Shoji Matsuura

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.

The Impact of Sunlight Conditions on the Consistency of Vegetation Indices in Croplands—Effective Usage of Vegetation Indices from Continuous Ground-Based Spectral Measurements

A ground-based network of spectral observations is useful for ecosystem monitoring and validation of satellite data. However, these observations contain inherent uncertainties due to the change of sunlight conditions. This study investigated the impact of changing solar zenith angles and diffuse/direct light conditions on the consistency of vegetation indices (normalized difference vegetation index (NDVI) and green-red vegetation index (GRVI)) derived from ground-based spectral measurements in three different types of cropland (paddy field, upland field, cultivated grassland) in Japan. In general, the vegetation indices decreased with decreasing solar zenith angle. This response was affected significantly by the growth stage and diffuse/direct light conditions. The decreasing response of the NDVI to the decreasing solar zenith angle was high during the middle growth stage (0.4 < NDVI < 0.8). On the other hand, a similar response of the GRVI was evident except in the early growth stage (GRVI < 0). The response of vegetation indices to the solar zenith angle was evident under clear sky conditions but almost negligible under cloudy sky conditions. At large solar zenith angles, neither the NDVI nor the GRVI were affected by diffuse/direct light conditions in any growth stage. These experimental results were supported well by the results of simulations based on a physically-based canopy reflectance model (PROSAIL). Systematic selection of the data from continuous diurnal spectral measurements in consideration of the solar light conditions would be effective for accurate and consistent assessment of the canopy structure and functioning.

Ammonia exchange on grasslands in an intensive dairying region in central Japan

Abstract In an intensive dairying region, N flow through ammonia (NH3) is comparatively important because of a high-N loading condition based on livestock manure. To elucidate part of the N flow in Orchardgrass (Dactylis glomerata L.) and Italian ryegrass (Lolium multiflorum Lam.) dominant cutting grasslands in an intensive dairy farming region in central Japan, the NH3 flux was measured using a gradient method over 3 years. The 3-year means of the annual balance of NH3 fluxes as the difference between emission and deposition were −14.4 kg N ha−1 in the manure plot and −18.6 kg N ha−1 in the chemical fertilizer plot, averaging −16.5 kg N ha−1. The balance shows the dominance of NH3 dry deposition in both plots, indicating that these grasslands acted as a net sink of NH3, receiving 16.5 kg N ha−1 year−1 of NH3 from the atmosphere. Applications of chemical fertilizer and composted manure caused temporary NH3 emissions equivalent to losses of 11.6 and 4.4%, respectively, of the applied NH4 +-N. A previous study has shown that wet deposition was 18 kg N ha−1 year−1 in this intensive dairy farming region, so atmospheric N input to the grassland was estimated to be 34.5 kg N ha−1 year−1as both dry and wet deposition. This amount equalled 17.3% of the 199 kg N ha−1 year−1 generated locally as manure in the region. Assuming that 25% was selected as a representative NH3 emission factor from livestock manure, atmospheric deposition of ammoniacal N corresponded to 69.5% of the emitted NH3 from livestock manure in the study area, indicating that emission and deposition of NH3 in the area is an important internal flow of the N cycle in this intensive dairying region in central Japan.

Mitigation Effect of Farmyard Manure Application on Greenhouse Gas Emissions from Managed Grasslands in Japan

Applying manure can lead to decrease of chemical nitrogen (N) fertilizer use and increase of soil carbon (C) sequestration. The effect of manure application on net ecosystem C balance (NECB), methane (CH4) and nitrous oxide (N2O) emissions and global warming potential (GWP) was examined at four managed grasslands on Andosols in different climatic regions in Japan for 3 years. At adjoining manure and fertilizer plots in each site, net ecosystem exchange (NEE) and CH4 and N2O fluxes were measured by the eddy covariance method and dark chamber methods, respectively. Manure application decreased fertilizer N application rate in manure plot to 65–88 % in fertilizer plot. NECB (= NEE−C applied in manure + harvested C) was higher in fertilizer plot (1.9 ± 0.9 MgC ha−1 year−1) than in manure plot (−1.8 ± 1.8 MgC ha−1 year−1), indicating that the soils in fertilizer plots lost C. There was no significant difference in harvested C between fertilizer and manure plots (4.3 ± 0.8 and 4.1 ± 0.6 MgC ha−1 year−1, respectively). NEE showed more CO2 uptake in fertilizer plots (−2.4 ± 1.1 MgC ha−1 year−1) than in manure plots (−1.6 ± 0.7 MgC ha−1 year−1), but manure application could compensate for the shortage in NEE. CH4 emission was close to zero, while the N2O emission was greater in manure plots (6.2 ± 3.7 kgN ha−1 year−1) than in fertilizer plots (3.6 ± 3.2 kgN ha−1 year−1). The difference of GWP between manure and fertilizer plots showed a negative relationship with manure C application rate (y = −4.45 ln(x) + 2.84; R 2 = 0.85; p < 0.01), indicating that manure application rate more than 2 MgC ha−1 year−1 can mitigate global warming in the Japanese grasslands.

Estimation of the amount of nutrients in livestock manure

(Jpn. J. Soil Sci.Plant Nutr., 77, 283–291, 2006) Nutrient amounts in livestock manure management, including manure treatment and use, were estimated using published statistical data and other information. The eight categories for manure treatment were defined in this study as composting at facility, composting at stockyard, raw feces, dried feces, urine, slurry, purification and other. The three categories for use of manure were defined as application to farmland, sale and exchange and other. The regional daily excretion units per head of dairy and beef cattle, including the amount of excreta, nitrogen (N), phosphorus (P) and potassium (K), were calculated based on the quantities and qualities of feed in each region. There was found to be a difference in the values for Hokkaido and other regions. Concerning manure treatment methods in the dairy sector, the sum of the proportion of raw feces and compost at stockyard was high in Hokkaido. On the other hand, the sum of the proportion of composting at facility and dried feces was high in Hokuriku, Tokai, Kinki and Shikoku. In Kyushu, the proportion of slurry production was higher than in any other region. The amounts of N, P, and K in compost estimated in this study were compared with those calculated from published statistics. The results were as follows. The amounts of N, P, and K in dairy cattle compost, N and K in beef cattle compost, and N in poultry compost in this study were similar to the amounts cited in reported statistics. The amounts of P in beef cattle, swine, and poultry compost in this study were lower than those cited in reported statistics. As for the use of manure, application to farmland is the most common use of manure in the dairy and beef cattle sector. The proportions of purification, and sale and exchange were high for the swine and poultry sectors, respectively. Large amounts of liquid manure, such as urine and slurry, are applied to farmland. To clarify the nutrient load resulting from liquid manure, the usable amount of dairy slurry was calculated based on both the standard application rate of fertilizer and the area of grassland and forage crops. As a result, the amount of usable N was lower than the amount of liquid manure N in the Kanto-Tosan, Tokai and Kinki regions.