, which is particularly relevant under rainfed conditions where water availability cannot be controlled. By working over longer periods, organomineral fertilization helps ensure that the tree is not left nutritionally depleted after a heavy crop year and reaches autumn in better condition to replenish reserves.

The role of organomineral fertilization in olive grove regularity should not be understood as a standalone solution or as a tool to eliminate alternate bearing, but rather as a support within a broader soil and nutrition management strategy. Its main contribution lies in reducing extreme imbalances between seasons by improving the stability of nutrient supply and promoting a more functional soil. In a rainfed system, where the olive tree’s physiological margin is limited, any improvement in the continuity of soil and tree functioning translates into a greater likelihood of more regular production.

Ultimately, the regularity of rainfed olive groves depends on the tree’s ability to replenish the reserves it consumes in heavy crop years and on the stability of the environment in which it develops its cycle. Properly integrated organomineral fertilization does not replace water management, pruning or crop health practices, but it can play a relevant role as a tool to buffer the production cycle and move towards a more balanced and predictable olive grove.

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