In order to elucidate the differences in chemical constituent of cow slurry on dry matter production of timothy (Phleum pratense L.) grassland in a field experiment, 18 different types of slurries collected from dairy farms in Konsen district, Hokkaido, were applied to grassland surfaces. The range of dry matter, total nitrogen (N), and ammonium N content in the cow slurry was 53 to 116, 2.9 to 6.1, and 0.9 to 3.3g kg^<-1>, respectively, in fresh weights. The application rate of the cow slurry was 50Mg ha^<-1>. 1. In the first year, grass yield on cow slurry-treated plots was higher than that on non-slurry treated plots. Although the application rate of the cow slurry was the same, great differences were found in the grass yield among the slurry applications. However, in the following year, small amounts of increases in the grass yield on cow slurry-treated plots compared with that on non-slurry-treated plots were found. 2. The form of N in the applied cow slurry which showed close relations between the uptake of N by the timothy differed between the 1st and 2nd cutting: ammonium N in the applied cow slurry for the 1st cutting and organic N in the applied cow slurry for the 2nd cutting. 3. Great differences were found in the recovery rate of N from the timothy grasslands when cow slurry was applied. It was considered that the fertilizer efficiency of cow slurry applied to timothy grasslands fluctuated depending on the difference between the chemical constituents of cow slurry. 4. It was possible to evaluate the fluctuations in N efficiency of the cow slurry by the ratio of NH_4-N/DM of the cow slurry. 5. From these results, N efficiency of the cow slurry applied to timothy grassland can be evaluated by multiplying the total N content of the cow slurry with the N fertilizer efficiency rate. Other factors, such as quality of the cow slurry, application rate of the cow slurry, time of application of the cow slurry, weather conditions when the cow slurry was applied, and soil conditions of grassland should also be considered.

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A stable isotope tracer technique was applied to a field experiment in order to establish a tracer technique for field experiments and to elucidate cadmium (Cd) uptake by soybean (Glycine max var. Enrei) and further translocation into its grain. The enriched ^<113>Cd (94.8%±0.3 content%) was used as a tracer. A hundred milliliters of tracer solution (^<113>Cd 10mg L^<-1>) was supplied to each soybean plant, totaling 1mg of ^<113>Cd application to each soybean plant. The Cd tracer (Cd_<tr>) was detected in all soybean leaves, pods and seeds sampled at the stages of R3 and R5, and it was also detected from almost all soybean pods, seeds and stems harvested at the stage of R8. These result indicates that 1mg of ^<113>Cd-tracer application is enough to detect it in soybean under field conditions. The total amount of Cd_<tr> injected into the soil is equivalent to 0.009mg kg^<-1>, which concentration is below one twentieth of the natural abundance of Cd in soil. An advantage of the stable isotope tracer compared with the radioisotope tracer is its high usability. This technique also carries the advantage that the ^<113>Cd-tracer and the soil-indigenous Cd in soybean plants can be determined simultaneously. A total of 6 ^<113>Cd applications was made at different growth stages of soybean. The Cd_<tr> concentration of leaves in the 1st injection plot (V3 stage) sampled at the R3 stage was significantly higher than that in the 2nd (R1) injection plots. This result indicates that leaves vigorously accumulate Cd only at the very early growth stage. The Cd_<tr> concentration in the soybean stems at harvesting was not significantly different up to the 5th injection plot (R6). The Cd_<tr> concentration of seeds, however, significantly fell after the 4th injection plot (R5), namely, Cd absorbed before the R5 stage causes an increase of Cd concentration in seeds. These results suggest that the Cd concentration in seeds hardly increases even if the Cd accumulated in leaves is translocated to the seeds. Additionally, the plant roots in the lower layer (30cm depth) and those in the upper layer (10cm depth) did not differ much in the Cd uptake activity until its R5 stage.

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Slurries with different chemical characteristics were applied to the soil packed in Wagner pots. Used slurries were untreated cow manure slurry, aerated slurry, and anaerobically digested slurry. Plots treated with compost and chemical fertilizers were also installed for the control. The ratio of humic substances to the total carbon was higher in the order of digested slurry > aerated slurry, untreated slurry ≫ compost. These materials were mixed in the upper 9cm of the soil in the pots, while the amounts of carbon contained in these materials were adjusted to the same amount. Three consentive crops of Brassica campestris subsp. napus var. komatsuna were grown in these pots. Application of slurries increased the organic matter contents and CEC of the soil, as did compost. The number of fungi colonies and the weight of crop roots also increased remarkably due to the slurry application. The application of slurry also increased remarkably the amount of macro aggregate (> 250μm) in the soil, and the amount was larger in the order of digested slurry > aerated slurry > untreated slurry > compost. When macro-aggregate was disaggregated, both the particulate organic matter fraction (> 53μm) and mineral-associated organic matter fraction (< 53μm) increased in the slurry-treated plots, while the increase in the mineral-associated organic matter fraction was tremendous. The distribution of carbon among aggregates with different sizes revealed that the carbon was accumulated in the mineral-associated organic matter fraction in the macro-aggregates in the slurry applied plots, which was presumed to be due to the contribution of fine humic substances in the slurry. On the other hand, when compost was applied to soil, only the weight and carbon contents of particulate organic matter fraction in the macro-aggregate increased, but this did not lead to the formation of macro-aggregate. Weights of crop roots and the numbers of fungi colonies both showed positive correlations with the amount of macro-aggregate. Application of slurries also brought about the decrease in soil bulk density, and the increase in porosity for gravitational water and saturated permeability. As shown above, the application of slurries improved physico-chemical characteristics of soils, which was caused by the increase in mineral-associated organic matter fraction due to the humic substances contained in the slurries as well as due to the formation of macro-aggregates, due to the increase in the number of fungi colonies and the weights of crop roots. These mechanisms were different from the mechanism estimated in the case of compost application.

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Three types of cow manure slurry (anaerobically digested slurry, aerated slurry, and untreated slurry) were applied to fine textured brown lowland soil packed in Wagner pots and aggregate composition of the soil was compared with plots amended with chemical fertilizers and compost. Due to the application of slurry, formation of macro-aggregate was enhanced, and their amounts increased in the order of the plots treated with digested slurry>aerated slurry>untreated slurry>compost=chemical fertilizers. When macro-aggregate was disaggregated, organic matter was accumulated in the mineral-associated organic matter fraction (<53μm) and the formation of macro-aggregate (>250μm) was enhanced in the slurry-treated plots. In this paper, the slurries used in the pot experiment were fractionated according to particle sizes, and viscosimetric characteristics and soil permeability were examined to clarify the physical characteristics of slurries. In addition, humic substances were extracted from the mineral-associated organic matter fraction of macro-aggregates in the soil amended with slurry. From the chemical characteristics, the origin of humic substance in the mineral-associated organic matter fraction was estimated, and the mechanism of soil aggregate formation due to the application of cow manure slurry was estimated. Solid fractions contained in slurries were low in the coarse fraction (>500μm) while high in the fine fraction (<53μm). The proportions of fine fractions were larger in the order of digested slurry>aerated slurry>untreated slurry>compost. The fluidity of the slurries and permeability into soil were larger in the order of digested slurry=aerated slurry>untreated slurry. Humic acids extracted from mineral-associated organic matter fraction of macro-aggregates belonged to type A in the plots amended with chemical fertilizers and compost as well as in the original soil (<53μm). On the other hand, the humic acids extracted from slurries and compost belonged to type Rp. Furthermore, humic acids from the mineral-associated organic matter fraction in the macro-aggregates of the soils amended with digested slurry, aerated slurry and untreated slurry all belonged to type B, indicating the decrease in the degree of humification compared with the plots amended with chemical fertilizers and compost. It was estimated from the FT-IR spectra of humic acids and PVP-adsorbed fulvic acids extracted from mineral-associated organic matter fraction that humic acids with low degree of humification were accumulated in the mineral-associated organic matter fraction of slurry-applied soil. From the above results, it may be concluded that the formation of mineral-associated organic matter was enhanced by the binding of soil particles and humic substances in slurries, which led to the further formation of macro-aggregates. It was also clarified that the formation of macro-aggregate was influenced by the physical properties of slurry, and the fermented slurries were more effective in the formation of macro-aggregates. Therefore, it became clear that cow manure slurry functions effectively as soil improving material like compost and farm yard manure.

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When wheat is grown after soybeans, it is necessary to reduce the amount of nitrogen applied compared to when wheat is cultivated after rice. Although soil analysis is effective for estimating the reduction in nitrogen, it does not reflect the effect of soybean residue left on the field until the field is plowed for wheat, because soil is generally analyzed after the bulky matter has been removed. Therefore, we compared the nitrogen uptake by wheat cultivated in the absence or presence of soybean residue to estimate the effects of the residue. In addition, we investigated the decomposition of soybean residue, the mineralization and organization of nitrogen derived from the residue, and the difference in the amount of nitrogen available in the soil before and after soybean cultivation. We found that the decomposition of soybean residue organized the soil mineral nitrogen in the early stage of wheat cultivation, and the organized nitrogen was remineralized in the later stage of wheat cultivation, which raised the nitrogen content of the wheat. However, soybean residue did not affect the nitrogen uptake by wheat at harvest time. Since there was more available nitrogen and greater nitrogen uptake by wheat in the field in which soybeans had been cultivated, the effect of soybean cultivation on the subsequent wheat cultivation may be small as a result of soybean residue and large as a result of the remaining soil. Accordingly, with double cropping, the basal nitrogen application for wheat cultivation following soybean cultivation could be estimated by analyzing soil from which the soybean residue has been removed. The topdressing nitrogen application may be reduced by an amount that corresponds to the increase in wheat nitrogen uptake caused by soybean residue in the later stage of wheat cultivation.

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An experiment was conducted to examine the absorption of zinc and copper by Brassica campestris L. cultivated in arable fields (Brown Forest soil, Andosol, and Brown Lowland soil) after five years' applications of chemical fertilizer, cattle farmyard manure, and pig farmyard manure. The results obtained in this study are summarized as follows. 1) Zn concentration in Brassica campestris was higher in the plant tops cultivated in Andosol and in both the roots and tops cultivated in Brown Forest soil with pig farmyard manure applications than in those with chemical fertilizer applications. Accumulation of Cu in the plant by amendment of animal manures was not observed, unlike Zn. 2) Cu had less ability to move into plants than has Zn. Cu tended to be absorbed by the plant after it accumulated in soils. On the other hand, Zn tended to be absorbed by the plant from both pig farmyard manure and soil accumulations. 3) Absorption of Zn by one plant was higher in the plant cultivated in Andosol and Brown Forest soil with pig farmyard manure applications than those with chemical fertilizer applications. Amounts of Zn and Cu absorbed by the plants relied upon their biomass rather than their concentrations; therefore, accumulations in the plant roots were remarkably lower than those of the tops. We concluded that long-term applications of pig farmyard manure to the soils which have high ability to retain soluble-metals such as Brown Forest soil would enhance Zn absorptions by the plant even when the application amount of pig farmyard manure is within recommended levels.

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This study evaluated the major factors that cause yearly fluctuation in the difference in sugar beet yield between the Eastern area and the Western area, characterized by various soil types, of Abashiri, Hokkaido. We focused on the dependence of yearly fluctuation of sugar beet yield on rooting depth in different soil types and under different weather conditions. The results obtained were as follows: 1) The difference in sugar and root yield between the higher-productivity Eastern area and the lower-productivity Western area was significant and was positively related to mean temperature in August. The harvest index increased with increasing temperature in August regardless of soil type. In the haplic andosol occupying the Eastern area, the total yield decreased slowly and the root yield tended to increase in hotter summer years. In contrast, the total yield decreased rapidly and the root yield tended to decrease in the cambisol belonging to the Western area. In the umbric andosol belonging to the Western area, the fluctuation tendency of total and root yield was intermediate. 2) During hot, sunny daytime conditions, sugar beet plants grown in haplic andosol having the deepest root system maintained the greatest stomatal aperture regulating CO_2 uptake and water loss, whereas plants grown in cambisol having the shallowest root system showed the most stomatal closing tendency, even under sunshine. The extent of stomatal aperture of plants grown in umbric andosol having moderate rooting depth showed an intermediate tendency. However, during the daytime at near-optimum temperature, stomata of plants grown in umbric andosol and cambisol were both open. 3) The major factor controlling yearly changes in the difference in sugar beet yield between the Eastern area and the Western area can be attributed to the difference in photosynthetic ability, which is based on the rooting depth and the water supply in response to summer temperature regimes.

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