The Effects Of Different Fertilizer Treatments On The Soil And Leaf Nutient And The Metbolism Of Citric Acid Of Navel Orange In Zigui

A field trial with two navel orange cultivars,’Newhall’and’Cara cara’, grafted on trifoliate orange were conducted. The study focused on the research as follows. The first one is the effect of applying different ratio of PK fertilizer and different micro-nutrients and meso-nutrients fertilizer on soil and leaf nutients,the fruit content of the titratable acid in the navel orange park. The second one is the regulating action of applying different fertilizers on the citrate concentration and the ralated enzyme activities in the two kinds of navel orange. The aim is to provide a theoretical basis and practical guidance on improving fruit quality. The main resuits were as follows:(1) The effects of applying different fertilizers on soil and leaf nutients in navel orangeryApplying different fertilizers can significantly improve orchard soil and leaf nutrient status in the two kinds of navel orangery. Applying different level of PK fertilizers can increase the ratio of the corresponding soil and leaf nutrient content. The nutrient content in soil and leaf Newhall and Cara cara navel orange were different in Newhall and Cara cara navel orange. The dynamics variation characteristics of nutrient-element in leaf were as the same. Different leaf nutrient-elements were difference in the nutrients dynamic changes, and the same nutrient-element in various cultivars navel orange had the different dynamics variation characteristic in two years.Leaf PK concentration began to rise from March and reach the highest in July,then declined in the two kinds of navel oranges. Applying different micro-nutrients and meso-nutrients fertilizers had the better effect on the related nutrient content in the soil and leafs of navel orangery.and the total fertilization had the same performance. Applying Fe and Zn fertilizer could promote the absorption of Mg in the trees.(2) The effects of applying different fertilizers on the content of titratable acidThe content of titratable acid in Newhall and Cara cara navel orange were decreasing with the apllying of phosphate fertilizer,so it was good for reducing fruit acidity. The appropriate amount of potassium fertilizer could reduce fruit titratable acid. However, excessive potassium fertilizer had the oppsite effects. Reasonable control of the potash applied were important to improve fruit flavors.(3) The effects of applying different fertilizers on the citrate concentration and the ralated enzyme activities in the two kinds of navel orangeThe content of Citric acid in fruit appears to decline after rising first, and reaches the highest on the105days after anthesis. Increasing the amount of phosphate and iron fertilizer could effectively reduce the accumulation of citric acid in the navel orange. But, applying potassium fertilizer had an oppsite effect.The key enzyme on the synthesis of citric acid were PEPC and CS, they have the same changing tendency compared to the content of Citric acid in fruit; the key enzyme on the decomposition of citric acid were Cyto-ACO and IDH,their activity kept on rising during the development of fruit; the PEPC and CS activities kept on decline with the applying of phosphate fertilizer. After the application of phosphate and iron fertilizer, the PEPC and CS activities would declined,but the IDH activity increased. So, the synthesis of citric acid diminish and the decomposition were promoted. The PEPC and CS activities kept on rising with the applying of potash, promoting the synthesis of citric acid.