A Holistic Approach for Enhancing the Efficacy of Soil Microbial Inoculants in Agriculture

Abstract

Microbial inoculants can be an efficient tool to manage the soil and plant microbiomes providing direct beneficial effects, and for modulating native soil and plant-associated microbiota. However, the application of soil microbial inoculants as biofertilizers and biopesticides in agriculture is still limited by factors related to their formulation, application method, and the knowledge about the impact and interactions between microbial inoculants and native soil and plant host microbiomes. The review is thus describing and discussing three major aspects related to microbial-based product exploitation, namely: i) the discovery and screening of beneficial microbial strains; ii) the opportunities and challenges associated with strain multifunctional features; iii) the fermentation and formulation strategies also based on the use of wastes as growth substrates and the technical and regulatory challenges faced in their path to field application. All these issues are addressed in activities performed by the EXCALIBUR project (www.excaliburproject.eu), which aims to expand the current concept about microbiomes interactions, acknowledging their interactive network that can impact agricultural practices as well as on all living organisms within an ecosystem.

Safety Level of Microorganism-Bearing Products Applied in Soil-Plant Systems

“…Therefore, another important point is the fate of the introduced microorganism-bearing fertilizers, particularly biostimulants, in soil and their effect on the microbial community structure, including autochthonous soil pathogens. In general, we should know the ecological behavior of introduced microorganisms, and the possibility of interactions must be considered in risk assessment actions ( Malusà et al, 2021 ). As suggested by van Elsas et al (2012) , soil microbial diversity and the level of its metabolic activity is the key regulating the fate of a given microorganism introduced in soil.…”

“…Undoubtedly, these interrelations have been historically affected by the conventional agricultural activities aimed at increasing the yields of crops ( Perez-Jaramillo et al, 2015 ). Introducing microorganisms and organic fertilizers into soil-plant systems is considered an important tool in overcoming problems associated with the excessive use of chemical fertilizers and pesticides ( Bashan et al, 2014 ; Malusà et al, 2021 ; Shaji et al, 2021 ). By this reason, there is a strong tendency to stimulate application of microorganism-bearing products to re-establish and enhance soil fertility and crop production and quality particularly in a stressed environment ( Shilev et al, 2019 ).…”

“…It should be distinguished between traditional microorganism-bearing fertilizers, such as compost or animal manure and formulated biofertilizers. While in the traditional microorganism-bearing fertilizers, there is a wide range of well-studied and categorized, including pathogenic, microorganisms, which in some cases are difficult to control, BF/biocontrol products normally containing one or more microbial cultures, with guaranteed quality and cell quantity and, in some products, controlled release after introduction into the soil-plant system ( Venglovsky et al, 2006 ; Young et al, 2012 ; Malusà et al, 2021 ). It should be noted, however, that there is a discussion in the scientific literature on the potential risk for humans and animals when commercial plant beneficial microbial formulations are introduced into soil-plant systems ( Deising et al, 2018 ).…”

Rhizospheric microorganisms: The gateway to a sustainable plant health

“…Microbial-based solutions are currently one of the rapidlygrowing agricultural sectors which are potential alternatives or complement the use of synthetic fertilizers and pesticides (Malusà et al, 2021). Microbial pesticides are biopesticides created from beneficial microorganisms that promote plant development, and nutrient utilization efficiency which results in higher agricultural yields (Asad, 2022).…”

Special Issue: Microorganisms and Plant Nutrition

“…Plant-beneficial microorganisms affect plant nutrition and health, as a key part of prebiotic-, probiotic-, and symbiotic-based interactions [1]. However, the application of soil microbial inoculants as biofertilizers and biopesticides in agriculture is still limited by factors related to their formulation, application method, and the lack of sufficient knowledge about the impact and interactions between microbial inoculants and native soil and plant host microbiomes [2,3].…”