comparison between physicochemical properties and clay mineralogy of paddy soils of noorabad (fars province) and adjacent virgin lands

rice is one of the most important staple foods for more than half of the world's population. paddy soils are among the widest wet lands being affected by human activities. long term rice cultivation and especially flooding conditions have great influence on soil characteristics. this study was conducted in noorabad county, fars province. the aim of this study was to evaluate the effects of long-term rice cultivation on physico-chemical properties and clay mineralogy of the soils of two regions and comparison with the adjacent virgin lands. according to the results, paddy soils showed significant increase in soil organic carbon and oxalate extractable fe and mn (feo, mno) and significant decrease in soil ph and dithionite extractable fe and mn (fed, mnd). no significant change was observed between total amounts of these two elements in both land uses. clay mineralogy investigation showed that rice cultivation has drastically decreased palygorskite and increased smectite contents. transmission electron microscope (tem) images showed longer palygorskite fibers (2-3 μm in length) in virgin soils compared to the paddy soils with shorter fibers (0.5 μm), suggested the effect of the physical destruction or transformation of palygorskite to smectite in paddy soils.