Soil amendments for sustainable agriculture: Microbial organic fertilizers

There is an enormous body of the literature, proving that soil amendments enhance plant growth/yield and prevent the impact of pathogens/toxins. To the best of our knowledge, there is no comprehensive assessment focused on the synergistic effects of microorganisms and soil amendments with biochar or compost for upgrading the current fertilizers towards a more sustainable agriculture. The main objective of the present work is to discuss the most current information needed for developing advanced soil amendments using microorganisms along with safe, sustainable and low-cost waste sourced materials. The first step in designing the biofertilizer is the selection of a microorganism from among a variety of bacterial/fungi strains that have been identified as plant growth promoting (PGP) in the literature. This study classifies the effective types of soil microorganisms with respect to their functionality to facilitate the choice of the best compatible microbial strain(s) in order to satisfy the host environment requirements. The second part is dedicated to various inorganic and organic carriers, such as perlite, peat, fly ash and compost, for delivering of microorganism into the soils. The role of carriers in the survival and the functional contribution of the microbes to soil-plant systems are investigated. Lastly, biochar is evaluated as a promising microbial carrier together with its influence on the soil biota including microorganisms and plants. The superior features of biochar, for example high surface area, porosity, customizable structure, high stability, carbon sequestration and synergy, with other fertilizers are also discussed.