Study on continuous days of water logging and excessive soil water as drainage index of wheat

To explore the possibility of taking continuous stress-day from surface and subsurface water logging (CSDI) as drainage index during the heading and flowering period of winter wheat, influence of different continuous stress-day from surface and subsurface water logging during heading and flowering period on yield of winter wheat by test pits was studied. Model about relative crop yield and CSDI was established. The results showed that water logging and excessive soil water markedly inhibited leaf photosynthesis stomatal conductance and transpiration rate. The bigger of continuous dynamic state of groundwater, the more serious yield reduction was at the same cumulative depth of surface water. The relative yield decreased with the increase of continuous dynamic state of groundwater, however, the difference among the treatments was not significant. There was better linear relationship between crop relative yield and SEW50 and CSDI. Weight coefficient of water logging (CW) was a state variable which changed with status of surface and subsurface water logging. It was showed that the utilization of CSDI was reasonable in determination of controlled drainage index under the condition of continuous stress from surface and subsurface water logging.