Experimental Study On Submergence Tolerance And Drainage Index Of Vegetable Crops In Southern Jiangsu Province

The area in southern Jiangsu,China,where the terrain is low-lying,always with abundant rainfall,excessive soil moisture and high groundwater level.So the growth of vegetable crop is vulnerable to waterlogging disaster threat,resulting in reduced yield and quality degradation.Therefore,it is very important to carry out the test of flood tolerance of vegetable crops,and to study the upper limit indexes of controlling drainage,which is of great significance to ensure the high and stable yield of vegetable crops.In this paper,three kinds of vegetable crops,such as Suzhou green,cucumber and green pepper,which were sensitive to farmland moisture in southern Jiangsu were selected as the tested varieties.At the early stage of their harvest,the pot and pit experiment were carried out with different flooding depth and flooding duration,to ascertain the growth traits and yield loss of the three flooded vegetables in the mature period and their submergence tolerance characteristics,to study on management indexes of vegetable crop drainage.The main research results were as follows:(1)From the southern Jiangsu hydrometeorological data statistical analysis obtained,the short duration of heavy rainfall or continuous rainfall frequent.Vegetables crops suffer from not less than 2 times of waterlogging during the early stages of harvest(March to April,April to May,May to mid June,June to late August),the rainfall return period was 6.3,2.4,2.9 and 1.3 years.(2)Flooding lasted more than 12h,the plant height of Suzhou green showed the trend of increased-decreased-and then recovery.Crop advance into the flowering period,which cause the rapid growth of the stem;Flooding no more than 12h of Suzhou green and cucumber plant height showed a rising trend,but its growth rate is relatively slow.At the same time,the plant height of green pepper is stagnant.Compared with the control,the waterlogging stress significantly reduced the plant height of the three vegetables,and with the increase of flood depth and flood time,the inhibitory effect was more obvious.(3)Vegetable chlorophyll formation was significantly inhibited by flooding.The chlorophyll of Suzhou green showed the trend of increase first and then decreased after the flooding and drainage.The results showed that the chlorophyll of 6h treatment increased slightly,and the rest of the chlorophyll decreased,the decline was 0.47%?26.21%.Compared with the control group,the difference is significant.Compared to the depth of 10cm treatment and 5cm treatment,chlorophyll decline is not obvious.The chlorophyll of cucumber,green pepper which flooding depth were 15cm dropped quickly early days,leveled off and even a slight rebound later.(4)Under the condition of waterlogging,the growth and dry matter formation of the root system of Suzhou were inhibited,and the significant effect was dry weight>root length>root thickening.The root length decreased with the increase of flooding stress.Compared with the control.At the same flooding duration,the difference between the same depth was not significant.There was no significant difference in the treatment of root thickening.Moreover,the number of secondary roots of the treatment for a long period of time was decreased.(5)Waterlogging stress will result in the loss of Suzhou green yield.The longer the flooding duration is,the bigger the depth is,the higher the yield rate is.The flooding duration factor has a significant effect on the yield rate.When the flooding duration is the same,the reduction rate increases with the depth increased,but the difference was not significant;When the flooding depth was 15cm,the flooding duration was 12h,24h and 48h,the yield loss of cucumber and green pepper was 26.7%?76.3%and 35.5%?63.3%,indicating that the submergence tolerance of cucumber and green pepper was similar,and it was very sensitive to water stress.(6)To ensure that vegetable crops were protected from waterlogging,the maximum flood depth was 10cm,and the flooding period lasted for 12h was the critical value of waterlogging and storage in southern Jiangsu.Excluding vegetable surface water in 12h,during the sensitive period,the intensity of the falling water leakage is 10-50mm/d,and the drainage works will ensure that the groundwater will drop from below 40 to 60cm within 3?4 days.(7)There was a significant linear negative correlation between the relative yield Ry of cucumber(JY13)and green pepper(SJ16)and the excess water depth(SFEWx).If the crop yield was less than 30%as the selected drainage control index.The ideal drainage control index SFEW30 of cucumber and green pepper was 107.1cm · d and 88.2cm · d.