Journal of the Society of Agricultural Structures, Japan

An experimental device for composting has been developed. The device has a cylindrical fermenter, similar in height to a material pile in practical composting facilities. The top end of the fermenter is open and the sides are covered with several thermal insulation units, vertically oriented. The thermal insulation units are constructed by wrapping the exterior of the fermenter tank insulant with sheet heaters. Sheet heater heating value is controlled independently for each insulation unit, so as to minimize insulant external and internal temperature differential. Heat radiation from the fermenter surface is thus controlled without obstructing temperature distribution, which occurs in the vertical direction of the material.
This device reproduces phenomena that occur in a practical composting facility, such as compression of the lower material due to the dead weight of the piled material itself, movement of heat and water due to aeration or top layer surface contact with outside air, and change in oxygen concentration in the airflow passing through the material.
This device enables composting experiments under conditions similar to practical composting, using only a small amount of material.

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To study the effects of air temperature on yield and re-growth after harvest of Chinese chive (Allium tuberosum Rottler), seeds of ‘Green road’ were sown every two months and seedlings were grown for 40 days. Then, seedlings were transplanted to the sand-bed in a plastic house and cultivated with sufficient fertigation for 150 days until first harvest. Leaves of Chinese chive plants were harvested every two months and yield and re-growth were measured.
Yield and re-growth were different depending on the month of harvest. In case that plant age and times of harvest were equal, re-growth of leaves after harvest was strongly affected by the air temperature and was different depending on the month of harvest. However, if the plant has the different age and different sowing time, when plants were harvested at the same time, the pattern and the speed of re-growth of leaves were almost equal. The influence of day length on re-growth of leaves after harvest seemed to be small. Re-growth of leaves had significant correlation with the cumulative air temperature and the best re-growth was obtained when the cumulative air temperature became about 470°C during 20 days after harvest (that is 23 to 25°C of average air temperature).

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