Effects Of Irrigation Time And Irrigation Amount On Growth And Yield Of Drip-irrigated Sugar Beet After Emergence

Objective: Xinjiang is an important sugar beet(Beta vulgaris L.)production area in northwest China.Sugar beet in this area generally emerges in the middle and late April,and there are about 30-60 days(June)after emergence without irrigation.At this time,wheat,cotton,corn,processing tomato and other crops need irrigation.Xinjiang has a temperate continental climate,with spring being the main drought season.Whether the water consumption of sugar beet in spring can be reduced by delaying the first irrigation time after emergence combined with the adjustment of irrigation amount throughout the growth period is of great significance for saving water and reducing drought-induced yield loss.Methods: A split-split plot design was used in this experiment,with the first irrigation time after emergence as the main plot,the irrigation amount in the growth period as the split plot,and varieties as the split-split plot.Three treatments of the first irrigation time after emergence(including advance irrigation(T1,70% FC),normal irrigation(T2,60% FC)and delay irrigation(T3,50% FC)),three treatments of irrigation amount(including excess irrigation(I1,120% full irrigation),normal irrigation(I2,100% full irrigation)and deficit irrigation(I3,80% full irrigation)),two sugar beet varieties with different water sensitivity(V1,Beta 796 and V2,KWS 3410)were designed in order to study the effects of water management on dry matter accumulation,yield and water use efficiency of sugar beet.Results:(1)Under the delay irrigation treatment of the first irrigation time after emergence(T3),the total water content,free water content,transpiration rate and glucose content of leaves,root activity and sucrose synthase,invertase activities in root tuber were significantly decreased during canopy development stage.The occurrence time of maximum dry matter accumulation rate and the end time of rapid dry matter accumulation period were advanced.Leaf area index,dry matter accumulation and water consumption decreased significantly,but yield,sugar production,water use efficiency,root head length,root neck length and green head proportion increased significantly during the whole growth period.(2)Under the deficit irrigation treatment of decreased irrigation amount(I3),water consumption intensity,number of green leaves,leaf area index,glucose content in leaves,root activity and fructose content in tubers significantly decreased during canopy development stage,but the lateral root length of0-20 cm and sucrose synthase activity in tubers significantly increased.Finally,sugar yield decreased significantly,while water use efficiency increased significantly.(3)The accumulation of leaf and petiole dry matter accumulation,maximum dry matter accumulation rate,starting time of dry matter rapid accumulation,total number of leaves,leaf area index,sucrose content and glucose content during the early growth stage(canopy development stage and storage root development stage),total chlorophyll content,0-20 cm lateral root length,root activity,sucrose phosphate synthase activity in root tuber,soluble total sugar and sucrose content in root tuber,yield,root head length,green head length,root length and green head proportion in late growth stage(sugar accumulation stage)of KWS3410 were significantly higher than those of Beta796.However,the end time of maximum dry matter accumulation rate,duration of rapid accumulation period,fructose content in tuber during leaf cluster stage,total water content,bound water content and relative water content in tuber during storage root development stage were significantly lower than those of Beta796.(4)After interaction of the three factors,the yield,sugar yield,percentage of green head and water use efficiency of sugar production in T3I1 treatments were significantly higher than those in other treatments.The dry matter accumulation,water consumption and water consumption during sugar accumulation stage,water consumption intensity during canopy development stage in T3I3 treatments were significantly lower than those of other treatments.Conclusion: The delay of the first irrigation time after emergence had the most obvious effect on the leaf and root system during the canopy development stage,and the growth of beet recovered gradually with the supplement of irrigation amount in the growth stage.With the reduced irrigation amount,aboveground growth was inhibited while the lateral root length from 0-20 cm increased,and the increased lateral root length could not change the decrease of sugar production.The drought tolerance of beet variety KWS3410 was stronger than that of Beta796.Adequate irrigation during the growth period can compensate for the negative effects of late irrigation time on the yield and sugar yield of sugar beet,but cannot reduce the green head which formed in the seedling stage of sugar beet.Therefore,on the basis of selecting varieties with drought tolerance,delaying the first irrigation time after seedling emergence and increasing irrigation amount during growth period can not only improve the yield and water use efficiency of drip irrigated sugar beet,but also alleviate the spring water contradiction of crops in arid areas.