Effects Of Biochar And Polyacrylamide On Sunflower Growth In Salinized Soil

China is one of the countries most seriously affected by soil salinization.The area of saline-sodic soil accounts for approximately 10.3%of the country's land area.The salinization of large areas of land has already endangered the effective and normal use of cultivated land.The serious reduction and lack of cultivated resources led to the reduction of agricultural production and the decrease of farmers'income,and a series of severe problems occurred.It makes people realize that it is urgent to remediate and reuse saline-sodic soil.Numerous studies have shown that the biochar and polyacrylamide as soil amendments,At present,there are many researches on the applications of amendments in the remediation of saline-alkali soil at home and abroad,but the research results concentrate on the changes of soil nutrients,physical structure and salinity,and the study on the effects on the growth,physiological and biochemical characteristics and uptake of plants cultivated on the improved soil is less and still a gap.In this research,the greenhouse pot experiment was used to study the effects of individual and combined application of biochar and polyacrylamide on soil pH,soil EC and soil aggregate size distribution by simulating saline soil with different levels(0,0.8,1.6 and 2.4 g·kg^-1).Furthermore,the biomass,plant height,stem coarse,mineral nutrient uptake,C:N:P stoichiometric ratio,Na⁺uptake,salt ion balance and physiological and biochemical characteristics of sunflower were studied simultaneously.The results impled that the soil EC after plant harvest was increased significantly by from 71.59?s·cm^-11 to 822.08?s·cm^-11 with the increase of salt concentration,and the shoot,root and total dry weight of sunflower were significantly decreased by 11.34-45.93%,9.68-70.97%and 10.98-51.03%,and the shoot and root Na⁺concentration of sunflower was increased significantly by162.79-819.53%and 96.55-263.72%,respectively.The root P and K concentrations were decreased by 10.81-62.82%.The shoot and root K⁺:Na⁺,Ca²⁺:Na⁺and P:Na⁺of sunflower were significantly decreased by 61.04-98.88%and 58.42-93.36%,respectively.With the single and mixed application of biochar,the soil p H and EC significantly were decreased 4.65-7.00%and 7.46-20.90%respectively,and the particle size?over 0.25 mm?distribution of soil aggregate was increased by 31.87%under NaCl concentration was 1.6 g·kg^–1,the sunflower biomass and plant height were significantly increased by 14.63-70.73%and 10.53-35.05%,P and K uptake of sunflower were increased by 67.80-264.52%,and 33.54-180.72%,the shoot Na⁺concentration was significantly decreased by 35.46-65.03%,C:N of sunflowers were significantly increased by 20.88-46.93%,C:P and N:P were significantly decreased41.32-77.71%and 35.73-82.99%,respectively.On the whole,shoot and root K⁺:Na⁺and P:Na⁺of the sunflowe were increased by 25.00-687.50%.With the increase of soil salt concentration,the content of soluble protein in sunflower leaves was increased by 1.49-67.12%under the salt concentration below 2.4 g·kg^–1,the content of the sunflower Proline?PRO?was decreased by 81.78-91.86%,under salt concentration was 2.4 g·kg^–1,The photosynthetic rate,transpiration rate,stomatal conductance of sunflower leaves were increased by 128.67%,206.76%and 203.31%with only biochar.It was preliminarily proved that the application of biochar could effectively reduce the degree of soil salinization and promote sunflower growth,by improving the nutritional status of sunflower and regulating ionic balance in plants,the salt tolerance of plantswas increased.However,there was no significant effect of polyacrylamide on soil salinization and plant growth in the condition of this experiment.Based on the study of the effect of biochar and polyacrylamide on the growth of sunflower in salinized soil,the further study will be systematically concentrated on the molecular level mechanisms and factors of the amendments on increasing salt tolerance in sunflower,which may provide the theoretical basis and basic data for better application the amendments in the remediation and reuse of salinized soil.