Cheapest and most sustainable plant-based fertilizer

Normally, traditional fertilizers have disadvantages such as the degradation of agricultural soils, bad odors and contamination of aquifers, among other issues. To reduce the environmental impact of these fertilizers, some scientists propose doing without them altogether and using a revolutionary alternative.

A research team from the University of Almería in Spain has used biomass from local horticulture to produce a compound that improves the fertility of agricultural soil. This product equals the effectiveness of conventional fertilizers, is less polluting, more sustainable, cheaper and can be used every seven months, coinciding with the usual growing periods in the area.

The new biofertilizer is made from tomato plant waste. Specifically, the experts propose applying a thermal treatment to the crop residues from the previous year, which are usually discarded in waste management centres. With the use of the new product, the consumption of water by each plant is also reduced and the fertility of the soil is improved.

The new compound is effective against pathogens such as fungi, bacteria and viruses. “This is an alternative option, more sustainable and cheaper than the compounds that are normally used, given that the raw material is the waste from the previous cultivation campaign,” Francisco, a researcher at the University of Almería, explains to the Discover Foundation. Jose Castillo Diaz.

To make the biofertilizer, the researchers used biosolarization. This technique combines the remains of the previous year’s harvest with a thermal treatment to obtain the fertilizer.

Likewise, they uninstalled the irrigation system and deposited the tomato plant waste to be crushed in the central corridor of a greenhouse. They then mixed them into the top 20 centimeters of soil with a rotovator (agricultural tillage machine) and reinstalled the irrigation system. After verifying that it worked properly, they covered the biomass with a plastic sheet on the ground, sealed on all its edges, so that a faster decomposition of the organic matter would take place.

Lastly, they irrigated these plant remains until they reached field capacity, that is, like when a sponge is removed from water and the liquid is expelled through the pores until it is in equilibrium. “The time it takes for the biomass to be converted into fertilizer can vary depending on the needs of the farmer. But normally it is ready in a period that oscillates between 30 and 90 days”, adds Francisco José Castillo Díaz.

One of the phases to obtain biofertilizer: preparation of plant remains. (Photo: University of Almería / Discover Foundation)

The trial of this study has been carried out over three consecutive years at the UAL-ANECOOP Experimental Farm, in a plot that simulates the characteristics of Almeria horticulture. On the one hand, they grew tomato plants and fertilized them with traditional fertilizers; on the other, they used the new biofertilizer in another area. Thus they were able to compare the results of the new biofertilizer with those of the others.

The results obtained have led the experts to conclude that this biofertilizer equals the effectiveness of conventional fertilizers, is less polluting and can be used approximately every seven months, coinciding with the usual growing periods in the area.

In this way, as the scientists argue, the new biofertilizer would serve as a sustainable resource to address one of the challenges posed by the European Union: a 20% reduction in the use of fertilizers.

Francisco José Castillo Díaz and his colleagues expose the technical details of the new biofertilizer in the academic journal Agronomy, under the title “Biodisinfection as a Profitable Fertilization Method for Horticultural Crops in the Framework of the Circular Economy”. (Source: Discover Foundation)