Soil Fertility and Soil Biological Activity

Fertility of soil depends, to a great extent, on interactions between the soil, plants and soil organisms in the rhizosphere. This is an area of active interchange between plants and soil bacteria, where photosynthate fuels growth and activity of rhizospheric microorganisms. In such extremely heterogeneous environment act bacterial populations co-operatively and do so by the process, known as quorum sensing. Immediate capturing of available nutrients from the soil solution by microorganisms is followed by their rapid growth and activity. Soon are current available nutrient sources exhausted. Microorganisms respond to this pulse by production of extracellular enzymes for the mineralization of insufficient nutrients from mineralizable part of soil organic matter. Increased amount of microbial biomass attracts predators, particularly protozoa, for which the elemental composition of bacterial cells are stochiometrically very similar and easier to digest than plant biomass residues. Consequently, beneficial effects of bacteriovores on plant growth have been assigned to nutrients released from consumed bacterial biomass. Despite the initial nutrients uptake by microorganisms, their much shorter life cycle compared with that of plant roots leads to the release of acquired nutrients back into the soil; these nutrients are then available for root uptake in higher amounts than at the beginning.