Studies On Foliar Nutrients Of The Short Rotation Triploid Populus Tomentosa Plantations

Triploid Populus tomentosa is the superior series for the papermaking raw material. In order to combine trees production with paper and pulp engineering advancely, and implement scientific nutrient management, foliar nutritional charicteristics and foliar nutrient diagnosis of triploid Populus tomentosa were studied in this paper. Large samples were selected from triploid Populus tomentosa clones plantations for 5 years. The results of researches are as follows:1. From Apri. to Sept. in the five years old plantations, leaves were collected to study the monthly dynamics of foliar nutrients. Results shows foliar N, P and K concentration were highest in Apri. in spring, N and K concentrations were higher again in June or July in summer; foliar nutrient concentrations differed significantly from the month and clone factor; foliar N, P, and K. concentraions in the control clone 1319 (diploid) were significantly higher than those of the four triploid clones, while foliar Ca, Mg, Fe, Mn, Cu and Zn concentrations in clone 1319 were significantly lower than those of the four triploid clones.2. To study foliar nutrient differences from the factors of seasons and stand ages, leaves were collected in spring, summer and autumn in the 2,3,4, and 5 years old triploid Populus tomentosa plantations. The results suggests that seasonal nutrient concentrations dynamics varied significantly. Foliar N, P and K concentrations turned down with time gone, while foliar Ca, Fe, Mn, Cu and Zn concentrations increased gradually; Mg concentrations were higher in summer.The order of foliar nutrient elements concentrations were N>Ca>K>Mg>P>Fe>Zn>Mn>Cu. As for the nutritional charicteristics of different ages of plantions, foliar N, P and K concentrations were highest in the third or fourth year, while Ca, Mg, Fe, Mn, Cu and Zn concentrations were highest in the fifth year.3. According to results of the data reduction analysis, foliar Fe, Mn, Ca, P, K, Mg, Zn, N and Cu concentrations were in sequence important for the growth of trees plantations in 'New Series Testing Plantation'(Plot I), while foliar N, Mg, Cu, Fe, Mn, Zn and P concentrations were important sequencely for the growth of the trees in'Variety Comparative and Regionalization Testing Plantation'(Plot II). Clones were tentatively classified with the results of data reduction.In addition, the results of the regression between the growth and foliar nutrients concentrations indicated foliar K, N, Ca, Mg, Fe and Zn were correlated closely to the growth of trees in the plantations.Soil samples were collected in the same block in Plot I and II every autumn from 2005 to 2009. The results of the regression between soil total and availabe nutrients contents and the growth demonstrated that pH, soil total nitrogen, total phosphorus, total potassium, total calcium, total magnesium, total iron, total manganese, total copper and total zinc contents were correlated closely to the growth of triploid Populus tomentosa plantations in the plantations. Nitrogen and calcium fertilizers were reconmended to applied to satisfy the need of the trees growth.4. According to the results of the foliar nutrients diagnosis by four ways of critical value approach, relative growth rate (RGR), standard concentrations and diagnosis and recommendation integrated system (DRIS), the ranges of optimum foliar nutrient concentrations of the triploid Populus tomentosa plantations were:N 22.91-27.99 g/kg, P 0.96-1.11 g/kg, K 10.29-12.13 g/kg, Ca 11.83-17.27 g/kg, Mg 3.72-4.93 g/kg, Fe 249.9-300.7 g/kg, Mn 69.8-72.3 g/kg, Cu 20-24 g/kg, Zn 121-134.3 g/kg in Plot I; and N 25.96-40.09 g/kg, P 1.50-1.53 g/kg, K 9.46-11.59 g/kg, Ca 12.3-14.94 g/kg, Mg 3.82-4.64 g/kg, Fe 202.5-208.1 mg/kg, Mn 72.8-103.4 mg/kg, Cu 18.6-21 mg/kg, Zn 112.6-142.9 mg/kg in Plot II. The yield was highest when the foliar concentrations were within the optimum values. The ranges for critical foliar nutrients concentrations were larger than those of the optimum concentrations.The orders for the requirement of fertilizations of triploid Populus tomentosa plantations were Ca>P>Cu>Fe>K>N>Zn>Mg>Mn in Plot I and P>Mg>N>K>Ca>Zn>Fe>Mn>Cu in Plot II.Recommendations for 2,3,4 and 5 years old of triploid Populus tomentosa plantations were calculated respectively by the way of standard concentrations and DRIS, which would be benefit for the nutrient management for triploid Populus tomentosa plantations.