The Effects Of Three Kinds Of Calcium Fertilizations On Cracked Fruit And Quality Of Citurs Gonggan

Gonggan（Citrus reticulata blanco var.Gonggan）is one of excellent traditional citrus variety planted in China,which is widely welcomed by the people,and its high economic value is also favored by the fruit farmers.However,cracking of the fruits of citrus Gonggan is one of the serious problems in the orchard of citrus since it causes loss of the fruit market value.Calcium is an essential nutrient element for the growth and development of citrus,and is directly involved in the structure and composition of cell wall.The content of calcium in fruit often determines the hardness and flexibility of fruit pericarp,and also plays an important role on the quality and flavor of fruit.In this study,four representative citrus Gonggan orchards in Wuming District of Nanning City were investigated to the relationships among the soil pH value,available calcium content in soil,calcium content in citrus Gonggan leaves.Moreover,we selected these representative orchards to study the effects of soil lime application,foliar spraying of calcium acetate and foliar spraying of calcium chloride tests on the fruit cracking of citrus Gonggan,by analyzing soil pH value,available calcium content,leaf calcium content,pericarp and leaf calcium content at different stages and fruit cracking rate.Herein,we also investigated the effect of these three three kinds of calcium fertilization on the quality of citrus Gonggan,by analyzing the contents of total soluble solids,Vc,soluble sugar and titratable acid in Gonggan fruits.The main results of this study are as follows:（1）The soil pH values of Gonggan orchards in Wuming District were generally acidic.The soil pH values of four representative orchards were was generally low with the range of 4.40～6.80.The soil available calcium content was generally low,with the average value of 330.9～813.0mg·kg^-1,and the difference between them was significant,and the whole soil was in the state of lack of available calcium.The mean value of calcium content in leaves was1.661%～2.015%.Soil available calcium content and soil pH value,calcium content in leaf and soil pH value,calcium content in leaf and soil available calcium content showed extremely significant positive correlation;（2）The application of lime could significantly increase the soil pH value and soil available calcium content of citrus Gonggan orchard.The soil pH value increased highest in the citrus Gonggan orchard with lowest the soil pH value.The A3 treatment（1.0kg/tree）had the largest extent of improvement in soil pH value.（3）Application of calcium fertilizer could significantly reduce the fruit cracking rate and increase the calcium content of pericarp and leaves.Compared with the control,application of lime,calcium acetate and calcium chloride reduced the fruit cracking rate of citrus Gonggan by the range of11.80%～76.13%.Calcium content in pericarp increased by the range of5.47%～30.50%,in the expansion stage,and increased by the range of6.19%～31.34%in the maturity stage.The calcium content in leaf increased by the range of 9.98%～53.84%in the expansion stage,and increased by12.67%～60.44%in the maturity stage.Fruit cracking rate and calcium content in leaf,calcium content in pericarp showed extremely significant negative correlation;The calcium content in pericarp was significantly positively correlated with that in leaf.application of lime,calcium acetate and calcium chloride could increase the calcium content in leaf and pericarp significantly,but the effect is slow and the persistence is high.（4）Calcium application could significantly increase the content of total soluble solids,Vc and soluble sugar,and significantly decrease the content of titratable acid,thus increasing the ratio of sugar to acid and solid to acid,and improving the quality of citrus fruits.Compared with the control,application of lime,calcium acetate and calcium chloride could increase the content of soluble solids by the range of 8.58%～10.21%,increase the content of Vc by the range of25.98%～37.27%,increase the content of soluble sugar by the range of4.97%～5.55%,reduce the content of titrable acid by the range of13.98%～21.11%.The content of total soluble solids,Vc and soluble sugar in the fruit of citrus Gonggan was significantly positively correlated with the calcium content in the pericarp,while the content of titratable acid was significantly negatively correlated with the calcium content in the pericarp.