Organo-mineral fertilisers for maintaining soil fertility in a sustainable way
When we talk about soil fertility, we mean the soil’s ability to produce crops, a quality that is directly linked to the soil’s chemical, physical and biological characteristics.
Soil is all the more fertile the more:
- it facilitates the uptake of water and nutrients by the roots;
- it promotes the activity of soil microorganisms;
- it accumulates and retains water and nutrients over time;
Organic matter is a fundamental component of soil and influences all the fertility factors described above; it consists of plant and animal residues, living biomass and humic substances, such as humic acids, fulvic acids and humin. These substances constitute stable humus, the main component of organic matter (up to 85 per cent) in a soil in equilibrium.
Humus has a carbon content approximately ten times greater than that of nitrogen and is a macromolecule with marked colloidal and chelating activity. By binding to mineral compounds in the soil, humus forms aggregates of various shapes and sizes which, by joining together, leave empty spaces (soil porosity) that can be filled by water, gases and other compounds. In this way, humus improves soil structure, effectively increasing its field capacity, workability and aeration. Furthermore, the chelating and complexing effect of humic substances protects certain elements such as Fe, Cu and Zn from processes such as insolubilisation and leaching, thereby making them more readily available to plants. Finally, the soil’s buffering capacity – that is, its ability to neutralise pH fluctuations within certain limits – also depends on the chemical nature of humic substances.
In agricultural land, an organic matter content of between 3 and 4 per cent is considered good, but in Italy levels generally fall below these figures. The gradual decline in soil fertility, which is becoming increasingly evident in our country too, is caused by a variety of factors, both human-induced and climatic, which give rise to erosion, urbanisation, soil compaction and excessive soil salinity.
However, careful and sustainable farming – which, amongst other things, employs efficient fertilisation techniques – can help to slow down and, in some cases, reverse this trend.
Although organo-mineral fertilisers are not soil conditioners, they do in fact improve nutrient use efficiency (NUE) because the organic matter they contain chelates the mineral content, making it more readily available to the plant and limiting losses through leaching or reaction with other elements present in the soil. One example is phosphorus, which, by binding to humic substances, forms humo-phosphate compounds that protect it from retrogradation.
Furthermore, the organic nitrogen present in organo-mineral fertilisers is considered to be slow-release, as it must first undergo various transformations by microorganisms and enzymes (mineralisation) before it becomes available; this enables the plant to absorb it according to its own requirements. Finally, the organic matrix of these fertilisers helps to improve microbial activity in the soil.
Fert Premium and Fert fertilisers, combining high-quality organic matter, humic and fulvic acids, and a mineral matrix that is fully utilisable by plants, are an efficient and sustainable choice.
The stable, slow-release organic nitrogen, together with phosphorus chelated with humic acids, makes these fertilisers particularly suitable for autumn and winter application, when crop growth in the field slows down and traditional fertilisers – which are faster-acting but unprotected – would only be partially utilised, resulting in significant losses to the soil.
Sources:
Figura 1: Associazione Studenti di Agraria IAAS Sassari, suolo-parte-iv, https://iaassassari.wordpress.com, 2012
Figura 2: Ramona Magno, Desertificazione, cause, impatti, soluzioni e il ruolo del suolo, https://www.vglobale.it, 2023
Figura 3: Y. Bouhia, M. Hafidi, Y. Ouhdouch, M. El Mehdi El Boukhari, Conversion of waste into organo-mineral fertilizers: current technological trends and prospects, Reviews in Environmental Science and Bio/Technology, https://www.researchgate.net, 2022 (adattamento in italiano)