부산대학교 도서관

To discuss the extraction method of plant nutrients accumulated in crop residues, oilseed sunflowers were cultivated at different planting densities in a university farm in Tokyo, Japan. Sunflower stems were collected in the flowering, ripening and harvesting stages to obtain test materials with different traits. The dry matter yield of sunflower stems per unit planting area increased at higher planting densities. From the flowering to harvesting stages, the carbon content of plant nutrient elements contained in sunflower stems was slightly reduced, the nitrogen and phosphorus content was very slightly reduced, the potassium content was almost unchanged, and the calcium content was slightly increased. Each extraction ratio of specific plant nutrients elements in the liquid fraction obtained by hot-compressed water treatment to the original material element varied depending on the element. Thus, under the condition of 180ºC in temperature and 40 min in holding time, the extraction ratio for potassium ranged from 0.90 to 0.95; magnesium, 0.84 to 0.94; nitrogen, 0.78 to 0.85; phosphorus, 0.58 to 0.82; calcium, 0.31 to 0.64; and carbon, 0.32 to 0.40. The Nut / N ratio which is the ratio of the total amount of plant nutrients element in the original material to the amount of nitrogen element, and the C / N ratio which is the ratio of the amount of carbon element to the amount of nitrogen element, showed a strong linear relationship, and the same relationship was observed for the extracted nutrient elements in the liquid fraction. When the temperature of the hot-compressed water treatment was raised, the extraction ratio for carbon and calcium, which originally had relatively low extraction ratio, increased in proportion to the temperature, while the ratio for phosphorus decreased significantly. The effect of treatment retention time on the extraction ratios of plant nutrients was small for all elements.