Rational use of natural resources

Regenerative agriculture, which emulates natural processes, aims to close the nutrient cycles that return organic matter to the biosphere, thus improving the soil and avoiding the need for costly chemicals.

To do this, it is important to consider the soil and the plant as a whole and not as individual parts. In the first week of the course we focused on the plant and how it functions in order to understand the processes housed in its cells.

For the plant to function, it needs a living and dynamic soil. This means that the practices employed should aim to improve the soil food web, the set of organisms that live in the soil. Microorganisms need organic matter for food and shelter. When that happens, they manage to process the organic matter and minerals so that the plant can feed itself.

The nutrition of the food web and the preservation of a favourable habitat for the life of these organisms are the basis of a sustainable production system. A system managed according to these criteria results in high soil fertility and health and therefore high plant productivity.

To maintain the relationships between soil organisms and plants, it is important to work on the pillars that allow this symbiosis; multiplying and preserving life and microorganisms and ensuring their establishment through the supply of organic matter and minerals.

For this purpose, there are different techniques that drastically reduce the dependence on external inputs and favour the development and maintenance of the microbial food web. In the following we will describe the best known techniques for recycling natural materials used to improve soil structure and fertility.

Bois Raméal Fragmenté (BRF)

BRF is a technique developed in Canada in the 1980s, where it is known as Bois Raméal Fragmenté (BRF). The technique consists of chipping small tree branches. It forms a stable humus that improves soil structure and the capacity to hold water.

BRF production

The basic material for the production of BRF is branches smaller than 7 cm, which contain soluble or slightly polymerised lignin, a necessary basis for the formation of a highly reactive humus. These branches are shredded after felling with a shredder, before the wood has dried. If cut in summer, the branch dries out within a few days and must be shredded quickly. In winter, the branches dry more slowly and more time is available for chipping.

The chips obtained in this way initiate a fungal decomposition process driven by basidiomycetes , which, from the lignin, produces fulvic and humic acids. These acids are the basis for the formation of aggregates in the soil forming a stable, long-lasting humus, similar to forest humus, and different from humus produced from other organic waste that does not contain lignin. In this way, compost, for example, is useful for improving soil life and providing nutrients for plants.

The limiting factor for its production is therefore the presence of significant volumes of freshly cut branches smaller than 7 cm. In mountain areas, where forest is an important resource, the availability of branches from forest clearings often represents an abundant resource for BRF production.

Two of the determining factors in the amount and type of humus produced are tree size and species type. + Tree size largely determines the weight of branches <7cm. The larger the diameter, the greater the amount of material obtained after delimbing. To obtain a sufficient amount of material efficiently, it is best to use trees with a diameter of more than 20 cm at breast height. + The type of species used for chipping also plays an important role in the type of humus produced. All studies recommend limiting the use of conifers to less than 10% of the total material used.

The best results are achieved with deciduous trees, due to their lignin structure. In contrast, evergreen hardwoods perform worse due to the transformation of their lignin by “brown rots” which produce polyphenols and aliphatic compounds.

The main benefits of BRF are the reduction of water use as humus has a better water holding capacity. It also allows for increased carbon sequestration and improved biodiversity as it provides structure and balances pH, which favours microbial growth.

Biochar

Biochar is the name given to charcoal produced from the heating of biomass of organic material, known as pyrolysis. Biochar improves the physical properties of the soil, as it has a high organic content, is highly resistant to degradation and has high micro- and meso-porosity, which gives it a high capacity to retain water, nutrients and microorganisms.

Biochar production

Biochar can be obtained through the pyrolysis of any type of organic material. The production of biochar can be done by different methods. The biochar production process starts with a small fire in a container that can be used as a reactor (Figure 1).

_{Figure 1. Biochar production. Source: Carbón Vivo, Javier Fernández Caracena}

As plant biomass is added, the oxygen in the lower part of the boiler is consumed, switching from combustion to pyrolysis, which is the reaction that will result in charcoal. When the entire boiler has been filled, the top of the pile is allowed to reach a high temperature and begins to turn white from the ashes of the combustion itself.

At this point, the fire is put out with water and covered so that no oxygen enters, which causes the pyrolysis of the whole pile to take place. The next day the pile can be uncovered, to reveal biochar (from the pyrolysis) with remains of ashes (from the combustion).

This pile should be spread on the ground so that it can cool down and avoid the possibility of restarting a combustion which would transform the whole product into ash.

Biochar can have important benefits for farms, including:

• Improved soil structure. Biochar helps to regulate the pH of highly acidic soils, improves their physical and chemical properties and has the capacity to buffer sudden temperature changes.
• Increased water and nutrient retention. Biochar has a high water retention capacity, which improves root irrigation and allows nutrients to be captured and retained by reducing leaching losses.
• Stimulation of microbial activity. In soils where biochar has been applied, microbial activity is stimulated.
• Improvement of fertilisers and manures. The use of biochar as an additive in organic fertilisers and manures can improve their efficiency.
• Increased crop productivity. Biochar significantly increases the agronomic productivity of degraded soils and improves the physiological response of crops to periods of water stress.

_{Figure 2. Biochar. Source: Carbón Vivo, Javier Fernández Caracena}

Bocashi

Bocashi fermented organic fertiliser is the result of aerobic semi-decomposition of organic waste, using populations of microorganisms that produce a slowly decomposing, partially stable material. This product is able to fertilise plants and, at the same time, improve the soil. The word Bocashi comes from Japanese, and means cooking the compost materials by using the heat generated by the aerobic fermentation of the compost.

The main ingredients used to make Bocashi type fermented compost are:

• Charcoal, which improves the physical characteristics of the soil, facilitating better root distribution, aeration and moisture absorption.
• Manure is the main source of nitrogen in the production of fermented organic fertilisers.
• Rice husk improves the physical characteristics of the soil by facilitating aeration, moisture absorption and nutrient filtration.
• Rice bran, promotes the fermentation of organic fertilisers and is very rich in nutrients such as phosphorus, potassium, calcium and magnesium.
• Cane molasses, is the main energy source for the fermentation of organic fertilisers and favours the multiplication of microbiological activity.
• Forest humus is the main source of microbiological inoculation for the production of fermented organic fertilisers.
• Common soil has the function of making the compost more physically homogeneous and distributing its moisture.
• Rock flour and ashes provide minerals.
• Water ensures the homogenisation of the humidity of all the ingredients that make up the compost.

The ingredients are mixed by placing different layers of the different components in dry form and, at the end, the whole mass is turned until a balanced mixture is obtained. At this point, water is added to achieve the desired moisture content. Once the mixture of all the compost ingredients is finished, the mix is left on the ground at a depth of one and a half metres for three days to start fermentation.

During these first three days, the mixture is turned twice a day to prevent the temperature from rising too high. After the first three days, the mixture is spread out to form a cover about 30 cm thick. For the first few days, the mixture is turned over once a day using a power tiller. As the days go by, the turning time is spaced out. After 15 days, the fermented compost has reached maturity and its temperature is equal to room temperature. At this time it is light grey in colour, with a sandy powdery appearance.

Bocashi is an efficient and economical way to produce very complete fermented fertilisers based on the reproduction of native microorganisms. Moreover, it can be produced in most environments and climates where agricultural activities are carried out, as the materials from which it is made are well known to farmers and readily available locally.

Mountain microorganism biofertilisers

Biofertilisers are high-energy fertilisers prepared from microorganisms from different origins dissolved in water enriched with milk, molasses and minerals, and fermented under anaerobic conditions. They serve to nourish and strengthen plants without blocking the biological processes that occur in healthy soil. The forest is the source of mountain microorganisms from which fertilisers are made.

Multiplication of mountain microorganisms

Mountain microorganisms, which are the basis for obtaining biofertilisers, are a group of organisms that come directly from the humus of the nearest forest and are therefore adapted to the area of application. They are obtained in a non-selective way, as all organisms in a soil humus sample are reproduced.

This sample includes yeasts, fungi, protozoa and bacteria. Mountain microorganisms are obtained by mixing humus from the forest soil with rice bran (in equal parts), adding molasses as an energy source and, if necessary, water to reach the right humidity.

The two important aspects to consider for the process to work properly are:

1. that the mixture has been mixed evenly, as if you were making dough for bread; and
2. that the mixture has the correct moisture content, which can be checked by the fist test: when you pick up a sample of the mixture with your fist and squeeze it, it should form a solid ball, but when this ball is thrown into the air and dropped on the same hand that threw it, the ball should crumble into small pieces.

Once homogeneity and adequate moisture have been reached, the mixture is placed in airtight containers. As the container fills, it should be compacted to prevent air from remaining. When the container is full, it is hermetically sealed and left for approximately one month. The result is a compact, silo-scented mass that is stored in the same container.

The main ingredients used for the production of biofertilisers are:

• Mountain microorganisms (yeasts, fungi, protozoa and bacteria), which are the ones that fermentation of the biofertiliser takes place, placed in a mesh bag, rather like a large tea bag.
• Whey has the function of reactivating the preparation and providing proteins, vitamins and fats.
• Molasses provides the necessary energy to activate the microbiological metabolism during the fermentation process.
• Rock flour, which activates and enriches the fermentation process, as its main function is to fertilise the soil and the plants.
• Ash provides minerals and elements to activate and enrich the fermentation.
• Water provides the liquid medium where the chemical reactions of anaerobic fermentation multiply.

_{Figure 3. Mountain microorganisms to be multiplied. Source: Huerto 2.0}

Conclusion

The recycling of materials and co-elements from crop waste is one of the foundations of regenerative agriculture. The aim is to reduce, or even eliminate, dependence on external inputs in order to improve economic performance.

Microbial biofertilisers can increase crop growth and productivity by improving the availability of nutrients in the soil. As the micro-organisms are native to the same production area, their adaptation is fast and sustainable in time. As part of a holistic regenerative agriculture strategy, they can play an important role in repairing degraded soils worldwide, leading to increased food security while mitigating CO₂ emissions.