Effects Of Calcium And Oxygen Supplementation On Microorganisms And Nutrient Absorption In Apple Rhizosphere And Production Performance Of Big Trees

Calcium is the main element affecting fruit quality.Due to the long-term excessive application of nitrogen,phosphorus and potassium fertilizer,the imbalance of soil nutrients and the prevalence of calcium deficiency in trees and fruits;Root system is the main organ of calcium absorption.Poor soil ventilation in root zone leads to insufficient O₂ supply in root zone and strong anaerobic respiration of root system,which not only affects the growth and development of root system,but also reduces the nutrient absorption capacity of root system,which in turn further aggravates the symptoms of calcium deficiency.In this study,calcium oxide and calcium peroxide were used to treat Fuji apple young trees grafted with Malus hupehensis and Malus robusta,and calcium oxide and calcium peroxide were applied respectively,through normal soil,calcium deficient soil and applying calcium oxide and calcium peroxide respectively under normal soil and calcium deficient soil,the effects of calcium supplementation and oxygen on Apple rhizosphere microorganisms,root nutrient absorption and tree production performance were explored,the results show that:1.Among rhizosphere soil bacteria,actinomycetes and Proteobacteria have the highest relative abundance,which are 37.83%-61.95%and 19.53%-40.24%respectively,followed by Curvularia（6.64%-13.97%）and acidobacteria（3.74%-10.38%）.At the bacterial genus level,Subgroup-6,KD4-96,Streptomyces and actinomycetes account for the largest proportion.Calcium peroxide treatment had the best effect on increasing the relative abundance of actinomycetes in the rhizosphere of Malus hupehensis under normal soil conditions,and had the best effect on increasing the abundance of actinomycetes in the rhizosphere of Malus robusta under calcium deficient soil.Chao1 index showed that calcium oxide and calcium peroxide treatment could improve the richness of rhizosphere bacterial community under normal soil and reduce the richness of rhizosphere bacteria in calcium deficient soil.Chao1 index and Simpson index of calcium deficient soil treatment were significantly higher than those of normal soil treatment;Simpson index showed that calcium oxide and calcium peroxide treatment improved the rhizosphere bacterial diversity of normal soil and calcium deficient soil,and the effect of calcium peroxide treatment was better.The results of differential bacteria analysis showed that calcium oxide and calcium peroxide treatment increased the abundance of dominant bacteria（Proteobacteria,Acidobacteria and Bacteroidea）in Malus hupehensis rhizosphere soil,and calcium peroxide had a significant effect on improving Proteobacteria and Bacteroidea of Malus robusta under calcium deficient soil.2.The proportion of Ascomycota（58.42%-91.55%）was the highest at the level of rhizosphere soil fungal community,followed by Basidiomycota（2.75%-33.74%）;Compared with calcium oxide,calcium peroxide significantly increased the abundance of Basidiomycota,decreased the relative abundance of Ascomycota and significantly increased the abundance of Fusarium in the rhizosphere of Malus hupehensis and Malus robusta under calcium deficiency soil;Calcium oxide and calcium peroxide treatment reduced the abundance of Pseudomonas in the rhizosphere of Malus hupehensis and increased the abundance of Pseudomonas in the rhizosphere of Malus robusta,but there was no significant difference between calcium oxide and calcium peroxide treatment.The Chao1 index and Shannon index of rhizosphere fungi in Malus hupehensis and Malus robusta chinensis were higher than those in calcium deficient soil.The richness and diversity of rhizosphere Fungi Community in Malus hupehensis under calcium deficiency soil were the highest under calcium peroxide treatment;The richness and diversity of rhizosphere fungal community in the two soils were the highest in calcium oxide treatment.The results of flora difference showed that calcium oxide and calcium peroxide treatment significantly increased the abundance of rhizosphere Ascomycota,Olpidiomycota and Mucoromycota in normal soil,and Basidiomycota in calcium deficient soil;Calcium peroxide can increase the abundance of Ascomycota in the rhizosphere of Malus angustifolia under normal soil,reduce the abundance of Basidiomycota,reduce the abundance of Ascomycota in Malus angustifolia under calcium deficient soil,and improve the abundance of Basidiomycota.The effect is better than calcium oxide treatment.3.Calcium oxide and calcium peroxide treatments significantly increased the contents of nitrate nitrogen,available phosphorus,available potassium,exchangeable calcium,exchangeable magnesium,available zinc and available copper in the root zone of young apple trees;Increase the content of total nitrogen,total phosphorus,total potassium,total calcium,total magnesium and total zinc in roots,and reduce the content of total iron in roots of young trees;The increase of soil and root nutrient content in the root zone of calcium deficient soil was higher than that of normal soil,and the effect of calcium peroxide treatment was better than that of calcium oxide treatment.4.After calcium oxide treatment and calcium peroxide treatment,the contents of nitrate nitrogen,available phosphorus,available potassium,exchangeable calcium,exchangeable magnesium,available zinc,iron and copper in 0-20 cm and 20-40 cm soil layers of orchard trees were higher than those in the control,and the nutrient content in the root zone of calcium peroxide treatment was higher,and the contents of total nitrogen,total potassium,total calcium,total magnesium,total iron and total zinc in roots were higher,and the effect of calcium peroxide treatment was better.5.After calcium oxide and calcium peroxide treatment,the root shoot ratio and root activity of young apple trees and big apple trees increased,and the growth of new shoots increased,and the effect of calcium peroxide was better than that of calcium oxide;After treatment,the leaf chlorophyll content of apple tree increased,the net photosynthetic rate increased,the fruit hardness,soluble solid content,fruit calcium and magnesium content increased,the fruit acidity decreased,and the effect of calcium peroxide treatment was better than that of calcium oxide.In conclusion,the richness and diversity of rhizosphere bacterial and fungal communities in normal soil and calcium deficient soil can be changed by applying calcium oxide and calcium peroxide.Among them,calcium peroxide has the best effect on increasing the dominant rhizosphere flora of Malus robusta octagonum in calcium deficient soil,and calcium oxide and calcium peroxide have a better effect on improving the rhizosphere flora of Malus hupehensis in normal soil;Calcium oxide and calcium peroxide treatment can also significantly increase the effective nutrient content of Rhizosphere Soil and roots,improve photosynthetic performance and improve fruit quality,and the effect of calcium peroxide is better than that of calcium oxide.