The relationship between leaf nutrients and fruit quality of navel orange in southern Jiangxi province of China

To explore the relationship between leaf nutrients and fruit quality of Newhall navel orange (Citrus sinensis Osbeck), 12 nutrient elements in leaves, the fruit total soluble solid (TSS) content, titratable acid (TA) content and single fruit weight (SFW) of Newhall navel orange (Citrus sinensis Osbeck) on trifoliate orange Poncirus trifoliata (L.) rootstocks were investigated in 58 orchards in southern Jiangxi province. The results show that the leaf N levels of most orchards exceed the optimum range, while the P and K levels of all orchards are within or above the optimum ranges. About 87.9%, 55.2% and 5.2% orchards are below the optimum Mg, Ca and S ranges, respectively. For microelements, the Mo levels are within the optimum range, and the Fe levels are within or above the optimum range for all orchards. Furthermore, there are several orchards in which both the B and Mn levels are below the optimum ranges, and one third of the orchards in which the leaf Cu levels are below the optimum range. The Zn levels of 96.6% orchards are below the optimum range. With the improvement of the fruit quality, TSS and TA are increased significantly, while SFW is decreased significantly. There is a significantly negative correlation between the fruit TSS and the leaf K level. However, the correlations between the fruit TSS and the leaf Mg and Zn levels are significantly positive, and there arent any significant correlations between the fruit SFW and the 12 leaf nutrient elements. For the fruit TA, it shows remarkably positive correlations with the leaf N and Mn levels. For the fertilizer practices of Newhall navel orange in south Jiangxi province, it should be focused on supplements of Mg and Zn, moderately supplements of Ca and Cu, and decreasing in N, P and K applications.