Humic & Fulvic: It’s All About The Carbon

By Frans Olivier, Technical Adviser at AECI Plant Health

From school geography you will recall what happens to carbon over time, at different pressure levels and temperatures in the earth’s crust.  Prehistoric decomposed plant material, consisting of high percentages of carbon, is found in the earth’s crust at different depths. Generally speaking, the deeper the layer the older it is and the higher the pressure impact from other top layers as well as the temperature influence from the earths center.

In the deepest layers, diamonds are formed and consists of almost 100% carbon. The hardest natural substance on earth and also a girl’s best friend. Fast-forward a few million years and a few 1000 meters shallower, is where coal is formed and consists of around 80% carbon. This is the stuff fueling the worlds increasing energy demands and what we desperately need to find alternatives for. Closer to the surface and another few million years younger is where brown coal is found. Also referred to as lignite or leonardite. Depending on the carbon content that can differ from 30% to 60%, brown coal has little value to the mining industry but has excellent properties for the agricultural industry. humates and fulvates can be derived from this layer.

Before we delve deeper into humates and fulvates, let’s just take another look at carbon and why the concentration and occurrence of this single element is so important.

Carbon occurs naturally in the earth’s atmosphere in the form of carbon dioxide at a rate of around 0,04%. This is also the gas that we exhale after inhaling air. Oxygen makes up 21% of atmospheric gasses and nitrogen accounts for about 78% of the atmospheric gasses. Disturb this delicate balance and relatively quickly, in terms of the earths existence, you run into problems like global warming. With industries burning huge amounts of fossil fuel (coal) we have rapidly increased the amount of carbon dioxide released into the air. It is estimated that carbon dioxide contributes 76% of the greenhouse gasses, responsible for global warming. To try and combat global warming, more and more companies are realizing the importance of measuring and reducing their carbon footprint.

Plants holds a solution to this ever increasing disaster and this is the reason why deforestation and soils that lay barren, should be avoided at all cost. Approximately 45% of living plant material consist of carbon. To obtain this, plants extract carbon dioxide from the air and release oxygen back into the air through the process of photosynthesis.

In soils, carbon has many advantages. Some of the healthiest and most fertile soils are found in natural forests. This is because of the high amount of plant material deposited on the forest floor. The plant material is broken down, by various micro fauna and flora, into compost and humates. Eventually the nutritional elements and carbon, necessary for plant growth, are returned to the soil and again becomes available for new growth. Because of its porosity, carbon has a much larger surface area than soil particles. This gives carbon the ability to attract a much larger quantity of nutritional elements, effectively increasing the soils CEC (Cation Exchange Capacity – This is the soils capability to hold on to elements like potassium, magnesium, zinc, manganese etc. and make these available to plant roots). This leads to less elements leaching out of soils and contaminating the subsoil and waterways. Not losing nutritional elements through leaching, of course holds obvious advantages to the farmer. Furthermore, carbon also increases the water holding capacity of soils thereby decreasing water wastage - another very limited resource. As many would know carbon detoxifies harmful chemicals and heavy metals. Just think about carbon filters for purifying water and even given to people/animals as treatment after poisonous substances are ingested. Likewise, carbon also has this purifying capability in soils, reducing the harmful effects of chemicals and heavy metals. Probably the most important value of carbon is that it serves as a very important food source for soil-microorganisms. The positive effects of a healthy microorganism population in soils and the benefits transpiring to plant growth because of it, are of enormous value. The benefits of Trichoderma-, Mycorrhizae-, Bacillus-, Metarhizium-, Pseudomonas species, to name but a few are by now well-known, but scientist are still just scraping the surface of this astonishing subsurface world. Just think again about the healthy state of a natural forest where these microorganisms are in abundance.

Unfortunately, through agricultural practices like ploughing, soil carbon is released from the soil and lost to the atmosphere. This is a double whammy since more undesired carbon is added to the atmosphere and beneficial soil carbon is lost. This is one of the main reasons why more and more farmers are embracing practices like minimum tillage. Furthermore, most plant material is removed from the fields during harvesting which means that carbon and other minerals are not naturally replaced into the soil. This is the nature of farming, hence the need to put back what we take out of the soil, if we want to grow subsequent crops to feed the world populations’ ever increasing demands.

Replacing minerals can be done by fertilizing but replacing carbon is not that easy. Various practices like composting, not burning leftover plant material after harvest, mulch layers in fruit crops and the use of cover crops are all ways to combat carbon lost and/or replace carbon. Another way is by adding humates and fulvates to the soil. It is however important to note that soil carbon levels cannot economically be built up with the use of humates and fulvates alone, and therefore additional regenerative practices are encouraged.

Apart from adding carbon, the use of humate and fulvate has other additional benefits as well. Used together with water-soluble fertilizers it will chelate elements. Chelated elements are protected from leaching, are more easily taken up by plant roots and have a lower risk of binding with other elements that can form plant-unavailable complexes, especially under less favorable pH conditions. When humates or fulvates are sprayed onto granular fertilizers, after application, it has the added benefit of decreasing volatilisation of nitrogen fertilizers like urea (volatilisation is the loss of nitrogen to the atmosphere).

Now, let’s take a closer look at humates and fulvates. Both are humic substances formed naturally from humus (the collective term used to describe the final decomposed stage of plant material) or as mentioned before, it can be derived from brown coal using various extraction methods. In the production process for agricultural use, the humic substances are further differentiated into humic and fulvic because of their solubility in water at various pH levels. Humic is only soluble in water with pH > 2, while fulvic is soluble at all pH levels. For this reason, it is actually incorrect to use the term Humic acid, since this is not a true acid and the final product has a pH value of 9 or 10. On the other hand fulvic acid has pH of < 3. Other differences between humic and fulvic to take note of, specifically concerning its uses in agriculture are the following. Humic is a bigger, heavier and more complexed molecule than fulvic; humic has a higher carbon content than fulvic; Humic has a lower oxygen content and lower solubility, also in the soil.

Because of these different characteristics, the choice between using humic or fulvic acid should be made based on the following analysis To improve soil structure and microbial life - humic is the better choice because of the larger structure, molecular mass and higher carbon content. For chelating fertilizers or nutrients - fulvic acid is the better choice because of its stability at all pH ranges and therefore its compatibility with all fertilizers. The smaller molecules not only makes it suitable to use with soil applied fertilizers, but also with leaf applied fertilizers to increase uptake through its chelating properties.

With rising input cost, it makes a lot of sense to ensure that your fertilizer applications are as effective as possible. If you can achieve this, and at the same time start regenerating soil fertility and thereby decreasing the negative impact on the environment, it should be a serious consideration in your agricultural practices.

AECI has a large range of products to assist with all of your needs towards improving plant and soil health. Contact your AECI Crop adviser to find out more.

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