It’s not enough to say ‘organic matter’

The lack of organic matter that today characterizes most cultivated soils, due to their excessive exploitation, the application of intensive agricultural practices and climate change, is a much debated topic in the technical field.

Even we, at Agribos Italiana, often address this topic in our in-depth studies, in order to sensitize the technical and production worlds to such an important critical issue.

Addressing the problem means, on the one hand, acting to slow down the loss of organic matter from agricultural land and on the other hand, at least partially reintegrating the lost share. But can any material containing Carbon be used to provide organic matter to the soil? The answer is negative. And to understand the reason, we need to focus on the concept of the rate of humification.

The quantity and quality of soil organic matter depend on a series of processes to which organic residues are subjected: humification, mineralization and interaction with the mineral fraction.

Humification involves a series of reactions that lead to the formation of molecules with a structure that is increasingly complex and far from the original one, as the reactions proceed.

The result is the synthesis of humic acids, fulvic acids and umine.

Mineralization, which is favored in well-aerated environments with intense biological activity, leads to the decomposition of organic matter. It takes place in the presence of microorganisms, which need energy and nitrogen sources to perform their functions and the synthesis of their compounds. During mineralization, organic matter is degraded to carbon dioxide and water, while Nitrogen is released and reused in various processes, with a

consequent reduction in the ratio between Carbon and Nitrogen. This ratio is in fact used as an index of the greater or lesser stability of the organic matter.

Finally, the interaction of organic matter with the mineral fraction leads to the formation of very stable complexes, which generally increase the aggregation state and stability of the soil and slow down the processes of microbial degradation of organic matter.

When soil is used for agricultural purposes, there is normally a reduction in the organic carbon content. Soil tillage mixes surface horizons and changes its temperature, as well as causing humus losses as a result of erosion processes due to wind and leaching linked to precipitation. In addition, the aeration that invests the soils following plowing, the exposure of particles of organic matter previously shielded by the presence of the mineral fraction and systematic irrigation intensively stimulate the degradative activity of the microbial biomass present in the soil, leading to a drastic reduction in the levels of organic matter and to greater emissions of greenhouse gases into the atmosphere.

Maintaining a certain level of organic matter in soils assumes that the amount of carbon that reaches the soil (fertilization, natural inputs) is approximately equal to that emitted into the atmosphere in the form of carbon dioxide, so in a soil subject to agricultural activity the balance between the carbon entering the system and that lost as a result of mineralization is shifted considerably towards the second term.

As we mentioned in the introductory part of this article, to combat the loss of organic matter from cultivated soils, we must act both on the reduction of losses (for example, avoiding unnecessary processing) and on that of reintegration, with regenerative agriculture in mind. This second point is precisely what we should be reflecting on. It is not enough to distribute any organic matrix to the soil to obtain an increase in this precious component of fertility. The humification rate of the organic or organo-mineral fertilizers we administer makes a big difference. By humification rate we mean the ratio between Carbon from humic and fulvic acids and total Carbon. It can take values from zero to one hundred and the higher it is, the greater the stable fraction of the organic substance contained in the matrix.

To understand the risks deriving from the contribution of unstable organic substance to agricultural land, here is a passage from the article entitled “Fertilization, the role of organic matter” published in the 11/2024 issue of the magazine “Earth is Life”, signed by Pierlorenzo

Brignoli (University of Siena – Center for Geotechnology): “Unripe and inadequately stabilized organic substances can create problems in the soil, undergoing putrefactive processes that are harmful to the roots. They can cause peaks in the release of ammonia nitrogen which, in the presence of nitrifying bacteria, undergoes rapid nitrification with a consequent unbalanced “push” that weakens the plant, reducing its resistance to adversity and its qualitative yield. The distribution in the soil of fresh or insufficiently stabilized organic matter, easily decomposable, also favors the release of carbon dioxide in the soil and the formation of carbonates, with a consequent significant increase in the risk of iron chlorosis and nutritional imbalances”.

Brignoli himself points out: “Unfortunately, in the current agricultural environment, good quality organic matter is increasingly rare and expensive. Intensive farming on the one hand and the maturation and stabilization times of organic materials, often not sufficient, result in a supply to the soil of substances that are often not stable and devoid of the microbiological vitality that characterized good mature manure”.

At Agribios Italiana, we strongly believe in the value of high-quality organic matrices and we know that one of the fundamental elements of this quality is the rate of humification. This is why the matrices with which we produce our organic and organo-mineral fertilizers, whether of animal or vegetable origin, undergo long periods of maturation under natural conditions before entering the formulations.