In this study, we used hydrothermal reactions to produce liquid manure from crop residues, thereby effectively utilizing biomass, and investigated the influence of raw material properties on the liquid manure. Three types of residues were used: dried sugarcane leaves, broad bean stems and leaves, and discarded pak-choi (Chinese cabbage). Each sample was adjusted to a 1:20 dry-weight-to-water weight ratio (kg) and heated at 170 ℃ at 0.7 MPa for 30 min in a hydrothermal reactor. The reaction products were filtered through 2-mm mesh to obtain a filtrate that could be used as liquid manure. The quantity and composition of nutrients and organic acids in the filtrate differed among the materials. Differences in the carbon migration rate might be a result of different quantities of neutral detergent fiber (NDF) in the materials. Differences in inorganic nitrogen and organic acid composition in the filtrate might be due to differences in nutrient contents of the starting materials. Germination experiments were also performed. Mesh filtrates from broad bean stems and leaves and pak-choi inhibited root growth of Japanese mustard spinach, but filtrate from dried sugarcane leaves did not. These findings suggest that the influence of liquid manures on plant growth differs according to the materials used to produce the filtrate. For mesh filtrate to be used as liquid manure, the mechanisms by which different residues inhibit root growth must be determined.

Soil maps provide essential information for developing strategies for sustainable land use as well as for issues related to environmental mitigation and adaptation. Major soil maps in Japan have been delineated independently for different land uses; as a result, there is no available map on a practical scale produced using a single soil-classification framework. To address the need for a consistent national soil mapping framework, we delineated a new soil map of Hokkaido by using the Comprehensive Soil Classification System of Japan, First Approximation (CSCJ). We used the 1:200,000 soil map published in the national land survey project (NLS) as a benchmark for delineating the CSCJ soil map. To reclassify soil names from the NLS to the CSCJ system in the working map, we used a database of existing soil profile information, and we conducted a soil survey in a forested area. From the new soil map, the dominant soil great group in Hokkaido is Andosols (distribution area: 43%), followed by Brown Forest soils (30%) and Lowland soils (11%). Allophanic Andosols and Non-Allophanic Andosols were mainly distributed in the southern and northern parts of the Andosols distribution area, respectively. Andic Brown Forest soils were mainly distributed at the boundary between Andosols and Brown Forest soils. Comparing the NLS and CSCJ soil maps, the distribution of Andosols increased from 18% (NLS) to 43% (CSCJ) of the map area, and Brown Forest soils decreased from 57% (NLS) to 30% (CSCJ). These results indicate that the basis for the CSCJ map is comparable to that for the international soil classification system, and that the CSCJ map accurately estimates soil organic carbon stocks.