Hydrological Process in Filed Vulnerable to Water-logging and Its Influence on Cotton Yield

Agriculture in control and evaluation of waterlogged disaster that hydrological process of cropland vulnerable to water-logging and hydrological process in a filed vulnerable to water-logging and its influence on cotton yield are studied based on field investigation in 6years from 2003to 2008.The results showed that : cropland vulnerable to water-logging is characterized by a shallow groundwater and being sensitive to rainfall,more than 30mm of precipitation may result in an obvious rise of groundwater table;rainfall may cause cotton field suffering from intermittent subsurface water-logging and surface water-logging repetitiously,and result in reduction of the output to varying degree.When cotton field underwent surface water-logging(the accumulated water in the fields is about 5～15cm) for 3days(or 5～6days) and meanwhile the accumulated time of groundwater depth less than 30cm lasted for 12～22days(or 21～33days),the reduction of output may be 13%～22%(or 35%～50%).When cotton field was merely exposed to subsurface water-logging,the accumulated time of groundwater depth less than 30cm was up to 3～4weeks(or more than 5weeks) the reduction of output may reach 14%～31%(or more than 50%).Regression analysis indicated that the reduction of crop output(R d) has an extremely significant correlativity with indicators that reflect cotton field meet with surface and subsurface water-logging,subsurface water-logging impact on cotton is severe than surface water-logging in case that groundwater table is on the high side over a long period of time and the field was submerged in shallow water for 6days.