Closed Chamber Method Research Articles

Detailed effects of particle size and surface area on 222Rn emanation of a phosphate rock

The dependency of radon emanation on soil texture was investigated using the closed chamber method. Ground phosphate rock with a large specific surface area was analyzed, and the presence of inner pores, as well as a high degree of roughness and heterogeneity in the phosphate particles, was found. The average radon emanation of the dry phosphate was 0.145 ± 0.016. The emanation coefficient was highest (0.169 ± 0.019) for the smallest particles (<25 μm), decreasing to a constant value (0.091 ± 0.014) for the larger particles (>210 μm). The reduction rate followed an inverse power law. As expected, a linear dependence between the emanation coefficient and the specific surface area was found, being lower than predicted for the large specific surface area. This was most likely due to an increase in the embedding effect of radon atoms in adjacent grains separated by micropores. Results indicate that knowledge of grain radium distribution is crucial to making accurate emanation predictions.

Response of N2O emission to straw retention under two contrasting paddy water conditions: a field experiment over rice–rice-fallow rotation

Few studies are available on comprehensive impacts of straw retention and water regimes on nitrous oxide (N2O) emission from rice–rice-fallow rotation systems. A field experiment with or without rice straw (5000 kg ha−1 each rice season) retention under two contrasting water regimes (1. continuous flooding; 2. rain-fed with exception flooding irrigation about 15 days after transplanting) was conducted in south China. N2O emission was monitored using the closed chamber method over the entire rice–rice-fallow rotation. The results demonstrate that there were significant differences in the responses of N2O emission to water regime, straw retention, and their interaction. N2O emission was negligible in the continuously flooded treatments, with annual N2O emission of 0.052 kg ha−1 with straw and − 0.008 kg ha−1 without straw, respectively. In contrast, substantial N2O fluxes were observed under rain-fed condition when water layer disappeared, with annual N2O emission of 0.969 kg ha−1 with straw and of 0.618 kg ha−1 without straw, respectively. About 50–60% of annual N2O emission occurred in fallow season under rain-fed treatments. The results indicate that rice straw retention has a potential to accelerate N2O emission depending on paddy water conditions.

Analysis of uncertainty for N2O fluxes measured with the closed‐chamber method under field conditions: Calculation method, detection limit, and spatial variability.

AbstractThe search for agricultural practices that mitigate N2O emissions, and the validation and development of models, would benefit if the uncertainty of emission estimates would be reduced relative to current levels. This uncertainty has different sources, such as the error of the flux measurements, the error caused by spatially scaling up measurements to the field or regional level, and the error caused by estimating emissions for the time intervals between measurements by interpolation. This paper focuses on the uncertainty of flux measurements and on flux spatial variability, which is a major cause of error when measured fluxes are scaled up spatially. The analysis focuses on 2415 flux measurements made with the closed chamber method over a monitoring campaign of approximately 3 years.Statistically significant nonlinearities in the changes of N2O concentrations during chamber closure were infrequent (8.3%). Further analysis of significant non‐linear concentration changes indicates that, for positive fluxes, nonlinearity might not always be an artifact caused by chamber placement, but that it can reflect natural temporal variability of the flux during chamber placement in a significant number of cases. The analysis of the coefficients of determination (R2) and of the normalized root mean squared errors (NRMSE) of the linear regressions shows that, below emission rates of 5 g N2O‐N ha−1 d−1, the uncertainty of flux estimates strongly increases. The flux detection limit was 3.5 g N2O‐N ha−1 d−1, which is consistent with the outcome of the analysis of the R2s and NRMSEs. Flux measurements based on less than five N2O concentrations per flux led to estimates with considerably larger confidence intervals. When the number of N2O concentrations per flux was reduced from five to four, the detection limit increased to 7.5 g N2O‐N ha−1 d−1. The individual fluxes of spatially replicated plots show strong dispersion around the mean: the average coefficient of variation for fluxes above 5 g N2O‐N ha−1 d−1 was 54.3% and the data suggest that the spatial variability of fluxes correlates positively with flux magnitude.Our results suggest that, for measurements performed with the closed static chamber method, (1) linear regression might generally lead to the best estimates of the average fluxes during closure time, and that the chamber sampling strategy might be designed accordingly, (2) there is considerable potential to reduce the uncertainty for fluxes lower than 5 g N2O‐N ha−1 d−1 by employing analytical instrumentation with higher precision, (3) flux uncertainty and detection limit are strongly affected by the number of concentrations measured for each flux, and (4) large numbers of replicated chambers could be particularly beneficial if high fluxes are expected.

A simplified sampling procedure for the estimation of methane emission in rice fields.

Manual closed chamber methods are widely used for CH4 measurement from rice paddies. Despite diurnal and seasonal variations in CH4 emissions, fixed sampling times, usually during the day, are used. Here, we monitored CH4 emission from rice paddies for one complete rice-growing season. Daytime CH4 emission increased from 0800h, and maximal emission was observed at 1200h. Daily averaged CH4 flux increased during plant growth or fertilizer application and decreased upon drainage of plants. CH4 measurement results were linearly interpolated and matched with the daily averaged CH4 emission calculated from the measured results. The time when daily averaged emission and the interpolated CH4 curve coincided during the daytime was largely invariant within each of the five distinctive periods. One-hourly sampling during each of these five periods was utilized to estimate the emission during each period, and we found that five one-hourly samples during the season accurately reflected the CH4 emission calculated based on all 136 hourly samples. This new sampling scheme is simple and more efficient than current sampling practices. Previously reported sampling schemes yielded estimates 9 to 32% higher than the measured CH4 emission, while our suggested scheme yielded an estimate that was only 5% different from that based on all 136-h samples. The sampling scheme proposed in this study can be used in rice paddy fields in Korea and extended worldwide to countries that use similar farming practices. This sampling scheme will help in producing more accurate global methane budget from rice paddy fields.

Biophysical controls of soil respiration in a wheat-maize rotation system in the North China Plain

Croplands play a vital role in regional carbon budgets. We hypothesized that biophysical factors would be important for soil respiration in a wheat-maize rotation cropping system. Soil CO2 efflux was measured using the closed chamber method, and net CO2 exchange between the cropland and the atmosphere obtained by the eddy covariance technique in a winter wheat-summer maize double cropping system over four years (Oct 2002–Oct 2006). In addition to soil temperature, soil respiration was controlled by leaf area index and soil moisture in the wheat field and soil moisture in the maize field. Temperature sensitivity (Q10) of soil respiration was 2.2 in the wheat and maize growing seasons. In the wheat field, the Q10 value during the sowing–returning green period (4.9) was more than that during the returning green–ripening period (2.0). On a monthly time scale, soil respiration was controlled by gross primary productivity in the wheat field, indicating that soil respiration was coupled with ecosystem photosynthesis. Annual soil respiration was 825±73gCm−2 in the wheat–maize rotation system in 2003–2006. Over a 4–year average, soil respiration was 355±50gCm−2 in the wheat growing season and 470±67gCm−2 in the maize growing season, which accounted for 43% and 57% of the annual value respectively. At an annual time scale, soil respiration contributed to 72% of ecosystem respiration in the winter wheat–summer maize double cropping system.

Efficacy of agronomic strategies for mitigation of after-harvest N 2 O emissions of winter oilseed rape

Abstract Winter rapeseed is one of the most important field crops in Germany. In comparison to other crops, nitrogen (N) surplus of rapeseed is usually high and increased values of mineral nitrogen are observed in soil after harvest. N losses via nitrate leaching or emissions of nitrous oxide (N 2 O) have a negative impact on the greenhouse gas (GHG) balance of biodiesel produced from rapeseed. So far, the effects of different post-harvest management options on these losses after rapeseed cultivation have not been assessed. The aim of this study was to investigate agronomic measures, such as different following main crops (wheat and barley) as well as different catch crops (mustard respectively ryegrass) and varied tillage intensity for their effectiveness in reducing high soil nitrate contents and the associated N 2 O emissions after rapeseed harvest. A field trial was conducted in Southern Germany at a site characterized by a silty loam soil, temperate climate and high precipitation. N 2 O fluxes were measured twice a week with the closed chamber method. In 2013/14 and 2014/15 the calculated N-balance (N input – N output) showed a surplus after rapeseed harvest of 61 kg N ha −1 and 117 kg N ha −1 , respectively. N 2 O-N emissions were relatively low from August to March in both years, remaining within a range of 0.3 and 2.0 kg ha −1 . The biomass N uptake of the succeeding crops increased significantly in both years and all treatments over winter with the exception of the mustard treatment which lost N due to freezing off. No clear relationship between N 2 O emissions and the course of soil mineral nitrogen (SMN) dynamics was observed. In both years, there were no significant differences in N 2 O emissions between all treatments. Our results indicate that as far as N 2 O emissions under well-managed soils in southern Germany are concerned, there is no need to change the established crop sequence of rapeseed – winter wheat.

A closed-chamber method to measure greenhouse gas fluxes from dry aquatic sediments

Abstract. Recent research indicates that greenhouse gas (GHG) emissions from dry aquatic sediments are a relevant process in the freshwater carbon cycle. However, fluxes are difficult to measure because of the often rocky substrate and the dynamic nature of the habitat. Here we tested the performance of different materials to seal a closed chamber to stony ground both in laboratory and field experiments. Using on-site material consistently resulted in elevated fluxes. The artefact was caused both by outgassing of the material and production of gas. The magnitude of the artefact was site dependent – the measured CO2 flux increased between 10 and 208 %. Errors due to incomplete sealing proved to be more severe than errors due to non-inert sealing material.Pottery clay as sealing material provided a tight seal between the chamber and the ground and no production of gases was detected. With this approach it is possible to get reliable gas fluxes from hard-substrate sites without using a permanent collar. Our test experiments confirmed that CO2 fluxes from dry aquatic sediments are similar to CO2 fluxes from terrestrial soils.

Nitrous Oxide Emission of a Tropical Peat Soil Grown with Pineapple at Saratok, Malaysia

Draining of peatland for agriculture could affect the release of nitrous oxide into the atmosphere. Presently, there is dearth of information on soil nitrous oxide emission from tropical peat soils cultivated with pineapples. Lysimeter and closed chamber methods were used to quantify nitrous oxide emission from root respiration, microbial respiration, and oxidative peat decomposition under controlled water table condition. Treatments evaluated were: peat soil grown with pineapple, uncultivated peat soils, and bare peat soil fumigated with chloroform. Cultivation of Moris pineapple on drained peat soils resulted in the higher release of nitrous oxide emission (15.7 t N2O ha/yr), followed by fumigated peat soil with chloroform (14.3 t N2O ha/yr), and uncultivated peat soil (10.2 t N2O ha/yr). Soil nitrous oxide emission was affected by nitrate fertilization but emission was not affected by soil temperature nor soil moisture.

Changes of methane and nitrous oxide emissions in a transition bog in central Germany (German National Park Harz Mountains) after rewetting

During the last decades, various renaturation programmes have been initialized to recover nutrient sink and ecological functions of peatlands by rewetting. Rewetting, however, often results in the formation of hotspots for methane (CH4) emissions and in temporal dieback of local vegetation. The present study aimed at quantifying changes of CH4 and nitrous oxide (N2O) emissions in a peatland currently under continuous rewetting conditions. Emissions where studied at a permanently flooded site and a non-flooded peat site with fluctuating water tables by using common closed chamber method. The permanently flooded site revealed extremely high CH4 emissions (up to 1195 mg C m−2 d−1) which were positively correlated with temperature, nutrient content, dissolved organic carbon and nitrogen concentration of the peat soil water. In contrast, the non-flooded peat site, with lower and fluctuating water tables (WT), showed significantly lower CH4 emissions and an increasing trend of CH4 release associated with a generally increasing WT caused by the progressing rewetting process. Lower N2O emissions (<24 µg N m−2 d−1) were observed at the flooded site. By contrast, the non-flooded peat site with fluctuating WT showed significantly higher N2O emissions (up to 4178 µg N m−2 d−1), in particular at high temperatures during summer time. The present results indicate that permanently flooded conditions during rewetting processes might cause higher CH4 emissions compared to fluctuating WT which in contrast might enhance N2O emissions. In total, however, no decreasing trend for CH4 emissions throughout the five-year renaturation period could be found. At least for N2O we observed a decreasing trend during rewetting.

Evaluating MODIS vegetation products using digital images for quantifying local peatland CO2 gas fluxes

AbstractIn peatlands plant growth and senescence affect annual ecosystem carbon dioxide (CO2) exchange, and CO2 fluxes show considerable inter‐annual variability. Phenology is a fundamental indicator of ecosystem carbon dynamics and can be measured from remote sensing systems, but the extent to which satellite products provide useful proxies of peatland vegetation phenology is not well known. Using MODIS vegetation products coupled with field observations of phenology from a basic camera system and measurements of Gross Primary Productivity (GPP) measured using a closed chamber method, we sought to establish the extent to which satellite observations capture phenological processes at a UK peatland site. Daily, true‐colour digital images were captured with a time‐lapse camera (Brinno TLC100) between 23‐Apr‐2013 and 29‐Oct‐2013 and converted into a Green‐Red Vegetation Index (GRVI). These were compared with a range of MODIS vegetation products at various spatial resolutions. We found that vegetation products with finer spatial resolution (&lt;500 m) more accurately captured spring green‐up (e.g. Normalized Difference Vegetation Index 16‐day product), whereas those with 8‐day temporal resolution better captured whole‐season dynamics. The 8‐day Gross Primary Productivity (GPP8) and the fraction of absorbed photosynthetically active radiation (fPAR8) products had the strongest daily Pearson's correlations with camera‐derived GRVI (r &gt; 0.90). The camera‐GRVI (P = 0.005, r = 0.98) and MODIS‐GRVI (P = 0.041, r = 0.89) products showed the strongest significant correlations with gross primary productivity measured using static chambers in the field. This work demonstrates that freely available MODIS data captured up to 92% of the daily variation in phenology over an upland peatland. This approach shows great potential for capturing ecosystem carbon dynamics which underpin carbon trading schemes, a budding funding source for peatland restoration projects.

Effects of nitrogen application rate, nitrogen synergist and biochar on nitrous oxide emissions from vegetable field in south China.

Globally, vegetable fields are the primary source of greenhouse gas emissions. A closed-chamber method together with gas chromatography was used to measure the fluxes of nitrous oxide (N2O) emissions in typical vegetable fields planted with four vegetables sequentially over time in the same field: endive, lettuce, cabbage and sweet corn. Results showed that N2O fluxes occurred in pulses with the N2O emission peak varying greatly among the crops. In addition, N2O emissions were linearly associated with the nitrogen (N) application rate (r = 0.8878, n = 16). Excessive fertilizer N application resulted in N loss through nitrous oxide gas emitted from the vegetable fields. Compared with a conventional fertilization (N2) treatment, the cumulative N2O emissions decreased significantly in the growing seasons of four plant species from an nitrogen synergist (a nitrification inhibitor, dicyandiamide and biochar treatments by 34.6% and 40.8%, respectively. However, the effects of biochar on reducing N2O emissions became more obvious than that of dicyandiamide over time. The yield-scaled N2O emissions in consecutive growing seasons for four species increased with an increase in the N fertilizer application rate, and with continuous application of N fertilizer. This was especially true for the high N fertilizer treatment that resulted in a risk of yield-scaled N2O emissions. Generally, the additions of dicyandiamide and biochar significantly decreased yield-scaled N2O-N emissions by an average of 45.9% and 45.7%, respectively, compared with N2 treatment from the consecutive four vegetable seasons. The results demonstrated that the addition of dicyandiamide or biochar in combination with application of a rational amount of N could provide the best strategy for the reduction of greenhouse gas emissions in vegetable field in south China.

Nitrous Oxide Emission from Organic Fertilizer and Controlled Release Fertilizer in Tea Fields

A field experiment was conducted for two years in the Green Tea Laboratory of Saitama Prefectural Agriculture and Forestry Research Center, Iruma, Saitama, Japan from March 2014 to December 2015. Controlled release fertilizers (CRF) or organic fertilizers (ORG), which are a mixture of chicken manure and oil cake, were applied with the amount of 450 kg·N·ha−1·year−1 in 2014 and 397 kg·N·ha−1·year−1 in 2015. Nitrous oxide (N2O) emissions from soil in green tea fields were measured by the closed chamber method. The results showed that CRF has significantly lower N2O compared to ORG. The cumulative N2O emissions from CRF accounted for 51% of N2O emissions from ORG fields and 138% of control with no fertilizer treatment. The N2O flux from the row was higher than that under the canopy, since fertilizer was applied on the row. However, the total emission from the area between the rows was lower than that under the canopy because the area ratio between the row and canopy was 1:5.

Influences of drip and flood irrigation on soil carbon dioxide emission and soil carbon sequestration of maize cropland in the North China Plain

The need is pressing to investigate soil CO2 (carbon dioxide) emissions and soil organic carbon dynamics under water-saving irrigation practices in agricultural systems for exploring the potentials of soil carbon sequestration. A field experiment was conducted to compare the influences of drip irrigation (DI) and flood irrigation (FI) on soil organic carbon dynamics and the spatial and temporal variations in CO2 emissions during the summer maize growing season in the North China Plain using the static closed chamber method. The mean CO2 efflux over the growing season was larger under DI than that under FI. The cumulative CO2 emissions at the field scale were 1959.10 and 1759.12 g/m2 under DI and FI, respectively. The cumulative CO2 emission on plant rows (OR) was larger than that between plant rows (BR) under FI, and the cumulative CO2 emission on the irrigation pipes (OP) was larger than that between irrigation pipes (BP) under DI. The cumulative CO2 emissions of OP, BP and bare area (BA) under DI were larger than those of OR, BR and BA under FI, respectively. Additionally, DI promoted root respiration more effectively than FI did. The average proportion of root respiration contributing to the soil CO2 emissions of OP under DI was larger than that of OR under FI. A general conclusion drawn from this study is that soil CO2 emission was significantly influenced by the soil water content, soil temperature and air temperature under both DI and FI. Larger concentrations of dissolved organic carbon (DOC), microbial biomass carbon (MBC) and total organic carbon (TOC) were observed under FI than those under DI. The observed high concentrations (DOC, MBC, and TOC) under FI might be resulted from the irrigation-associated soil saturation that in turn inhibited microbial activity and lowered decomposition rate of soil organic matter. However, DI increased the soil organic matter quality (the ratio of MBC to TOC) at the depth of 10–20 cm compared with FI. Our results suggest that the transformation from conventional FI to integrated DI can increase the CO2 emissions and DI needs to be combined with other management practices to reduce the CO2 emissions from summer maize fields in the North China Plain.

Mitigating Global Warming Potential and Greenhouse Gas Intensities by Applying Composted Manure in Cornfield: A 3-Year Field Study in an Andosol Soil

A 3-year study was conducted in cornfield to evaluate how composted cattle manure application affects net global warming potential (GWP; the sum of nitrous oxide (N2O) and methane (CH4) minus net ecosystem carbon balance (NECB)) and greenhouse gas intensity (GHGI; net GWP per unit of plant biomass yield). In the first experiment, conducted from 2010 to 2012, five fertilization strategies that included an unfertilized control plot, inorganic fertilizer-only plot, two plots with inorganic fertilizer plus composted cattle manure, and composted cattle manure-only plot were established. In the second experiment composted cattle manure was applied in autumn 2012 and the field was subdivided into three plots in spring 2013, with one plot receiving additional composted cattle manure, the second plot received additional inorganic fertilizer and the third plot did not receive any additional fertilization. Fluxes of N2O, CH4 and CO2 were measured using the static closed chamber method. NECB was calculated as carbon (C) inputs minus C output (where a negative value indicates net C loss). In experiment 1, manure application significantly increased NECB and reduced net GWP by more than 30% in each of the three years of the study. GHGI in the manure-amended plots was lower than in other plots, except in 2012 when the manure-only plot had higher GHGI than fertilizer-only plot. Application of inorganic fertilizer alone increased GWP by 5% and 20% in 2010 and 2011, but showed a 30% reduction in 2012 relative to the unfertilized control plot. However, due to higher net primary production (NPP), fertilizer-only plot had lower GHGI compared to the control. Application of inorganic fertilizer together with manure showed the greatest potential to reduce GWP and GHGI, while increasing NPP and NECB. In experiment 2, additional manure or inorganic fertilizer application in spring increased NPP by a similar amount, but additional manure application also increased NECB, and decreased GWP and GHGI. Manure application, as a partial substitute or supplemental fertilizer, shows potential to mitigate GWP and GHGI.

Impact of slurry strip-till and surface slurry incorporation on NH3 and N2O emissions on different plot trials in Central Germany

Greenhouse gases (GHG) cause damage to the biosphere and atmosphere, and essentially lead to a reduction in fertilization efficiency. Different slurry application techniques can influence the emission of GHG. In the years 2014 and 2015, two parallel trials (sites: Lückstedt and Kossebau) and one lysimeter trial (site: Falkenberg) were set up in Central Germany (federal state: Saxony-Anhalt) in order to investigate the influence of the slurry strip-till method on ammonia (NH3) and nitrous oxide (N2O) emissions when compared to surface slurry incorporation. The effect of the nitrification inhibitor (NI) (PIADIN®) on GHG emissions was also examined. NH3 was measured using a combination of passive samplers and the Dräger Tube method (DTM). N2O was measured using the closed chamber method (CCM) both in the maize row and in the interrow space. In the two years of the experiment, NH3volatilization fluctuated between 0.6 and 3.5kg NH3-N ha−1. In 2014, the slurry strip-till treatments in Lückstedt emitted significantly less NH3 than surface slurry incorporation. In 2015, at the Kossebau site NH3 volatilization was significantly lower in the treatments with NI than those with no NI. In both years, N2O emissions were between 0.5kg and 2kgN2O-Nha−1.In the lysimeter trial, in 2014 significantly higher N2O emissions were detected in the unfertilized control than in the fertilized treatments. In the plot trial in Kossebau, in 2015 significantly lower N2O emissions were recorded in the row than interrow. These differences are probably due to the uptake of mineral nitrogen by the plants in the row as a starting material for nitrification and denitrification. In Kossebau there were significant correlations between N2O emissions and soil temperature. As regards the slurry strip-till method, no significant reduction in N2O emissions was observed in comparison to surface slurry incorporation. The influence of the slurry strip-till method on NH3 and N2O emissions depends on annual weather conditions and it cannot generally be regarded as preferable to conventional, surface slurry incorporation.

Water table fluctuation and carbon dioxide emission from a tropical peat soil cultivated with pineapples (Ananas comosus L. Merr.)

Tropical peat land is an important buffer for climate change as it absorbs atmospheric carbon and stores large carbon reserve. Inappropriate drainage and agricultural development on peat land results in GHG emissions such as CO2 and CH4which could shift the peat land ecosystem from carbon sink to carbon source. The objectives of this study were to: (i) quantify CO2 loss in a tropical soil under simulated water table fluctuation and (ii) determine the relationship between depth of water table and CO2 loss of a tropical soil cultivated with pineapples. Soil CO2 emission was captured using closed chamber method in field lysimeter and quantified using gas chromatography. It was carried out in July (dry month) and December 2015 (wet month). The peat soil water table fluctuation did not significantly affect emission of CO2 in pineapple cultivation. For lower water table, 147.5 t CO2 ha-1 yr-1 was emitted in the dry month whereas for higher water table, 19.6 t CO2 ha-1 yr-1. In the wet month, CO2emission of the lower water table was 23.7 t CO2 ha-1 yr-1whereasfor high water tables the emission was 25.6 t CO2 ha-1 yr-1. Soil CO2 emission for the lower water table was higher than that of the high water table whereas the opposite was true for the higher water table because of increase in soil temperature in the dry month. Regardless of season and depth of peat soil water table, this study will provide significant understanding of the effect of water table management on carbon loss in peat soils under pineapple cultivation.

Effect of cover cropping on the net global warming potential of rice paddy soil

In temperate rice paddy fields, winter cover cropping and its biomass application are strongly recommended to increase soil organic carbon (SOC) stock and decrease global warming potential (GWP). However, its biomass application may increase greenhouse gas (GHG) emissions, particularly methane (CH4), during flooded rice cultivation. To evaluate the effect of cover cropping and its biomass application on the annual net GWP in a mono-rice cultivation system, we evaluated the emission rates of CH4, nitrous oxide (N2O), and carbon dioxide (CO2) under different cover cropping during the fallow and rice-growing seasons. In cover cropping treatments, barley, hairy vetch, and a barley and hairy vetch mixture were cultivated as winter cover crops without fertilization during the fallow season. Moreover, the total aboveground biomass was incorporated as a green manure one week before rice transplanting. The recommended levels of chemical fertilizers were applied for rice cultivation in the control treatment (NPK) for comparison. The emission rates of CH4, soil respiration, and N2O gases were simultaneously monitored once a week using the closed-chamber method. However, the soil respiration fluxes included only soil respiration and excluded soil C sequestration through cover cropping and its biomass recycling. The net ecosystem C budget (NECB), which is defined as the difference between the total organic C input and output, was estimated to ascertain the pure soil respiration emission fluxes by mass balance approach. Finally, the net GWP was compared among treatments for the two cultivation seasons. During the dry fallow season, cover cropping significantly increased the soil respiration, and this treatment mineralized C loss significantly increased the seasonal net GWP. In comparison, the cover crop biomass application as green manure increased the soil C balance (NECB) during the rice growing season but more significantly increased the CH4 emission. As a result, the cover cultivation and its biomass application greatly increased the annual net GWP scale upon cover cropping rice paddy soil. Therefore, soil management practices that can decrease CH4 emission during rice cultivation should be adopted in cover cropping of the rice paddy soil.

Effects of climate factors and vegetation on the CO2fluxes and δ13C from re-established grassland

The relationship between stable carbon isotope composition (δ13 C -CO2 ) of soil CO2 flux, vegetation cover and weather conditions was investigated in a short-term campaign at a temperate re-established grassland in Germany. During August-September 2016, we measured surface CO2 flux with a closed-chamber method at high and low soil moisture content (‘wet’, ‘dry’), with and without above ground vegetation (‘planted’, ‘clear-cut’) and estimated the effects of treatments on respective δ13 C -CO2 values. The concentration and stable carbon isotope composition of CO2 were determined using the gas chromatography and mass spectrometry analyses. The δ13 C -CO2 of the soil fluxes decreased over sampling time for the ‘dry-warm’ conditions and canopy manipulation. The ecosystem-derived δ13 C -CO2 values (corrected for the atmospheric δ13 C -CO2 ) which included predominately soil-and rhizosphere respiration were –26.2 ± 0.8‰ for the ‘dry-warm’ conditions and decreased down to –28.1 ± 1.4‰ over a period of 28 days from late August to the end of September. The decrease coincided with the lowering of CO2 flux and could be attributed to changes in plant physiological processes at the end of the vegetation season. Though the removal of shoots did not significantly affect the δ13 C -CO2 values as compared with the control, the pattern of further δ13 C -CO2 decrease (down to –28.8 ± 0.8‰) supported the role of living vegetation in a contribution of 13 C-enriched CO2 to the ecosystem respiration.

Greenhouse gas emissions, soil carbon sequestration and crop yields in a rain-fed rice field with crop rotation management

Field experiments of two consecutive years (2010–2011) were conducted to investigate the effect of crop-rice rotation systems on greenhouse gas (GHG) emissions, soil carbon sequestration, and rice yield. Rotation crops were cultivated in the dry season, while rain-fed rice was grown in the wet season. Four different treatments were investigated: fallow-rice (RF), rice–rice (RR), corn-rice (RC) and sweet sorghum-rice (RS). The closed-chamber method was used for flux measurements of methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) in the field. Parameters such as soil carbon budgets (SCBs), soil organic carbon (SOC) stocks, and crop yields were also measured. In this study, it was found that RC and RS rotations reduced CH4 emissions by 78–84%, and reduced net CO2 equivalent emissions (CH4 and N2O) by 68–78%, as compared with RR. After two consecutive years of crop cultivation, SCBs were reclaimed by positive values in the RC and RR treatments. The SOC stocks were maintained in the RR, RC and RS treatments, but decreased in the RF. Although RF also reduced the net CO2 equivalent emissions by 72–84% as compared with RR, there were losses in soil carbon sequestration and agricultural land utilization. The rice grain yields of RC and RS were stable in both years, while RF fell slightly by 11%, and RR significantly reduced by 39% from the first year.

POTENSI PENURUNAN EMISI GAS RUMAH KACA PADA PENGELOLAAN KOTORAN HEWAN SAPI MELALUI PEMBERIAN PAKAN TAMBAHAN

On the integration of crop-livestock systems, waste biomass is used as feed for livestock. Low feed quality may increase emissions of greenhouse gases (GHG). Therefore, to reduce emissions from livestock sector is to improve the quality of animal feed. The purpose of this study was to obtain additional information about the effect of feeding (silage, hay ammoniation and UMMB) against greenhouse gas emissions from cattle manure in crop-livestock integration system. The experiment was conducted at the experimental field of Indonesia Agricultural Environment Research Institute (IAERI/Balingtan), Pati in May-July 2014. The method used to measure the GHG emissions is close chamber method, with an interval of 10 minutes.&#x0D; Samples of CO2, CH4 and N2O were analyzed using gas chromatography. The results showed that treatment of conventional feeding + feed supplement could reduce GHG emissions as 19 % compared to a conventional feeding. GHG emissions from animal manure fed conventional feed of 9.13 kg/head/year, whereas with&#x0D; conventional feed + additional feed of 7.39 kg/head/year.