Response of wheat to waterlogging and determinationof drainage index

Abstract: Hubei plain area is characterized by plenty of rainfall in spring, which results in frequent occurrence of waterlogging of winter wheat (Triticum aestivum L.) field. Subsurface waterlogging is often found in these fields. Therefore, it is necessary to understand the influence of waterlogging on the growth and yield of winter wheat and develop a drainage index for the waterlogged fields. This study aimed to investigate the response of wheat growth to waterlogging condition and to determine a drainage index. In order to achieve the objectives, tube-shaped concrete facilities were used for irrigation and drainage adjustment. Wheat was planted in the facility. Waterlogging period for 5, 15, and 20 d was designed. The waterlogging was conducted in the booting and filling stages of wheat. The soil moisture in the waterlogging treatment was kept at 90% water holding capacity. Meanwhile, the facility for wheat cultivation in soil with moisture kept at 70%-80% water holding capacity was used as the control. The chlorophyll content (Chla, Chlb, Chl(a+b)), malonaldehyde content (MDA), peroxidase content (POD), catalase content (CAT), and superoxide dismutase content (SOD) were measured. The yield and its component of wheat were determined. The results showed that: wheat suffering from waterlogging in the booting and filling stages resulted in a decline of Chla, Chlb and Chl(a+b) content, which was increased with increasing waterlogging periods. The content of Chla, Chlb, and Chl(a+b) was significantly (p<0.05) lower than that of the control treatment when the wheat was waterlogged for 5 days in booting stage. The chlorophyll content decreased significantly (p<0.05) in filling stage. When the wheat field was waterlogged in the both stages, the activity of CAT in the wheat flag leaf, root system and young panicle was increased first and then decreased, and was maximal in the root system at the booting stage when wheat was suffered from subsurface waterlogging for 15 days and in the parts of the other stages for 10 days. The activity of CAT in the young panicle went up continuously with increasing waterlogged stress. The activity of POD increased continuously except in the young panicle at booting stage and in the root system at the filling stage. Moreover, the severe the waterlogged stress was, the higher the amplification of POD activity could be. The POD activity in the young panicle at the booting stage changed in the opposite trend. The POD activity in the root system at the filling stage tended to decrease first and then increase, which reached the minimum when wheat suffered from subsurface waterlogging for 10 days. The activity of SOD in the flag leaf, root system and young panicle declined with the prolonged waterlogged stress. Wheat suffering from continuous waterlogging caused a severe reduction in wheat yield. The actual yield reduction per test-pit was 18.4% for 5 d of stress, 45.5% for 10 d of stress, 63.9% for 15 d of stress and 85.5% for 20 d of stress in booting stage, and 7.6% for 5 d of stress, 17.8% for 10 d of stress, 43.7% for 15 d of stress and 70.2% for 20 d of stress in filling stage, respectively. The reason of yield reduction caused by stress in booting stage could be that waterlogging stress led to decreasing in number of productive panicle and kernels per spike. In the filling stage, the waterlogging stress may decrease number of kernels per spike and 1000-kernal weight. Assuming that the 15% decrease in the wheat yield could be tolerant and used as the standard of waterlogging drainage, the waterlogging time that the wheat could tolerate in the booting and filling stages was 3.6 and 6.4 days, respectively with the premise was that the groundwater table should be lowered down after the surface waterlogging was eliminated until the crop could tolerate waterlogging from the underground water.