Relationships between chemical composition and nitrogen mineralization characteristics of 14 brand samples of caged layer manures (free from secondary materials) on the market were examined to find simple and quick methods for evaluation of available nitrogen content in poultry manure. 1) Total nitrogen (T-N) content on dry matter basis of poultry manure in this investigation ranged 24-70 g kg^-1, C/N ratio 3.5-9.4, 0.1 M sodium hydroxide soluble nitrogen (Na-N) 8-45 g kg^-1, and inorganic nitrogen (Ino-N) 0.8-7.6 g kg^-1. 2) The absorption spectra of 0.1 M sodium pyrophosphate extract of poultry manure with low C/N ratio showed a maximum at around 290 nm which indicates the existence of uric acid. Uric acid nitrogen (UAN)^^^- content was tentatively estimated from the difference of absorbance between 290 and 260 nm, ΔA290-260 (equation 1). UAN^^^- content ranged 0-34 g kg^-1, and occupied up to 54% of T-N or 75% of Na-N. Sum of UAN^^^- and Ino-N correlated closely with Na-N and T-N. 3) Judging from the time course of nitrogen mineralization rate, available nitrogen from poultry manure was hypothetically divided into three categories, i.e., instantly available, earlier slow-release and later slow-release. Instantly available nitrogen content corresponded nearly to the sum of Ino-N and UAN^^^-, and also correlated closely with Na-N and T-N. Earlier slow-release nitrogen showed some significant correlations with these nitrogen components. However, no correlation was found between later slow-release nitrogen and any chemical components analyzed in this experiment. 4) Ino-N after 1 d incubation with soil at 30℃ had high correlations with Ino-N after longer incubation. 5) We could evaluate available nitrogen content in poultry manures by using any one of T-N, Na-N, UAN^^^-+Ino-N and Ino-N after 1 d incubation with soil at 30℃.

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Soils have not only functions in producing food and materials for human life but also functions in holding water and materials, conserving water quantity and quality in ground, river and lake. But until now there has been no available method that can quantitatively evaluate the functions of soils in a small watershed. In this paper, we are presenting a method of grouping soils for evaluation of water conservation functions of a small watershed. Several water holding capacities (whole, 0-5 kPa, 5-50 kPa), percolation index and saturated hydraulic conductivity were utilized as the indicators to express water holding capacity and permeability. In addition, the phosphate adsorption coefficient, anion exchangeable capacity and cation exchangeable capacity were used as the indicators to express material (phosphate, nitrate, ammonium, bases, etc.) retention capacities. Soils with different sequence and thickness of horizons having different combination of the above indicator values were divided into 10 soil groupings on lowland, 15 soil groupings on terrace, and 20 soil groupings on mountain in the Hosaki research watershed of Ibaraki prefecture. The standard profiles were given for each soil grouping. Water conservation indicators of each horizon grouping and water conservation capacities of each soil grouping were also estimated.

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The estimation methods of water holding capacities and material retention capacities of the soils, and the mapping methods of soil groupings and water conservation capacities were studied in a small watershed. The water conservation capacities of the soils in the Hosaki small watershed were also estimated. 1) For the Hosaki River small watershed, a 1/5,000 large-scale soil map divided into 45 soil groupings was produced. 2) The map was digitized with a 10 m grid, and the distribution area of every soil grouping was estimated. By multiplying the water conservation capacity by the distribution area of the soil grouping, the water conservation capacity of every soil grouping in the small watershed was estimated. 3) The whole soil volume in 288.9 ha of the small watershed was 6,399,785 m^3, the maximum water retention capacity 3,976,696 m^3, the 0-5 kPa water retention capacity 983,867 m^3, and the 5-50 kPa water retention capacity 446,303 m^3. In addition, the small watershed had PAC of 5,685 Mg, AEC of 118,192 kmol(-), and CEC of 852,587 kmol(+). 4) Though the water holding capacities of the soils were the biggest in the mountain and comparatively big even in the upland, they were small in the lowland. 5) Though the material retention capacities of the soils were the biggest in the upland and comparatively big even in the mountain, they were small in the lowland.

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In order to study the possible use of tofe refuse (okara) as a fertilizer or inorganic soil amendment, the effects of charbureted tofu refuse on the soil chemical and physical properties and the growth of kidney bean were studied. The results were as follows. 1) Since charbureted tofu refuse contained a large amount of exchangeable potassium, the application of charbureted tofu refuse to soil increased the level of exchangeable potassium in the soil. 2) Since (the particles of) charbureted tofu refuse had various sizes of holes on the surface and bulk density, porosity and hydraulic conductivity were 0.492, 0.990 m^3 m^-3 and 3.2×10^-2 cm s^-1, respectively, the hydraulic conductivity would be increased by the application of charbureted tofu refuse in the soil. 3) When the application ratio (v/v) of charbureted tofu refuse to soil was 1 : 9 or 2 : 8, charbureted tofu refuse improved the growth and yield of kidney bean plants. However, when the application ratio (v/v) of charbureted tofu refuse to soil was 3 : 7, the growth of kidney bean was inhibited and the young pod yield was reduced.

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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