Accumulation and distribution characteristics of mineral nutrients at mature stage of Citrus reticulata ‘Gonggan’

Abstract: 【Objectives】This work aimed to study the distribution characteristics of dry matters and nu-trients at mature stage of‘Gonggan’(Citrus reticulata) and the parameters of nutrient need, and to pro-vide basic data for nutrient management strategy of‘Gonggan’.【Methods】The biological characteris-tics of three 6-year-old plants were investigated at harvest in the main production areas of Gunagdong province, and then they were excavated. The characteristics of accumulation and distribution of biomass and nutrient were studied by measuring the biomass and nutrients in different plant organs, including ni-trogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), manga-nese (Mn), copper (Cu), zinc (Zn), boron (B), and molybdenum (Mo).【Results】The fresh mass of the whole tree was 123.47 kg with a yield of 74.97 kg per tree, which accounted for 60.7% of the biomass of the whole plant. The biomass ratio of leaf to fruit was 1∶3.61. The biomass of leaves, trunks, roots,and fruit accounted for 8.4%, 34.3%, 26.9%, and 30.4% of the plant, respectively, while the biomass of the pericarp, pulp, and core accounted for 32%, 64%, and 4% of the total biomass of fruit, respectively. N, P, K, Ca, Mg, S, Cu, and B contents were the highest in the leaves; the highest content of Fe and Zn contents were found in the roots; and the highest contents of Mn were observed in the leaves and roots. In fruit, the highest content of N, P, K, Mg, S, Cu, and Zn were found in the core, and the highest con-tent of Ca, Fe, and B were observed in the peel. The lowest macro nutrient and micronutrient were S  and Mo in fruit tissues, respectively. Except for the significantly lower Ca and Mo in the leaves and sig-nificantly higher P and B in the fruit, the distribution rates of N, P, Ca, B, and Mo were similar in differ-ent organs. However, the distribution rates of K, Zn, Mg, S, and Cu were different. The accumulation of K was in a descending order of fruit > roots > leaves ≈ trunk, while that of Zn occurred in a descending order of roots > trunk > leaves ≈ fruit. A significantly higher accumulation of Mg was found in the fruit than that in the trunk and roots. Significantly higher accumulation of S, Fe, and Mn were found the roots compared with the fruit and the trunk, and a relatively higher accumulation of Cu was observed in the trunk and roots than that in the fruit and leaves. Generally, most of the macro nutrients mainly accu-mulated in the fruit, while most of the micronutrients mainly accumulated in the root. There was consid-erable difference in the accumulation of mineral nutrients among different tissues in the fruit. Expect for a higher accumulation of Ca in the pericarp, the highest distribution rate of macro nutrients was found in the pulp, and distribution rate of all mineral nutrients was lowest in the core. In addition, the produc- tion of 50 kg fruit requires removal of 208.0 g of N, 17.4 g P, 103.1 g of K, 176.6 g of Ca, 14.2 g of Mg,12.8 g of S, 1.05 g of Fe, 0.26 g of Mn, 0.05 g of Cu, 0.21 g of Zn, 0.48 g of B, and 1.2 mg of Mo from the aboveground. And 85.5 g of N, 8.9 g of P, 61.5 g of K, 25.7 g of Ca, 6.1 g of Mg, 3.6 g of S, 0.25 g of Fe, 0.03 g of Mn, 0.01 g of Cu, 0.04 g of Zn, 0.11 g of B, and 0.4 mg of Mo were carried away with 50 kg of fruit harvested, which accounted for 29.6%, 40.8%, 43.5%, 11.1%, 34.7%, 18.0%, 5.5%, 3.3%,21.4%, 5.8%, 17.6% and 23.9% of total N, P, K, Ca, Mg, S, Fe, Mn, Cu, Zn, B, and Mo accumulated in the whole trees, respectively.【Conclusion】There is relatively high nutrient absorption capacity, nutri-ent utilization ratio for yield, as well as nutrient demands for N, K, Ca, Fe, and B in‘Gonggan’. Due to approximately one third of the macro nutrients in the tree removed from fruit harvest, mineral elements should be supplemented in time, and pruned branches should be effectively recycled to maintain soil fer-tility.