Z.B. Zhanga b H. Zhoua Q.G. Zhaoa H. Linc X. Penga 
. Characteristics of cracks in two paddy soils and their impacts on preferential flow. Geoderma 2013 http://dx.doi.org-10.1016-j.geoderma.2013.07.026
Abstract
Soil cracks generated in paddy fields upon drying may be main pathways of preferential flow. In this paper we aimed to characterize soil cracks in paddy field and to assess their role in preferential flow. Two paddy fields one cultivated for 20 years (YPF) and the other cultivated for more than 100 years (OPF) were subjected to either alternate flooding and drying (AFD) or continuous flooding (CF) as a control during rice growing season. After the harvest of late rice crop soil cracks were analyzed in 2D and 3D and their contributions to hydraulic conductivity and preferential flow were assessed by tension infiltrometer and dye tracer respectively. Our results showed that cracks were generated under AFD condition but not under CF condition. Under AFD condition the YPF presented 10-fold more cracks in quantity but these cracks were finer and shallower as compared to those generated in the OPF. All the cracks did not penetrate through the plow pan existed at 15–25 cm. Soil hydraulic conductivity at near saturation (> − 6 cm pressure head) was increased by 2.5–4.5 times in paddy field with cracks as compared to non-crack paddy field. Cracks represented the pathw
