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Jianghanplain area is characterized by plenty of rainfall in spring, which results in frequent occurrence of waterlogging of wheat field. Subsurface waterlogging is often found in these fields. It is necessary to investigate the influence of shallow groundwater table and waterlogging followed by submergence on the growth and yield and develop a suitable groundwater depth drainage index for the waterlogged fields. In order to achieve the objectives, tube-shaped concrete facilities were used for the irrigation and drainage adjustment experiment in 2014 and 2015. Wheat was planted in the facility. The treatment of shallow groundwater table at 0, 20, 40 and 60 cm sustained 18 d and different degrees of waterlogging followed by submergence were designed. The treatments were conducted in the booting and filling stages of wheat. The flooding depth in the waterlogging treatment was kept at 5 cm. Meanwhile, the facility for wheat cultivation in soil with moisture kept at 70%-80% of water holding capacity was used as a control. The results showed when the 0-cm groundwater table sustaining 18 d at booting and filling stage could reduce wheat yield by 44.78% and 67.72%, the 20-cm groundwater table sustaining 18 d could reduce the yield by 17.31% and 33.70%, the 40-cm groundwater table sustaining 18 d decreased the yield by 10.44% and 10.34% and the 60-cm groundwater table sustaining 18 d could had higher yield than the that under 100 cm, suggesting that the groundwater table kept at 50 cm at booting and filling stage of winter wheat was suitable. The yield reduction might be due to the decrease of kernels per and thousand seed weight. The regression showed that the yield could reach 95.1%-99.8% and 89.8%-96.9% of the control when the underground water depth was 40- 50 cm, it could reach 100% of the control when the underground water depth was 50.7 and 57.1 cm and it may slightly increase when the underground water depth was 60-80 cm. The wheat suffering from the damage of waterlogging followed by submergence after anthesis caused a severe reduction in wheat yield, and the surface waterlogging had the larger influence than subsurface waterlogging on yield of winter wheat. Different types of drainage indexes including surface and subsurface waterlogging duration days, sum of waterlogging or water table within 50 cm of soil surface, sum of both flood depth and water table within 50 cm of soil surface under surface waterlogging, sum of water table within 50 cm of soil surface after draining surface water logging, and comprehensive water depth of waterlogging were evaluated. The regression between relative yield and these indexes showed that the indexes with surface and subsurface waterlogging duration days, drainage model based on time classification and comprehensive water depth of waterlogging were reliable. If the wheat yield decrease by 15% was allowed, the comprehensive water depth of waterlogging should be 275.6-283.6 cm·d after anthesis. The research may provide support for wheat drainage management in booting and filling stage in the middle and lower reaches of the Yangtze River. [ABSTRACT FROM AUTHOR]

Cotton production is frequently limited by periods of subsurface waterlogging and heat stress in Hubei plain area of China in summer, but the combined effects of surface waterlogging and heat stress on cotton have been rarely studied. In order to investigate the effects of groundwater table (WT) on main morph-physiological traits and yield of cotton under high temperature (HT) condition as well as determination of drainage index, the combination of WT and HT stresses was carried out by test-pit in Irrigation and Drainage Experimental Station of the Four Lake Engineering Management Bureau, Jingzhou, China in 2012 and 2013. WT were set as 0, 30 and 50 cm with waterlogging for 10 days and HT duration for 6 days (from 10:00 to 16:00 per day) during flowering and boll-forming period of cotton. The morphological indexes as plant height (PH) and complex ratio of red stem to green stem (R/G), and physiological traits as photosynthetic efficiency, leaf pigments and antioxidant enzymes along with yield components were measured and analyzed. The results were as follows: the PH and R/G of cotton were decreased in WT treatments of 0 and 30 cm, whereas they were not significantly different in HT situation. Chlorophyll (Chl) content and photosystem II potential photochemical conversion efficiency of leaf (4 th from top) decreased with increasing WT under HT condition. The relationship of either Chl or photochemical conversion efficiency with WT and HT could be described by linear models (R2=0.961-0986, P<0.01). Superoxide dismutase (SOD) and peroxidase (POD) activities of leaves (4th from top) increased firstly and then declined and catalase (CAT) activity declined with the increment in WT, but malondialdehyde (MDA) content increased. SOD and POD activities decreased remarkably while MDA content increased rapidly at WT of 0-30 cm with HT stress, indicating that HT exacerbated the degree of membrane lid peroxidation. However, HT contributed to subsurface waterlogging tolerance by maintaining a higher SOD and POD activities at WT of 50 cm. The yield losses of the combination of WT and HT attributed principally to a reduction of boll numbers and boll quality. The reduction of seed yield was highest in the treatment of WT+HT (33.7%), followed by WT (26.2%) and HT (7.5%). Assuming the reduction of 15%-20% of seed yield was accepted, the sum of excess soil water of 80 cm (SEW80) during flowering and boll-forming period was 216.0-321.2 cm·d with 6 days of HT for WT 0-50 cm. The study may provide valuble information for cotton stress-resistance cultivation and drainage management in Hubei plain lake region of China. [ABSTRACT FROM AUTHOR]