Study On The Physiological Mechanism Of Waxy Corn With Water Saving And High Yield Under Different Planting Methods And Irrigation Systems

As the contradiction between food demand and water shortage becomes increasingly prominent,it is imperative to explore more scientific and reasonable field management methods.The ridge-furrow mulching system with complete plastic film（RFMS）integrates the advantages of multiple technologies such as micro-collection,water storage,and plastic film covering（such as steam suppression,temperature increase,and moisture preservation,etc.）in the same mode,improving the spatial and temporal consistency of crop water demand and soil water supply,which could be widely promoted in northern dry farming areas.The combination of supplementary irrigation with insufficient irrigation method is conducive to promote the growth of maize and improve the utilization rate of water resources.Based on this,taking Jinnuo 41 as the research object,a two-year plot field experiment was conducted at a site in Dongyang Experimental Demonstration Base,Yuci,Jinzhong,Shanxi from 2018 to 2019.The field experiments were conducted with six treatments,randomized blocks design.Three planting modes were set（CK:conventional planting in bare land;RF:ridge-furrow mulching system with complete plastic film,narrow ridge with 40 cm width and 15 cm height,wide ridge with 70 cm width and 10 cm height;RFE:ridge-furrow mulching system with complete plastic film,equal ridge with 55 cm width and 15cm height）;meanwhile,according to the key water demand period of Jinnuo 41,two irrigation schedules were set(I₀:sowing time（75%-85%）₁),seedling stage to prophase of jointing（65%-75%）₁),anaphase of jointing to booting stage（70%-80%）₁),booting stage to flowering stage（70%-80%）₁)),and I₁(sowing time（75%-85%）₁),anaphase of jointing to booting stage（70%-80%）₁)).The research methods combined field experiment,theoretical analysis and model simulation were adopted to study the water-saving and high-yield mechanism of waxy maize under different planting methods and irrigation strategies.The main research contents and conclusions were as follows:（1）The effects of different planting methods and irrigation strategies on soil moisture and heat in waxy maize growth period were determined.The results showed that the stability of soil temperature and soil moisture content was higher under the total film mulching,and decreased with the advance of growth period and the increase of soil depth.The effect of different planting methods on soil moisture and heat preservation was in the order of RF>RFE>CK,and the stability of soil temperature at I₀ level was slightly higher.The MRE of the soil moisture and heat coupling simulation based on HYDRUS-2D was less than7.03%,hence the simulation effect was good.The film hole infiltration formed a wet sphere near the depth of 20cm,while the furrow irrigation formed a wet front inward and downward infiltration.With the infiltration of water during rainfall or irrigation,soil temperature showed a similar change zone with the infiltration of water,showing an obvious water-heat coupling process.（2）The water consumption law of waxy corn under different planting methods and irrigation strategies was explained,and the water-saving mechanism of waxy corn was revealed.Combined with the double crop coefficient method and water balance equation,the evapotranspiration calculation model of waxy corn under whole plastic-film mulching on double ridges was established considering the compensation effect of ground accumulated temperature on air accumulated temperature and film hole evaporation under the condition of that.The NRMSE between simulated and measured soil water storage in two years was less than 8.26%,indicating a good simulation effect.The results showed that the water consumption of waxy corn was 199.9-335.94mm,compared with CK,RF and RFE significantly reduced soil evaporation by more than 90%,increased crop transpiration by 11.75%-60.05%,and significantly reduced the total water consumption by 25.14%-35.30%;there was little difference between different furrow settings,RF could slightly increase the transpiration rate and T/ET by 1.5-3%compared with RFE;I₀ increased Kc by 2.18%-20.1%compared with I₁,and increased total water consumption;（3）The response mechanism of waxy maize leaf defense system to soil moisture and heat under different planting methods and irrigation strategies was revealed.The results showed that there was a positive correlation between leaf antioxidant enzymes and soil temperature.The activity of antioxidant enzymes was as follows:plastic film mulching>open field cultivation,I₁>I₀,and there was no significant difference between RF and RFE.Malondialdehyde accumulation in leaves showed as follows:film mulching<open field cultivation and I₁>I₀.When there was no water stress or the days of mild water stress were less than 3 days,the soil hydrothermal condition increased the activity of antioxidant enzymes and reduced the accumulation of malondialdehyde in leaves,while the expression of antioxidant enzymes in leaves was induced and the activity of that was increased when there was mild water stress.（4）The internal mechanism of high yield of waxy maize under different planting methods and irrigation strategies was expounded from the perspective of source-sink theory.The results showed that the population structure,leaf chlorophyll content and population growth rate from superior to inferior in each treatment were RF>RFE>CK,I₀>I₁,while the leaf area index and photosynthetic potential from large to small were RFE>RF>CK,I₀>I₁;mulching with plastic film and increasing irrigation could effectively increase the dry matter accumulation of waxy maize from jointing to maturity,I₀ increased the dry matter weight at maturity by 1.8%-6.7%compared with I₁;there were no significant differences in ear length,ear diameter and grain number per ear among different treatments,the100-grain dry weight of RF and RFE increased by 18.1%-56.32%and 9.30%-61.15%compared with CK,and the 100-grain dry weight of I₀increased by1.36%-5.41%compared with that of I₁;the ratio of grain weight to leaf in each treatment from large to small was RF>RFE>CK.RF increased ventilation and lighting,improved the growth population structure of waxy maize,and its grain weight to leaf ratio was the highest,the leaf area index was relatively suitable in silking stage,hence the source-sink relationship in RF was the most harmonious among the three planting modes.（5）The yield,quality and water use efficiency of waxy maize under different planting methods and irrigation strategies were compared and analyzed,and the optimal scheme was selected by entropy weight TOPSIS comprehensive evaluation method.The results showed that plastic film mulching could significantly reduce water consumption,increase fresh ear yield,grain yield and water use efficiency of waxy corn;I₀ increased fresh ear yield and grain yield compared with I₁;film mulching increased the yield of waxy corn,but decreased the content of crude protein and soluble sugar in waxy corn grains to a certain extent.Based on this,the comprehensive evaluation method of entropy weight TOPSIS was used to evaluate different waxy corn cultivation and management programs,the suitable local planting mode of waxy corn was selected as RF（ridge-furrow mulching system with complete plastic film,narrow ridge with 40cm width and 15 cm height,wide ridge with 70 cm width and 10 cm height）;the selection of irrigation strategy should be based on hydrological year type,and I₁irrigation strategy should be selected in plain years（that is,the soil moisture content at sowing stage,late jointing stage and booting stage should be 75%-85%of field water capacity）,while in excessive drought year,the I₀ irrigation strategy should be selected（that is,the soil moisture content of sowing stage,seedling stage to early jointing stage,late jointing stage to booting stage and booting stage to flowering stage should be 75%-85%,65%-75%,70%-80%and 70%-80%of the field water capacity,respectively）,however,when the irrigation water source is insufficient,or in areas with limited irrigation conditions,I₁ irrigation strategy could still be selected and relatively better comprehensive results can be achieved.