Effect Of Organic Fertilizer Application At Different Times On Soil Physicochemical Properties And Fruit Quality In ’Harum’ Citrus Orchards

In this experiment,organic fertilizer was applied to 5-year-old’Harum’citrus for two consecutive years in 2021 and 2022,respectively,after fruit harvesting in spring（January15）and in autumn（September 15）.By studying the effects of organic fertilizer application in different periods on soil physical and chemical properties,spring and autumn characteristics,leaf nutrient status,fruit yield and quality,the effects of organic fertilizer application on orchard soil properties and citrus growth were clarified,and the best period of organic fertilizer application in the growth of citrus was determined,so as to effectively improve orchard soil quality,fruit yield and quality.The results of the study are as follows.The results of the study are as follows:（1）At the same organic fertilizer application rate,soil p H and organic matter content increased significantly in the fall fertilizer treatment compared to the spring fertilizer treatment;the highest soil organic matter content was 36.78 g.kg^-1.at 15 kg/plant fertilizer application in the fall.Soil nutrients such as fast-acting phosphorus,fast-acting potassium,and alkaline decomposition nitrogen were increased with the increase of organic fertilizer application under the same fertilization period.（2）With the same amount of organic fertilizer application,the leaf area,length,number of tresses,stem thickness,and number of nodes of spring and autumn tresses of’Harum’citrus were significantly higher than those of spring fertilizer treatment.The maximum number of shoots was 370.23,This indicates that the application of organic fertilizer in autumn is beneficial to promote flower bud differentiation in’Harum’.（3）Fruit yield was significantly higher under the fall fertilizer treatment than the spring fertilizer treatment,and the control group had the lowest fruit yield.The highest yield of 23.56 kg/plant was obtained with 15 kg/plant fertilizer treatment in autumn.Under the same fertilization period,the organic fertilizer application rate had no significant effect on the fruit ripening stage of’Spring See’,and had a significant effect on the increase of fruit weight per plant at the ripening stage of’Harum’.（4）Both the application period and the application rate of organic fertilizer had significant effects on the appearance quality of’Harum’,such as single fruit weight,longitudinal and transverse fruit diameter,and fruit shape index,among which the highest fruit shape index was 0.92 under the treatment of 15 kg/plant in autumn.The soluble solids,total sugar,vitamin C content,solid to acid ratio,juice yield and edibility rate of’Spring See’were all significantly higher than those of spring fertilized and control treatments without organic fertilizer.The total acid,citric acid and malic acid contents were significantly lower than those of the spring fertilization and control treatments,and tended to increase and then decrease with the increase of organic fertilization during the same fertilization period.In conclusion,the application of organic fertilizer in autumn could better enhance soil nutrients and improve the yield and quality of’Harum’.The organic fertilizer application period and application rate both had significant effects on citrus fruit appearance indices such as single fruit weight,longitudinal diameter,transverse diameter,fruit shape index and intrinsic quality such as soluble solids,total sugar,VC content,sugar-acid ratio,sucrose,glucose,fructose and total sugar.In conclusion,the best time to apply organic fertilizer to’Harum’citrus is autumn.