Emissions of carbon dioxide, methane, and nitrous oxide from short- and long-term organic farming Andosols in central Japan

ABSTRACTChanges in weather and management practices such as manure and fertilizer applications have a major effect on nitrous oxide (N2O) and nitric oxide (NO) emissions from soils. N2O and NO emissions exhibit high intra- and inter-annual fluctuations, which are also highly influenced by land-use change. In this study we investigated how land-use change between grassland and cornfield affects soil N2O and NO emissions using long-term field measurements in a mollic andosol soil in Southern Hokkaido, Japan. Soil N2O and NO emissions were monitored for 5 years in a 30-year old grassland (OG), which was then plowed and converted to a cornfield for 3 years and then converted back to grassland (new grassland, NG) for another 3 years. We established four treatment plots: control, without any nitrogen (N) input (CT plot); chemical fertilizer only (F plot); chemical fertilizer and manure (MF plot); and manure only (M plot).Changing land use from OG to cornfield increased annual N2O emissions by 6–7 times, while the change from cornfield to NG resulted in a 0.3–0.6 times reduction in annual N2O emissions. N2O emissions in the newly established grassland were 2–5 times higher than those in the 30-year old grassland. Soil mineral N (NO3− and NH4+) was higher in cornfield, followed by NG and lowest in OG, while water extractable organic carbon (WEOC) did not significantly change with changing land use but tended to be higher in OG and NG than in cornfield. The ratio of WEOC to soil NO3− was the most important explanatory variable for differences in N2O emissions as land use changed. High N input, surplus soil N, and precipitation and low soil pH led to increased N2O emissions. N2O emissions in fertilizer- and/or manure-amended plots were 3–4, 2–5 and 1.4–2 times higher than those in the control treatment in OG, cornfield and NG, respectively. NO emissions were largely influenced by soil mineral N and N addition, and showed less response to changing land use. There were high inter-annual variations in both NO and N2O emissions in all plots, including the control treatment, highlighting the need for long-term measurements when determining local emission rates.

Greenhouse gas emission from direct seeding paddy field under different rice tillage systems in central China

Abstract. It is generally known that managed, drained peatlands act as carbon (C) sources. In this study we examined how mitigation through the reduction of the intensity of land management and through rewetting may affect the greenhouse gas (GHG) emission and the C balance of intensively managed, drained, agricultural peatlands. Carbon and GHG balances were determined for three peatlands in the western part of the Netherlands from 2005 to 2008 by considering spatial and temporal variability of emissions (CO2, CH4 and N2O). One area (Oukoop) is an intensively managed grass-on-peatland area, including a dairy farm, with the ground water level at an average annual depth of 0.55 (±0.37) m below the soil surface. The second area (Stein) is an extensively managed grass-on-peatland area, formerly intensively managed, with a dynamic ground water level at an average annual depth of 0.45 (±0.35) m below the soil surface. The third area is a (since 1998) rewetted former agricultural peatland (Horstermeer), close to Oukoop and Stein, with the average annual ground water level at a depth of 0.2 (±0.20) m below the soil surface. During the measurement campaigns we found that both agriculturally managed sites acted as C and GHG sources and the rewetted former agricultural peatland acted as a C and GHG sink. The ecosystem (fields and ditches) total GHG balance, including CO2, CH4 and N2O, amounted to 3.9 (±0.4), 1.3 (±0.5) and −1.7 (±1.8) g CO2-eq m−2 d−1 for Oukoop, Stein and Horstermeer, respectively. Adding the farm-based emissions to Oukoop and Stein resulted in a total GHG emission of 8.3 (±1.0) and 6.6 (±1.3) g CO2-eq m−2 d−1, respectively. For Horstermeer the GHG balance remained the same since no farm-based emissions exist. Considering the C balance (uncertainty range 40–60%), the total C release in Oukoop and Stein is 5270 and 6258 kg C ha−1 yr−1, respectively (including ecosystem and management fluxes), and the total C uptake in Horstermeer is 3538 kg C ha−1 yr−1. Water bodies contributed significantly to the terrestrial GHG balance because of a high release of CH4. Overall, this study suggests that managed peatlands are large sources of GHGs and C, but, if appropriate measures are taken, they can be turned back into GHG and C sinks within 15 years of abandonment and rewetting. The shift from an intensively managed grass-on-peat area (Oukoop) to an extensively managed one (Stein) reduced the GHG emissions mainly because N2O emission and farm-based CH4 emissions decreased.

Abstract. This article provides an overview of the effects of land-use on the fluxes of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and from peatlands in the Nordic countries based on the field data from about 100 studies. In addition, this review aims to identify the gaps in the present knowledge on the greenhouse gas (GHG) balances associated with the land-use of these northern ecosystems. Northern peatlands have accumulated, as peat, a vast amount of carbon from the atmosphere since the last glaciation. However, the past land-use and present climate have evidently changed their GHG balance. Unmanaged boreal peatlands may act as net sources or sinks for CO2 and CH4 depending on the weather conditions. Drainage for agriculture has turned peatlands to significant sources of GHGs (mainly N2O and CO2). Annual mean GHG balances including net CH4, N2O and CO2 emissions are 2260, 2280 and 3140 g CO2 eq. m−2 (calculated using 100 year time horizon) for areas drained for grass swards, cereals or those left fallow, respectively. Even after cessetion of the cultivation practices, N2O and CO2 emissions remain high. The mean net GHG emissions in abandoned and afforested agricultural peatlands have been 1580 and 500 g CO2 eq. m−2, respectively. Peat extraction sites are net sources of GHGs with an average emission rate of 770 g CO2 eq. m−2. Cultivation of a perennial grass (e.g., reed canary grass) on an abandoned peat extraction site has been shown to convert such a site into a net sink of GHGs (−330 g CO2 eq. m−2). In contrast, despite restoration, such sites are known to emit GHGs (mean source of 480 g CO2 eq. m−2, mostly from high CH4 emissions). Peatland forests, originally drained for forestry, may act as net sinks (mean −780 g CO2 eq. m−2). However, the studies where all three GHGs have been measured at an ecosystem level in the forested peatlands are lacking. The data for restored peatland forests (clear cut and rewetted) indicate that such sites are on average a net sink (190 g CO2 eq. m−2). The mean emissions from drained peatlands presented here do not include emissions from ditches which form a part of the drainage network and can contribute significantly to the total GHG budget. Peat soils submerged under water reservoirs have acted as sources of CO2, CH4 and N2O (mean annual emission 240 g CO2 eq. m−2). However, we cannot yet predict accurately the overall greenhouse gas fluxes of organic soils based on the site characteristics and land-use practices alone because the data on many land-use options and our understanding of the biogeochemical cycling associated with the gas fluxes are limited.

Conventional agriculture on peatlands requires drainage, but this practice causes high emissions of the greenhouse gases (GHG) carbon dioxide (CO2) and nitrous oxide (N2O). Paludiculture is an option to mitigate these adverse environmental effects while maintaining productive land use. Whereas the GHG exchange of paludiculture on rewetted bog peat, i.e. Sphagnum farming, is relatively well examined, data on GHG emissions from fen paludicultures is still very scarce. As typical fen paludiculture species are aerenchymous plants, the release of methane (CH4) is of particular interest when optimising the GHG balance of such systems. Topsoil removal is an option to reduce the CH4 emissions upon rewetting but retaining a nutrient rich topsoil might foster the biomass growth.In this project, Typha angustifolia, Typha latifolia, and Phragmites australis are grown at a fen peatland formerly used as grassland. Water levels will be kept at the surface or slightly above it. In parts of the newly created polder surrounded by a peat dam, the topsoil is removed. Four smaller sub-polders are installed to separate the effects of topsoil removal and water level. Here, the water levels can be adjusted independently from the main polder. Greenhouse gas exchange is measured for all three species with and without topsoil removal. Additionally, a reference grassland site close by and a site on the dam are included in the measurements. GHG measurements are carried out every two to four weeks on a campaign basis using manual chambers and a portable analyser for both CH4 and CO2. Here we present GHG balances of the first two years after planting the paludicultures.Despite of imperfect water management during the first year after planting, all paludiculture species were both a net CO2 and GHG sink regardless the topsoil treatment. During this period, fluctuating water levels resulted in low CH4 emissions while N2O emissions were of greater importance regarding the GHG balance. Due to more stable water levels in the second year, higher methane emissions are expected. Carbon export by the first biomass harvest will also be taken into account.

Crop residue removal and nitrification inhibitor application as strategies to mitigate N2O emissions in sugarcane fields

Spatial variation of nitrous oxide emission between interrow soil and interrow plus row soil in a long-term maize cultivated sandy loam soil

Managed grassland is occasionally renovated to maintain plant productivity by killing old vegetation, ploughing, and reseeding. This study aimed to investigate the combined effect of grassland renovation and long-term manure application on the temporal dynamics of nitrous oxide (N2O) emission and nitrate nitrogen (NO3−–N) leaching. The study was conducted from September 2013 to September 2016 in a managed grassland renovated in September 2013. In this grassland, two treatments were managed—chemical fertilizer application (F treatment) and the combined application of chemical fertilizer and beef cattle manure (MF treatment)—for eight years before the renovation. The control treatment without fertilization (CT) was newly established in the F treatment. The soil N2O flux was measured using a closed chamber method. A leachate sample was collected using a tension-free lysimeter that was installed at the bottom of the Ap horizon (25 cm deep), and total NO3−–N leaching was calculated from leachate NO3−–N concentration and drainage volume was estimated by the water balance method. In the first year after renovation, the absence of plant nitrogen uptake triggered NO3−–N leaching following rainfall during renovation and increased drainage water after thawing. NO3−–N movement from topsoil to deeper soil enhanced N2O production and emission from the soil. N2O emission in MF treatment was 1.6–2.0 times larger than those of CT and F treatments, and NO3−–N leaching in MF treatment was 2.3–2.6 times larger than those of CT and F treatments in the first year. Mineral nitrogen release derived from long-term manure application increased NO3−–N leaching and N2O emission. In the second year, N2O emission and NO3−–N leaching significantly decreased from the first year because of increased plant N uptake and decreased mineral nitrogen surplus, and no significant differences in N2O emission and NO3−–N leaching were observed among the treatments. In the second and third years, NO3−–N leaching was regulated by plant nitrogen uptake. There were no significant differences in NO3−–N leaching among the treatments, but N2O emission in MF treatment was significantly smaller than in the F treatment. Long-term manure application could be a possible option to mitigate N2O emission in permanent grassland; however, the risk of increased NO3−–N leaching and N2O emission in the renovation year induced by manure nitrogen release should be noted.

Long term effects of fire on the soil greenhouse gas balance of an old-growth temperate rainforest

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.

Greenhouse gas (GHG) emissions from paddy fields depend on water management practices and rice varieties. Lysimeter experiments were conducted to determine the effect of rice varieties (lowland; Koshihikari (KH) and upland; Dourado Precoce (DP)) on GHG emissions under two water management practices: alternate wetting and drying (AWD) and continuous flooding (CF). A repeated cycle of drying and wetting in AWD irrigation was performed by drying the soil to −40 kPa soil matric potential and then rewetting. Consequently, the closed chamber method was used to measure direct emissions of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2). The result revealed that water management significantly affected CH4 and N2O emissions (p < 0.05), while no significant effect was observed between different rice varieties. Although, AWD irrigation reduced CH4 emissions, it increased N2O emissions compared to CF irrigation, likely due to increased oxygen supply. AWD irrigation decreased GWP by 55.6% and 59.6% in KH and DP, respectively, compared to CF irrigation. Furthermore, CH4 and N2O emissions significantly correlated with soil redox potential and volumetric water content. These results suggest that AWD irrigation might be an effective water management method for mitigating GHG emissions from rice fields in central Japan.

Nitrous oxide is an important greenhouse gas and it is considered that cropping systems may considerably affect N2O emissions. A field experiment was conducted to examine N2O emissions from three upland cropping systems, which included 0, 1, or 2 legumes cultivated in annual rotations in China. The three cropping systems were as follows: 1) winter fallow followed by summer upland rice, 2) winter rape followed by summer peanut, and 3) winter pea followed by summer soybean. Each cropping system, for both winter and summer crops, included two fertilization treatments 1) N, P, and K application at the local conventional rate, and 2) P and K application at the local conventional rate without N. A total of six treatments consisting of three replicates (5 × 5 m plots) were used according to a random block design in the sub-tropical region (Udic ferrisols) of China. N2O emissions were measured frequently from the planting day to harvest day along with the soil temperature and moisture. This experimental design was used to determine the differences in N2O emissions between the summer versus winter cropping, the effect of N fertilization, and the effect of legume versus non-legume cultivation. The cumulative N2O emissions were 0.86, 1.00, and 0.93 N2O-N kg ha−1 from the winter fallow-upland rice, rape-peanut, and pea-soybean cropping systems, respectively without N application, while from the winter fallow-upland rice, rape-peanut, and pea-soybean cropping systems with N, the emissions were 0.99, 1.45, and 1.27 N2O-N kg ha−1, respectively. The results indicated that both N fertilizer application and legume crop cultivation were one of the most important sources of N2O emissions. N2O emissions were significantly different among crop species and among cropping systems. This study showed that cropping systems considerably affected N2O emissions and that both N fertilization and legume crops contributed to N2O emissions.

How well can we assess impacts of agricultural land management changes on the total greenhouse gas balance (CO2, CH4 and N2O) of tropical rice-cropping systems with a biogeochemical model?

Irrigation practices change the soil moisture in agricultural fields and influence emissions of greenhouse gases (GHG). A 2 yr field study was conducted to assess carbon dioxide (CO2) and nitrous oxide (N2O) emissions from surface and subsurface drip irrigated tomato (Solanum lycopersicum L.) fields on a loamy sand in southern Ontario. Surface and subsurface drip irrigation are common irrigation practices used by tomato growers in southern Ontario. The N2O fluxes were generally ≤50 μg N2O-N m−2 h−1, with mean cumulative emissions ranging between 352 ± 83 and 486 ± 138 mg N2O-N m−2. No significant difference in N2O emissions between the two drip irrigation practices was found in either study year. Mean CO2 fluxes ranged from 22 to 160 mg CO2-C m2 h−1 with cumulative fluxes between 188 ± 42 and 306 ± 31 g CO2-C m−2. Seasonal CO2 emissions from surface drip irrigation were significantly greater than subsurface drip irrigation in both years, likely attributed to sampling time temperature differences. We conclude that these irrigation methods did not have a direct effect on the GHG emissions from tomato fields in this study. Therefore, both irrigation methods are expected to have similar environmental impacts and are recommended to growers.

Livestock manure is a major source of the greenhouse gases (GHGs) methane (CH4) and nitrous oxide (N2O). The emissions can be mitigated by production of biogas through anaerobic digestion (AD) of manure, mostly together with other biowastes, which can substitute fossil energy and thereby reduce CO2 emissions and postdigestion GHG emissions. This paper presents GHG balances for manure and biowaste management as affected by AD for five Danish biogas scenarios in which pig and cattle slurry were codigested with one or more of the following biomasses: deep litter, straw, energy crops, slaughterhouse waste, grass–clover green manure, and household waste. The calculated effects of AD on the GHG balance of each scenario included fossil fuel substitution, energy use for transport, leakage of CH4 from biogas production plants, CH4 emissions during storage of animal manure and biowaste, N2O emissions from stored and field applied biomass, N2O emissions related to nitrate (NO3−) leaching and ammonia (NH3) losses, N2O emissions from cultivation of energy crops, and soil C sequestration. All scenarios caused significant reductions in GHG emissions. Most of the reductions resulted from fossil fuel substitution and reduced emissions of CH4 during storage of codigestates. The total reductions in GHG emissions ranged from 65 to 105 kg CO2-eq ton−1 biomass. This wide range showed the importance of biomass composition. Reductions were highest when straw and grass–clover were used as codigestates, whereas reductions per unit energy produced were highest when deep litter or deep litter plus energy crops were used. Potential effects of iLUC were ignored but may have a negative impact on the GHG balance when using energy crops, and this may potentially exceed the calculated positive climate impacts of biogas production. The ammonia emission potential of digestate applied in the field is higher than that from cattle slurry and pig slurry because of the higher pH of the digestate. This effect, and the higher content of TAN in digestate, resulted in increasing ammonia emissions at 0.14 to 0.3 kg NH3-N ton−1 biomass. Nitrate leaching was reduced in all scenarios and ranged from 0.04 to 0.45 kg NO3-N ton−1 biomass. In the scenario in which maize silage was introduced, the maize production increased leaching and almost negated the effect of AD. Methane leakage caused a 7% reduction in the positive climate impact for each percentage point of leakage in a manure-based biogas scenario.