Soil Greenhouse Gas Emissions Research Articles

Short-term effect of Eucalyptus plantations on soil microbial communities and soil-atmosphere methane and nitrous oxide exchange

Soil greenhouse gas (GHG) emissions are a significant environmental problem resulting from microbially-mediated nitrogen (N) and carbon (C) cycling. This study aimed to investigate the impact of Eucalyptus plantations on the structure and function of a soil microbial community, and how resulting alterations may be linked to GHG fluxes. We sampled and monitored two adjacent Eucalyptus plantations—a recently logged site that harbored new seedlings and an adult plantation—and compared them to a site hosting native vegetation. We used 16S rRNA gene sequencing and qPCR amplifications of key nitrogen and methane cycle genes to characterize microbial structure and functional gene abundance and compared our data with soil parameters and GHG fluxes. Both microbial community attributes were significantly affected by land use and logging of Eucalyptus plantations. The genes nosZ and archaeal amoA were significantly more abundant in native forest than in either young or old Eucalyptus plantations. Statistical analyses suggest that land use type has a greater impact on microbial community structure and functional gene abundance than Eucalyptus rotation. There was no correlation between GHG fluxes and shifts in microbial community, suggesting that microbial community structure and functional gene abundance are not the main drivers of GHG fluxes in this system.

Effects of different agricultural organic wastes on soil GHG emissions: During a 4-year field measurement in the North China Plain

Large quantities and many varieties of agricultural organic wastes are produced in China annually. Applying agricultural organic wastes to soil plays an essential role in coping with the environmental pollution from agricultural wastes, solving the energy crisis and responding global climate change. But there is little information available on the effects of different agricultural organic wastes on soil greenhouse gas (GHG) emissions. The objectives of this study were to investigate and compare the impacts of different organic wastes on soil GHG emissions during a 4-year field experiments in the North China Plain, as well as analyze the influential factors that may be related to GHG emissions. The treatments were: crop straw (CS), biogas residue (BR), mushroom residue (MR), wine residue (WR) and pig manure (PM) returning to soil, as well as a control with no organic waste applied to soil but chemical fertilizer addition only (CF). The results showed that compared with CF treatment, organic material applied to soil significantly increased GHG emissions and emissions followed the order of WR(27,961.51 kg CO2-eq/ha/yr) > PM(26,376.50 kg CO2-eq/ha/yr) > MR(23,366.60 kg CO2-eq/ha/yr) > CS(22,434.44 kg CO2-eq/ha/yr) > BR (22,029.04 kg CO2-eq/ha/yr) > CF(17,402.77 kg CO2-eq/ha/yr), averagely. And considering the affecting factors, GHG emissions were significantly related to soil temperature and soil water content. Different organic wastes also affected soil total organic carbon (TOC), microbial carbon (MBC) and dissolved organic carbon (DOC) contents, which related to GHG emissions. Further analysis showed that characteristics of organic wastes affected GHG emissions, which included C-N ratio, lignin, polyphenol, cellulose and hemicellulose. Our study demonstrates that biogas residue returning to soil emitted minimum GHG emissions among these different types of organic wastes, which provided a better solution for applying organic wastes to mitigate soil GHG emissions.

Greenhouse gas mitigation potential in crop production with biochar soil amendment—a carbon footprint assessment for cross‐site field experiments from China

AbstractBiochar soil amendment (BSA) had been advocated as a promising approach to mitigate greenhouse gas (GHG) emissions in agriculture. However, the net GHG mitigation potential of BSA remained unquantified with regard to the manufacturing process and field application. Carbon footprint (CF) was employed to assess the mitigating potential of BSA by estimating all the direct and indirect GHG emissions in the full life cycles of crop production including production and field application of biochar. Data were obtained from 7 sites (4 sites for paddy rice production and 3 sites for maize production) under a single BSA at 20 t/ha−1 across mainland China. Considering soil organic carbon (SOC) sequestration and GHG emission reduction from syngas recycling, BSA reduced the CFs by 20.37–41.29 t carbon dioxide equivalent ha−1 (CO2‐eq ha−1) and 28.58–39.49 t CO2‐eq ha−1 for paddy rice and maize production, respectively, compared to no biochar application. Without considering SOC sequestration and syngas recycling, the net CF change by BSA was in a range of −25.06 to 9.82 t CO2‐eq ha−1 and −20.07 to 5.95 t CO2‐eq ha−1 for paddy rice and maize production, respectively, over no biochar application. As the largest contributors among the others, syngas recycling in the process of biochar manufacture contributed by 47% to total CF reductions under BSA for rice cultivation while SOC sequestration contributed by 57% for maize cultivation. There was a large variability of the CF reductions across the studied sites whether in paddy rice or maize production, due likely to the difference in GHG emission reductions and SOC increments under BSA across the sites. This study emphasized that SOC sequestration should be taken into account the CF calculation of BSA. Improved biochar manufacturing technique could achieve a remarkable carbon sink by recycling the biogas for traditional fossil‐fuel replacement.

Effects of fertilizer regimes on greenhouse gas emissions in a Gray Luvisol from central Alberta, Canada

This study investigated how different fertilizer regimes with a long-term repeated N application experiment affected on the soil Greenhouse gases (GHGs) emissions in a Gray Luvisolic from central Alberta, Canada. The results showed fertilizer regimes significantly influenced on GHGs emissions. The higher emissions of N2O and CH4 induced by NPKS soils were due to the superior utilization rate of mineral N and organic N. The CO2 emission rates indicated that soil organic carbon (SOC) was upper after Manure application than that after NPKS and Lime applications. The lowest Global Warming Potential (GWP) and highest pH of Lime soils suggested that liming application cause a significant decrease of GHGs by changing soil properties, such as pH. As for CH4 emissions during the incubation period, NPKS soil acted as sources, whereas the Lime and Manure soils acted as CH4 sinks. In addition, the fertilization history with higher SOC stocks in the Manure soils did not affect higher N2O emissions. In conclusion, this research showed liming application could be a better policy for improving soil properties in the acid Gray Luvisol from central Alberta, but liming may result in lower emissions of N2O and CO2 than the treatment of mineral fertilizer or farmyard manure.

Greenhouse gas emissions from temperate permanent grassland on clay-loam soil following the installation of artificial drainage

Shallow drainage (e.g. mole and gravel mole drainage installed at 0.55 m below soil surface) is used on pasture-based farms to reduce soil moisture, deepen water table depth and thus increase grass utilization on soils with impeded drainage. There is, however, a lack of research on the effect that these drainage techniques have on soil greenhouse gas (GHG) emissions. Hence the objective of this study was to investigate the effects of mole and gravel mole drainage on soil GHG fluxes. Soil nitrous oxide (N2O), soil root respiration (CO2) and soil methane (CH4) fluxes were measured in two experiments conducted over a 36 month period. The experiments were conducted on permanent grassland with impeded drainage on a eutric gleysol (humic) in Ireland (52°30′N, 08°12′W). Both experiments were arranged in randomized complete block design. There were three treatments: (i) undrained control, (ii) mole drainage and (iii) gravel mole drainage. Soil GHG fluxes, soil water filled pore space (WFPS) and soil temperature were measured on a weekly basis and soil mineral nitrogen (N), herbage N uptake, soil organic carbon (SOC) and soil total N (TN) were measured seasonally and annually over the sampling period. Drainage treatments (P < 0.05) deepened (mean ± SE) the water table by 0.17±0.03 m and decreased WFPS by 7±0.2%. However no (P > 0.05) impact of drainage treatment was detected on soil average daily GHG fluxes (9.84±6.34g N2O-N ha−1day−1, 34.05 ± 12.90 kg CO2-C ha−1day−1 and −0.91 ± 3.70 g CH4-C ha-1day-1), soil N mineralisation, soil N nitrification, SOC and TN in both experiments. The results indicate that mole and gravel mole drainage can be installed on farms with similar management and soil type to that described in the present study without impact on the soil GHG emissions.

Converting conventional agriculture to poplar bioenergy crops: soil greenhouse gas flux

ABSTRACTConversion of agricultural fields to bioenergy crops can affect greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). Soil GHG emissions were measured seasonally in poplar bioenergy and agricultural fields at three Northwestern US locations. A forest stand was also used at one location for comparison. A portable gas analyzer was used to measure CO2 efflux and CH4 and N2O fluxes were first measured with chambers and later with gradients. Agricultural soil had 17% larger CO2 efflux rates than poplar soil. Chamber fluxes showed no differences in CH4 uptake but did show higher N2O fluxes in poplar than agricultural soil. Gradient CH4 uptake rates were highest in agricultural soil in the summer but showed no N2O flux differences. Forest soils had smaller quarterly CO2 efflux rates than agricultural soils and greater CH4 uptake rates than poplar soils. The largest GHG contributor to soil GHG flux was CO2, with those being ∼1000 times larger than CH4 flux rates and ∼500 times larger than N2O flux rates based on CO2 equivalences. Converting conventional agricultural cropland to poplar bioenergy production does not have adverse effects on soil greenhouse gas flux and these results could be useful for modeling or life cycle analysis of land use conversion.

Greenhouse gas emissions from soil amended with agricultural residue biochars: Effects of feedstock type, production temperature and soil moisture

The conversion of agricultural residues into biochar produces a material with agronomic and environmental benefits. Biochars have been found to positively or negatively affect soil greenhouse gas (GHG) emissions, with the variability being explained by differences in biochar properties and environmental conditions. This study evaluated the effect of soil moisture conditions on the emissions of GHGs from soils amended with different types of biochar. For that, we added biochars to a sandy soil and incubated the samples at 23 °C for 90 days under two moisture conditions. While CH4 fluxes remained not significantly different from zero in all treatments, CO2 effluxes were stimulated at higher soil moisture contents, though the stimulating effect varied with biochar type. Soils amended with biochars with a narrow C:N ratio showed a higher CO2 efflux than soils amended with biochars with a wide C:N ratio. There were significant main effects of pyrolysis temperature and soil moisture conditions on the N2O fluxes from the treatments, however total N2O fluxes from biochar amended soils were overall not significantly different from the control due to treatment interactions. Our study indicates that the main effect of biochars on the GHG balances of soils is related to an increase in soil C stocks, with little short-term changes in soil CH4 and N2O fluxes. Nevertheless, short-term increases in GHG emissions due to biochar addition to soils can be easily mitigated by use of biochars with high C:N ratios produced under high temperatures and by avoiding application to moist soils.

Model Based Regional Estimates of Soil Organic Carbon Sequestration and Greenhouse Gas Mitigation Potentials from Rice Croplands in Bangladesh

Rice (Oryza sativa L.) is cultivated as a major crop in most Asian countries and its production is expected to increase to meet the demands of a growing population. This is expected to increase greenhouse gas (GHG) emissions from paddy rice ecosystems, unless mitigation measures are in place. It is therefore important to assess GHG mitigation potential whilst maintaining yield. Using the process-based ecosystem model DayCent, a spatial analysis was carried out in a rice harvested area in Bangladesh for the period 1996 to 2015, considering the impacts on soil organic carbon (SOC) sequestration, GHG emissions and yield under various mitigation options. An integrated management (IM, a best management practice) considering reduced water, tillage with residue management, reduced mineral nitrogen fertilizer and manure, led to a net offset by, on average, −2.43 t carbon dioxide equivalent (CO2-eq.) ha−1 year−1 (GHG removal) and a reduction in yield-scaled emissions intensity by −0.55 to −0.65 t CO2-eq. t−1 yield. Under integrated management, it is possible to increase SOC stocks on average by 1.7% per year in rice paddies in Bangladesh, which is nearly 4 times the rate of change targeted by the “4 per mille” initiative arising from the Paris Climate Agreement.

Effects of light-felling on non-growing season greenhouse gas emission from soils in Korean pine forests in Maoer Mountains, China.

Non-growing season soil greenhouse gas emission may play an important role in the forest ecosystem carbon and nitrogen cycle. However, it is not clear about the effects of the cutting distur-bance on soil greenhouse gas emissions during non-growing season. The CO2, CH4 and N2O fluxes and related environmental factors (soil temperature, water content, carbon and nitrogen, etc.) were monitored in the Korean pine plantation (fifty year-old) under different light-felling manners (control, no cutting; the half light-felling, cutting 50% of broad-leaved trees in canopy; the whole light-felling, cutting 100% of broad-leaved trees in canopy), using static chamber technique and gas chromatography during non-growing season in Maoer Mountains of China. The main aim was to reveal the influence of cutting disturbance on soil greenhouse gases emission during non-growing season and its controlling factors. The results showed that the whole and half light-felling manners significantly decreased CO2emission flux by 21.0% and 22.8%, and N2O by 23.5% and 11.2%, and decreased CH4uptake by 16.0% and 16.4%. The contribution of non-growing season CO2, CH4 and N2O emission to annual total was 11.7%-14.2%, 13.1%-17.0% and 63.9%-72.6%, respectively. Light-felling manners decreased annual cumulative contribution of CO2 by 1.4%-2.5%, that of CH4 by 0.7%-3.9%, but increased that of N2O by 2.4%-8.7%. Furthermore, light-felling increased the correlations of soil CO2 fluxes with soil temperature, soil water content, nitrate and ammonium, and decreased its correlation with soil organic carbon content. Light-felling increased the correlations of soil CH4 flux with soil water content, soil pH, soil organic carbon, ammonium, and decreased its correlation with nitrate. Light-felling increased the correlations between soil N2O flux and soil temperature, decreased the correlations with nitrate and ammonium, and changed the positive correlation with soil pH to negative. Therefore, light-felling had significant effects on the emission fluxes of the greenhouse gas during non-growing season, with the whole light-felling decreased more soil N2O emission flux than the half light-felling.

Potentials to mitigate greenhouse gas emissions from Swiss agriculture

There is an urgent need to identify and evaluate management practices for their biophysical potential to maintain productivity under climate change while mitigating greenhouse gas (GHG) emissions from individual cropping systems under specific pedo-climatic conditions. Here, we examined, through DayCent modeling, the long-term impact of soil management practices and their interactions on soil GHG emissions and GHG intensity from Swiss cropping systems. Based on experimental data from four long-term experimental sites in Switzerland (Therwil, Frick, Changins, and Reckenholz), we robustly parameterized and evaluated the model for simulating crop productivity, soil C dynamics and soil N2O emissions across a range of management practices and pedo-climatic conditions. Net soil GHG emissions (NSGHGE) were derived from changes in soil C, N2O emissions and CH4 oxidation. Soils under conventional management acted as a net source of soil GHG emissions (1361–1792 kg CO2eq ha−1 yr−1) and NSGHGE were dominated by N2O (50–63%). Reduced tillage and no-tillage reduced long-term NSGHGE by up to 31 and 58%, respectively. Organic farming, represented by organic fertilization, reduced NSGHGE by up to 31% compared to systems based solely on mineral fertilization. Replacement of slurries with a composted FYM led to an additional reduction in NSGHGE by 46%, although our approach considered only soil GHG emissions and thus did not take into account GHG emissions from the composting process. Cover cropping did not significantly influence NSGHGE, however vetch tended to reduce NSGHGE (-19%). The highest mitigation potential was associated with organic farming plus reduced tillage management, it reduced long-term NSGHGE by up to 128%. Soil C sequestration accounted, on average, for 89% of GHG mitigation potentials, consequently N2O dominated NSGHGE across all treatments and sites (60 − 80%). This indicates that these mitigation potentials are time limited and reversible, if the management is not maintained, in contrast to the reduction in N2O emissions, which is considered permanent. Not all the management practices sustained crop yields. Nevertheless, composting of organic manures, reduced tillage and no-tillage effectively reduced NSGHGE and GHG intensity without a noticeable yield reduction. Our results suggest that implementation of the above soil management practices in Swiss cropping systems have a considerable potential for climate change mitigation, although time-limited.

Effects of Mushroom Residue Application Rates on Net Greenhouse Gas Emissions in the Purple Paddy Soil

China is the leading country for production of edible mushrooms and also outputs numerous mushroom residues. The recycling of mushroom residue can solve environmental pollution problems, provide nutrients for the farmland, and play an important role in reducing greenhouse gas emissions and increasing soil carbon sequestration capacity. In order to investigate the effects of mushroom residue amounts on net greenhouse gas emissions in purple paddy soil, potted experiments using static opaque chamber and gas chromatography methods were used to study the changes of greenhouse gases, soil carbon sequestration, and net greenhouse gas emissions (NGHGE) in the paddy soil with five treatments: no fertilizer (CK), conventional fertilization (NPK), 9 t·hm-2 mushroom residue+NPK (LM), 18 t·hm-2 mushroom residue+NPK (MM), and 36 t·hm2 mushroom residue+NPK (HM) from March 2017 to September 2017.The results showed that: ① The greenhouse gas emissions (including CH4, CO2, and N2O) increased with increasing additions of mushroom residue. The emissions of CH4 from highest to lowest followed: HM > MM > LM≈NPK > CK. The HM treatment significantly increased the CH4 emission flux (P<0.01) more than the other treatments and showed an obvious single peak curve, while the CH4 emission flux with the LM treatment showed a bimodal curve, and the MM treatment showed a multiple peak curve. The CO2 emission flux followed: MM > NPK≈LM > HM > CK; and the curves for the LM, MM, and HM treatments were a single peak curve, bimodal curve, and multiple peak curve, respectively. The N2O cumulative emission from the NPK treatment was significantly higher than with the other treatments. The N2O emission flux of the NPK treatment was a bimodal curve and that of the HM treatment was a single peak curve, while the N2O emission flux of treatments LM and MM showed multiple peak curves. ② The carbon sequestration capacity with the LM treatment was lower than that of the other treatments and that from the MM treatment was the highest. The carbon sequestration capacity of the MM treatment increased by 59.2% compared to that of the NPK treatment and increased by 87.79% and 65.65% compared to that of the LM and HM treatments. The LM treatment has the highest carbon sequestration capacity, which was higher than that of the NPK and MM treatments and about 2.1 times greater than the CK treatment and HM treatment. ③ The minimum NGHGE value was -490.29 kg·hm-2 for the whole rice production period, and 18 t·hm-2 mushroom residue applied to the soil was the best way to reduce net greenhouse gas emissions in purple paddy soil.

Soil structure and soil organic matter in water-stable aggregates under different application rates of biochar

Soil structure and soil organic matter in water-stable aggregates under different application rates of biochar

Global warming potential of a Mediterranean irrigated forage system: Implications for designing the fertilization strategy

Abstract Under Mediterranean conditions, the impacts of both organic and mineral N fertilization on soil Greenhouse Gases (GHG) emission can be controversial. The aim of this study was to assess the soil GHG emissions and the net Global Warming Potential (GWP) in a Mediterranean irrigated forage system under different fertilization treatments. Three N fertilization options were compared for two years in a double-crop rotation of silage maize and Italian ryegrass for hay: cattle slurry (SL), solid fraction of slurry (SO) and mineral fertilizer with a nitrification inhibitor (MI). The soil CO2, N2O and CH4 fluxes were highly influenced by the interaction between treatment and date. The maximum values of GHG emissions were observed after fertilizations, to a different extent depending on the fertilizer. In the net GWP reference year, soil respiration (SR) was higher in SO (46.26 ± 3.26 Mg ha−1 yr−1 of CO2) than SL (30.03 ± 0.40 Mg ha−1 yr−1) and MI (23.71 ± 0.57 Mg ha−1 yr−1). However, the C sequestration was higher in SO than in the other treatments. The N2O fluxes were higher in SL (11.5 ± 5.2 kg ha−1 yr−1 of N2O) than in SO (3.4 ± 1.8 kg ha−1 yr−1), while the MI had intermediate values (6.5 ± 1.4 kg ha−1 yr−1). No differences were observed in cumulative CH4 emissions. The SO resulted as a net GWP sink (-9.86 ± 3.05 Mg yr−1 of CO2eq based on SR), while the SL and MI (9.79 ± 1.41 and 1.34 ± 1.87 Mg yr−1, respectively, based on SR) resulted as a source. The SO seemed to have a higher potential in terms of reducing GHG emissions by maintaining adequate levels of agronomic efficiency. This study put in evidence how different organic fertilizers can have contrasting impacts on GHG emissions providing some insights on their different potential mitigation roles under Mediterranean conditions.

Effects of Biochar Application Rates on Greenhouse Gas Emissions in the Purple Paddy Soil

In order to explore the effects of different amounts of biochar applied in purple paddy soil on greenhouse gas (GHG) emissions, potted experiments using a static opaque chamber and gas chromatography method were used to study the regulations and influences of biochar on soil greenhouse gas emission using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10 t ·hm-2 biochar+NPK (LBC), 20 t ·hm-2 biochar+NPK (MBC), and 40 t ·hm-2 biochar+NPK (HBC). ① Soil CH4 emission flux reduced significantly with all biochar application treatments; the emission flux followed the order, from large to small, of NPK > CK > LBC > MBC > HBC. The CH4 emission flux of each treatment showed a single peak curve, and the peak value was mainly concentrated in the late growth stage of the paddy cropland. During the entire observation period, the emission flux of CH4 was between -0.05 mg ·(m2 ·h)-1 and 47.34 mg ·(m2 ·h)-1. The CO2 emission flux of each treatment was complicated and ranged from 32.95 mg ·(m2 ·h)-1 to 1350.88 mg ·(m2 ·h)-1. The CO2 emission flux of the LBC and MBC treatments showed bimodal curves, and the CO2 emission flux of other treatments showed single peak curves. In addition, all biochar treatments delayed the peak time of the CO2 emission flux. The N2O emission flux of each treatment ranged from -309.39 to 895.48 μg ·(m2 ·h)-1, and the N2O emission flux of the LBC treatment showed a bimodal curve, while other treatments showed single peak curves. ② Compared with the CK treatment, biochar treatment can significantly reduce the cumulative emissions of CH4 and promote the cumulative emissions of CO2 and N2O. The average amount of CH4 cumulative emissions followed the order CK > LBC > MBC > HBC, while the average amount of CO2 cumulative emissions followed LBC > MBC > HBC > CK, and the average amount of N2O cumulative emissions followed HBC > MBC≈LBC > CK. Compared with conventional fertilization treatment, different application rates of biochar addition significantly reduced CH4 and CO2 emissions. As more biochar was added, CH4 and CO2 cumulative emissions were lower. Although the regulation of N2O cumulative emissions on biochar addition was not obvious, the application of nitrogen fertilizer could promote the emission flux of N2O to some extent. ③ Over the time scale of 100 years, the integrated global warming potentials (GWP) of CH4 and N2O emission under different biochar treatment were decreased significantly, indicating that biochar combined with chemical fertilizer is an effective GHG emission reduction measure.

Effect of six engineered biochars on GHG emissions from two agricultural soils: A short-term incubation study

Biochar production for soil amendment was recently proposed as a tool to mitigate climate change, reducing soil greenhouse gas (GHG) emissions and sequestrating carbon (C) in soil. The aim of this research project was to test the hypothesis that only biochars with specific requirements (low H/Corg and O/Corg ratios, high C/N ratio) can reduce soil N2O emissions without increasing CO2 emissions in the short term. A 45-days incubation study was carried out, in which six engineered biochars made from the pyrolysis of wood, switchgrass and the solid fraction of pig manure (SFPM), were amended to two agricultural soils (loamy sand and silt loam) at a dose of 2% (w/w) in 1-liter jars. Soil moisture content was adjusted at 80% of water-filled pore space with a solution of ammonium nitrate that corresponds to 170 kg of nitrogen per hectare. N2O and CO2 emissions were analysed on days 2, 3, and then weekly. Soil chemical properties and bacterial richness, composition and taxonomy were analysed after the incubation period. When compared to the control soils without biochar, N2O emissions were decreased by 42 to 90%, but only in the silt loam amended with biochars made from wood and switchgrass, these biochars having a high C/N ratio (>30). Lower N-NH4+ and N-NO3− concentrations were observed in these biochar treatments than in control soil. Moreover, two bacterial classes (Deltaproteobacteria and Thermoleophilia) were correlated with a decrease in N2O emissions. For each type of biochar, those produced at the highest temperature with low O/Corg and H/Corg ratios resulted in the lowest increase in CO2 emissions, which could indicate a higher biochar carbon stability. Overall, results of this study demonstrated that biochar can either increase or decrease soil GHG emissions depending on its properties, and that the effect can differ according to soil properties. Future long-term studies in the field in the presence of crop should be carried out in order to validate the conclusions of this study.

Exploring the Relationships between Greenhouse Gas Emissions, Yields, and Soil Properties in Cropping Systems

Relationships between greenhouse gas emissions, yields, and soil properties are not well known. Utilizing two datasets from long-term cropping systems in Illinois, USA, our we aim to address these knowledge gaps. The objective of this study was to explore the relationships between the physical and chemical properties and greenhouse gas (GHG) emissions of soil, and cash crop yields over a four-year time-period and following 15 years of treatment implementation in Illinois, USA. The experimental layout was a split-plot arrangement involving rotation and tillage treatments in a randomized complete block design with four replications. The studied crop rotations were continuous corn [Zea mays L.] (CCC), corn-soybean [Glycine max (L.) Merr.] (CS), continuous soybean (SSS), and corn-soybean-wheat [Triticum aestivum L.] (CSW), with each phase being present for every year. The tillage options were chisel tillage (T) and no-tillage (NT). We used an array of multivariate approaches to analyze both of our datasets that included 31 soil properties, GHG emissions (N2O, CO2, and CH4) and cash crop yields. The results from our analyses indicate that N2O emissions are associated with a low soil pH, an increased Al concentration, the presence of soil nitrate throughout the growing season, an increase in plant available water (PAW) and an increased soil C concentration. Likewise, soil CO2 respiration was correlated with low pH, elevated Al concentrations, low Ca, increased PAW, higher levels of microbial biomass carbon (MBC), and lower water aggregate stability (WAS). Emissions of CH4 were associated with increased levels of MBC. Lastly, the yield index (YdI) was correlated with lower levels of soil Ca and available P and lower values of WAS. The association between high YdI and lower WAS can be attributed to tillage, as tillage lowers WAS, but increases yields in highly productive cropping systems in the Midwest.

Effects of Near Natural Forest Management on Soil Greenhouse Gas Flux in Pinus massoniana (Lamb.) and Cunninghamia lanceolata (Lamb.) Hook. Plantations

Greenhouse gases are the main cause of global warming, and forest soil plays an important role in greenhouse gas flux. Near natural forest management is one of the most promising options for improving the function of forests as carbon sinks. However, its effects on greenhouse gas emissions are not yet clear. It is therefore necessary to characterise the effects of near natural forest management on greenhouse gas emissions and soil carbon management in plantation ecosystems. We analysed the influence of near natural management on the flux of three major greenhouse gases (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) in Pinus massoniana Lamb. and Cunninghamia lanceolata (Lamb.) Hook. plantations. The average emission rates of CO2 and N2O in the near natural plantations were higher than those in the corresponding unimproved pure plantations of P. massoniana and C. lanceolata, and the average absorption rate of CH4 in the pure plantations was lower than that in the near natural plantations. The differences in the CO2 emission rates between plantations could be explained by differences in the C:N ratio of the fine roots. The differences in the N2O emission rates could be attributed to differences in soil available N content and the C:N ratio of leaf litter, while the differences in CH4 uptake rate could be explained by differences in the C:N ratio of leaf litter only. Near natural forest management negatively affected the soil greenhouse gas emissions in P. massoniana and C. lanceolata plantations. The potential impact of greenhouse gas flux should be considered when selecting tree species for enrichment planting.

Varieties of active soil organic carbon of four forest types with varying incubation temperatures in Fengyang Mountain.

As an important part of the active soil organic carbon (SOC) pool, microbial biomass carbon (MBC) is the impetus and key to nutrient and energy cycling in the soil ecosystem. To provide important scientific references for forest soil carbon sequestration and greenhouse gas emission in this region, the warming effect on forest soil MBC and dissolved organic carbon (DOC) were determined using an incubation experiment. The content dynamics of MBC and DOC of an evergreen broadleaf forest, a Cunninghamia lanceolata forest, a mixed coniferous and broadleaf forest, and a Cryptomeria fortunei forest in the National Nature Reserve of Fengyang Mountain were studied using an incubation experiment at 10℃, 20℃, and 30℃. Results showed that SOC and DOC in the Cryptomeria fortunei forest were significantly higher (P 20℃ > 10℃; whereas, DOC was 10℃ > 20℃ > 30℃. For the same temperature, MBC and DOC in the evergreen broadleaf forest as well as the mixed coniferous and broadleaf forest declined larger on the whole than in the C. lanceolata forest and the C. fortunei forest after the 56 days of incubation experiment.

Climatic versus geochemical controls on soil organic matter stabilization and greenhouse gas emissions along altitudinal transects in different mountain regions

Climatic versus geochemical controls on soil organic matter stabilization and greenhouse gas emissions along altitudinal transects in different mountain regions

Long-term crop rotation and tillage effects on soil greenhouse gas emissions and crop production in Illinois, USA

Two of the most important agricultural practices aimed at improving soil properties are crop rotations and no-tillage, yet relatively few studies have assessed their long-term impacts on crop yields and soil greenhouse gas (GHG) emissions. The objective of this study was to determine the influence of tillage and crop rotation on soil GHG emissions and yields following 15 years of treatment implementation in a long-term cropping systems experiment in Illinois, USA. The experimental design was a split-plot RCBD with crop rotation as the main plot: (continuous corn [Zea mays L.] (CCC), corn-soybean [Glycine max (L.) Merr.] (CS), continuous soybean (SSS), and corn-soybean-wheat [Triticum aestivum L.] (CSW); with each phase of each crop rotation present every year) and tillage as the subplot: chisel tillage (T) and no-tillage (NT). Tillage increased the yields of corn and soybean. Tillage and crop rotation had no effect on methane (CH4) emissions (p = 0.4738 and p = 0.8494 respectively) and only rotation had an effect on cumulative carbon dioxide (CO2) (p = 0.0137). However, their interaction affected cumulative nitrous oxide (N2O) emissions significantly (p = 0.0960); N2O emissions from tilled CCC were the greatest at 6.9 kg-N ha−1-yr−1; while emissions from NT CCC (4.0 kg-N ha−1-yr−1) were not different than both T CS or NT CS (3.6 and 3.3 kg-N ha−1−yr−1, respectively). Utilizing just a CS crop rotation increased corn yields by around 20% while reducing N2O emissions by around 35%; soybean yields were 7% greater and N2O emissions were not affected. Therefore results from this long-term study indicate that a CS rotation has the ability to increase yields and reduce GHG emissions compared to either CCC or SSS alone, yet moving to a CSW rotation did not further increase yields or reduce N2O emissions.