| The northwest dryland of China,light and heat resources are abundant,with much more land for cultivation and much less population than other areas in China.Therefore,dryland agriculture development potential is huge.The poor rainfall disatribution and inefficient rainwater management were the major factors,causing water stress and limiting dryland wheat production.Plastic film mulch plays an important role in water conservation,promoting crop growth and development and increasing grin yield.Wheat is the major source of energy,protein,sulfur,zinc and other tolerance elements in northern China,and nutritional quality of wheat grain is receiving more and more attention.In recent years,many studies reported the mechanism of yield increase under plastic film mulch,few studies focused on the effect of plastic film mulch on grain nutrional quality,especially the critical nutrion concentration.Therefore,it is important to understand the effects of plastic film mulch on grain yield,critical nutrients accumulation and remobilization,and grain nutrients concentration for high-yield and nutritional-quality wheat production.In the 2014-2015 and2015-2016 growing seasons,we carried out field experiments in seven locations of three provinces in Northwest China.To compare the biomass,grain yield,yield components,protein content,protein components content,grain sulfur（S）and zinc（Zn）concentrations,and N,S and Zn uptake and distribution of dryland winter wheat between no mulch and plastic film mulch.The main results were as follows:（1）Plastic film mulch significantly increased dryland wheat grain yield and decreased post-anthesis N remobilization and uptake,consequently reduced the grain protein content.Compared to no mulch,plastic film mulch showed 13.7%increases to grain yield through higher spike number,but decreased grain protein content by 7.8%and especially in the wet year.The N accumulation in stem leaf,ear,and aboveground plant part at anthesis increased by 21.6%,20.3%and 21.2%,respectively,in plastic film mulch than in no mulch;however,the N remobilization amount increased by 16.0%during grain filling period.Under plastic film mulch,the N remobilization efficiency,post-anthesis N uptake and N harvest index decreased by 16.0%,23.7%and 5.7%,respectively.As a result,no significant increase of N accumulation in grain part at maturity.Therefor,grain protein content decreased owing to the increased grain yield.Grain protein content was significantly related to the N application rates（P<0.05）,and the wheat grain protein content was observed to increase more quickly with the N application rates increase under plastic film mulch,compared to no mulch.Accordingly,to make a trade-off between grain yield and its protein content under plastic film mulch,the estimated N application rates were 88-120 kg N ha-1 in a wet year and 173-180 kg N ha-1 in a dry year.（2）Plastic film mulch increased the grain albumin,globulin content and the ratio of gliadin and glutenin.Meanwhile,plastic film mulch also increased the percentage of albumin,globulin and gliadin to total protein of dryland wheat,but decreased the glutenin content and the percentage of glutenin to total protein,and that change is violence against the processing quality.Increased the application of nitrogen can improve the grain albumin,globulin and glutenin content.For plastic film mulch,the average albumin and alobulin content were increased by 11.3%and 30.8%,and the grain gliadin and glutenin content were decreased by3.4%and 15.1%,and thus the ratio of gliadin/glutenin was increased by 15.1%.Meanwhile,the percentage of albumin,globulin and gliadin to total protein were increased by 22.3%,44.2%and 5.5%,respectively.Differently,the percentage of glutenin to total protein was significantly decreased by 7.4%.The responses of albumin and glutenin content to N application rate were consistent with a linear-plateau model,i.e.,grain albumin and glutenin content increased as the N application rate increased to 167 and 100 kg N ha-1,respectively,but then plateaued at higher application rates.There is positively correlation between the grain globulin content and N application rate under plastic film mulch.For 100 kg N ha-1applied,grain globulin content was increased by an average of 0.11%.However,the ratio of gliadin/glutenin was significantly and negatively correlated with N application rate:for every100 kg ha-1increase in N fertilizer,the ratio of gliadin/glutenin decreased by 0.13%for dryland winter wheat under plastic film mulch.（3）Decreased soil available S concentration at anthesis and post-anthesis S uptake are responsible for the grain S concentration decrease under plastic film mulch.It is unfavorable to the synthesis and accumulation of protein in grain and improving the grain quality.Compared with no mulch,the plastic film mulch showed 9.0%decrease of grain S concentration.The S accumulation in stem and leaf,ear,and aboveground plant part at anthesis increased by 19.9%,16.1%and 19.2%,respectively,in plastic film mulch than in no mulch;however,the S remobilization amount and efficiency increased by 36.2%and 17.9%,respectively,during grain filling.Under plastic film mulch,soil available S at anthesis stage decreased by 24.5%,and the S uptake during grain filling greatly declined by 77.9%.As a result,no significant increases of S accumulation in plant aboveground part at maturity and S harvest index.The grain S concentration decreased owing to the increased grain yield.Under plastic film mulch,the response of grain S concentration to N appliacation was consistent with a linear-plateau model.（4）Plastic film mulch decreased the grain Zn concentration,but increased the molar ratio of P/Zn,consequently decreased the grain Zn bioavailability and the Zn nutritional quality.Compared with no mulch,plastic film mulch decreased the grain Zn concentration by 15.3%.The Zn accumulation in stem and leaf,ear,and aboveground plant part at anthesis increased by 12.1%,18.3%and 14.1%,respectively,in plastic film mulch than in no mulch;however,the Zn remobilization amount increased by 14.2%during grain filling.Under plastic film mulch,Zn uptake during grain filling stage decreased by 28.7%,and the Zn harvest index declined by 4.3%.As a result,no significant increases of Zn accumulation in aboveground plant part at maturity.The grain Zn concentration decreased owing to the increased grain yield.Meanwhile,plastic film mulch increased the molar ratio of P/Zn by 26.2%,decreased the grain Zn bioavailability.Under plastic film mulch,grain Zn concentration and aboveground plant part Zn accumulation are positively correlated with N application rates（linear and linear plus plateau model）,for every 100 kg N ha-1 increase in N fertilizer,the grain Zn concentration increased by 2.3 mg kg-1.There is positively correlation between grain Zn concentration and grain N concentration,each increase grain N concentration 1 g kg-1 leads to by 1.7 mg kg-1 of increase Zn concentration in grain.Furthermore,Increasing the N application rate can reduce the molar ratio of P/Zn,and improve the grain Zn bioavailability.In conclusion,plastic film mulch increased the dryland wheat grain yield,but the grain nutrient uptake showed no difference between the plastic film mulch and no mulch.The grain nutrient elelment concentration decreased owing to the increased grain yield.Therefore,precise N fertilizer management and additional medium and micro fertilizer should be applied for improving wheat grain nutritional and processing quality in northwest dryland of China. |
PDF Full Text Request