For a long time, it was mistakenly believed that the hazelnut tree was self-sufficient, a hardy crop that required little care. However, the current reality is quite different; to achieve consistent production and a truly profitable business, a well-thought-out technical strategy is essential . In regions like southern Chile, where the planted area has grown exponentially, nutrient management has become the cornerstone of profitability.
When we talk about feeding these trees, it's not just about adding fertilizer and that's it; it's about understanding that each plot is unique. The key lies in adjusting fertilization to the actual needs of the crop , taking into account that factors such as soil type, climate, and the variety planted, like Tonda di Giffoni or Barcelona, ​​directly influence how the tree absorbs minerals and, therefore, the quality of the hazelnut we will harvest.
The challenge of acid soils and aluminum
In areas with soils derived from volcanic ash, known as Andisols, acidic pH is very common. The serious problem arises when the pH drops below 5,5, as this causes aluminum to solubilize in toxic forms (Al+3) . This element is a real headache for farmers, as it directly attacks the root tips, blocking cell division and preventing the root system from growing.
This toxicity not only stunts the roots but also creates a domino effect: the tree loses its ability to explore the soil and, therefore, cannot absorb water or essential nutrients like calcium and magnesium. Furthermore, in these volcanic soils, phosphorus tends to become fixed, inaccessible to the plant, which worsens the orchard's nutritional situation and can lead to smaller trees with a much shorter lifespan.
Accurate diagnosis: Soil and Leaves
To avoid going in blind, it's essential to perform a physical and chemical analysis of the soil before even planting. Using soil pits is fundamental to detecting physical limitations such as iron or impermeable layers that impede drainage. If water accumulates in winter, it creates hypoxic conditions that suffocate the roots, affecting critical processes like pollen maturation and pollination, which ultimately impacts the final yield.
On the other hand, foliar analysis is the tool that tells us what is really happening inside the tree. Sampling is recommended between January and February, as this is when the leaf tissue is most stable. This diagnosis allows for adjusting annual fertilization based on reference values ​​or standards, enabling the correction of nitrogen, potassium, or phosphorus deficiencies before they become a serious problem that reduces production.
Correction and Fertilization Strategies
If the analysis indicates that the soil is too acidic, the solution is liming. Applying materials like lime-calcite or lime-dolomite helps raise the pH and precipitate toxic aluminum , converting it into insoluble compounds. However, it's crucial to be very careful with the dosage, because over-liming can cause zinc, boron, or iron deficiencies, leaving us in the same situation or worse.
- Phosphorus Management: Since volcanic soils fix a lot of phosphorus, the strategy should be to apply partial corrections over time to improve efficiency.
- Nutrient Replacement: In already productive orchards, fertilization should focus on replenishing what the fruit removes. It is vital to know the extraction factors of N, P2O5, K, CaO, and MgO per ton of fruit.
- Vegetative Balance: The goal is to maintain a healthy balance between branch growth and fruit production to avoid alternate bearing.
One detail that is sometimes overlooked is the relationship between nutrition and commercial quality. It has been observed that poorly filled fruits (those with internal voids) tend to have a higher concentration of aluminum in their peel . This demonstrates that, if we don't control soil toxicity, the toxic element can reach the fruit, lowering its market value.
Nutritional Value of Hazelnuts for the Consumer
Beyond the fields, hazelnuts are a highly valued superfood. They are particularly prized for their monounsaturated fats, especially oleic acid , and their ability to provide vitamin E and phenolic compounds that act as antioxidants. These components help combat oxidative stress and protect cells, making this nut a valuable ally in the Mediterranean diet for improving lipid profile and cardiovascular health.
From a dietary perspective, they provide a considerable amount of fiber, which promotes satiety and intestinal transit. They are also rich in minerals such as manganese, copper, and magnesium . It is important to note that processing, such as roasting, can slightly alter the concentration of some micronutrients, although they generally remain an excellent source of energy and folate, essential for proper brain function and heart health.