Study On Theory And Technique Of Supplemental Irrigation Based On Measuring Soil Moisture In Wheat

A field experiment was performed using wheat cultivar Jimai 22 obtained in Shijiawangzi Village,Yanzhou,Shandong,China during the 2012-2016 wheat-growing seasons.The aim was to study the physiological mechanisms and supplemental-irrigation techniques based on the measurement of soil moisture in wheat.Another aim was to provide theoretical basis for the high-yielding and water-saving cultivation of wheat.In the 2012-2013 growing season,two levels of target relative soil water content(W1,65%at jointing stage and 70%at anthesis;and W2,70%at jointing stage and 70%at anthesis),two soil depths for calculating the supplemental irrigation in each target relative soil content level(D1,0-40 cm;and D2,0-140 cm),and two control treatments(W1,no irrigation;and Wck,60 mm irrigation at both jointing and anthesis stages)were designed for this study.Further,during the growing seasons from 2013-2014,three levels of target relative soil water content(W1,65%at jointing stage and 70%at anthesis;W2,70%at jointing stage and 70%at anthesis;and W3,75%at jointing stage and 70%at anthesis)under two soil depths(D1,0-40;and D2,0-140)for calculating supplemental irrigation and two control treatments(W0,no irrigation treatment;and Wck,for quota irrigation treatment at 60 mm in both jointing and anthesis stages)were designed.The split design plots were arranged and repeated thrice.This experiment was conducted to study the optimal soil depth for calculating supplemental irrigation and target soil relative soil water content.During the growing seasons from 2014-2016,three micro-sprinkling hose length treatments(60 m for DL1,80 m for DL2 and 100 m for DL3)as well as,micro-sprinkling hose widths under each hose length(65 mm,80 mm,and 100 mm for DK1,DK2 and DK3,respectively)were designed for this study.In each treatment,sampling districts were set along the laying direction of micro-sprinkling hose in certain increments.Soil moisture and plant physiological indexes were measured at the end of each sampling district.The plots were in split design with 3 replicates.This experiment was conducted to study the effects of different micro-sprinkling hose lengths and widths on water characteristics,carbon and nitrogen metabolism of wheat.1 Study on the optimal soil depth for calculating irrigation amount and target soil relative soil water content level of target soil for supplemental irrigation based on soil moisture1.1 Effects of different soil depths on the water consumption characteristics,carbon,and nitrogen on wheat metabolism under the same target relative soil water content for calculating supplemental irrigation1.1.1 Effects of different treatments on water consumption characteristics of wheatUnder the same target relative soil water content,the irrigation amount of D1 was significantly lower than that of Wck and D2.Furthermore,the soil water consumption of D1 was significantly higher than that of Wck and D2.The water consumption from anthesis to maturity stage,and evaporation in the field at grain filling stage of D1 were significantly lower than that of Wck.The flag leaf and soil potentials at middle and late grain filling stages in D1 were significantly higher than that of D2.Results showed that D1 had decreased the irrigation and evaporation in the field at grain filling stage,obtaining the highest flag leaf and soil water potentials,which were beneficial to decrease soil evaporation and increase soil water uptake in roots,saving irrigation water.1.1.2 Effects of different treatments on photosynthetic characteristics and dry matter production of wheatIn 2012?2013 growing season,under the W1 and W2 condition,the net photosynthetic rate(Pn),stomatal conductance(Gs),water use efficiency(WUEf)and SPS activity of flag leaf,grain filling rate at middle and late grain filling stage,dry matter(DM)at maturity and current assimilates distributed directly to the grains from anthesis to maturity(ADA)of D1 were significantly higher than that of D2.In 2013?2014 growing season,under W2 and W3 conditions,these parameters in D1 were significantly higher than those in Wck and D2.These results indicated that D1 improved photosynthetic capacity at middle and late grain fillings and the DM and assimilates distributed directly to grain after anthesis is conducive to produce more assimilates and promote grain filling.1.1.3 Effects of different treatments on nitrogen accumulation and translocation and soil nitrate nitrogen of wheatIn 2012?2013 growing season,under the W1 and W2 condition,the amount of nitrogen accumulated at anthesis and maturity stages and the amount of nitrogen redistributed from vegetative organs of anthesis to grain(NRA)of D1 were significantly greater than that of D2.In 2013?2014 growing season,under the W2 and W3 condition,the parameters mentioned above of D1 were significantly greater than that of Wck and D2.In 2012?2014 growing seasons,under W1,W2 and W3 condition,the nitrate-nitrogen content in 40-140 cm soil layers of D1 was much lower than of D2.These results showed that D1 was beneficial for nitrogen accumulation and the redistribution of the nitrogen stored in the vegetative organs to grain,promote the absorption and utilization of nitrate nitrogen and reduce the pollution of nitrate nitrogen to soil.1.1.4 Effects of different treatments on flag leaf senescence characteristicsIn 2012?2013 growing season,under the W1 and W2 condition,the SOD activity,CAT activity and soluble protein content of D1 were significantly greater than that of D2,however,the MDA content of D1 was significantly lower than that of D2 at middle and late grain filling stages.In addition,in 2013?2014 growing season,under the W2 and W3 condition,D1 obtained significantly higher SOD activity,CAT activity and soluble protein content,but lower MDA content at middle and late grain filling stages in comparison of those in Wck and D2.These results indicated that D1 is conducive to maintain a high oxygen-scavenging ability and delay flag leaf senescence at the middle and late grain filling stage.1.1.5 Effects of different treatments on grain yield,water use efficiency,irrigation benefit,and nitrogen fertilizer partial productivity of wheatIn 2012?2013 growing season,under the W1 and W2 condition,the grain yield(GY),water use efficiency(WUE)and nitrogen fertilizer partial productivity(NfP)of D1 were significantly higher than that of D2,irrigation benefit(IB)of D1 were significantly higher than that of Wck and D2.In 2013?2014 growing season,under the W1 condition,the GY and NfP of Wck,D1 and D2 had no significant difference.However,D1 obtained a greater WUE in comparison to Wck,and greater IB in comparison to Wck and D2.Moreover,under W2 and W3 condition,the GY,IB and NfP of D1 were significantly greater than that of Wck and D2.The WUE of D1 was also significantly higher than that of Wck.These results indicated that under similar target relative soil water content level,calculating the supplemental irrigation amount based on the relative soil water content of 0-40 cm layer(D1)was optimal under this experimental condition.1.2 Effects of different target relative soil water contents on water consumption characteristics,carbon and nitrogen metabolism of wheat under the same soil depth for calculating supplemental irrigation amount1.2.1 Effects of different treatments on water consumption characteristics of wheatUnder the D1 condition,the irrigation amount,water consumption amount from anthesis to maturity stage and evaporation in field at grain filling stage of W2 was significantly lower than that of Wck.However,soil water consumption of W2 was significantly higher than that of Wck.The flag leaf potential and soil potential of 0-40 cm layer at middle and late grain filling stage in W2 was significantly higher than that of Wck and W1.These results showed that W2 was beneficial to decrease the irrigation amount,increase soil water uptake and maintain better water content of plants and soil.1.2.2 Effects of different treatments on photosynthetic characteristics and dry matter production of wheatUnder the condition of D1,the Pn,Gs,WUEf and SPS activity of flag leaf,the grain filling rate at middle and late grain filling stage,DM at maturity,and ADA of W2 were significantly higher than that of Wck and W1.This result indicated that under the D1 condition,W2 maintains a high photosynthetic capacity at middle and late grain filling stage,which is conducive to enhance the DM accumulation,increase the assimilates distributed directly to the grain after anthesis and improve grain weight.1.2.3 Effects of different treatments on nitrogen accumulation and translocation and soil nitrate nitrogen of wheatUnder the D1 condition,the amount of nitrogen accumulation at anthesis and maturity stage and NRA of W2 were significantly greater than that of Wck and W1.The nitrate-nitrogen content in 40-140 cm soil layers at maturity of W2 was much lower than of Wck.This result showed that under D1 condition,W2 had increased the nitrogen accumulation and the redistribution to grain,reducing nitrate-nitrogen leaching to 40-140 cm soil layer,which is conducive to the absorption of nitrogen.1.2.4 Effects of different treatments on flag leaf senescence characteristicsUnder the D1 condition,W2 obtained much higher SOD activity,CAT activity and soluble protein content,and lower MDA content than that of Wck and W1 at middle and late grain filling.These results indicated that under D1 condition,W2 can reduce cell membrane damage and delay flag leaf senescence at middle and late grain filling stage.1.2.5 Effects of different treatments on grain yield,water use efficiency,irrigation benefit and nitrogen fertilizer partial productivity of wheatUnder the condition of D1,the GY,WUE,EB and NfP of W2 were significantly higher than that of Wck and W1 from 2012-2014 growing seasons.These results indicated that the calculated supplemental irrigation water based on the relative soil water content under 0-40 cm(D1),bringing the target relative soil water content to 70%at both jointing and anthesis stages,W2 was the best treatment considering the water-saving capability and high yield under this experimental condition.2 Effects of different micro-sprinkling hose length and width on water characteristics,carbon and nitrogen metabolism of wheat2.1 Effects of different micro-sprinkling hose widths on water characteristics,carbon and nitrogen metabolism of wheat under the same micro-sprinkling hose length2.1.1 Effects of different micro-sprinkling hose width on water characteristics of wheatIn 2014-2016 growing season,under DL2 and DL3 conditions,DK3 obtained the highest Cu after irrigation at anthesis stage,followed by DK2 and DK1.Moreover,DK1 obtained highest value for Cv of relative soil water content in 0-40 cm layer of different sampling districts after irrigation at jointing and anthesis stages,followed by DK2 and DK3.In 2015-2016 growing season,under DL2 and DL3 conditions,DK3 obtained the higher soil water consumption and its ratio to total water consumption,and lower irrigation ratio to total water consumption in comparison of DK1 and DK2.These results showed that under DL2 and DL3 conditions,DK3 is conducive to the uniform distribution of irrigation water in wheat field and soil water uptake,and save irrigation water.2.1.2 Effects of different micro-sprinkling hose width on photosynthetic characteristics and dry matter production of wheatDuring the growing seasons from 2014-2016,under DL2 condition,the the average Pn,Gs,WUEf and SPS activity at late grain filling stage,DM at maturity and ADA of different sampling districts in DK2 and DK3 were significantly higher than that in DK1.Under DL3 condition,DK3 had the highest value in comparison of DK1 and DK2.These results showed that,DK2 and DK3 under DL2 condition and DK3 under DL3 condition improved the photosynthetic capacity of wheat at late grain filling stage,enhance the DM and increase assimilates that are distributed directly to the grain after anthesis.2.1.3 Effects of different micro-sprinkling hose width on nitrogen accumulation and translocation and soil nitrate nitrogen of wheatDuring the growing seasons from 2014-2016,under DL2 condition,the average nitrogen accumulation amount at maturity stage of different sampling districts in DK2 and DK3 was significantly higher than that of DK1.Under DL3 condition,with the parameters mentioned,DK3 had the highest value,followed by DK2 and DK1.Under DL2 and DL3 conditions,the average NRA of DK2 and DK3 was significantly higher than that of DK1.Moreover,the average soil nitrate-nitrogen content at maturity of different sampling districts in were significantly lower in DK2 and DK3 than in DK1 under the DL1 and DL2 condition.The results indicated that under DL2 and DL3 condition,DK2 and DK3 improved the nitrogen accumulation amount at maturity and nitrogen accumulation to the grain and enhanced the nitrogen uptake.2.1.4 Effects of different micro-sprinkling hose widths on flag leaf senescence characteristics of wheatDuring the growing seasons from 2014-2016,under the DL2 and DL3 condition,DK3 obtained the highest average SOD activity and soluble protein content among different sampling districts,followed by DK2 and then DK1.Furthermore,the average MDA content at late grain filling stage was the lowest in DK3 followed by DK2 and DK1 under DL2 and DL3 conditions,respectively.These results showed that under DL2 and DL3 conditions,DK3 enhanced the oxygen-scavenging ability and delay leaf senescence at late grain filling stage.2.1.5 Effects of different micro-sprinkling hose widths on grain yield and water use efficiency of wheatDuring the growing seasons from 2014-2016,the GY in DK1,DK2 and DK3 had no significant difference and the WUE of DK3 was significantly higher than that of DK1 and DK2 under DL1 condition.In addition,the GY and WUE of DK2 and DK3 were significantly higher than that of DK1 under DL2 condition.Moreover,DK3 obtained the greatest GY and WUE,followed by DK2 and DK1 under DL3 condition.These results indicated that the micro-sprinkling width of 100 mm(DK3)under 60 m length(DL1)obtained greatest GY and WUE among all treatments,making it the best treatment under this experiment.Similarly,the hose width of 100 mm(DK3)was the best treatment under the laying length of 60 m(DL1)and 100 m(DL3).in addition,the hose width of 80 mm(DK2)and 100 mm(DK3)was the best treatment under the laying length of 80 m(DL2).2.2 Effects of different micro-sprinkling hose lengths on water characteristics,carbon and nitrogen metabolism of wheat under same micro-sprinkling hose width2.2.1 Effects of different micro-sprinkling hose length on water characteristics in wheat fieldDuring the growing seasons from 2014-2016,DL1 obtained the highest value for Cu after irrigation at anthesis stage under the DK1 and DK2 condition followed by DL2 and DL3.Under DK1 and DK2 condition,different sampling districts after irrigation at jointing and anthesis stage in DL3 had the highest Cv of relative soil water content in 0-40 cm layer,as well as the soil water consumption amount,followed by DL2 and DL1.The irrigation water of DL1 was significantly lower than that of DL3 under DK1 and DK2 condition.These results showed that DL1 under DK1 and DK2 condition,DL1,and DL2 under DK3 condition is conducive for the uniform distribution of irrigation water in the wheat field and soil water uptake,and save irrigation water.2.2.2 Effects of different micro-sprinkling hose length on photosynthetic characteristics and dry matter production of wheatDuring the growing seasons from 2014-2016,the in DL1 was the highest under DK1 and DK2 condition,followed by DL2 and DL3.Moreover,the average DM at maturity and ADA of different sampling districts in DL1 was significantly higher than that of DL2 and DL3 under DK1 condition.However,under the DK2 condition,the average DM at maturity and ADA in DL1 and DL2 was significantly greater than that in DL3.Thus,the results showed that DL1 under DK1 condition,DL1 and DL2 under DK2 condition improved the photosynthetic capacity at late grain filling stage and enhanced the dry matter accumulation,which is conducive for the increase of assimilates that are distributed directly to the grain after anthesis.2.2.3 Effects of different micro-sprinkling hose length on nitrogen accumulation and translocation and soil nitrate nitrogen of wheatDuring the growing seasons from 2014-2016,DL1 obtained the highest average nitrogen accumulation amount at maturity stage of different sampling districts under DK1 condition,followed by DL2 and DL3.Under the DK2 condition,the average nitrogen accumulation amount at maturity stage in DL1 and DL2 was significantly higher than that of DL3.Moreover,the average NRA of different sampling districts in DL1 was significantly higher than that in DL2 and DL3 under DK1 condition.However,the average NRA of different sampling districts in DL1 and DL2 was significantly higher than that in DL3 under DK2 condition.In addition to this,the average soil nitrate-nitrogen content at maturity of different sampling districts in DL2 and DL3 was significantly higher than that in DL1 under DK1 condition;whereas under DK2 condition,the average soil nitrate-nitrogen content at maturity in DL3 was significantly higher than that in DL1 and DL2.These results indicated that DL1 under DK1 condition,and DL1 and DL2 under DK2 condition were conducive to the nitrogen accumulation to the grain and enhanced the nitrogen uptake.2.2.4 Effects of different micro-sprinkling hose length on grain yield,water use efficiency,irrigation benefit and nitrogen fertilizer partial productivity of wheatDuring the growing seasons from 2014-2016,DL1 obtained the greatest GY and WUE under DK1 condition,followed by DL2 and DL3.Moreover,the GY and WUE of DL1 and DL2 were significantly higher than that of DL3 under DK2 condition,whereas no significant difference was found among the three under the DK3 condition.These results indicated that the micro-sprinkling hose of 60 m(DL1)under 100 mm width(DK3)obtained greatest GY and WUE among all treatments,making DK3 as the best treatment under this experiment.Under the hose width of 65 mm(DK1)and 100mm(DK3),the hose length of 60 m(DL1)was the best treatment.Moreover,the hose length of 60 m(DL1)and 80 m(DL2)were the best treatments under the hose width of 80 mm(DK2).