Sunflowers are grown as an ornamental plant and a catch crop beside an oilseed crop in Japan. Seed residues after oil milling are recycled as a feed for livestock and a fertilizer. After harvesting, crop residue such as stem and leaves are returned to the soil by the tillage in conventional cultivation. This report discusses the appropriate circulatory management of crop residues and plant nutrition considering them as a new commodity and plant nutrients resource for activating small agriculture.
To study the characteristics of the nitrogen uptake from soil, sunflower cultivar named Hybrid Sunflower was grown with fixed row distance of 70 cm and varying hill distance of 10, 20, 30, 40 and 50 cm in a 5 m * 5m plot at a university farm, Tokyo, Japan. Growth survey was carried out every week. Sunflower whole crops sampled at each plot were dried in the oven at 70 °C for 1 day soon after the blanching treatment and stored until the extraction experiment.
Sunflower sample at the growth stage of after flowering had the largest mass compared with the stage of before flowering and seed harvesting. Total dried matter of whole crop in 10cm-plot was the largest among the planting density conditions for each growth stage. The dried matter of crop residue at the growth stage of seed harvesting was 613, 408, 323, 281 and 279 g/m2 for the plot of 10, 20, 30, 40 and 50 cm, respectively.
Nitrogen contained in sunflower stem was 2.5 to 5.5 g-N/m2 and that in seed was almost double, 5.9 to 7.5 g- N/m2. Sunflowers were processed to extract nitrogen by the hot-compressed water (HCW) treatment. Ground sample of sunflower stem mixed with water was heated at temperature of 180, 200 and 220 °C with gas pressure of 2 MPa in a pressure tight reactor for 5 and 30 min to release nitrogen from the solid fibre. Sample was separated into the solid matter fraction and the liquid matter fraction after the treatment. Extracted nitrogen as liquid matter was 37.9, 45.5 and 49.4 % at temperature of 180, 200 and 220 °C, respectively. Approximately 40 to 50 % of nitrogen contained in sunflower stem was recovered as the liquid matter. The liquid matter can be returned to the soil as a fertilizer while the solid matter containing cellulose and hemi- cellulose can be used as a raw material for bioethanol production.