Microbial diversity and multidimensional interactions in the rice ecosystem

The sustainability of rice production systems globally is intricately related to the chemistry, physics and biology of rice soils – with basic properties differing considerably in wet/dry land soils, tropical/temperate areas or even with the soil surface or rhizosphere niche of the field. Rice fields represent unique aqua-terrestrial ecosystems in which the tremendous diversity of soil microbes, soil fauna and plants – ranging in function from nitrogen fixers, nitrifiers, methanogens, methane oxidizers, phosphate-dissolving microbes, sulfur oxidizers to catabolizers of pesticides is observed. This diversity is inclusive of bacteria, cyanobacteria, archaea, planctomycetes and β-proteobacteria, besides the increasing members of endophytes associated. The complexity and dynamic nature of this ecosystem requires in-depth investigations of the tripartite interactions among plants, microbes and the soil–water environment. This needs to be complemented with studies on the ecological compartmentalization due to diffusion gradients of nutrients and gases, which is of extreme significance in the current scenario of problems associated with greenhouse gas emissions from agricultural areas, especially rice paddies. This article provides an overview of the interactions between the microflora and crop, with emphasis on nutrient transformations in the rhizosphere, so as to develop effective and efficient environmentally sustainable strategies for this crop.