Masayuki Hojito

Effects of Plant Species on CH4 and N2O Fluxes from a Volcanic Grassland Soil in Nasu, Japan

To investigate the effects of plant species in grassland on methane (CH4) and nitrous oxide (N2O) fluxes from soil, fluxes from an orchardgrass (Dactylis glomerata L.) grassland, white clover (Trifolium repens L.) grassland and orchardgrass/white clover mixed grassland were measured weekly from April 2001 to March 2002 using a vented closed chamber method. Related environmental parameters (soil inorganic N content, soil pH (H2O) value, soil moisture content, soil temperature, grass yield, and the number of soil microorganisms) were also regularly monitored. On an annual basis, CH4 consumption in the soil of the orchardgrass grassland, white clover grassland and orchardgrass/white clover mixed grassland was 1.8, 2.4, and 1.8 kg C ha−1 year−1, respectively. The soil bulk density of the white clover grassland was lower than that of the other grasslands. Fluxes of CH4 were positively correlated with the soil moisture content. White clover increased the CH4 consumption by improving soil aeration. Nitrogen supply to the soil by white clover did not decrease the CH4 consumption in the soil of our grasslands. On the other hand, annual N2O emissions from the orchardgrass grassland, white clover grassland, and orchardgrass/white clover mixed grassland were 0.39, 1.59, and 0.67 kg N ha−1 year−1, respectively. Fluxes of N2O were correlated with the NO3 − content in soil and soil temperature. White clover increased the N2O emissions by increasing the inorganic N content derived from degrading white clover in soil in summer.

N2O and CH4 fluxes from a volcanic grassland soil in Nasu, Japan: Comparison between manure plus fertilizer plot and fertilizer-only plot

Abstract We examined the effects of manure + fertilizer application and fertilizer-only application on nitrous oxide (N2O) and methane (CH4) fluxes from a volcanic grassland soil in Nasu, Japan. In the manure + fertilizer applied plot (manure plot), the sum of N mineralized from the manure and N applied as ammonium sulfate was adjusted to 210 kg N ha−1 year−1. In the fertilizer-only applied plot (fertilizer plot), 210 kg N ha−1 year−1 was applied as ammonium sulfate. The manure was applied to the manure plot in November and the fertilizer was applied to both plots in March, May, July and September. From November 2004 to November 2006, we regularly measured N2O and CH4 fluxes using closed chambers. Annual N2O emissions from the manure and fertilizer plots ranged from 7.0 to 11.0 and from 4.7 to 9.1 kg N ha−1, respectively. Annual N2O emissions were greater from the manure plot than from the fertilizer plot (P < 0.05). This difference could be attributed to N2O emissions following manure application. N2O fluxes were correlated with soil temperature (R = 0.70, P < 0.001), NH+ 4 concentration in the soil (R = 0.67, P < 0.001), soil pH (R = –0.46, P < 0.001) and NO− 3 concentration in the soil (R = 0.40, P < 0.001). When included in the multiple regression model (R = 0.72, P < 0.001), however, the following variables were significant: NH+ 4 concentration in the soil (β = 0.52, P < 0.001), soil temperature (β = 0.36, P < 0.001) and soil moisture content (β = 0.26, P < 0.001). Annual CH4 emissions from the manure and fertilizer plots ranged from –0.74 to –0.16 and from –0.84 to –0.52 kg C ha−1, respectively. No significant difference was observed in annual CH4 emissions between the plots. During the third grass-growing period from July to September, however, cumulative CH4 emissions were greater from the manure plot than from the fertilizer plot (P < 0.05). CH4 fluxes were correlated with NH+ 4 concentration in the soil (R = 0.21, P < 0.05) and soil moisture content (R = 0.20, P < 0.05). When included in the multiple regression model (R = 0.29, P < 0.05), both NH+ 4 concentration in the soil (β = 0.20, P < 0.05) and soil moisture content (β = 0.20, P < 0.05) were significant.

The effect of fertilizer and manure application on CH4 and N2O emissions from managed grasslands in Japan

The objectives of this study were to clarify the effect of chemical fertilizer and manure application on methane (CH4) and nitrous oxide (N2O) emissions from intensively managed grassland on Andosols in Japan and to determine the controlling factors of the CH4 and N2O emissions. The emission factors (EF) for both fertilizer- and manure-induced N2O emissions were calculated. Three experimental plots were set up in five grasslands across four climatic regions in Japan: one plot for treatment with chemical fertilizer (fertilizer plot); another plot for treatment with cattle manure and chemical fertilizer (manure plot), and the final plot was not treated with chemical fertilizer or manure (control plot). The type of chemical fertilizer was ammonium-based fertilizer or a combination fertilizer of ammonium and urea. CH4 and N2O emissions were measured at the study sites for six years. For the manure plot, a supplement of chemical fertilizer was added to equalize the supply rate of mineral nitrogen (N) relative to that of the fertilizer plots. There were no significant differences in CH4 emissions among the treatment plots, and the effect of fertilizer or manure application was not evident. CH4 emissions tended to be larger at sites with higher soil moisture content. The application of chemical fertilizer or manure increased N2O emissions at all the sites, and there were significant differences among the sites and across different years. Background N2O emissions (N2O emissions at the control plot) had strong positive correlations with air temperature and precipitation, along with weak positive correlations with soil carbon and N content. Therefore, an empirical model (Background N2O emission = 0.298 × air temperature + 0.512 × soil N content −3.77) was established. Fertilizer-induced N2O emission factor (EF) had a positive correlation (R2 = 0.50, p < 0.01) with precipitation (Fertilizer-induced EF = 0.0022 × precipitation −1.3), and increasing precipitation enhanced N2O production through the denitrification process due to applied fertilizer N. There were no significant differences in manure-induced EFs among the sites, and the average was 0.36% except for an outlier.

Grassland renovation increases N2O emission from a volcanic grassland soil in Nasu, Japan

Abstract To investigate the effects of renovation (ploughing and resowing) on nitrous oxide (N2O) emissions from grassland soil, we measured N2O fluxes from renovated and unrenovated (control) grassland plots. On 22 August in both 2005 and 2006 we harvested the sward, ploughed the surface soil and then mixed roots and stubble into the surface soil with a rotovator. Next, we compacted the soil surface with a land roller, spread fertilizer at 40 kg N ha−1 on the soil surface and sowed orchardgrass (Dactylis glomerata L., Natsumidori). In the control plot, we just harvested the sward and spread fertilizer. We determined N2O fluxes for 2 months after the renovation using a vented closed chamber. During the first 2 weeks, the renovated plot produced much more N2O than the control plot, suggesting that N was quickly mineralized from the incorporated roots and stubble. Even after 2 weeks, however, large N2O emissions from the renovated plot were recorded after rainfall, when the soil surface was warmed by sunshine and the soil temperature rose 2.7–3.0°C more than that of the control plot. In 2005, during the 67-day period from 19 August to 26 October, the renovated and control plots emitted 5.3 ± 1.4 and 2.8 ± 0.7 kg N2O-N ha−1, with maximum fluxes of 3,659 and 1,322 µg N2O-N m−2 h−1, respectively. In 2006, during the 65-day period from 21 August to 26 October, the renovated and control plots emitted 2.1 ± 0.6 and 0.96 ± 0.42 kg N2O-N ha−1, with maximum fluxes of 706 and 175 µg N2O-N m−2 h−1, respectively. The cumulative N2O emissions from plots in 2005 were greater than those in 2006, presumably because rainfall just after renovation was greater in 2005 than in 2006. These results suggest that incorporated roots and stubble may enlarge the anaerobic microsites in the soil in its decomposing process and increase the N2O production derived from the residues and the fertilizer. In addition, rainfall and soil moisture and temperature conditions during and after renovation may control the cumulative N2O emission.

Grazing Affects Exosomal Circulating MicroRNAs in Cattle.

Circulating microRNAs (c-miRNAs) are associated with physiological adaptation to acute and chronic aerobic exercise in humans. To investigate the potential effect of grazing movement on miRNA circulation in cattle, here we profiled miRNA expression in centrifugally prepared exosomes from the plasma of both grazing and housed Japanese Shorthorn cattle. Microarray analysis of the c-miRNAs resulted in detection of a total of 231 bovine exosomal miRNAs in the plasma, with a constant expression level of let-7g across the duration and cattle groups. Expression of muscle-specific miRNAs such as miR-1, miR-133a, miR-206, miR-208a/b, and miR-499 were undetectable, suggesting the mildness of grazing movement as exercise. According to validation by quantitative RT-PCR, the circulating miR-150 level in the grazing cattle normalized by the endogenous let-7g level was down-regulated after 2 and 4 months of grazing (P < 0.05), and then its levels in housed and grazing cattle equalized when the grazing cattle were returned to a housed situation. Likewise, the levels of miR-19b, miR-148a, miR-221, miR-223, miR-320a, miR-361, and miR-486 were temporarily lowered in the cattle at 1 and/or 2 month of grazing compared to those of the housed cattle (P < 0.05). In contrast, the miR-451 level was up-regulated in the grazing cattle at 2 months of grazing (P = 0.044). The elevation of miR-451 level in the plasma was coincident with that in the biceps femoris muscle of the grazing cattle (P = 0.008), which suggests the secretion or intake of miR-451 between skeletal muscle cells and circulation during grazing. These results revealed that exosomal c-miRNAs in cattle were affected by grazing, suggesting their usefulness as molecular grazing markers and functions in physiological adaptation of grazing cattle associated with endocytosis, focal adhesion, axon guidance, and a variety of intracellular signaling, as predicted by bioinformatic analysis.

Nitrous oxide and methane emissions from grassland treated with bark- or sawdust-containing manure at different rates

On the main Japanese island of Honshu, bark or sawdust is often added to cattle excreta as part of the composting process. Dairy farmers sometimes need to dispose of manure that is excess to their requirements by spreading it on their grasslands. We assessed the effect of application of bark- or sawdust-containing manure at different rates on annual nitrous oxide (N2O) and methane (CH4) emissions from a grassland soil. Nitrous oxide and CH4 fluxes from an orchardgrass (Dactylis glomerata L.) grassland that received this manure at 0, 50, 100, 200, or 300 Mg ha−1 yr−1 were measured over a two-year period by using closed chambers. Two-way analysis of variance (ANOVA) was employed to examine the effect of annual manure application rates and years on annual N2O and CH4 emissions. Annual N2O emissions ranged from 0.47 to 3.03 kg N ha−1 yr−1 and increased with increasing manure application rate. Nitrous oxide emissions during the 140-day period following manure application increased with increasing manure application rate, with the total nitrogen concentration in the manure, and with cumulative precipitation during the 140-day period. However, manure application rate did not affect the N2O emission factors of the manure. The overall average N2O emission factor was 0.068%. Annual CH4 emissions ranged from −1.12 to 0.01 kg C ha−1 yr−1. The annual manure application rate did not affect annual CH4 emissions.

The status of wet deposition of nitrogen compounds in an intensive dairy farming area in central Japan

(pp. 47–52) The wet deposition of nitrogen compounds in the intensive dairy farming area and its environs in the northern part of the Kanto region in central Japan was investigated from April 2003 to April 2005. Open-bulk samplers were used to collect open-bulk precipitation, which approximates the sum of wet and dry deposition. Furthermore, wet-only samplers were applied to collect the precipitation for every 1 mm in a rainfall, termed the wet sample. The concentrations of total nitrogen and ammonium ions in the open-bulk precipitation were high in the central part of the dairy farming area and low in the remote mountainous area more than 15 km away the concentrations were generally high during winter and spring, and low during summer and autumn. There was a large difference in the annual deposition of nitrogen between the farming area and the surrounding area. The annual deposition of nitrogen in the farming area was significantly high compared to the values of existing data in Japan and Europe. The concentrations of respective nitrogen compounds in the wet sample, which accounted for 40 of the total rainfalls events, were notably high at the beginning of precipitation and rapidly decreased by 8 mm of continuous precipitation. The nitrogen concentrations at the beginning of precipitation were high in the farming area, and relatively low in the surrounding area. It was thought that the cause of the large wet deposition in the farming area was due to ammonia emissions, mainly from cattle manure produced at dairy farms. The factors of the seasonal changes were considered to be the frequency and the amount of precipitation, and the change in ammonia emissions from manure management performed by dairy farmers.

EFFECTS OF LIMING ON GRASS GROWTH, SOIL SOLUTION COMPOSITION, AND MICROBIAL ACTIVITIES

In order to determine the effect of liming on grass growth, the chemical composition of the soil solution and microbial activities were analyzed. Ground limestone (CaCO3) was topdressed at the rates of 0, 2, 4, and 8 t/ha to a 9 year old orchardgrass sward. The effects of liming on the soil were observed only in the surface layer (0–5 cm) during the 6 month period after lime application. Although the yield of grass was not distinctly affected by Iiming, the amount of phosphorus (P) and calcium (Ca) absorbed by the grass was considerably increased. With increasing rates in lime application, the concentrations of Ca and sulfate (S), and the value of the pH in the soil solution (0–2 cm layer) were increased, while the concentrations of a1uminum (AI), P, and nitrogen (N) were decreased. No change was observed in the chemical composition of the soil solution from the layers below 5 cm. The microbial activities 2,3,5-triphenyltetrazoJium chloride (TTC)-reducing activity. fructose or urea-decomposing activity, a...

Effect of dairy manure type and supplemental synthetic fertilizer on methane and nitrous oxide emissions from a grassland in Nasu, Japan

Abstract We investigated the effects of different types of manure on greenhouse gas (GHG) emissions from grassland for 2 years using a closed chamber method to measure methane (CH4) and nitrous oxide (N2O) fluxes from plots that received no nitrogen (“−N” plots), dairy cattle slurry plus synthetic N fertilizers (“slurry” plots) and farmyard manure plus synthetic N fertilizers (“FYM” plots). The application rates of slurry (65.8 to 66.4 Mg ha−1 y−1) or FYM (36.5 to 39.2 Mg ha−1 y−1) were determined so that the annual potassium supply from slurry or FYM roughly covered the annual potassium requirement for forage grass production. Supplemental ammonium sulfate and superphosphate were applied to cover the annual N and phosphorus (P) requirements. Sharp peaks of CH4 flux were observed shortly after slurry applications, whereas CH4 fluxes only slightly increased following FYM applications. The annual CH4 emissions from −N, slurry, and FYM plots ranged from −1.17 to −1.16, 0.21 to 1.84 and −1.67 to −0.27 kg CH4-C ha−1 y−1, respectively. The CH4 emissions from slurry plots tended to be greater than those from −N (P = 0.066) and FYM plots (P = 0.097). No significant difference was observed between −N and FYM plots (P = 0.973). The annual N2O emissions from −N, slurry, and FYM plots ranged from 0.35 to 0.81, 1.77 to 7.58 and 2.24 to 7.59 kg N2O-N ha−1 y−1, respectively. The N2O emissions in the first year were greater than those in the second year (P = 0.012). The N2O emissions in slurry and farmyard manure (FYM) plots tended to be greater than those in −N plots (P = 0.076, P = 0.059). No significant difference was observed between slurry and FYM plots (P = 0.989). Both the cumulative precipitation following fertilization and soil moisture content at time of fertilization substantially affected the interannual differences in N2O emissions. In terms of carbon dioxide equivalents (CO2-eq), the N2O emissions (0.83 to 3.55 Mg CO2-eq ha−1 y−1) were substantial in comparison to the CH4 emissions (−0.06 to 0.06 Mg CO2-eq ha−1 y−1). These results collectively suggest that the types of manure, from different storage conditions, had little impact on annual GHG emissions under optimized fertility management. Environmental factors had much greater impact.

Influence of Agricultural Activity on Nitrogen Budget in Chinese and Japanese Watersheds

Abstract To analyze the effect of agricultural activity on nitrogen (N) budget at the watershed scale, a comparative study was conducted at two Japanese watersheds, the Shibetsu River watershed (SRW) and Upper-Naka River watershed (UNRW), and one Chinese watershed, the Jurong Reservoir watershed (JRW). The total area and the proportion of agricultural area (in parentheses) of the watersheds were 685 (51%), 1 299 (21%), and 46 km2 (55%) for SRW, UNRW, and JRW, respectively. The main agricultural land use in SRW was forage grassland, while paddy fields occupied the highest proportion of cropland in UNRW (11% of total area) and JRW (31% of total area). The farmland surplus N was 61, 48, and 205 kg N ha−1 year−1 for SRW, UNRW, and JRW, respectively. The total input and output for the whole watershed were 89 and 76, 83 and 61, and 353 and 176 kg N ha−1 year−1 for SRW, UNRW, and JRW, respectively. The proportion of discharged N to net anthropogenic N input was 31%, 37%, and 1.7% for SRW, UNRW, and JRW, respectively. The two watersheds in Japan showed similar proportions of discharged N to those of previous reports, while the watershed in China (JRW) showed a totally different characteristic compared to previous studies. The high N input in JRW did not increase the amount of discharged N at the outlet of the watershed due to high proportions of paddy fields and water bodies, which was an underestimated N sink at the landscape scale.