Seasonal changes of mineral nutrients in the fruit of navel orange plants grafted on trifoliate orange and citrange

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To clarify whether the rootstock can affect the uptake dynamics of mineral nutrient in the fruit of navel orange, changes in the concentration and quantities of macronutrients (N, P, K, Mg, and Ca) and micronutrients (B, Fe, Mn, Cu, and Zn) in the fruit of Newhall navel orange grafted on trifoliate orange and citrange were measured at semi-monthly intervals during fruit development. The macronutrients measured in this study, except Ca, decreased in concentration on a whole fruit basis during stage I and then remained constant or decreased very slightly during stages II and III of fruit development. Calcium concentration in whole fruit increased during stage I. The elements Mn, Cu and Zn declined in concentration on a whole fruit basis at two rates, very sharply during early stage I and then gradually in the following days to maturity. An exception to this general pattern was boron, where the concentration remained constant during stage I and early stage II and then decreased slightly. For the element Fe, the concentrations showed a large increase and then declined immediately from 120 to 150 days after full bloom (DAFB). With few exceptions (e.g., Fe, Mn, and Zn), the quantity of each element accumulated increased steadily throughout the growth period to reach a maximum by harvest in both grafted plants. Fe accumulation in whole fruit increased from a minimum just after fruit set to a maximum by 135 DAFB. For a number of elements (N, P, K, B, and Mn), there was a strong linear correlation (R2 > 0.95, P < 0.001) between the dry mass yield and the amount accumulated throughout the growth period. Potassium and N are the two nutrients that accumulated in greatest amounts by fruit. Boron and Fe are the micronutrients that accumulated in the highest quantities in Newhall navel orange fruit. The patterns of seasonal change in the concentrations of macro- and micronutrients for trifoliate orange-grafted and citrange-grafted navel orange trees were generally similar.