Studies On Water Requirement Characteristic For High Quality And Yield And On Nitrogen Cycle Of Plant-soil System In Wheat

1 Effects of irrigation rate on water utilization characteristic and on kernel quality and yield formation mechanismCultivar Jimai 20 (J20), a strong-gulten winter wheat cultivar and cultivar Taishan 23 (T23), a medium-gluten winter wheat cultivar were used. The experiment was laid out in a split-plot design. Main-plot treatments were irrigation rate, consisting of zero irrigation (WO), irrigation applied at jointing stage (W1), irrigations applied at jointing stage and anthesis (W2), irrigations applied at jointing stage, anthesis and filling stage (14 days after anthesis) (W3), 60mm water used at each stage. Sub-plot treatments were nitrogen application rate, consisting of 0kg N·hm^-2 (NO) and 180kg N·hm^-2 (N1). Effects of irrigation rate on water utilization characteristic and on kernel quality and yield formation mechanism were studied in this experiment. The principal results were as follows.1.1 The soil water content dynamic of high-yield fieldAccording to the developing rule of wheat root, soil layer of 0～100cm were divided into 3 layers, 0～20cm, 20～60cm and 60～100cm. When water contents of 0～20cm, 20～60cm, 60～100cm soil layer were 17.73%, 17.02%, 16.90% before planting, the water contents of the above-mentioned soil layers of high-yield treatment were 10.46%～10.74%, 12.18%～12.52%, 16.28%～16.77% at jointing stage, 9.73%～9.81%, 14.67%～14.73%, 15.65%～16.65% at anthesis, 8.87%～9.12%, 12.51%～12.94%, 14.24%～14.48% at 14 days after anthesis, 6.07%～6.81%, 8.10%～9.66%, 10.79%～12.38% at maturity, respectively. To ensure get higher yield, 20～60mm soil layer from jointing stage to anthesis and 60～100mm soil layers from anthesis to filling stage must be contained higher water content.1.2 Effects of irrigation rate on water utilization Under the nitrogen level of N1, water consumption amount (WCA) of treatment W2, which got the highest grain yield, ranged from 429.8mm to 453.0mm. The contribution rate of precipitation to WCA ranged from 43.29% to 45.62%, the contribution rate of irrigation rate to WCA ranged from 26.49% to 27.92%, the contribution rate of soil water rate to WCA ranged from 26.46% to 30.22%. At the base of treatment W2, more irrigation rate improved the proportion of irrigation rate to WCA, but decreased the proportion of soil water rate to WCA, so decreased grain yield. The module index of WCA at planting to jointing stage, jointing stage to anthesis and anthesis to maturity was 27.63%～30.17%, 17.54%～19.00%, 50.83%～54.83%, respectively.Under the nitrogen level of N1, treatments W1 and W2 had higher water-use efficiency (WUE) of yield than other water treatments. Treatment W2 had the highest WUE of population from anthesis to maturity, and treatment W3 had the lowest WUE of population of whole growth period. Treatment W2 increased the WUE of leaf at the later filling stage.Under the nitrogen level N1 and N0, treatments W1 and W2 had a high WUE. Nitrogen application increased the WUE of yield and WUE of population. Cultivar T23 had higher WUE of yield than cultivar J20 when nitrogen and water applied.1.3 Effects of irrigation rate on nitrogen absorption, translation, and distribution in wheat plantIrrigation increased the nitrogen accumulation amount at anthesis, improved the nitrogen translocationamount from vegetative organs to kernel. Nitrogen accumulation amount after anthesis increased with the increasing of irrigation rate. Treatment W2 had the highest nitrogen accumulation amount in kernel for its higher nitrogen accumulation amount after anthesis and nitrogen translocationamount from vegetative organs.Nitrogen application increased the nitrogen accumulation amount at anthesis, nitrogen translocationamount from vegetative organs to kernel and nitrogen accumulation amount at maturity. Cultivar T23 had higher nitrogen accumulation amount than cultivar J20 at maturity.1.4 Effects of irrigation rate on protein qualityUnder the nitrogen level of N1, for cultivar J20, gliadin component content and HMW-GS content increased with the increasing of irrigation rate, and the HMW-GS content of treatment W2 was higher than other treatments. For cultivar T23, content ofω1,2-gliadin andα- gliadin increased with the increasing of irrigation rate, and the HMW-GS content of treatment W2 was higher than other treatments. Protein content, sedimentation volume and dough stability time of treatment W2 were higher than other treatments. Sedimentation volume and dough stability time of cultivar J20 was higher than that of cultivar T23. For cultivar J20, nitrogen application increased the gliadin component contents, glutenin component contents, gliadin content and glutenin content, and improved the sedimentation volume and dough stability time. For cultivar T23, nitrogen application decreased the contents of HMW-GS and glutenin, sedimentation volume and dough stability time.Under the nitrogen level of N1,ω5-gliadin content,α-gliadin content, HMW-GS content, LMW-GS content, glutenin content and the ratio of glutenin / gliadin of cultivar J20 were significantly higher than that of cultivar T23.1.5 Effects of irrigation rate on nitrogen metabolismTreatment W2 increased the Glutamine synthetase (GS) activity in flag leaf at 21day after anthesis (DAA) and the endopeptidases (EP) activity in flag leaf from 21 to 28 DAA, improved the soluble acid amino content in flag leaf at 21 DAA, and decreased the soluble acid amino content in flag leaf at 28 DAA. Treatment W3 delayed the increasing of EP activity in flag leaf.Nitrogen application increased the activities of GS and EP in flag leaf and the soluble acid amino content in flag leaf.GS activity and EP activity in flag leaf of cultivar J20 were significantly higher than that of cultivar T23.1.6 Effects of irrigation rate on starch quality in wheat kernelUnder the nitrogen level of N1, both treatment W2 and W1 had higher ratio of amylopectin/amylose among the irrigation treatments. The ratio of amylopectin/amylose of treatment W3 was significantly lower than that of treatment W2 and W1.Nitrogen application decreased the amylopectin and amylose content, increased the ratio of amylopectin/amylose. The ratio of amylopectin/amylose of cultivar T23 was higher than that of cultivar J20.1.7 Effects of irrigation rate on carbon metabolismTreatment W2 increasedΦPSâ…¡of flag leaf after anthesis, net photosynthesis rate from 20 DAA to 30 DAA, prolonged the high value duration of the photosynthesis of the flag leaf, and increased the sucrose-phosphate synthase (SPS) activity in the flag leaf of cultivar J20 from 21 DAA to 28 DAA and cultivar T23 after anthesis, respectively. Treatment W2 decreased the activity of granule bounded starch synthase (GBSS) at the late grain filling stage, and increased the activity of soluble starch synthase (SSS) at medium and late grain filling stage..Nitrogen application improvedΦPSâ…¡of flag leaf, SPS activity and sucrose content in flag leaf, but decreased the activity of SSS and GBSS in kernel.TheΦPSâ…¡of flag leaf, SPS activity and sucrose content in flag leaf, and SSS activity in kernel of cultivar T23 were higher than that of cultivar J20. The GBSS activity in kernel of cultivar J20 was lower than that of cultivar T23 before 7 DAA, while was higher than that of cultivar T23 from 21 DAA to 28 DAA.1.8 Effects of irrigation rate on biomass and grain yieldUnder the nitrogen level of N1, biomass and grain yield increased with the increase of irrigation rate until irrigation rate of treatment W2, then declined, Treatment W2 had the highest biomass and grain yield. Cultivar J20 and cultivar T23 had the same trend. At the nitrogen level N0, biomass and grain yield increased with the increase of irrigation rate, but were lower than that of treatment N1.The yield of cultivar T23 was higher than that of cultivar J20 when nitrogen and water were applied, while yield of cultivar T23 was lower than that of cultivar J20 when nitrogen and water were scarcity.2 Effects of irrigation rate and nitrogen application rate on quality and yield and its physiological basis2.1 Effects of irrigation rate on water requirement characteristic and on nitrogen cycle in plant-soil system and on quality and yieldCultivar Jimai 20 (J20), a strong gulten winter wheat cultivar and cultivar Taishan 23 (T23), a middle gluten winter wheat cultivar were used. The experiment was laid out in a split-plot design. Main-plot treatments were irrigation rate, consisting of zero irrigation (W0), irrigation applied after planting and at jointing stage (W2), irrigation applied after planting, at jointing stage and anthesis (W3), irrigation applied after planting, at jointing stage, anthesis and filling stage (14 days after anthesis) (W4), 60mm water used at each stage. Sub-plot treatments were cultivars. Effects of irrigation rate on water requirement rule and on nitrogen cycle in plant-soil system and on quality and yield were studied in this experiment. The principal results were as follows.2.1.1 Effects of irrigation rate on water utilizationThe WCA of treatment W2, which got the highest grain yield, ranged from 423.8mm to 427.3mm. The contribution rate of precipitation to WCA ranged from 29.95% to 30.21%, the contribution rate of irrigation rate to WCA ranged from 28.08% to 28.32%, the contribution rate of soil water rate to WCA ranged from 41.48% to 41.96%. At the base of treatment W2, more irrigation rate decreased the proportion of soil water rate to WCA, so decreased grain yield. The module index of WCA at planting to before winter stage, before winter to jointing stage, jointing stage to anthesis and anthesis to maturity was 17.09%～17.67%, 22.61%～25.33%,13.45%～16.63%,43.08%～44.13%, respectively. The WUE of yield and WUE of population from jointing to maturity of treatment W2 were highest among all the treatments. And treatment W2 also increased the WUE of flag leaf.2.1.2 Effects of irrigation rate on nitrogen balance in soilIrrigation promoted the soil NO₃^--N to move in deeper soil layers. At maturity, soil NO₃^--N content in 80～180cm soil layer increased with the increasing of irrigation rate, and there were soil NO₃^--N accumulation peaks at this layer of treatment W3 and W4. soil NO₃^--N content of treatment W2 was a little higher than that of treatment W0, but did not form obvious accumulation peak in soil. Treatment W2 kept relative nitrogen balance during the growth stage and had the lowest apparent budget of nitrogen. The apparent budget of nitrogen increased with the increasing of irrigation rate. The apparent budget of nitrogen of cultivar J20 was lower than that of cultivar T22.2.1.3 Effects of irrigation rate on kernel qualityTreatment W2 increased protein content, sedimentation volume and dough stability time, while treatments W3 and W4 decreased sedimentation volume and dough stability time. Sedimentation volume and dough stability time of cultivar J20 was distinctly higer and longer than that of cultivar T22.2.1.4 Effects of irrigation rate on grain yieldThe grain yield of both cultivar J20 and T22 increased with the increasing of irrigation rate until the treatment W2, then decreased when excessive irrigation rate. Cultivar J20 got higher yield under no irrigation, while got lower yield than cultivar T22 under irrigation.2.2 Effects of the interaction of irrigation rate and nitrogen application rate on water utilization characteristic and on quality and yieldCultivar Jimai 20 (J20), a strong-gulten winter wheat cultivar was used. The experiment was laid out in a split-plot design. Main-plot treatments were irrigation rate, consisting of zero irrigation (W0), irrigation applied after planting and at jointing stage (W2), irrigation applied after planting, at jointing stage and anthesis (W3), irrigation applied after planting, at jointing stage, anthesis and filling stage (14 days after anthesis) (W4), 60mm water used at each stage. Sub-plot treatments were nitrogen application rate, consisting of 0kg N-hm^-2 (N0), 120kg N·hm^-2 (N1), 210kg N·hm^-2 (N2) and 300kg N·hm^-2 (N3). Effects of the interaction of irrigation rate and nitrogen application rate on water utilization characteristic and on quality and yield. The principal results were as follows.2.2.1 Effects of irrigation rate and nitrogen application rate on water-use efficiency Water-use efficiency of yield of treatment W2 was the highest among the different irrigation treatments. At the irrigation rate level of W2, the WUE of yield increased with the increasing of nitrogen application rate until the treatment N2, and then declined. Treatment W2 increased the WUE of population of the whole growth stage; excessive irrigation rate than treatment W2 decreased the WUE of population. WUE of population increased with the increasing of nitrogen application rate, but there were no significant difference between treatment N2 and treatment N3. Treatment W2 promoted WUE of flag leaf at middle and late grain filling stage. Treatment N2 improved the WUE of flag leaf at middle and late grain filling stage under irrigation applied.2.2.2 Effects of irrigation rate and nitrogen application rate on nitrogen circle in plant-soil systemThe soil NO₃^--N content increased in deeper soil layers with the increasing of irrigation rate, under the nitrogen level of N1 and N2, there was no obvious soil NO₃^--N accumulation peak in deeper soil layers of treatment W2. When nitrogen, rate increased, soil NO₃^--N content in 80～200cm soil layers also increased at maturity.2.2.3 Effects of irrigation rate and nitrogen application rate on carbon metabolism and protein qualityIrrigation increased the GS activity in flag leaf. Treatment W2 increased the EP activity in flag leaf, but treatments W3 and W4 decreased the activity of EP in flag leaf.With the increasing of irrigation rate, the contents of gliadin and its components increased, while contents of HMW-GS and LMW-GS increased until certain irrigation level, and then decreased. Under the nitrogen level of N2 and N3, treatment W2 had the highest HMW-GS and LMW-GS contents. Treatment W1 had the highest HMW-GS and LMW-GS contents under the nitrogen level of N1.With the increasing of nitrogen application rate, the contents of gliadin and its components increased, while contents of HMW-GS and LMW-GS increased until treatment W2, and then decreased.Under nitrogen application, sedimentation volume and dough stability time increased with the increasing of irrigation rate until a certain level, and then decreased. Under the nitrogen level of N1, treatment W3 had the highest sedimentation volume and dough stability time, but under the nitrogen levels of N2 and N3, treatment W2 had the highest value.Sedimentation volume and dough stability time increased with the increasing of nitrogen applicaiotn rate until N2 level, and then decreased. 2.2.4 Effects of irrigation rate and nitrogen application rate on carbon metabolism and protein qualityTreatment W2 increased the photosynthesis rate of flag leaf after anthesis, enhancedΦPSâ…¡of flag leaf at medium and late grain filling stage, and improved Fv/Fm of flag leaf at late grain filling stage. Excessive irrigation rate decreased the photosynthesis rate, andΦPSâ…¡of flag leaf.Treatment N2 increased the photosynthesis rate after antheis and enhancedΦPSâ…¡and Fv/Fm of flag leaf at late grain filling stage. Excessive nitrogen rate decreased the photosynthesis rate,ΦPSâ…¡and Fv/Fm of flag leaf at late grain filling stage.Treatments W0 and W2 enhanced SSS activity in kernel at early and medium grain filling stage. Treatments W3 and W4 enhanced SSS activity at 28 DAA. Irrigation increased the GBSS activity at medium and late grain filing stage.Nitrogen application decreased the activity of SSS at early grain filling stage, while decreased GBSS activity at medium and late grain filling stage, and there was no distinct difference between treatment N2 and treatment N3. The ratio of amylopectin / amylose of treatment W2 was higher than other irrigation treatments. Under different irrigation rate levels, the ratio of amylopectin / amylose increased with the increasing of nitrogen rate until treatment N2, and then decreased.2.2.5 Effects of irrigation rate and nitrogen application rate on grain yieldUnder the nitrogen rate levels of N2 and N3, biomass and grain yield increased with the increasing of irrigation rate firstly, and reached the highest at treatment W2, then declined with excessive irrigation rate. Biomass and grain yield of treatments N2 and N3 were higher than that of treatments N0 and N1. Under the irrigation rate of W2, biomass and grain yield increased with the increasing of nitrogen rate, while decreased after reached the highest at treatment N2.