| 1Effects of tillage and nitrogen fertilizer on the water consumption characteristics andgrain yield formation in dryland farming systems of wheatThe field experiment was conducted in the hilly dryland region of the Bianhe village inLinzi, Shandong Province during the2009to2012growing seasons. The winter wheatcultivars Jimai22, Shannong16, and Yannong0428were used for the2009to2010,2010to2011, and2011to2012wheat growing seasons, respectively. The treatments included fourtillage patterns and six levels of N, which was applied before sowing. The tillage patternswere, namely, strip rotary tillage (SR), strip rotary tillage after subsoiling (SRS), rotary tillage(R), and rotary tillage after subsoiling (RS). The nitrogen treatments were six levels of Napplied before sowing:0,90,120,150,180, and210kg N ha1, designated as N0to N5,respectively. Subsoiling treatments were only conducted during the2009to2010growingseason.1.1Effects of tillage and nitrogen fertilizer rate on water consumption characteristics indryland farming systems of wheatUnder the same tillage condition, the amount of water consumption in the N3treatmentfrom jointing to maturity was significantly higher than that in N0, N1, and N2treatments. Bycontrast, no significant differences were observed in the water consumption of the N3and N4treatments from jointing to maturity. The N3treatment had the capability to absorb morewater from deep soil layers below100cm, as compared with the N0, N1, and N2treatments.The amount of soil water consumption and its ratio to the amount of total water consumptionwere significantly increased as the N rate increased from N0to N3. The amount of waterconsumed from deep soil layers below100cm did not significant change as the N rateincreased from N3to N5. The water potential of the flag leaf during the middle and late grainfilling stages in the N3treatment was not significantly different from the N4or N5treatments, but it was significantly higher than that of the N0, N1, and N2treatments. The soilevaporation after jointing in the N3treatment was not significantly different from that in theN4or N5treatments, but it was significantly lower than that in the N0, N1, and N2treatments.These results suggested that N3treatment allowed for sufficient soil water consumption indeep soil layers, with higher amounts of water consumed after jointing. The N3treatment alsoreduced the level of soil evaporation after the jointing stage.Under the same N rate condition, the soil water content before sowing with subsoilingwas increased after subsoiling in the first growing season. The amount of soil water consumedin the SRS and RS treatments were not significantly difference, but were significantly higherthan those in the SR and R treatments. This finding suggested that subsoiling improved theconsumption of soil water. The amount of water consumed from the sowing to the jointingstage in the SR and SRS treatments was significantly lower than that in the R and RStreatments. The amounts of water consumed from the jointing to the maturity stages in theSRS treatment were the highest, whereas the amounts in the R treatment were the lowest. Thesoil evaporation at various stages was significantly lower in the SR and SRS treatments thanin the R and RS treatments. The SRS treatment had the advantages of the improved use of soilwater by wheat and the reduced level of soil evaporation after jointing. This treatmentconsumed a larger amount of water amount after jointing, despite its lower amount of waterconsumption before jointing; this trend was beneficial to meet the water demand afterjointing.1.2Effects of tillage and nitrogen fertilizer rate on carbon metabolism in drylandfarming systems of wheatUnder the same tillage conditions, the photosynthetic rate and SPS activity of the flag leafat the middle and late grain filling stages in the N3treatment were not significantly differentfrom those in the N4treatment. However, these rate and activity were significantly higherthan those in the N0, N1, and N2treatments, which promoted sucrose accumulation. Theseresults were reduced when the nitrogen application rate was increased in the N5treatment.During the2009to2010and the2011to2012growing seasons, the dry matter accumulationafter jointing in the N3treatment was not significantly different from that in the N4and N5treatments; however, it was significantly higher than those in the N0, N1, and N2treatments. During the2010to2011growing season, the dry matter accumulation at maturity in the N3treatment was not significantly different as compared with that in the N4or N5treatment butwas significantly higher than that in N0, N1, and N2treatments. The dry matter accumulationafter anthesis in the N3and N4treatments was significantly higher than that in the other Ntreatments. The N3and N4treatments under the same tillage conditions likewise hadrelatively higher dry matter translocation after anthesis.The photosynthetic rate of the flag leaf at the middle and late grain filling stages underthe same N rate conditions was not significantly different in the SR and RS treatments, butthis rate was significantly higher in the SRS treatment. This photosynthetic rate in the Rtreatment was the lowest among all treatments. The SPS activity of the flag leaf at the middleand late grain filling stages in the SRS treatment was significantly higher than that in othertreatments, which was beneficial for sucrose synthesis. The SRS treatment had the highest drymatter accumulation at maturity. This accumulation was not significantly different among theSR and RS treatments, whereas the R treatment had the lowest value of all the treatments. Thedry matter accumulation after anthesis and its contribution to grain in the SRS treatment weresignificantly higher than those in other treatments, whereas the R treatment had the lowestvalues. These results suggested that the SRS treatment had a favorable effect on dry matteraccumulation after anthesis.1.2Effects of tillage and nitrogen fertilizer rate on nitrogen metabolism in drylandfarming systems of wheatThe nitrogen accumulation at anthesis and maturity in the N3, N4, and N5treatmentswas significantly higher than that in N0, N1, and N2treatments, given the same tillageconditions. The N3, N4, and N5treatments had relatively higher accumulation of nitrogentranslocated from absorbed N before anthesis to grain. During the2009to2010and2011to2012growing seasons, the nitrogen absorption after anthesis in the N3and N4treatments wasnot significantly different, as compared with the N5treatment, but these values weresignificantly higher than those in the N0, N1, and N2treatments. During the2010to2011growing season, the N3and N4treatments had relatively higher nitrogen absorption afteranthesis. These results suggested that the N3treatment led to sufficient nitrogen accumulationtranslocation and absorption after anthesis. The nitrate nitrogen contents of the different soil layers increased with the increasing N rates. The nitrate nitrogen contents of soil layers from0cm to100cm at maturity in the N3treatment were not significantly different, as comparedwith those in the N2treatment. The N5treatment had a nitrate accumulation peak at soillayers from120cm to180cm.The nitrogen accumulation at maturity under the same N rate conditions was notsignificantly different in the SR and RS treatments, but it was significantly lower than that inthe SRS treatment. The R treatment had the lowest nitrogen accumulation among all thetreatments. The SRS treatment had relatively higher nitrogen translocated from the absorbedN before anthesis to grain, with the highest nitrogen absorption after anthesis. By contrast, theR treatment had the lowest nitrogen absorption after anthesis. The nitrate nitrogen contents atsoil layers from0cm to100cm at maturity in the SRS treatment were significantly lowerthan those in other treatments. In addition, the nitrate nitrogen contents at120cm to180cmwere significantly lower than those in the RS treatment. The SRS treatment allowed wheat toutilize the nitrate nitrogen contents at soil layers from0cm to100cm, whereas the RStreatment demonstrated a nitrate accumulation peak at soil layers from120cm to180cm.1.3Effects of tillage and nitrogen fertilizer rate on the grain yield, water use efficiency,and nitrogen use efficiency in dryland farming systems of wheatThe grain yield in the N3treatment was significantly higher than that in N0, N1, and N2treatments under the same tillage conditions. The N3treatment also had relatively higherwater use efficiency. The grain yield and water use efficiency in the N4treatment was notsignificantly different from the N3treatment. The N5treatment had relatively lower grainyield, as compared with the N3and N4treatments. As the N rates increased in the N3to N5treatments, the N productive efficiency and N agronomic efficiency were significantlydecreased. The N application of150kg ha1was considered to be optimum rate under thegiven experimental conditions.The SRS treatment gained the highest grain yield under the same N rate conditions,whereas the SR and RS treatments were not significantly different. The R treatment had thelowest yield. The SRS treatment also had relatively higher water use efficiency and Nproductive efficiency; this treatment was considered to be the optimum method for the givenexperimental conditions. 2Effects of nitrogen application rate and depth on water consumption characteristicsand grain yield formation in dryland farming systems of wheatThe field experiment was conducted in the hilly dryland region of the Bianhe village inLinzi, Shandong Province during the2010to2012growing seasons. The winter wheatcultivars Shannong16and Yannong0428were used for the2010to2011and the2011to2012wheat growing seasons, respectively. The treatments included four levels of N rateapplied before sowing combined with four nitrogen application depths. The N rates included0,90,150, and210kg N ha1, designated as N0, N1, N3, and N5, respectively. The nitrogenapplication depths were designed to have four levels, namely, surface application (D1) as wellas the application depths of10cm (D2),20cm (D3), and30cm (D4).2.1Effects of nitrogen application rate and depth on water consumption characteristicsin dryland farming systems of wheatUnder the N1condition during the2010to2012growing seasons, the amounts of soilwater consumption and water consumption from anthesis to maturity in the D2, D3, and D4treatments were significantly higher than those in the D2treatment. During the2010to2011growing season, the soil evaporation after anthesis in the D2, D3, and D4treatments wassignificantly lower than that in the D1treatment. Under the N3and N5conditions during the2010to2012growing seasons, the amount of water consumption from jointing to maturity aswell as the water potential of the flag leaf at the middle and late grain filling stages in the D3and D4treatments were significantly higher than those in D1and D2treatments. During the2010to2011growing season, the amounts of water consumption and soil water consumptionat soil layers from60cm to140cm in the D3and D4treatments were significantly higherthan those in the D1and D2treatments. The soil evaporation after anthesis in the D3and D4treatments was significantly lower those in the D1and D2treatments. During the2011to2012growing season, the amount of soil water consumption at soil layers from40cm to160cm was significantly higher in the D3and D4treatments than in the D1and D2treatments. The D3and D4treatments promoted the use of soil water by wheat and reducedthe soil evaporation after jointing. The D3and D4treatments likewise had higher waterconsumption from jointing to maturity as well as higher water potential of the flag leaf at themiddle and late grain filling stages; these properties were beneficial to meet the water demand after jointing.Under the same nitrogen application depths during the2010to2012growing seasons,the amounts of soil water consumption at soil layers from60cm to140cm in the N3and N5treatments were significantly higher than that in the N1treatment. The amount of waterconsumed from jointing to anthesis as well as the water potential of the flag leaf at the middleand late grain filling stages in the N3and N5treatments were likewise significantly higherthan those in the N1treatment. In the2010to2011growing seasons, the soil evaporation atanthesis stage of the N3and N5treatments was significantly lower than that in the N1treatment for all nitrogen application depths. The amounts of water consumption fromanthesis to maturity in the N3and N5treatments were significantly higher than that in the N1treatment. Under the D1, D3, and D4conditions during the2011to2012growing seasons, theamount of water consumed from anthesis to maturity in the N3and N5treatments wassignificantly higher than that in the N1treatment. The N3treatment had the highest amount ofwater consumption under the D2condition. The amount of soil water consumption at soillayers from60cm to140cm was significantly higher in the N3and N5treatments than in theN1treatment under the D3and D4conditions. The N3treatment promoted the use of soilwater at soil layers from120cm to160cm and reduced the soil evaporation at anthesis. TheN3treatment demonstrated the higher amounts of water consumption after jointing and higherwater potential of the flag leaf at the middle and late grain filling stages; both properties werebeneficial for meeting the water demand after jointing.2.2Effects of nitrogen application rate and depth on carbon metabolism in drylandfarming systems of wheatUnder the N1condition during the2010to2012growing seasons, the photosyntheticrate and SPS activity of the flag leaf at the middle and late grain filling stages as well assucrose content of flag leaf at middle grain filling in the D2, D3, and D4treatments weresignificantly higher than those in the D1treatment. The dry matter accumulation at maturityand dry matter accumulation after anthesis in the D2, D3, and D4treatments were alsosignificantly higher than those in the D1treatment. Under the N3and N5conditions duringthe2010to2012growing seasons, the photosynthetic rate and SPS activity and the sucrosecontent of the flag leaf at the middle and late grain filling stages in the D3and D4treatments were significantly higher than those in the D1and D2treatments. The dry matteraccumulation at maturity and dry matter accumulation after anthesis in the D3and D4treatments were also significantly higher than those in the D1and D2treatments. The D3andD4treatments demonstrated higher dry matter accumulation after anthesis and dry matteraccumulation at maturity.Under all nitrogen application depth conditions during the2010to2012growing seasons,the photosynthetic rate of flag leaf at grain filling in the N3and N5treatments wassignificantly higher than that in the N1treatment. The SPS activity of flag leaf at grain fillingand sucrose content of flag leaf at middle grain filling were significantly higher in the N3andN5treatments than in the N1treatment under the D3and D4conditions. During the2010to2011growing seasons, the dry matter accumulation at maturity in the N3and N5treatmentswas significantly higher than that in the N1treatment under the D1, D3, and D4conditions.The N3and N5treatments had relatively higher dry matter accumulation at maturity under theD2condition. During the2011to2012growing seasons, the dry matter accumulation atmaturity in the N3and N5treatments was significantly higher than that in the N1treatmentfor all nitrogen application depths. During the2010to2012growing seasons, the dry matteraccumulation after anthesis in the N3and N5treatments was significantly higher than that inthe N1treatment under all nitrogen application depths. The N3treatment promoted the higherphotosynthetic rate of the flag leaf at grain filling, and the accumulation of dry matter afteranthesis was significantly increased.2.3Effects of nitrogen application rate and depth on nitrogen metabolism in drylandfarming systems of wheatDuring the2010to2012growing seasons, the nitrogen accumulation at maturity, as wellas the nitrogen absorption after anthesis, was significantly higher in the D2, D3, and D4treatments than in the D1treatment under the N1conditions. Under the N3and N5conditions,the D3and D4treatments had relatively higher nitrogen translocation from absorbed N beforeanthesis to grain. The nitrogen accumulation at maturity and the nitrogen absorption afteranthesis in the D3and D4treatments were significantly higher than those in the D1and D2treatments. Under different N rates during the2011to2012growing season, the nitratenitrogen contents at soil layers from40cm to100cm at maturity in the D3treatment had no significant difference compared with those in the D2treatment. Under the N1condition, thenitrate nitrogen contents at soil layers from40cm to100cm at maturity were significantlylower in the D3treatment than in the D4treatment. Under the N3and N5conditions, thenitrate nitrogen contents at soil layers from60cm to140cm at maturity in the D3treatmentwere significantly lower than those in the D4treatment. These results suggested that the D3and D4treatments were beneficial for nitrogen accumulation at maturity as well as thenitrogen absorption and translocation after anthesis. The D3treatment allowed wheat toabsorb nitrate nitrogen in soil layers from40cm to100cm, whereas the D4treatment formeda nitrate accumulation peak at soil layers from120cm to140cm.Under all nitrogen application depths during the2010to2012growing seasons, thenitrogen accumulation at maturity and the nitrogen translocation from absorbed N beforeanthesis to grain were significantly higher in the N3and N5treatments than in the N1treatment. During the2010to2011growing season, the nitrogen absorption after anthesis inthe N3and N5treatments was significantly higher than that in the N1treatment under the D1conditions. No significant differences were observed between the different nitrogenapplication depths in nitrogen absorption after anthesis under the D2, D3, and D4conditions.During the2011to2012growing seasons, the nitrogen absorption after anthesis in the N3andN5treatments was significantly higher than that in the N1treatment under the D1, D3, andD4conditions. The effects of the different nitrogen application depths were not significantlydifferent in terms of the nitrogen absorption after anthesis under the D2condition. The nitratenitrogen contents at soil layers from0cm to60cm at maturity in the N3treatment was notsignificantly different, as compared with those in the N1treatment under the D1conditions.No significant differences existed between the N1and N3treatments in terms of the nitratenitrogen contents at soil layers from0cm to80cm at maturity under the D2, D3, and D4conditions. The nitrate nitrogen contents at soil layers from20cm to120cm at maturity weresignificantly higher in the N5treatment than in the other treatments under the D1and D2conditions. The N5treatment had the highest nitrate nitrogen contents at soil layers from0cmto140cm at maturity. Under the D4conditions, the N5treatment had the highest nitratenitrogen contents at soil layers from40cm to180cm. These results suggested that the N3treatment was beneficial for nitrogen absorption and translocation. The N3treatment promoted the absorption of nitrate nitrogen by wheat from the surface soil layers, whereas theN5treatment had a nitrate accumulation peak at soil layers from140cm to180cm.2.4Effects of nitrogen application rate and depth on the senescence of flag leaf and rootsystems in dryland farming systems of wheatUnder the N1condition during the2010to2011growing season, the SOD activity andsoluble protein content of the flag leaf as well as the root activity at the middle and late grainfilling stages in the D2, D3, and D4treatments were significantly higher than those in the D1treatment. By contrast, the MDA contents were significantly lower in the D2, D3, and D4treatments than in the D1treatment. Under the N3and N5conditions, the SOD activity andsoluble protein content of the flag leaf as well as the root activity at the middle and late grainfilling stages in the D3and D4treatments were significantly higher than those in the D1andD2treatments. The MDA contents were significantly lower than those in the D1and D2treatments. Under the N1condition during the2011to2012growing season, the root activityafter anthesis in the D2, D3, and D4treatments was significantly higher than that in the D1treatment. The root activity at middle and late grain filling was significantly higher in the D3and D4treatments than in the D1and D2treatments under the N3and N5conditions. Theseresults suggested that D3and D4treatments delays the senescence of flag leaves and rootsystems after anthesis.Under all nitrogen application depth conditions during the2010to2012growing seasons,SOD activity and soluble protein content of flag leaf and root activity at middle and late grainfilling in the N3and N5treatments were significantly higher than those in the N1treatment.The MDA contents were significantly lower in most treatments, as compared with those in theD1treatment. Therefore, the N3treatment could delay the senescence of the flag leaf and rootsystem after anthesis.2.5Effects of nitrogen application rate and depth on the grain yield, water use efficiency,and nitrogen use efficiency in dryland farming systems of wheatDuring the2010to2012growing seasons, the grain yield, N uptake efficiency, and Nproductive efficiency in the D2, D3, and D4treatments were significantly higher than those inthe D1treatment under the N1conditions. No significant differences were observed in thewater use efficiency between different nitrogen application depths. The grain yield, N uptake efficiency, nitrogen fertilizer apparent efficiency, and N productive efficiency in the D3andD4treatments were significantly higher than those in the D1and D2treatments under the N3and N5conditions. The nitrogen application depth of20cm was the optimal soil depth ofnitrogen fertilizer application under the experimental conditions.Under all nitrogen application depths during the2010to2012growing seasons, the grainyield in the N3treatment was not significantly different from that in the N5treatment, but itwas significantly higher than that in the N1treatment. During the2010to2011growingseason, the N3and N5treatments had relatively higher water use efficiency under the D1conditions. No significant differences in the water use efficiency were observed betweendifferent nitrogen application depths under the D2, D3, and D4conditions. Under all nitrogenapplication depths during the2011to2012growing season, the water use efficiency did notsignificantly differ between the different nitrogen application depths. With the increasing Nrates, the N uptake efficiency, nitrogen fertilizer apparent efficiency, N agronomic efficiency,and N productive efficiency in all different nitrogen application depths were significantlydecreased. The optimal nitrogen application rate under the experimental conditions was150kg ha1.3Evaluation of water consumption and grain yield in different wheat cultivarsThe field experiment was conducted at the experimental farm of the ShandongAgricultural University during the2008to2009growing season. The winter wheat cultivarsShannong15, Jimai22, Yannong21, Shannong8355, Weimai8, and Tai9818were used.Four irrigation regimes were designed for each cultivar: W0had no irrigation; W1had arelative content of70%at the jointing and anthesis stages; W2had relative contents of70%at8d after jointing and70%at8d after anthesis; W3had relative contents of75%at8d afterjointing and70%at8d after anthesis.3.1Water consumption characteristics in different wheat cultivarsThe six wheat cultivars were divided into three groups based on the cluster analysis ofgrain yield and water use efficiency. The three groups were, namely, the high water useefficiency group (Group I), the moderate water use efficiency group (Group II), and the lowwater use efficiency group (Group III). The Shannong8355, Shannong15, and Weimai8cultivars were selected for further analysis from Groups I to III, respectively. Under the conditions of different irrigation treatments, the amount of water consumptionfrom sowing to jointing in Shannong8355was significantly lower than that in Weimai8.Shannong8355had relatively lower amounts of water consumed from jointing to anthesis.The amount of water consumption from the anthesis to maturity stage in Shannong8355wassignificantly higher than that in Shannong15and Weimai8. Under the W0and W1conditions,the amount of water consumed at soil layers from100cm to140cm was highest in Shannong8355. The amount of water consumed at soil layers from80cm to120cm in Shannong8355was significantly higher than that in Shannong15under the W2conditions. By contrast, theamount of water consumed at soil layers from100cm to160cm in Shannong8355wassignificantly higher than that in Weimai8. Under the W3conditions, the amount of waterconsumption at soil layers from80cm to120cm was the highest in Shannong8355. Theseresults suggested that Shannong8355could most efficiently use soil water from deep soillayers. The Shannong8355cultivar reduced the amount of water consumption before anthesis,which was beneficial for meeting the water demand during grain filling.3.2Dry matter accumulation and transporation in different wheat cultivarsUnder the W0condition, the dry matter accumulation at anthesis and maturity inShannong8355was not significantly different from that in Shannong15, but wassignificantly higher than that in Weimai8. Shannong8355had the highest dry mattertranslocation after anthesis to grain. The dry matter transporation ratio, contribution of drymatter translocation after anthesis to grain, and dry matter accumulation after anthesis in weresignificantly higher in Shannong8355than in Weimai8. Under the W1and W3conditions,Shannong8355gained the highest dry matter accumulation at maturity and dry matteraccumulation after anthesis. This cultivar had relatively higher dry matter translocation afteranthesis to grain. Under W2condition, the dry matter accumulation at maturity in Shannong8355was significantly higher than that in Weimai8. Shannong8355demonstrated the highestdry matter accumulation after anthesis and had relatively higher dry matter translocation afteranthesis to grain. The results suggested that Shannong8355had higher dry matteraccumulation at maturity and dry matter accumulation after anthesis. Furthermore, Shannong8355had relatively higher dry matter translocation after anthesis to grain.3.3Nitrogen accumulation and transporation in different wheat cultivars Under the W0, W1, and W3conditions, no significant differences were observed innitrogen accumulation at maturity between the different wheat cultivars. Under the W2condition, the nitrogen accumulation at maturity in Shannong8355was significantly higherthan that in Weimai8. Under the W0condition, the nitrogen translocation from absorbed Nbefore anthesis to grain and its contribution to grain nitrogen in Shannong8355and Shannong15were significantly higher than those in Weimai8. Under the W1condition, Shannong8355and Shannong15had relatively higher nitrogen translocation from absorbed N before anthesisto grain. Under the W2condition, Shannong15had the highest nitrogen translocation fromabsorbed N before anthesis to grain. Under the W3condition, the cultivars were notsignificantly different in terms of the nitrogen translocation from absorbed N before anthesisto grain, the nitrogen translocation ratio, and the contribution of nitrogen translocation tograin nitrogen. |
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