Changes Of CO₂ And O₂ Concentration In Orchard Soil And Biological Effect Of Oxygenation In Apple Root Zone

“Gas”is one of the four major factors of soil fertility.However,due to the particularity of“gas”and the limitation of research methods,research progress of soil gas is far inferior to the other three factors.In the present study,soil gas of apple root zone was used to investigate changes of concentration of O₂ and CO₂ in orchard soil.Effect of oxygen control in root zone on Malus hupehensis（Pamp.）Rehd.var.pinyiensis Jiang seedlings was analyzed and a compound oxygen fertilizer which is capable of releasing O₂ was developed.Moreover,effect of aerobic measures,such as chemical aeration and ventilation by drilled holes on gas exchange in root zone,characters of apple root system,plant growth,yield and quality of apple was discussed under pot cultural and orchard conditions.Experimental results showed that:1.During experimental period of a year,the highest concentration of O₂ and CO₂ at the depth of 20 cm,40 cm and 60 cm under the ground appeared in August and September.During experimental period of a day,concentrations of O₂ and CO₂ at the depth of 20 cm under the ground changed with temperature and humidity and peaked at 14:00-16:00.2.O₂ concentration in root zone was significantly changed by calcium peroxide and reductive iron powder.When the O₂ concentration in root zone changed from 17.47%-19.35%in control group to 21.24%-22.47%,the total root length,root tip number,root surface area,number of root branching,fractal dimension,root activity,dry matter accumulation,and root/shoot ratio significantly increased.When the O₂ concentration in root zone fell to15.91%-17.08%,number of root branching,fractal dimension and root activity decreased significantly while there was no significantly change in dry matter accumulation and root/shoot ratio.When the O₂ concentration in root zone fell to 14.03%-15.37%,all the indicators decreased significantly except for dry matter accumulation and root/shoot ratio.When the O₂concentration in root zone fell to 10.51%-11.95%,almost all the seedlings died within 7 days.Roots are more sensitive to O₂ concentration changes in root zone than the shoots.3.Applying appropriate amounts of hydrogen peroxide and calcium peroxide in root zone can increase the oxygen concentration in soil.Injecting 10 mL 0.5%hydrogen peroxide solution into the soil of each seedling and applying 4 g calcium peroxide per plant significantly promoted the growth of apple seedlings and young apple trees.Hydrogen peroxide and calcium peroxide promoted the growth of root more significantly than shoot,and significantly increased the root/shoot ratio.4.A new type of fertilizer-compound oxygen fertilizer was developed.The fertilizer will split and release O₂ when soaked in water.The O₂ layer formed in the splitting process can continuously release O₂.After the O₂ is released,a porous structure can be formed.The process of releasing O₂ was slow and can last for about 15 days.After applying compound oxygen fertilizer tablets equivalent to 4 g of calcium peroxide to each young apple tree,the development of root system and the growth of plant were significantly promoted,and root activity and root/shoot ratio increased significantly.5.By drilled holes and drilled holes inserted corn stalks and apple branches during the fruiting stage of apple trees,concentrations of O₂ and CO₂ at the depth of 20 cm,40 cm and60 cm below the surface significantly reduced;Gas exchange in every layer of soil especially middle and lower layers was promoted;Specific root length,root length density,root weight density and root activity were increased;Extension of roots into deep soil was accelerated;Quantity and quality of apple were improved.The overall effects of the treatments were in the following descending order:drilled holes and drilled holes inserted corn straws,drilled holes and drilled holes inserted apple tree branches,drilled holes and backfilled and non-drilling control.