| The ferilization expriment was tested using an L9(34) orthogonal design and regression analysis, for the studing the effects of the different combined fertilization of nitrogen (N), phosphorus (P) and potassium (K) on the characters of inorganic nutrients balance mechanism of Eucalyptus grandis × E.urophylla seedling. Through the comparison of different fertilization treatments on Eucalyptus grandis× E.urophylla growth, physiology, nutrition and soil nutrient, soil microorganism, soil enzyme activity index, we revealed the growing and feitilizing regulation of Eucalyptus grandis×E.urophylla, explored the soil nutrients under different fertilizer correlation with soil microbe number and enzyme activity. We found out the most favorable of fertilizing on physiological growth and soil fertility ratio (N2P3K1), and the recommended application rates of N, P2O5 and K2O were 15,9 and 6g/seedling, respectively.The main research results are as follows:(1) Nitrogen, followed by phospho and potassium, affected the plant height, ground diameter, volume and biomass, specific leaf weight. N fertilizer played a important part in plant height, ground diameter, volume and biomass, specific leaf weight has significant effect, and N fertilizer promote growth in a certain range, excessive decreased; P fertilizer played a important part in the biomass accumulation and distribution of the underground. K fertilizer played a important part in plant height and root cap ratio. All growth indicators of fertilization treatments, N2P3K1 in special, were significantly higher than CK.(2) N fertilizer is a main factor affecting the content of chlorophyll and soluble protein content, and K fertilizer play a important part in the effect of soluble sugar content. Fertilizer causes the difference of the leaves and root organic acid, and N and P is the main factor affecting the organic acid content. Four organic acids, such as methanoic acid, malic acid. Fourkinds oforganic acids, such as methanoic acid, malic acid, Oxalic acid and Citric acid, were detected in leaves and roots.The content of organic acid in leaves was significantly higher than the roots, the malic acid, citric acid and acetic acid accounted for 85.21% to 95.32% of all acids in the leaves, Malic acid and citric acid accounted for 54.99% to 85.21% of all acids in root system. Correlation analysis showed that the total organic acid content of leaves and roots was significantly correlated with malic acid and citric acid (p<0.05), those two acids, as the dominant acids of the eucalyptus, may be instructions type acid plant suffer from stress. With N2P3K1 suffered the least nutrient stress, organic acid content was the lowest, recommended the best fertilization. The analysis shows that PEPC is an important enzyme for the accumulation of organic acids in the seedlings of Eucalyptus, and NAD-IDH is related to organic acid decomposition. Photosynthesis, the proper amount of N fertilizer, the more P, a certain amount of K fertilizer to improve photosynthetic capacity of the Eucalyptus grandis ×E.urophylla, the fertilization treatment N2P3K3 could obviously promotethe photosynthes is indexs.(3) The result of principal component analysis showed that N2P3K1 fertilization treatment, as the bestoption, could obviously promote the physiological growth and photosynthesis indicators. Under the formula fertilization, and recommended application rates of N, P2O5 and K2O were 15,9and 6g/seedling, respectively. These results with the test in the Eucalyptus grandis×E.urophylla growth performance is consistent.(4) The Eucalyptus grandis×E.urophylla fertilization treatment in the three periods, the leaf TN, TP content are increased with the growth of the Eucalyptus grandis×E.urophylla, and reduced in the end. The element content in leaves was larger than that of stem and root. N in the leaves, stems, roots mainly affected by N, P in the leaves, stems and roots mainly by the mutual influence of N and P, K in the leaves, stems and roots mainly by the effect of K. N is advantageous to the aerial parts of the Eucalyptus grandis×E.urophylla the accumulation of Cu, the right amount of N fertilizer to improve the content of leaf and root of Mg, K fertilizer was beneficial to the accumulation of Mn in the leaves and roots, high levels of NPK ratio reduces the Zn content in different organs.(5) For establish DRIS, found that under the low N level of N fertilizer is most sensitive, and has synergistic effect on N and P, P fertilizer and K fertilizer are antagonism. In a moderate amount of N levels showed a better balance for N2P2K3. Excessive N fertilizer has a promoting effect of K. It is concluded that the optimal proportion of certified for N2P2K3, and recommended application rates of N, P2O5 and K2O were 15,9 and 12g/ seedling, respectively.(6)Correlation analysis showed that N and K has a positive correlation with the soil fertility indicators. In addition to the fungus, P has a positive correlation with the soil fertility indicators. N fertilizer had the greatest influence of urease, sucrose and catalase, P on the activity of acid phosphatase, and K is also the important factors that affects the soil enzyme activity. The sustainability the soil fertility rely on a reasonable ratio of NPK. Membership function of comprehensive evaluation results show that the highest N2P3K1 has a positive improvement in the soil microbial community, organic matter and the activity of soil enzyme. The combination is the most reasonable ratio of fertilizer combination. |
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