Till-up: how to improve fruit set and filling with

In organic agriculture, where the use of synthetic regulators is restricted, organic agricultural biostimulants offer an effective tool to counteract fruit drop, improving stress tolerance and nutrient use efficiency. Below, we analyze the causes, mechanisms, and practical solutions based on scientific evidence and field experience.

Physiological causes of fruit drop: abiotic stress and nutritional imbalance

Fruit drop originates from a combination of environmental and nutritional factors that alter the plant's hormonal balance. Among the main triggers are water stress, both from deficit and excess, extreme temperatures (frost or heat waves), soil or irrigation water salinity, and deficiencies of key nutrients such as boron, calcium, and zinc.

Water and thermal stress

Water deficit during flowering and fruit set reduces cell turgor and photosynthesis, limiting the availability of carbohydrates for fruit development. On the other hand, high temperatures (>35°C) accelerate transpiration and alter pollen viability, while frost damages floral tissues. In both cases, the plant increases the production of abscisic acid (ABA), a hormone that promotes abscission. A study from the University of Córdoba (Spain) showed that thermal stress during olive flowering can reduce fruit set by up to 40%.

Nutritional imbalance

Boron is essential for pollen germination and pollen tube growth; its deficiency leads to poor fertilization and subsequent fruit drop. Calcium, in turn, is necessary for cell wall stability and cell division in young fruits. Zinc deficiency affects the synthesis of auxins, hormones that prevent abscission. According to the FAO, micronutrient deficiencies affect more than 30% of agricultural soils worldwide, making fruit drop a recurring problem in many regions.

Organic biostimulants to mitigate fruit drop

Ecological biostimulants act on the physiological mechanisms that trigger fruit drop, improving stress tolerance and nutritional efficiency. Among the most effective are seaweed extracts, amino acids, humic and fulvic acids, and beneficial microorganisms.

Seaweed extracts (Chlorella, Scenedesmus)

Freshwater microalgae such as Chlorella vulgaris and Scenedesmus contain natural phytohormones (auxins, cytokinins, gibberellins), betaines, and polysaccharides that stimulate root growth, improve nutrient uptake, and increase stress tolerance. Foliar application during flowering and fruit set has shown increases in the number of set fruits in olive and vine. For example, a trial in organic olive groves using freshwater microalgae for agriculture reported an 18% increase in fruit set and a 25% reduction in fruit drop under water stress conditions.

Amino acids and peptides

Amino acids such as proline, glycine, and glutamic acid act as osmoprotectants and nutrient chelators, facilitating the absorption of boron and calcium. They also participate in the synthesis of stress proteins and hormonal regulation. The application of amino acids at critical times (pre-flowering, fruit set) helps maintain cell turgor and reduces ABA-induced abscission.

Fulvic acids

Fulvic acids for organic agriculture improve the availability of micronutrients in the soil and stimulate microbial activity. Their low molecular weight structure allows them to penetrate roots and leaves, acting as nutrient transporters and stress modulators. In citrus, the application of fulvic acids has been shown to reduce young fruit drop by up to 30% under saline conditions.

Agronomic strategies to prevent fruit drop in key crops

Preventing fruit drop requires an integrated approach that combines good management practices with the strategic application of biostimulants. Below are specific recommendations for high-value crops.

Olive groves

In olive trees, fruit set is especially critical during flowering and fruit set (April-June in the Northern Hemisphere). It is recommended to apply a biostimulant based on microalgae and amino acids at pre-flowering and repeat after 15 days. The typical dose is 2-3 L/ha per foliar application, in a sufficient water volume to cover the canopy. Additionally, maintaining adequate irrigation to avoid water deficits during this period significantly reduces fruit set issues. According to the technical guide on fruiting in olive groves with microalgae, yield increases can exceed 20%.

Grapevine

In grapevines, fruit set issues manifest as shatter or millerandage (seedless berries). Applications of biostimulants at flowering (stage of separated flower buds) and fruit set improve fertilization and berry development. The use of algae extracts rich in gibberellins and cytokinins, combined with chelated boron and zinc, is recommended. A trial on the Tempranillo variety showed a 15% reduction in shatter and a 12% increase in berry weight.

Citrus

In citrus, the physiological drop of young fruits (June in the Northern Hemisphere) can be aggravated by water stress and boron deficiencies. The strategy includes foliar applications of fulvic acids and microalgae at pre-flowering and post-fruit set, along with careful irrigation management. Incorporating organic matter into the soil improves water retention and nutrient availability, reducing the impact of fruit set issues.

Tomato

In tomatoes, fruit set issues occur when nighttime temperatures exceed 21°C or daytime temperatures exceed 35°C, affecting pollen viability. The application of biostimulants with amino acids and calcium at flowering improves fruit set and prevents blossom-end rot. An organic fertilization program for tomatoes can include weekly applications of biostimulants during the critical period.

Field results: improved fruit set and filling with biostimulants

Various field trials support the effectiveness of organic biostimulants in reducing fruit set issues and improving yield. Below are data from studies conducted in Spain and other Mediterranean countries.

These results demonstrate that biostimulation is an effective and sustainable tool to mitigate till-up, especially in organic production systems where the use of synthetic regulators is not allowed. The key lies in applying at the appropriate phenological stages and in combination with optimal agronomic management.

For more information on specific fertilization programs, consult the Ecoganic field trials and results or contact our technical team.

FAQ

What is till-up in agriculture?

Till-up is a physiological phenomenon that causes premature drop of flowers or young fruits due to abiotic stress or nutritional imbalances. It manifests as growth arrest followed by abscission, reducing the final crop yield.

How does water stress affect till-up?

Water stress during flowering and fruit set reduces photosynthesis and carbohydrate availability, while also increasing the production of abscisic acid, a hormone that promotes abscission. This can cause losses of up to 40% in olive groves if not properly managed.

What nutrients prevent till-up?

Boron, calcium, and zinc are essential for preventing till-up. Boron promotes fertilization, calcium stabilizes cell walls, and zinc participates in the synthesis of auxins that inhibit abscission. Their deficiency worsens the problem.

When to apply biostimulants to prevent till-up?

It is recommended to apply biostimulants at pre-flowering and during fruit set, critical moments for fruit setting. Foliar applications at these phenological stages maximize efficacy, improving stress tolerance and nutrition.

Are organic biostimulants effective against till-up?

Yes, organic biostimulants such as microalgae extracts, amino acids, and fulvic acids have been shown to significantly reduce till-up in field trials. They work by modulating stress hormones and improving nutrient uptake, without the need for synthetic products.