Responses Of Alfalfa Germination And Growth To Saline-sodic Stress And Control Measures

In China,alfalfa is mainly planted in salinized soil.The main salts of saline-sodic soil in the Songnen Plain are NaHCO3 and Na2CO3.Therefore,this paper studied the effects of saline-sodic stress on the growth and physiological indexes of alfalfa,and explored effective control measures to provide support and theoretical basis for improving alfalfa yield and effectively improving saline-sodic soil.This study was conducted on Gongnong No.1 alfalfa tested by the Animal Husbandry Branch of Jilin Provincial Academy of Agricultural Sciences.The research area is based on the soda saline-sodic soil in the Daan Alkali Land Ecological Experimental Station in China.Using non-saline-sodic soil and saline-sodic soil to prepare soils and soil extracts with different pH,and cultivate alfalfa based on the natural components of saline-sodic soil.Combined with Na₂CO₃,NaHCO₃ alkaline salt,the growth of alfalfa seedlings was investigated,and the appropriate saline concentration of seed germination and seedling growth of alfalfa was investigated.Based on this,according to the adaptation of alfalfa to saline-sodic soil in the field,applying organic fertilizer,aluminum sulfate and peat soil to improve saline-sodic soil,and the effects of different improved methods on the improvement of saline-sodic soil and its effects on the growth,physiology and photosynthetic index of alfalfa were studied.The results were as follows:（1）There was no significant difference in germination rate,when the seeds germinate at pH 7.00⁸.56.When the pH reached 9.22（EC=6.60 mS/cm）,the seeds did not germinate.The optimum pH of the alfalfa seeds under the saline-sodic soil extract was between 8.0 and 8.6（EC between 1.0 and 1.5 mS/cm）.（2）With the gradual increase of saline-sodic stress,the proline content,soluble sugar content,and Na⁺/K⁺in the alfalfa plant will gradually increase.Because moderate salinity can promote alfalfa growth,when the pH was 8.57,the proline content,soluble sugar content,and Na⁺/K⁺decreased.Alfalfa is suitable for growth in saline-sodic soil with pH between 8.0 and8.6（EC between 1.0 and 1.5 mS/cm）.When the pH was 8.57,the emergence rate was 54.7%and the survival rate is 64%.However,the emergence rate is much lower than the seed germination rate.（3）With the increase of salt concentration,the proline,soluble sugar,and malondialdehyde in the plant increased.Na2CO3 stress was more harmful to alfalfa seedlings than NaHCO3.The tolerance of Gongnong 1 alfalfa was 60 mmol/L under Na2CO3 stress and80 mmol/L under NaHCO3 stress.（4）The biomass of alfalfa was negatively correlated with soil pH,negatively correlated with EC,and positively correlated with soil nutrient content.Alkaline stress was more harmful than salt stress.（5）Through the application of organic fertilizer,aluminum sulfate,turf soil three kinds of improved methods can effectively reduce l pH,SAR and total alkalinity,so that the soil structure was improved.There is a cubic function relationship between the yield of alfalfa and soil pH.The formula is y=-1672.4+83.3x²-6.45x³（R²=0.582）.Alfalfa are suitable for growth in saline environments in the field between pH 8.0 and 9.0（EC 0.5¹.5 mS/cm）.There is an exponential relationship between total alkalinity and pH,the formula is:y=0.02exp（0.57x）.After comprehensive evaluation of the principal component analysis,the comprehensive improvement effect of organic fertilizer was the best,the highest score was0.81.（6）After applying organic fertilizer on the soil,the biomass of alfalfa was increased by108.9%compared with the control;the plant height increased by 65.8%compared with the control;the plant growth density was 4.09 times of the control;the proline content in the carp was increased by 26.9%compared with the control;the SOD activity was increased by 47.1%compared with the control;POD activity control increased by 47.8%;CAT activity was 3.9 times that of the control;net photosynthetic rate was 18.4%higher than that of the control;stomatal conductance was increased by 67.6%compared to the control;intercellular CO₂ concentration was increased by 14.2%compared to the control;transpiration rate was 36.4%higher than the control;the net photosynthetic rate,intercellular CO₂ concentration,transpiration rate,and SOD activity were significantly positively correlated with the dry matter weight of alfalfa.Through this experiment,in order to promote the growth of alfalfa and improve the effect of saline-sodic soil,the application of organic fertilizer should be an ideal method of improvement.