| Eucalyptus with the abilities of fast growth and varied adaptation is widely and economically used for multi-purposes. There are large areas grown eucalyptus but with the low lumber production in our country. Therefore, it seems reasonable to promote the growth of eucalyptus trees by rational fertilization and ectomycorrhizal fungus inoculation. The present experiment was established in the experimental farm of Southwest Agricultural University and the nutrition of eucalyptus trees was studied systematically from 2001.3 to 2002.2 in order to supply the guidance in cultivation and fertilization practices. The growth and nutrient absorption of eucalyptus with and without ectomycorrhizal fungus inoculation were compared in yellow and purplish soils. The arrangement of inoculation - no inoculation was adopted with 4 replications in the experiment. At the same times!, the distribution and seasonal changes of macronutrients (N, P, K, Ca, Mg and S) were recorded in eucalyptus trees. Following are the results obtained:1. Similar changes and important differences of N and K in the leaves of eucalyptus in different directions were found in accordance with South, east, west, north, even though there were no significant variations in directions. For other four elements (Ca, Mg, S and P) in the leaves, however, rose and fell little in directions yet if any.2. Similar evolution of N, P and K, the movable elements in trees, were observed in the leaves of eucalyptus. The contents of the three elements had a pattern of decrease-increase which reached the peak in the early growing period (March or April) and decreased with seasons and then increase in the later period. The concentrations of Ca in the leaves were remarkably higher in summer (from April to July), the fast growing period, than those in any other months. Positive correlation (r=0.599,p<0.05) was detected between the contents of Ca and monthly average temperatures. The variations of Mg in the leaves of eucalyptus, however, tended to be opposite to those of K and Ca. Obviously low Mg concentration were observed from March to August and varied very little each month if any. S in the leaves fluctuated similarly but largely compared to Mg. Significant correlations were established between N and P (r=0.886,p<0.01), N and K (r=0.922,p<0.01), P and K (r=0.808,p<0.01), indicating similar absorption and accumulation of N, P and K by eucalyptus trees. Moreover, The contentsbetween K and Ca(r=0.630,p<0.05), and between Mg and S (r=0.629,p<0.05) correlated positively in the leaves, while negatively between K and Mg (r= -0.678,p<0.01), and not significantly between N and S (r= -0.549,pX).05).3. There was a significant seasonal change in the contents of nutrient elements in branches, stems, barks and roots. The seasonal dynamic changes of all elements in branches were similar to those in leaves. The N, P, and K seasonal dynamic patterns showed similar in barks, i.e. highest in March and lowestin September. The Ca content in barks was highest in June while Mg and S concentrations in warmer seasons were lower than those in colder seasons. Very lower level of N, P, Mg, and S in the trunks were detected and changed very little among seasons while the relatively higher level of the K and Ca reached the peak in June. At the same time, the element concentrations in side roots were higher than that in main roots and the seasonal variations were similar, which were highest in June and fell in September and rose in December. However, the seasonal changes of Mg and S in the roots tended to another pattern of which were lowest in June and highest in September.4. Generally speaking, the average nutrient contents (mg/g) in various organs in .the Eucalyptus Maideni F.Muell were in the following orders. N: leaves(9.44)> branches(2.74)> barks(2.56)> side roots(2.12)> main roots(1.59)> trunks(0.44), P: barks(1.16)> leaves(1.14)> branches(1.09)> side roots(0.85)> main roots(0.45)> trunks(0.37), K: leaves(7.30)> branches(4.68)> side roots(3.04)> barks(2.81)> main roots(2.47)> tru...
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