Effects of Biochar and Phosphorus Fertilizer Combination on the Physiological Growth Characteristics of Alfalfa in Saline-alkali Soil of the Yellow River Delta
This study investigated the combined effects of biochar and phosphorus fertilizer application on the growth and physiological characteristics of alfalfa(Medicago sativa L.)grown in saline-alkali soil from the Yellow River Delta.A two-factor completely randomized design was employed with four biochar application rates(B0:0 g/kg,B5:5 g/kg,B15:15 g/kg,and B25:25 g/kg)and five phosphorus fertilizer rates(P0:0 mg/kg,P5:5 mg/kg,P10:10 mg/kg,P20:20 mg/kg,and P50:50 mg/kg)in a coastal saline soil substrate.Plant growth parameters and physiological indicators(biomass accumulation,osmotic pressure regulating substances,and antioxidant enzyme activity)were measured to assess alfalfa perfor-mance under various treatment combinations.The results showed that under constant biochar application,increasing phosphorus fertilizer rates initially stimulate plant growth and physiological parameters(plant height,stem diameter,root length,root surface area,relative water content of leaves,chlorophyll con-tent,and antioxidant enzyme activity).However,these parameters decreased at higher phosphorus levels.Conversely,leaf proline,soluble sugar,and malondialdehyde contents exhibited an opposite trend.The B15 treatment appeared to be more effective in mitigating the negative effects of saline-alkali stress on alfalfa growth.The combination of biochar and phosphorus fertilizer significantly enhanced both aboveg-round and underground biomass accumulation,especially under B25 treatment.With increased phosphorus fertilization,the effect on alfalfa yield was significantly enhanced.The results of subordination function showed that the comprehensive impact of biochar treatment on alfalfa was in the order:B15>B25>B5>B0.The growth and physiological indices of alfalfa were optimal under the B15P20 treatment,with total biomass increasing by 159.5%relative to the B0P0(control)treatment.In conclusion,a biochar applica-tion of 15 g/kg combined with 20 mg/kg phosphorus fertilizer resulted in the most favorable growth and physiological responses for alfalfa grown in this saline-alkali soil.
AlfalfaBiocharPhosphorus fertilizerGrowth characteristicsPhysiological indicatorsImprovement of saline-alkali land
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