Utilization of bark for soil conditioner, 2: Production of hardwood bark composts sufficiently suitable for agricultural use

To determine the effects of raw material composition of hardwood bark composts on the degree of maturity and heaping period required to produce a compost sufficiently suitable for agricultural use, four kinds of hardwood bark composts were produced from the following raw materials: hardwood bark, rice hull, chicken droppings, urea, and calcium superphosphate. The composts produced were named as type A (hardwood bark, chicken droppings, and urea), type B (hardwood bark, urea, and calcium superphosphate), type C (hardwood bark, rice hull, chicken droppings, and urea), and type D (hardwood bark, rice hull, urea, and calcium superphosphate). The results were summarized as follows: 1) The four types of composts were fermented satisfactorily, but the composts showed different fluctuation of EC, pH, C/N ratio and ratio of reducing sugar during the heaping. EC and pH tended to be higher in composts with chicken droppings than those with chemical fertilizers only. The amount of phenolic compounds extracted with cold water decreased markedly in each type during the one-month heaping period. C/N ratio decreased gradually in each type, and after the middle of the heaping period, this ratio was observed to be higher in composts with chemical fertilizers only than those with chicken droppings. The ratio of reducing sugar also decreased gradually. Throughout the heaping period, this ratio tended to be higher in composts with hardwood bark and rice hull as the main materials than those with hardwood bark only, and in composts with chemical fertilizers only as secondary raw materials than those with chicken droppings. 2) From totally judging degree of maturity of composts, heaping periods required for complete fermentation of composts were found to be six months for type A compost, nine months for types B and C, and twelve months for type D.