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Foliar fertilisation

This is undoubtedly the best way to start the teachings of regenerative agriculture. It is often said that good soil is needed for plants to grow well. This statement is correct but incomplete because in reality it is the plants that generate good soil in the first place. Without plants, the soil would be disintegrating rock.

Only healthy plants can improve soil properties by sending sugars through root exudates in the first place. Foliar applications can accelerate this process and there are additional benefits because they improve plant resistance, yield and quality.

The most important aspect is how to design foliar applications correctly because the results can change significantly. You have to be careful about the sequence of mixing the products in the barrel, the quality of the water and other aspects.

You have to think of foliar applications as a regenerative farming system and not as a spot treatment to solve a specific problem. Many people use foliar applications to correct a micro-nutrient deficiency or for a curative fungicide treatment.

In regenerative agriculture the most challenging part is to understand what is the point of maximum yield with minimum product distribution and let nature take its course. Foliar applications are the key to achieving this.

Definition - What does Brix mean?

Brix is a unit of measurement to evaluate the solids dissolved in fruit and vegetable juices. These solids include amino acids, proteins, minerals, vitamins and the sugars fructose and sucrose.

It is important to know the brix level (°Bx) of fruits and vegetables to determine and plan soil management practices. It also helps gardeners improve the soil by determining whether they need to increase organic matter and soil nutrient ratios.

Brix can also be known as plant sap analysis.

The higher the brix level in fruit and vegetables, the healthier the plant. Plants with a high brix level tend to taste better and can be stored for longer periods of time. In fact, high-brix fruit and vegetables do not rot as easily. High-brix plants are known to produce seeds that germinate faster, resisting both frost and heat damage.

To measure brix, gardeners often use a device known as a refractometer. This device is most often used in viticulture to monitor the ripening process of grapes. To use the refractometer, winegrowers roll a leaf sample into a ball and squeeze a few drops into the device. The brix level will appear on a graduated scale.

The starting point for a healthy crop and healthy soil

Leaf application is the best method at the start of a crop to gradually increase the brix in the plant until the symbiotic processes of regenerative agriculture are activated. As the system becomes healthier, the effect of foliar application will be greater and longer lasting. For example, a foliar application from a plant at brix level 4 can quickly reach 12 brix within 30 minutes or 3 hours at the most. If after 24 hours there is no noticeable change on the leaf, the application has had no effect and the reason for this must be understood. Obviously a single application at the beginning cannot last long and the brix level can drop to 4.5 brix within 3 days, so a second application is necessary, but the point is that the second application will have a better effect and last longer than the first and the minimum brix level will be slightly higher, for example 5. Gradually the third, fourth and all subsequent foliar applications will help to raise the minimum brix level, making the effect better and longer lasting up to six weeks.

It is known that when the minimum brix level is maintained above 16 the plants are largely resistant to diseases and insects.

When the minimum brix threshold is high enough we do not need to make any more foliar applications to maintain their health because we have in fact created the regenerative farming system.

Once a foliar application is planned it is always good to do plant sap analysis before and after the application. The analysis of the plant's sap will almost always tell us which elements are needed to be supplemented, but an important aspect that we can note is the fact that often, in addition to the elements applied, the plant tends to absorb other elements that were not present in the barrel. For example, a foliar application containing iron and manganese can have a positive effect not only on the increase of the applied elements but also on the increase of zinc, copper and boron. This is due to the optimisation of photosynthesis in the leaves which produces sugars to be sent through the roots to the micro-organisms in the soil and thus stimulate them to mineralise other elements from the soil and then release them to the plant in a more noble form.

Another way to test the effect of foliar application is to create the intended mix and then test it in a small area by measuring brix after 2-4 hours before and after treatment. In this way more mixtures can be tested before application. If, for example, from the first measurement we have 3 brix and after three hours we measure a peak of 6 brix or 8 brix there will certainly be an increase in the peak up to 24 or 48 hours.

In short, it is possible to measure the efficiency of the foliar application within a short time before the product is applied. In fact, you can see different results from one mixture to another than you would expect.

How to design an optimal foliar application.

In general, the following should be added to the barrel

  • Clean water
  • Dispersants/Collectants/Surfactants
  • Mineral plant nutrients
  • Biostimulants for plants (algae extracts)
  • Biostimulants for microorganisms (fulvic acids)
  • Inoculants for microorganisms (Mirco 5000)

Nutrients are minerals (N, P, K, Mg, Ca, S, Fe, Zn, Mn, Cu, B, Mo) that we consider to be necessary at a certain point in time or that are deficient after an analysis of the leaf sap.

Biostimulants for plants are growth hormones such as auxins, cytokinins, gibberellins and abscisic acid, or natural extracts from seaweed or enzymes.

Biostimulants for microorganisms are fulvic acids, humic substances and also natural extracts from seaweed and some enzymes that stimulate existing biological activity.

Inoculants for microorganisms are cultures of additional microorganisms to be integrated into the barrel.

Dispersants/Collectants/Surfactants are very useful to increase adherence to the leaf surface.

Integrate in the following sequence:

  1. Clean water
  2. Pesticides
  3. Mineral plant nutrients
  4. Plant biostimulants
  5. Biostimulants for microorganisms
  6. Inoculants for micro-organisms
  7. Dispersants/Collectants/Surfactants

After selecting and testing the clean water (see below) the barrel must be filled up to 80-90%, especially when applying a pesticide, so that it is diluted as much as possible before applying a biostimulant or inoculant. Otherwise, if a biostimulant is applied first, then an inoculant and then the pesticide, there is a risk of damaging the populations by the concentration of the pesticide when it falls into the barrel, even if it dilutes within a few seconds.

Dispersants/Collectants/Surfactants should be added last because they may interact differently when added in a very concentrated form.

What is clean water for a foliar application?

Clean water must contain less than 70 ppm (5 grains) of total hardness. What makes water hard is calcium, magnesium, bicarbonates and carbonates. The most common problem occurs with calcium bicarbonates. Bicarbonates and carbonates are the primary concern because they are anions that attach themselves to whatever you add to the barrel. Water with total hardness above 150 ppm (10 grains) can reduce the performance of the applied product by up to 70%. This applies to any product added to the barrel.

Water quality is the biggest limiting factor for almost all foliar applications. Use rainwater, reverse osmosis filtered water or clean, laboratory tested water to ensure quality.

Clean water with reverse osmosis requires an investment of 4-5 thousand euros but can reduce the application rate by 30-50%. The same applies to herbicides, insecticides and fungicides. There are some who after filtering water with reverse osmosis and structuring it have managed to reduce the dosage by up to 70%.

Please note: avoid water made soft because sodium and chlorine are present, filtered water because bicarbonates and carbonates are not removed, pond or stream water unless it is tested and found to be clean because often if it filters through rocks it can take bicarbonates and carbonates, aqueduct water because chlorine is present or acidified water because acidifiers in water with 500 ppm of total hardness can lower the pH from, for example, 7.4 to 5.5 but only neutralise 30-40% of the bicarbonates and carbonates in the water; after 24 hours the pH rises again because the remaining bicarbonates and carbonates bind with the acids and reduce the acidifying action, which can be calculated mathematically.

Product synergies

Synergistic product applications have a greater effect on the plant when applied with this priority:

  • Plant nutrient minerals à
  • Biostimulants for plants (algae extracts) à
  • Biostimulants for micro-organisms (fulvic acids) à
  • Fungal inoculants à
  • Bacterial inoculants.

Biostimulants work much better if the plants have the right amount of mineral nutrients that they need. If, for example, we have to make a foliar application and we have a lack of magnesium and manganese in the plant and we want to apply seaweed, the effect of the seaweed will be much better if the plant receives an adequate amount of magnesium and manganese. As the health of the plant improves, the use of bio-stimulants is less necessary because the plant is able to synthesise its own hormones, enzymes etc.

The characteristics of the foliar solution

  1. Check the pH for best results from the formulated solution. The optimum is between 5.2 and 6.4. Products usually have an acidifying action to bring the pH of the solution into this range without the use of additional acidifiers.
  2. Check the Electrical Conductivity if foliar applications are made every 10-14 days the EC must be below 3800 ppm. Otherwise we have too high EC on the leaves. However, if foliar applications are carried out every 30-40 days this is not a concern.
  3. Deliquescence point: this is the point of humidity in the atmosphere at which a droplet on the leaf surface dries out or remains liquid. Solutions must contain small amounts of materials with a high deliquescence point such as seaweed, magnesium chloride, potassium nitrate or calcium nitrate so that the droplet we have sprayed on the leaves remains liquid for longer even in dry conditions. We have to think differently about getting nutrients uptake from the leaf surface because we know that there is uptake through stomata, diffusion through membranes, but perhaps we underestimate the impact of micro-organisms on the leaves that can metabolise the nutrients in the water droplet and get them absorbed faster by the plants.

When to apply foliar treatments

The right time is in the evening or early in the morning. In the morning is the absolute best time, but it can also be more difficult to do.

You should avoid applying:

  • During rain
  • When there is heavy dew because the drops can fall with the dew and carry away the product; it depends of course on the amount of water needed for foliar application but above 140 lt/ha the drops will fall on the ground.
  • When the temperature at the leaf surface exceeds 25.5°C.

The efficiency of foliar application on healthy versus unhealthy systems

The yellow line represents the photosynthesis potential of the plant compared to its health status from left to right. On the left the plants have abiotic stress (drought) or nutrient deficiency so the photosynthesis potential is between 5-10%. At the point where the yellow line first crosses the blue line we have the healthiest plants, which use 15-20% more of their photosynthesis potential. As the health of the plant improves, it begins to use 40% of the photosynthesis potential.

The blue line represents the effect of foliar application. When the plant is under stress we have an explosion of the result of foliar application, but as mentioned above the effect lasts little longer. In the intermediate health range for a while the foliar application seems to have little effect, but from a certain point onwards when the health status improves the effect of the foliar application increases dramatically again with lower dosages at longer intervals.

  Plants in poor health

  Plants in very good health

  • Strong reaction to product
  • Requires higher dosages
  • Effect lasts only a short time (4-7 days)
  • Requires frequent replications
  • Excellent product performance
  • Requires lower dosages
  • Effect lasts up to six weeks
  • Requires less applications

Foliar fertilisation


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