Evaluation of nutrient loading technique potential of domestic tree species to promote forestation

Reclaimed lands, including reclaimed tidelands, usually have poor soil conditions, such as low nutrient and organic matter contents and poor soil structures, which hamper adaptation and survival of newly transplanted tree seedlings. Nutrient loading technique is the concept of accumulating more nutrient in plant parts while maintaining biomass, which can increase growth and survival rates after transplanting in nutrient poor soils. However, possibility of nutrient loading on domestic tree species has not been evaluated in Korea. This study was conducted to test and select the optimum nutrient loading models for domestic tree species. Three nutrient loading models, including conventional (constant fertilizer dose), exponential (increasing fertilizer dose as exponential curve), and modified exponential (exponential increase but compensate initial fertilization), were tested for three tree species; Pinus thunbergii, Quercus acutissima, and Zelkova serrata. Seedlings were grown in a greenhouse from June to September in 2020, and selected amount of fertilizer was applied weekly. Three seedlings were collected randomly every 4 weeks in each tree species and nutrient loading model, and dry matter and nitrogen (N) concentration in each part, including root, stem, and leaf, were analyzed, and seeding height was measured. Seedling height was not different with nutrient loading models for all tree species. For P. thunbergii, dry matter and N content were the highest with the conventional and modified exponential models, and for Q. acutissima and Z. serrata, the modified exponential model was the best. The modified exponential model resulted in the highest nutrient loading efficiency due to the compensation of N supply at the beginning of growing stage and the higher N supply rates at the late growing stage compared to the conventional model. However, survival rate of seedlings for exponential model decreased after middle growing stage because of toxicity of excessive N fertilization due to rapid supply of N. Therefore, diverse rate of N fertilization needs to be tested to select the optimum nutrient loading models for each species. Furthermore, field study is needed to test if nutrient loaded seedings grow better than conventional seedlings at poor soil condition lands.