Effect Of Fall Fertilization On The Larix Olgensis Seedling Quality

Olga Bay larch (Larix olgensis Henry) is an important forestation species in northeast China. Because of the poor natural regeneration of this species, efforts to plant large areas with Olga Bay larch have focused on planting seedlings from nurseries. Fertilization is the necessary step for the seedling cultivation so that optimum fertilization would play a key role in promoting seedling quality and forestation survival rate.Fall fertilization has proved to be an effective way to increase the nutrient content, survival rate and growth of new planted seedlings, which was widely used in Europe and America reforestation but little attention was received in China. Based on the theory of fall nutrient loading, we evaluated how fall nitrogen (N) fertilization affected the growth, cold hardiness and filed performance of bareroot Olag Bay larch with two seedling types (germinated seedling (1-0) and transplanted seedling (1-1)); The interaction between primary fertilization and fall fertilization was also studied to analyed the nutrient demanding characteristic of Olag Bay larch in the whole growing season; By using15N, the effects on N storage and translocation within seedlings for the deciduous conifer species Olga Bay larch were examined during the hardening period. The relations among fall nutrient loading, nutrient concentration change within seedlings and nutrient interal cycling in decidous conifer seedlings were discussed, which would help with improving the fall fertilization theory and providng feasible way to produce high quality Olag Bay larch seedlings.Our research shows that (1) the cold hardiness of fall N applied1-0seedlings were significant promoted when the average N concentration of stem and roots came to2.0%and2.1%, respectively.(2) Compared to the only primary fertilization seedlings (1-1), the height and relative height growth of outplanted fall fertilization represented high correlations with the stem and root N concentration, and the relevant increased values were13.8%and62.8%.(3) The interaction between primary fertilization and fall fertilization were found. Low rates of primary fertilization would make for the nutrient loading of seedling during hardening period.(4) The distribution pattern of N concentration and content in seedlings was found in this order:stems> fine roots> coarse roots> needles. Ttranslocation of N from needles to stems and fine roots prior to abscission negated overall N dilution in the seedling at the end of the growing season, and needle N concentrations were similar among all N fertilization levels.(5) Reduced N in foliage concurrent with an increase of N in stems and roots. Tissue N concentrations and contents of this deciduous species would increase as a result of fall additions of N, but fall fertilization use efficiency (FUE) decreased as N rate increased.(6) Our rate of25mg N-seedling-1of primary fertilization and10mg N-seedling-1of fall fertilization appeared to yield the highest N concentration and content in stem and root and was achieved with high FUE, suggesting fall N fertilization may be a way to promote the nutrient loading of deciduous conifer seedlings during nursery production.(7) Greater nutrient storage in Larix olgensis seedling stem could be used later to benefit future growth.