{"id":14554,"date":"2026-08-02T18:40:42","date_gmt":"2026-08-02T18:40:42","guid":{"rendered":"https:\/\/edapro.ch\/compost-tea-as-a-foliar-stimulant-what-really-matters\/"},"modified":"2026-08-02T18:40:42","modified_gmt":"2026-08-02T18:40:42","slug":"compost-tea-as-a-foliar-stimulant-what-really-matters","status":"publish","type":"post","link":"https:\/\/edapro.ch\/en\/compost-tea-as-a-foliar-stimulant-what-really-matters\/","title":{"rendered":"Compost Tea as a Foliar Stimulant: What Really Matters"},"content":{"rendered":"

Applying compost tea in the evening\u2014foliar application belongs in the cool hours.<\/p>\n

Hardly anything in compost tea is discussed as much as the fungal-to-bacterial ratio. In my opinion, it is a secondary criterion for use as a foliar stimulant. The decisive factor is the quality of the compost\u2014and that is exactly where we place our focus. <\/p>\n

In short:<\/strong> Compost tea is produced by brewing mature, high-quality compost\u2014at least 2% to 10% of the water volume\u2014in well-aerated water for 24 to 48 hours, without added sugar such as molasses. A good compost tea machine provides enough air capacity so that the dissolved oxygen remains above 6.5 mg\/l throughout the entire brewing process (rule of thumb: tank volume times 0.6 = required air volume in liters)\u2014this is achieved, for example, by our EdaLife Chrome brewing systems with an air-to-water ratio of almost 1:1. <\/p>\n

Any compost fed with wood contains fungi. In our Petri dish tests, Trichoderma species, known as promoters of plant health, regularly grow. Nevertheless, their hyphae are not always visible under the microscope. A microbiometer also detects fungi that are not microscopically recognizable. So, if you only count what you see in the microscope, you are not measuring the effect\u2014but the visibility. <\/p>\n

The five criteria we pay attention to<\/h2>\n
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1. Diversity of humic substances<\/strong>We make them visible using circular chromatography. Humic substances are essential for stimulating the plant. <\/div>\n<\/div>\n
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2. Maturity of the compost<\/strong>Mature compost no longer has harmful outgassing. We verify this with the closed Kress test. The absence of nitrite is another sign of fully matured compost. <\/div>\n<\/div>\n
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3. Microbial diversity<\/strong>The excretions of protozoa are excellent biostimulants. Regarding bacteria, we strive for the broadest possible diversity. <\/div>\n<\/div>\n
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4. The brewing process<\/strong>We monitor the oxygen over 24 hours. The content must not drop below 6.5 mg\/l, otherwise the aerobic microbiology collapses. For nutrition, we rely on complex carbohydrates, proteins, and herbs. <\/div>\n<\/div>\n
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5. The compost quantity<\/strong>International exchange shows: At least 2% compost<\/a> relative to the water volume is necessary. Smaller quantities reduce the valuable ingredients in the tea. <\/div>\n<\/div>\n

Why we avoid molasses<\/h2>\n

Molasses is standard in many recipes. We do not use it\u2014and there are two solid reasons for that. <\/p>\n

The first is oxygen. Sugar is immediately available to bacteria. Between the eighth and twelfth hour, this leads to such rapid multiplication that the dissolved oxygen crashes. At temperatures above 20\u00b0C, this is further exacerbated. <\/p>\n

The second reason carries more weight. If enterobacteria are present in the compost, they are co-multiplied by the molasses. We had this verified with a microbial analysis<\/a>: In the variants with molasses, genera appeared that you do not want on the leaf. <\/p>\n

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16S rRNA analysis: Enterobacteria appear in the molasses variants (TB, yellow)\u2014circled in red. TA = EDAPRO nutrition, TB = molasses, TC = without nutrients, K = compost. <\/figcaption><\/figure>\n

The same result was reached by USDA investigations<\/a> as well as a study in Compost Science & Utilization<\/a>.<\/p>\n

A practical side effect: The viscous consistency makes dosing tedious. That alone would not be a reason\u2014but combined with the rest, it is one more. <\/p>\n

More compost means more effect<\/h2>\n

Worldwide, usually 3% to 10% compost relative to the water volume is used. In German-speaking countries, the proportion is often below 1%. The reason is rarely technical in nature, but rather mechanical: Many machines lack the air capacity to keep the oxygen stable at higher concentrations. <\/p>\n

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Rule of thumb for air capacity<\/strong>Tank volume \u00d7 0.6 = required air volume in liters. Our EdaLife Chrome brewing systems<\/a> achieve a ratio of nearly 1:1. <\/div>\n<\/div>\n

Those who have the air capacity win in several ways: more microbial diversity, more humic and amino acids, more plant hormones like auxins and cytokinins. For foliar application, the higher concentration of secondary metabolites is what counts most\u2014they constitute the biostimulating effect. <\/p>\n

What this means for the application<\/h2>\n

Compost tea is not a fertilizer. The nutrients it contains are negligible in the overall balance. What works are the microorganisms and their metabolic products\u2014around 70% of the effect comes from this fraction. <\/p>\n

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Nozzles and pressure<\/strong>Nozzles with at least a 0.4 mm opening. The decisive factor is the impact velocity: Field sprayers that run close to the crop are best operated at no more than 2.5 bar. Air-blast sprayers in fruit growing can handle up to 7 bar\u2014the airflow swirls the compost tea, which reduces the impact velocity on the crop. <\/div>\n<\/div>\n

\ud83c\udfac The whole thing in a video<\/h2>\n

Production and application step by step\u2014recorded on our farm.<\/p>\n