Effects Of Rice Husk Biochar On The Environment Of Brown Soil,the Physiological Function And Growth Potential Of Young Apple Trees

To provide scientific basis for improving the soil in the orchard using rice husk biochar,a pot experiment of rice husk biochar applied on the physical and chemical properties of brown soil and the growth of one year old apple tree(cv.Purple Fuji)was carried out in the horticulture experimental station of Shandong Agricultural University during 2015-2016.The experiment consisted of nine treatments,1%(T1),2%(T2),3%(T3),4%(T4),5%(T5),6%(T6),7%(T7 has),8%(T8),0(CK)rice husk biochar was applied,respectively,accounting for total dry soil weight.The main results are as follows:1.Appropriate rice husk biochar applied could improve brown soil physiochemical properties and nutrient status.Rice husk biochar was applied to decrease the bulk density and increase the soil porosity.With the increase of rice husk biochar applied,bulk density decreased and soil porosity increased.These fitting relationships can be expressed as:y=-2.8063x+1.4004(R2=0.4396)and y=105.9x+47.155(R2=0.4396),repectively.Soil pH,cation exchange capacity and water-soluble Ca2+ content increased when rice husk biochar amount increased to 6%,4% and 5%,respectively,and then declined as rice husk biochar amount increased.These fitting relationships can be expressed as:y=-212.7x2+21.583x+6.2751(R2=0.7299)and y=-3399.1x2+329.71 x +18.696(R2=0.6871),repectively.Water-soluble K+ content in the soil linearly increased with the increase of rice husk biochar applied,and this relationship can be expressed as: y=289.58x+20.667(R2=0.6898).Total carbon,organic carbon and available potassium in the brown soil linearly increased with the increase of rice husk biochar applied,and these relationships could be expressed as:y=27.93x+1.6487(R2=0.8069),y=31.903x+1.0474(R2=0.9081),y=1669.4x+248.59(R2=0.5451),respectively.Rice husk biochar was supplied to the brown soil,which significantly increase the available phosphorus content at low amounts applied(?2%)and nitrate nitrogen content athigh amounts applied(?6%),respectively.Meanwhile,appropriate rice husk biochar was applied to improve the alkali hydrolyzable nitrogen and exchangeable calcium content.2.Appropriate rice husk biochar applied could improve physiological function of young apple trees.The root activity,net photosynthetic rate,stomatal conductance,chlorophyll contents of young apple trees increased when rice husk biochar amount increased to 4% and then declined as rice husk biochar amount increased.The relationships between root activity and net photosynthetic rate with rice husk biochar amounts were expressed as:y=-6839.7x2+521.89x+12.175(R2=0.3794),y=-1694.5x2+115.42x+12.768(R2=0.4525),repectively.Rice husk biochar was supplied to the brown soil,which significantly improve the transpiration rate at low and medium amounts applied(2%-6%)and maximal photochemical efficiency at medium and high amounts applied(3%-8%),respectively.The activities of antioxidant enzymes(SOD,POD,CAT)in the root and leaf with young apple trees was increased by applying appropriate rice husk biochar.With the increase of rice husk biochar applied,SOD activity of leaves and roots and CAT activity of leaves increased first and then decreased.SOD activity of leaves and roots was highest when 7% rice husk biochar was applied,and CAT activity of leaves was highest when 5% rice husk biochar was applied.POD activity of leaves and roots and CAT activity of roots was significantly increased when 2%-5% rice husk biochar was applied.POD activity of roots and leave was highest when 4% rice husk biochar was applied,and CAT activity of roots was highest when4% and 7% rice husk biochar applied.The soluble sugar and protein content in the root,phosphorus and potassium content in the leaf with young apple trees was increased by applying appropriate rice husk biochar.The soluble sugar and protein content in the root and potassium content in the leaf increased when rice husk biochar amount increased to 6%,4% and 6%,respectively,and then declined as rice husk biochar amount increased,the root phosphorus content in the leaf was highest when 8%rice husk biochar was applied.Root starch content and leaf nitrogen content was increased to the highest level when 1% and 3% rice husk biochar was applied,respectively.Therefore,4% rice husk biochar applied was better for the physiological function of young apple trees based on the physiological,biochemical and nutrition indexes of young apple trees.3.Appropriate rice husk biochar applied can increase the biomass of young apple trees.Rice husk biochar applied was conducive to increase the number of root tips,The number of root tips with 3%-6% rice husk biochar applied was significantly higher than CK,and was highest with 6% rice husk biochar applied.The total root length,root surface area,root weight,total shoot length,stem weight,leaf weight,specific leaf weight and leaf area was improved when appropriate rice husk biochar was applied to pot young apple trees.The total root length,root weight,total shoot length,stem weight,leaf weight and leaf area were highest when 4%rice husk biochar was applied,while root surface area and specific leaf weight was highest with 3% and 2% rice husk biochar applied,respectively.The root volume was increased to the highest level when 8% rice husk biochar was applied,which was significantly higher than CK.Therefore,4% rice husk biochar applied was best for improving the biomass of young apple trees.In conclusion,4% rice husk biochar,that is,about 9.00 kg/m2,applied with surface broadcasting and deep plowing to the brown soil was best for the growth of young apple trees.