LIFE Project: Microalgas with Aromatic Plants as Biostimulants with Biocidal Effect

The LIFE ALGAR-BBE project has demonstrated the efficacy of three safe, sustainable, and naturally derived formulations with biostimulant and biocidal properties. The biostimulant properties were achieved through the addition of microalgae, while the biocidal properties were achieved through the addition of aromatic plant extracts, Spirulina extraction waste, and olive oil industry residues. A sufficient volume of concentrated biomass (20% microalgae) of the species Nannochloropsis gaditana (49 kg | 288 liters of wet biomass) and Acutodesmus obliquus (20.6 kg | 200 liters of wet biomass) was produced and optimized to serve as raw material for the production of the new fertilizers. Three formulations containing aromatic plant extracts were developed and optimized: one for root application, one for foliar application, and one for home application.

The demonstrative nature of the project has been based on the application of formulations produced from microalgae and aromatic plants, considering the dual function on crop production (as a biofertilizer and a biocidal product), at pilot scale in experimental plots of tomato, corn, pepper and potato crops located in Spain, and at real scale (industrial) in tomato and corn plots located in two locations (Extremadura and Portugal), during 3 different growing seasons over 3 years. In each location, the trials have been carried out on an area of 3 ha for tomato crops and 3 ha for corn crops, and 1 ha in each case for pepper and potato crops.

Crop yields have generally improved by applying, alongside conventional fertilizers, formulations containing aromatic plant extracts at different concentrations, applied foliarly at 3 l/ha at four key stages of the crop, depending on the phenology: during growth, flowering, fruit set, and fruit fattening.

Some of the main findings have been:

• The ecotoxicological evaluation of the formulations revealed no symptoms or signs of phytotoxicity. No negative effects on beneficial organisms were observed at any of the sites.
• Nitrate concentrations in the soil solution decreased and reducing nitrogen fertilization between different plots resulted in a decrease in nitrate concentrations.
• The use of the formulations developed in the project led to a reduction in pesticide residues in leachate water.
• Sustainable management has been achieved, focusing exclusively on the area of agricultural soil free of residues, which represents 93.2% of the total area tested.
• Crop yields improved with the application of formulations containing microalgae and aromatic plant extracts. Plant development was greater in plots treated with foliar applications containing a higher percentage of aromatic plant extract.
• In terms of pest and disease prevention, the formulations have proven effective, as the application of chemical pesticides during cultivation has not been necessary. This means that the developed formulations can reduce the use of traditional fertilizers and replace the chemical pesticides used in agriculture.
• No pesticide residues were detected in either the tomato or corn produced during the seasons studied. Therefore, the use of chemically derived active ingredients was correct, and the field application of the new formulations fulfills its objective from a food safety perspective.
• Fewer pesticides and higher yields can result in savings in input costs, as well as lower labor and machinery costs associated with pesticide application.