Soil-microbe interactions and nutrient release in the cauvery floodplain sediments

Abstract

River basin sediments deposited in the flood plains and deltas newlineand the soils derived from them, all over the world are known to be newlinevery fertile, rich in plant nutrients and best suited for intensive newlineagriculture. From time immemorial, all over the world, civilizations newlinehave sprung up and flourished along the banks of maJor nver newlinesystems. The fertile alluvial sediments have supported continuous newlinefarming and have provided food for the masses. The flood plain, loess newlineand delta sediments are derived from weathered rocks, which have newlinebeen transported and deposited due to glacial, wind and water newlineactions. But why are these sediments fertile? This is because the newlinesediments have been derived from source rocks which are rich in newlineplant nutrients. As these are transported over long distances, they newlineundergo weathering and transformation, due to which many elements newlinetrapped in minerals are loosened and made bioavailable to plants. newlinePresently, our knowledge on the factors responsible for the newlinefertility of sediments is limited. Erosion of freshly formed or freshly newlineexposed rocks, after a limited extent of chemical weathering, leads to newlinethe production of cation-rich sediments (Chesworth, 1982). Owing to newlinethe action of wind, water and microbes (Huang and Keller 1970), there is newlinea gradual reduction in grain size and coarseness, leading to formation newlineof sand, silt and clay. This in turn increases the abundance of newlinechlorite, smectite, biotite and illite and with it the availability of free newlineions. Thus, the whole process is of a great importance in maintaining newlinethe fertility of the soil and in sustainable agriculture. newlineVI newlineABSTRACT newlineVery little is known about the role of microorganisms in nutrient newlinerelease and cycling of elements. Studies indicate that microbes, newlineespecially bacteria and fungi, readily adapt to extreme conditions of newlinesurvival such as low water level, high solar radiation, acidity, newlinealkalinity, salinity, pressure, oxygen concentration gradients as well newlineas extreme temperature fluctuations (Natarajan 1998).