Root-Zone Irrigation Combined With K Application Improves The Stress Resistance And Yield Of Summer Maize In Saline-Alkali Land

Improving the agricultural production potential of saline-alkali land is of great significance to China’s food security.Reducing ion toxicity and osmotic stress is the key to improving the productivity of saline-alkali land.The non-uniform distribution of soil water by root-zone irrigation can reduce soil salinity,improve the ability to resist osmotic stress and promote the growth for crop.K application could maintain the balance of K⁺and Na⁺,which improves the production potential of crops in saline-alkali land.In the experiment,the advantages of salt resistance,drought resistance and water saving due to root-zone irrigation and K application were integrated.Summer maize Zhengdan 958 was used as the test material,and the field experiment was carried out in Fumin Farm,Deping Town,Linyi County,Dezhou City,Shandong Province,and the pot test under the rain shelter was carried out in the Experimental Station of Shandong Agricultural University.The split plot design was adopted,in which the main plot was irrigation mode（uniform irrigation（CI）,fixed root-zone irrigation（FI）and alternate root-zone irrigation（AI））,the first split plot was irrigation rate（80 mm（W1）and 160 mm（W2））,and the second split plot was K application rate(0（K0）and 120（K1）kg K₂O ha^-1).Soil and plant samples were taken at the key growth stages to study the water and salt transportation in the root zone of summer maize with K application and root-zone irrigation,and to explore the regulation effect of K application combined with root-zone irrigation on the root distribution,root function,water stress signal,photosynthetic efficiency and anti-aging performance of summer maize.With K application combined with root-zone irrigation,the mechanism of the resistance of salt and drought,and increasing yield of summer maize in the system of"soil-roots-above-ground part of crops in saline-alkali land"was clarified in order to improve water and K utilization efficiency and yield.The results were as follows:（1）Compared with CI and FI,AI significantly increased the leaf area index,photosynthetic rate,antioxidant enzyme SOD,POD,CAT activity and proline content of summer maize,and significantly reduced transpiration rate and MDA content at VT and R6.The salinity of CI,AI and FI accumulated in the soil layers of 20-30 cm,30-40cm and 40-50cm,respectively.The total root length of AI was 14.3%and 10.7%higher than CI and FI at R6.The total root surface area,total root volume and total root dry weight of AI were significantly higher than CI at different growth stages.At VT and R6,the biomass of AI was15.8%,7.7%and 5.7%,2.2%higher than CI and FI,respectively.In the field experiment,compared with CI and FI,AI increased biomass by 6.5%,7.2%at VT and 3.4%,3.6%at R6,respectively.The yield increased by 8.8%and 5.1%（field）,and 10.1%and 3.7%（pot）,respectively.（2）Compared with W1,the salt content in different soil layers（A）of W2 in V9,VT and R6 stages decreased by 0.8-18.3%,0.8-14.5%and 0.5-19.3%,respectively.Increasing irrigation rate could reduce soil salinity.Compared with W1,W2 significantly increased leaf area index,root length,root surface area,root volume,root dry weight,photosynthetic rate,fluorescence Fv/Fm ratio and transpiration rate,and decreased proline content,antioxidant enzyme SOD,POD,CAT activities and MDA content.Compared with W1,the 1000-grain weight of W2 increased by 5.1%（field test）and 3.4%（pot test）,and the yield of W2 increased by 5.0%（field test）and 7.5%（pot test）.Compared with W1,W2 decreased irrigation water use efficiency and increased K use efficiency.（3）K application significantly increased the root length,root surface area,root volume and root dry weight of summer maize at different periods,maintained a higher leaf area index,photosynthetic rate,antioxidant activity of SOD,POD,CAT and proline content in the later growth period,increased the fluorescence Fv/Fm ratio and decreased MDA content,which was beneficial to the accumulation of photocontractile compounds in the later growth period.Compared to K0,K1 increased biomass by 5.9%（field）and 4.6%（pot）,and increased yield by 5.1%（field）and 12.8%（pot）.K application can improve irrigation water use efficiency.（4）The leaf area index and root index of AIW2K1 treatment were better than those of other treatments.AIW2K1 increased the soil water content of 0-40 cm in different soil layers,reduced the salt content of 0-40 cm,improved the soil p H,and formed a suitable soil environment for crop root growth.AIW2K1 resulted in the best root indexes,the highest photosynthetic rate,the lower transpiration rate,the highest anti-aging indexes,the higher proline content,and the highest of 1000-grain weight.Compared to other treatments,AIW2K1 increased yield by 6.5-24.5%（field test）,4.4-35.1%（pot test）,and finally promoted irrigation water use efficiency and K use efficiency.In summary,AI combined with K application and an appropriate irrigation rate can promote soil salt reducing in the root zone of summer maize in saline-alkali land,reduce the toxicity of saline-alkali ions,form a suitable soil environment for the root growth,and can cooperate with root growth to improve the salt resistance of summer maize,promote the growth of summer maize above ground in saline-alkali land,increase photosynthetic rate,reduce the water loss by luxury transpiration,improve water use efficiency,improve anti-aging performance,improve photosynthetic assimilation accumulation,promote maize yield increase efficiency,and promote the production performance of summer maize in saline-alkali land.