Toward a Sustainable Agriculture Through Plant Biostimulants: From Experimental Data to Practical Applications

Abstract

Modern agriculture increasingly demands an alternative to synthetic chemicals (fertilizers and pesticides) in order to respond to the changes in international law and regulations, but also consumers’ needs for food without potentially toxic residues. Microbial (arbuscular mycorrhizal and plant growth promoting rhizobacteria: Azotobacter, Azospirillum and Rizhobium spp.) and non-microbial (humic substances, silicon, animal- and vegetal-based protein hydrolysate and macro- and micro-algal extracts) biostimulants represent a sustainable and effective alternative or complement for their synthetic counterparts, bringing benefits to the environment, biodiversity, human health and economy. The Special Issue “Toward a sustainable agriculture through plant biostimulants: from experimental data to practical applications” compiles 34 original research articles, 4 review papers and 1 brief report covering the implications of microbial and non-microbial biostimulants for improving seedling growth and crop performance, nutrient use efficiency and quality of the produce as well as enhancing the tolerance/resistance to a wide range of abiotic stresses in particular salinity, drought, nutrient deficiency and high temperature. The present compilation of high standard scientific papers on principles and practices of plant biostimulants will foster knowledge transfer among researchers, fertilizer and biostimulant industries, stakeholders, extension specialists and farmers, and it will enable a better understanding of the physiological and molecular mechanisms and application procedure of biostimulants in different cropping systems.

Trends in Soil Microbial Inoculants Research: A Science Mapping Approach to Unravel Strengths and Weaknesses of Their Application

“…An example of such effort is represented by the EXCALIBUR project, entitled "Exploiting the multifunctional potential of belowground biodiversity in the horticultural farming" (www.excaliburproject.eu) funded by the H2020 Programme of the European Commission (grant n. 817946), which plans to test new multifunctional microbial inoculants (bio-inocula) and bio-effectors on three model crops (tomato, apple, strawberry) under different experimental and open-field conditions across Europe, thus aiming to deepen the knowledge on interactions between plant, soil, micro-, meso-, and macroorganisms, and the links and dynamics between native soil biodiversity and agricultural practices. The project aims to provide all the information on fermentation, formulation consortia, and plant-soil-microbe interactions that other authors in their recent issues [38,75] have encouraged to be given.…”

“…Such terms also indicate the increasing research moving forward a better understanding of the mechanism of interaction of the microbial inoculants with the native soil microbiomes, the fate and persistence of inoculants once added into the soil, and of the variety of potential microbes to be used. Therefore, understanding of plant-soil-microbe interactions, together with the persistence of microbial inoculants in soil, represents an important challenge for this research topic and for facilitating the diffusion of these bio-products across the relevant agricultural sectors, including organic farming [75]. For example, Trabelsi and co-workers demonstrated that inoculation of PGPM affects several native soil microbes in different ways [76].…”

Plant Biostimulants from Cyanobacteria: An Emerging Strategy to Improve Yields and Sustainability in Agriculture

“…Studies on the application of biostimulant products on different plants have highlighted that the effectiveness can vary in relation to the plant species and the cultivation conditions [9,30,31]. Among the possible causes, there is a lack of standardization but also the metabolic diversity of treated plants, as the sensitivity thresholds for one or more of the bioactive molecules in the product can vary among plant species or even among different cultivars of the same species [14].…”

Effect of Botanical Extracts on the Growth and Nutritional Quality of Field-Grown White Head Cabbage (Brassica oleracea var. capitata)

“…Biostimulants of plant growth could be used to increase the content of active compounds in cultivated plants. The agricultural production, apart from increasing the crops yields, should focus on enhancing their nutritional quality, particularly during unfavourable environmental conditions [ 21 ], along with the improvement of resource use efficiency (water and fertilisers) [ 22 ]. One of the most promising, cutting-edge, sustainable solutions is the use of biostimulants rich in bioavailable, bioactive compounds [ 23 , 24 ], which stimulate different physiological processes in plants and, as a result, provide potential benefits to growth and development, and have nutritional value, health-promoting potential, or stress response benefits [ 22 , 25 ].…”