Effects Of Applying Chloride-containing Fertilizers On Yield And Quality Of Citrus And Soil Chloride Content

In our study,the chloride-containing fertilizers application effects on yield,quality,mineral nutrients uptake and Cl~- residues in citrus were studied by using two citrus cultivars(Citrus sinensis Osbeck and Citrus unshiu Marc.).The aim was to provide theoretical basis for the rational application of chlorine fertilizer in citrus.The main findings are as follows:(1)The yield of citrus showed an increasing tendency with the application of chloride-containing fertilizers.The total potassium chloride treatment(T3)yield was more than that of potassium sulfate treatment(T1),and the yield of newhall navel orange and Satsuma mandarin was increased by 22.3% and 21.1% respectively.Potassium chloride plus calcium chloride treatment(KCl+Ca Cl2),the yield of newhall navel orange increased with potassium sulfate treatment(T1),and the yield of mandarin oranges increased by potassium sulfate treatment(T1)significantly.(2)Indexes,including the soluble solid,vitamin C,juice yield and single fruit weight of newhall navel orange and Satsuma mandarin fruit,were improved with chloride-containing fertilizers application.However,peel thickness,fruit weight,longitudinal and transverse warp,peel color was slightly influenced.Fruit soluble solids,the titratable acid,solid acid ratio,vitamin C,juice yield and aspect ratio index with total Potassium chloride treatment(T3)were better than that of potassium sulfate treatment(T1).Moreover,in 2017,compared with potassium sulfate treatment(T1),vitamin C content of Newhall navel orange and Satsuma mandarin were increased by 11.38% and 9.51%,respectively,while the soluble solids of Satsuma mandarin increased by 13.94% significantly with total potassium chloride treatment(T3).(3)The content of Cl~- in leaves can be significantly improved by applying chloride-containing fertilizers in Newhall navel orange and Satsuma mandarin,which has less influence on the content of Cl~- in Pulp and peel.The content of Cl~- in leaves was significantly correlated with the level of chlorine,and the content of Cl~- in leaves of Satsuma mandarin and Newhall Navel Orange remained at a lack level(0.2%)after two years of chloride-containing fertilizers application.According to the increasing speed of Cl~- content in leaves,apply potassium chloride,the content of Cl~- in leaves could not reach to a toxic level(0.7%)on the whole economic life of citrus.(4)The content of Cl~- in the soil is dynamic under the influence of precipitation,fertilization and other factors.Apply chlorine fertilizer in a certain time(June and September)can improve the content of Cl~- in the soil significantly.With the increase of precipitation and absorption of citrus,the effect of chloride-containing fertilizer on soil Cl~- content is getting smaller and smaller,the content of Cl~- in soil drops to a lower level at the end of Citrus growth(December).With the deepening of soil profile,the Cl~- content of each treated soil showed an increasing trend,that was due to the migration of Cl~- in soil to downward layer with water.An increase of residual Cl~- in the soil was found with the application of chloride-containing fertilizers,Soil Clresidues do not increase with years of chlorine fertilizer application,Chlorine fertilizer can be applied in the range of chlorine levels in the test settings.(5)The chloride-containing fertilizers application can significantly improve nitrogen content in Newhall navel orange and Satsuma mandarin leaves,and have less effect on N,P,K content in Pulp,Peel and P,K in leaves.Potassium chloride gradually replaced potassium sulfate,Ca content of fruit pulp and peel in Newhall navel orange and Satsuma mandarin increased.The content of Ca in Pulp and Peel is significantly higher in supplemented Calcium chloride treatment than that of potassium sulfate treatment(2017).With the increase of chlorine level,the Ca content in leaves of Citrus increased while newhall navel orange decreased firstly and then increased,it was possible that Cl could promote the transfer of Ca from Newhall navel orange leaves to fruits.In summary,chlorine level set by the test,can increase the yield of Newhall navel orange and Satsuma mandarin and also improves the quality,at the same time,on the other hand,it can increase the content of N and Ca in the leaves while the Ca content in pulp and peel.The content of Cl~- in soil and leaves would increase,but that was lower than the critical level of citrus poisoning by chlorine.Therefore,chlorine-containing fertilizers can be applied to Satsuma mandarin and Newhall navel orange.