Effects Of Soil Compaction On Sulfur Metabolism Of Young Apple Tree And Improvement Of Rice Husk Biochar

Soil compaction is one of the environmental stress factors affecting the growth and development of fruit trees,sulfur is an essential nutrient element,and its metabolic transformation is sensitive to environmental stress response.Apple is one of the most widely cultivated fruit trees in the world.Malus hupehensis var.pingyiensis and Malus robusta are common apple rootstocks.In this study,Malus domestica Borkh‘Red Fuji’with Malus hupehensis var.pingyiensis and Malus robusta as rootstock respectively,were used as the material.Analyze the influence of soil compaction on young apple tree growth and sulfur metabolism,and discuss the improvement effect of rice husk biochar on apple tree growth and sulfur metabolism in compact soil.The results that:1.Malus hupehensis var.pingyiensis seedling as test material,the root system of Malus hupehensis var.pingyiensis seedling was the highest at 1.45g·cm^-3 soil bulk density,whether root dry weight,the ratio of root to shoot,root length,root surface area,root tip number and fractal dimension,which indicated that root growth was the best at 1.45g·cm^-3 soil bulk density.When the soil bulk density was 1.65g·cm^-3,not only the soil oxygen concentration remained low,but also the root parameters decreased significantly.When the soil bulk density reached1.65g·cm^-3,not only the root system was in a hypoxic environment,but also the root growth was blocked.Affect the normal growth and development of roots.2.The two-year old potted apple trees,Malus domestica Borkh‘Red Fuji’with Malus hupehensis var.pingyiensis and Malus robusta as rootstock respectively,were used as the material in this experiment.We found no significant effect on leaf net photosynthetic rate,inter cellular CO₂ concentration,transpiration rate,stomatal conductance,relative chlorophyll content or root activity,root dry weight and root length density under moderate compaction conditions,but significantly decreased under severe compaction conditions,whether new slightly longer and thicker,photosynthetic characteristics or root activity,root dry weight and root length density.This indicated that young apple trees had some resistance under moderate compaction conditions,while the growth of young apple trees was severely inhibited under severe compaction conditions.In addition,under severe compaction,the growth index of Malus domestica Borkh‘Red Fuji’/Malus robusta was lower than that of Malus domestica Borkh‘Red Fuji’/Malus hupehensis var.pingyiensis,which indicated that under soil compaction,the growth of Malus domestica Borkh‘Red Fuji’/Malus robusta was better than that of Malus domestica Borkh‘Red Fuji’/Malus hupehensis var.pingyiensis.3.Soil compaction increases the adsorption of water-soluble sulfur by soil colloid and reduces the availability of water-soluble sulfur.The sulfate content,ATPS、OASTL、L/D-CD activity and H₂S content decreased significantly in roots and leaves,indicating that apple Sulfur metabolism was sensitive to soil compaction stress,severe compaction significantly decreased Sulfur metabolism level.The young apple tree with Malus hupehensis var.pingyiensis as rootstock was more susceptible to soil compaction than Malus robusta.4.Under the condition of maintaining similar compaction,rice husk biochar increased the porosity and oxygen concentration of compacted soil,and directly supplemented the soil sulfur source,and increased the sulfate content,ATPS、OASTL、L/D-CD activity and H₂S content of apple roots and leaves in compacted soil,indicating that the application of rice husk biochar enhanced the apple sulfur metabolism level in compacted soil;and not only increased the new slightly length and thicker,leaf net photosynthetic rate,inter cellular CO₂ concentration,transpiration rate,stomatal conductance and chlorophyll relative content of apple shoot in compacted soil,but also enhanced apple root activity,increased root length density,increased root total length,root surface area,root volume,fractal dimension and root tip number in compacted soil,and then promoted root growth.In addition,the promotion effect of Malus domestica Borkh‘Red Fuji’/Malus robusta is the best.