Historically, we have routinely used refractometers to measure the sugar content of fruits and, based on the results, to determine harvest dates. However, knowing the Brix level in mature leaves throughout the growing season allows us to understand how well-nourished the crop is.

Measuring Brix degrees in our crops gives us important information about their metabolic state, just as measuring temperature or blood pressure in our body gives us a quick, simple and effective reference regarding the general state of the crop.

Measurements can be taken with analog refractometers, but more accurately with digital ones, making it possible to know the solute or sugar content of the sap itself.

Analyzing the sap of a particular crop through a refractometer gives us the refraction of the light rays that pass through the plant's sap.

The deviation of light caused by the greater or lesser presence of solid structures such as sugars will give us a different gradation, providing us with information regarding:

• Amount of carbohydrates.
• Presence of minerals dissolved in the sap and circulating through the plant
• Alteration of the radiation received by the plant

By analyzing the Brix levels of a leaf or petiole, after first extracting the juice or sap, we will measure the sugar content present throughout the plant.

This allows us to indirectly determine whether or not the crop is effectively utilizing the fertilizers we are providing under normal light conditions.

Plants that are able to metabolize large amounts of sugars are plants that efficiently complete all their physiological cycles, such as fruit fattening, flowering, or rooting.

All these sugars are used by the plant to perform vital functions. For example, during the vegetative phase of the crop, without fruit present, the majority of these sugars are used for root growth. After flowering, when the fruit is developing, most of these sugars will be used for fruit growth, at the expense of root development.

In this stage of fruit growth, the greatest amount of sugars is generated , that is, a higher rate of transformation of the nutrients it extracts from the soil or those we provide, generating a greater capacity to allow fruit growth and thus allow continuous root development, without root death.

The important thing about knowing Brix degrees is that, unlike EC in sap, which only tells us the gross supply, Brix degrees tell us if the ions are actually being transformed into functional elements for the plant (amino acids, proteins, and sugars). In this way, we can have a better understanding of whether the nutrition we are providing is effective or not.

Studies have shown how Brix levels change according to the phenological stage of crops, tables that need to be refined according to the producing areas, but once they are known in each area they allow very efficient adjustments to both amendments and regenerative and conventional nutrition.

Crops with high Brix levels will have a greater amount of sugars and therefore of proteins, minerals, amino acids, specific weights of fruits and greater plant masses.

Factors that affect Brix in sap.

1. Variety and rootstocks of the crop.
2. Soil characteristics and moisture.
3. Electrical conductivity and plant stress.

At Agro Canepa we have started with periodic Brix measurements in sap in both citrus and avocado trees and the post-harvest decreases found in it are evident and how we must adopt the greatest number of strategies to reach flowering with the highest possible Brix content.

The periodic measurements we take are correlated with the sap analyses and the phytosanitary status of the orchards we review, in order to adjust lighting, specific nutritional inputs and phytosanitary treatments if necessary.

In this way, it is possible to guarantee with greater certainty not only the fruit set, but also that the fruits that last have a greater specific weight and therefore greater nutritional density, a concept that is gaining strength every day among consumers worldwide for a healthier and more nutritious diet of fruits and vegetables.

This has led some supermarket chains to be interested in measuring nutritional density, forcing suppliers to comply with higher certification requirements for export, such as the justifications that support each of the agronomic practices carried out in the fields.

Renzo Canepa Gutierrez Chile renzo@agrocanepa.cl - + 56 9 79053241 Agro Canepa SpA