Starving soil microbes: consequences to cotton plant and soil health.

Abstract

Soil biological health plays an important role in functions related to nutrition, health and productivity of Australian cotton crops. Surface soils in cotton growing regions are generally low in organic carbon levels hence C inputs from roots and crop residues are important sources of energy for soil biota. Effects of fallow as part of rota on in cotton systems on soil biological and chemical properties: microbial biomass (MB), microbial activity, diversity (gene c and catabolic) and disease suppression potential were investigated to determine consequences to plant and soil health in multi-year field experiments and farmer fields over multiple seasons. MB-C levels generally ranged between 100 - 600 µg C/g soil and >90% of cotton soils have microbial quotient values <5%, an attainable threshold for agricultural soils. Soils from the Fallow-Co on rota on generally showed significantly lower MB (the ‘engine’ for all biological functions), abundances of total fungi and bacteria, specific groups of beneficial bacteria, microbial catabolic and genetic diversity of bacteria and fungi and pathogen suppression potential thereby weakening the biological buffer compared to that under other rotations including continuous Cotton.
Overall, these results suggest that non-crop periods as part of cotton rota on system should be considered not only for their impacts on plant pathogens but also on MB and beneficial microbial communities to manage the health of cotton plants and soils.