Effect Of Different Fertilizer Treatments On The Sugar Accumulation In Newhall And Cara Cara Navel Orange

Field trials with two navel orange cultivars,’Newhall’ and ’Cara cara’, were conducted in two consecutive years. The paper studied the effect of different fertilization treatments on fruit yield and total soluble solid, accumulation of sugars of the fruit and metabolism, so as to provide reference for fertilization. The main results are as follows:(1) Nitrogen, phosphate and potassium fertilizers application increased fruit weight, fruit yield and fruit quality of Newhall and Cara cara navel orange, there are differences between annual. With the increase of phosphorus and potassium fertilizer rate, the fruit yield of Newhall and Cara cara navel orange increased, the fertilizer rates were N:0.80kg/hill, P2O5:0.40kg/hill, K2O:0.50kg/hill when the fruit yield of Newhall and Cara cara navel orange were the highest. In addition, applying different micronutrients and mesonutrients fertilizers can also increased the fruit yield. Nitrogen, phosphate, and potassium fertilizer application can increase the content of total soluble solid in fruit. According the results of fertilizer effects, the optimum fertilizer rates were N:0.80kg/hill, P2O5:0.40kg/hill, K2O:0.50kg/hill, in Newhall and Cara cara orchards. With the application of the PK treatment, applying micronutrients and mesonutrients fertilizers can increase the soluble solid and decreased titratable acid in fruit. The fruit quality in the total of Mg Fe and Zn treatment was the best in the different micronutrients and mesonutrients fertilizers treatments.(2) NPK and micronutrients fertilizers application increased fructose, glucose and sucrose content in fruit. With the increase of phosphorus and potassium fertilizer rate, the sugar content increased, but high phosphorus and potassium limitted the sugar in the fruit continues to rise. According the results of sugar content, the optimum fertilizer rates were N:0.80kg/hill, P2O5:0.40～0.60kg/hill, K2O:0.50～0.75kg/hill. For different micronutrients and mesonutrients fertilizers treatments, the amount of sugar in the fruit was in the order of the total of Mg Fe and Zn> Mg> Zn, Fe> CK. However, no significant (p>0.05) correlation was observed between Zn and Fe treatments.(3) Results showed that NPK and micronutrients fertilizers application increased the activity of sucrose-metabolizing enzyme in the fruit, the activity of sucrose-metabolizing enzyme in different fertilizer treatments were significantly (p<0.05). The activity of sucrose-metabolizing enzyme in the total of Mg Fe and Zn treatment was significantly (p <0.05) higher than that of other micronutrients fertilizer treatments. The activity of sucrose-metabolizing enzyme (decomposition enzymes) was higher during the early fruit enlargement, and decreased significantly in the late fruit enlargement. With the decreased of decomposition enzymes, the activity of sucrose-metabolizing enzyme (synthetic enzymes) increased, then sucrose content was rised rapidly. So the accumulation of sugar in the fruit was through decomposition enzymes and synthetic enzymes activity strength to adjust. In the actual production, mixing N, P, K and micronutrients fertilizers is favorable to increase the activity of sucrose-metabolizing enzyme and the fruit sugar accumulation, so as to improve the fruit quality.In conclusion, the basic rates of recommended fertilizer were N:0.80kg/hill, P2O5:0.40kg/hill, K2O:0.50kg/hill, MgSO40.25kg/hill, ZnSO4-7H2O0.04kg/hill, EDDHA-Fe0.06kg/hill.