Mechanisms of paddy soil cracks generation and its consequences on preferential flow Xinhua PENG, Zhongbin ZHANG State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, CAS, Nanjing, 210008, China In this paper we selected two paddy soils (one has been cultivated for 20 years and the other one for >100 years) to investigate Fe/Al leaching and soil organic matter accumulation on cracks generations. Wetting and drying intensity and frequency on soil shrinkage will be also presented. Pore rigidity will be proofed by aggregate pores changes using synchrotron radiation x-ray micro-CT method. We wish to find the agreement between pore change at microscale and bulk soil shrinkage at soil core scale. We also wish fill the gap between shrinkage of soil core determined in the laboratory and cracks in the field. Finally the consequences of cracks on water infiltration will be discussed. Keywords: Pore rigidity, Soil Shrinkage, Water infiltration, X-ray CT