Soil Greenhouse Gas Emissions Research Articles

Liming modifies greenhouse gas fluxes from soils: A meta-analysis of biological drivers

Acidic soils cover about 30% of the world’s land. Liming is a management practice applied worldwide to reduce the negative effects of acidification on soil fertility and plant growth. Liming also affects the biotic and abiotic soil properties controlling the production and consumption of the greenhouse gases (GHGs) carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4). Although our understanding of how liming regulates net GHG emissions is increasing, the impact of liming on soil biological drivers of GHG emissions has not been quantitatively synthesized. Here we conducted a global meta-analysis using 1474 paired observations from 124 studies to explore the responses of GHG emissions to liming, with a focus on soil biological factors. We show that the N2O mitigation capacity of liming could be linked to (i) increases in bacterial abundance of N2O reductase genes (NosZ) and decreases in fungi:bacteria ratio, both contributing to a lower N2O:N2 product ratio of denitrification; and (ii) reductions in soil mineral nitrogen (N) via stimulation of plant N uptake. The limited evidence available indicates that liming reduced CH4 emissions and the abundance of methanogens, but it had no effect on CH4 uptake and abundance of methanotrophs. Liming-induced increases in soil CO2 emissions can be explained by higher heterotrophic and/or autotrophic respiration. The strong coupling between liming effects on GHG emissions and on soil microbial communities involved in GHG production and consumption can be used to identify strategies to reduce GHGs in response to liming, and to improve process-based models for better predictions of soil GHG emissions.

Biochar-Induced Mitigation Potential of Greenhouse Gas Emissions Was Enhanced under High Soil Nitrogen Availability in Intensively-Irrigated Vegetable Cropping Systems

Intensive irrigation coupled with excessive nitrogen (N) fertilizer input has resulted in high soil greenhouse gas (GHG) emissions in vegetable cropping systems. Biochar as a soil amendment has been advocated as a desirable option to reduce GHG emissions in agricultural systems, but its interactive effects with soil N availability in vegetable systems have yet to be clarified. We performed a field study to examine how biochar interacts with N fertilizer in driving annual methane (CH4) and nitrous oxide (N2O) emissions from an intensively-irrigated greenhouse vegetable cropping system acting as both sources of atmospheric CH4 and N2O in subtropical China. Biochar amendment significantly increased soil CH4 emissions by 33% and 85%, while it decreased soil N2O emissions by 22% and 12% with and without N fertilizer input, respectively. Fertilizer N combination weakened the positive response of CH4 to biochar while it enhanced the mitigation potential of biochar for N2O. Annual direct emission factors of fertilizer N for N2O were estimated to be 1.35% and 1.94% for the fields with and without biochar amendment, respectively. Annual flux-sustained global warming potential (SGWP) and greenhouse gas intensity (GHGI) were significantly decreased by biochar amendment, and this mitigation effect was enhanced with fertilizer N combination. Altogether, we highlight that biochar can reconcile higher yield and lower climatic impact in intensive vegetable cropping systems in subtropical China, particularly in vegetable soils with high N availability.

Effect of Winter Cover Cropping on Soil Greenhouse Gas Emissions in a Dryland Spring Maize Field on the Loess Plateau of China

A field experiment was carried out to study the effects of winter cover cropping on soil greenhouse gas emissions in dryland maize. Four cover crop treatments, namely oat, lentil, a mixture of oat and lentil, and no cover crops (CK), were included during the winter fallow period. Greenhouse gas emission fluxes from soil were measured using the static chamber-gas chromatograph technique. The results showed that:both soil CO2 and N2O were emitted, but the soil acted as a sink for CH4. Compared with the that in CK, oat and lentil had no effect on the cumulative amount of soil CO2 emissions during the winter fallow period and increased the cumulative amount of soil CO2 emissions by 7.77% and 25.7% (P<0.05) in the spring maize growing period, respectively; the mixture increased the cumulative amount of soil CO2 emissions by 19.1% and 14.5% (P<0.05) during the winter fallow and spring maize growing periods. In the winter fallow and spring maize periods, compared with that in CK, oat declined the cumulative amount of soil N2O emissions by 11.6% and 14.7% (P<0.05), and lentil increased the cumulative amount of soil N2O emissions by 31.9% and 14.9% (P<0.05), respectively. Compared to that in the CK, the mixture declined the cumulative amount of soil N2O emissions by 19.2% (P<0.05) in the winter fallow period but had no effect in the spring maize period. Compared with the CK, oat, lentil, and their mixture resulted in a declined cumulative amount of soil CH4 uptake by 37.9%, 23.6%, and 29.6% (P<0.05) in the winter fallow period and by 19.4%, 33.5%, and 31.5% (P<0.05) in the spring maize growing period, respectively. Compared with the CK, oat had no effect on global warming potential (GWP), maize yield, and greenhouse gas intensity (GHGI). Lentil and the mixture increased GWP, and lentil showed a greater increase in GWP than that of the mixture. Compared with the CK, lentil and the mixture increased maize yield by 20.3% and 15.4% (P<0.05), respectively, and had no effect on GHGI. The findings from this study show that the lentil and oat mixture can significantly increase maize yield and decrease GHGI.

Determining the Effects of Compost Substitution on Carbon Sequestration, Greenhouse Gas Emission, Soil Microbial Community Changes, and Crop Yield in a Wheat Field.

Compost produced by straw and livestock and poultry manure under the action of micro-organisms is one of the main forms of organic alternative fertilizers at present. The present study explored the effects of compost substitution on soil greenhouse gas emissions, soil microbial community changes, and wheat yield to determine the best substitution ratio for reducing greenhouse gas emissions and soil microbial community changes and increasing wheat yield. Using the single-factor randomized block trial design, four treatments were employed, the characteristics of greenhouse gas emission, yield and yield components, and the changes of soil microbial community under different compost substitution ratio in the whole wheat growing season were determined by static box-gas chromatography. During the wheat season, both CO2 and N2O emissions were reduced, whereas CH4 emission was increased. That all treatments reduced the Global Warming Potential (GWP) and Greenhouse gas emission intensity (GHGI) in wheat season compared with T0. Compost substitution can alleviate the global warming potential to some extent. Under the condition of compost substitution, the wheat yield under T2 and T3 increased significantly compared with that under the control; however, the spike number and 1000-grain weight did not differ significantly among the treatments. When compost replacement was 30%, the yield was the highest. Under different ratios of compost substitution, the microbial communities mainly comprised Proteobacteria, Actinobacteria, Firmicutes, Patescibacteria, Chloroflexi, Acidobacteria, Bacteroidetes, Gemmatimonadetes, and Verrucomicrobia. The soil microbial community structure differed mainly due to the difference in the compost substitution ratio and was clustered into different groups. In conclusion, to achieve high wheat yield and low greenhouse gas emissions, compost replacement of 30% is the most reasonable means for soil improvement and fertilization.

Influence of Pig Slurry Application Techniques on Soil CO2, N2O, and NH3 Emissions

Greenhouse gas (GHG) emissions from agricultural soils can accelerate climate change, therefore, different soil fertilization techniques should be assessed before application to reduce GHG emissions. Pig slurry applications can greatly influence soil carbon dioxide (CO2), nitrous oxide (N2O), and ammonia (NH3) emissions of arable fields; thus, it is important to find site-specific techniques to lessen any negative environmental impacts. In this study, we examined the short-term effect of pig slurry application techniques of spreading and injection on soil greenhouse gas and NH3 emissions under different irrigation amounts. We used the dynamic chamber method with in-situ gas analyzers. Our study showed that there were elevated emissions during the first week after slurry application; however, the difference between GHG emissions of spreading and injection treatments were not significant. Elevated GHG emissions (213–338% and 250–594% in the case of CO2 and N2O emissions, respectively) were observed under dry circumstances compared to irrigated treatments, as well as significantly higher NH3 emissions occurred for surface spreading under non-irrigated (dry) circumstances compared to other treatments. There were no statistically significant differences between the soil chemistry of different application techniques. However, pig slurry increased the available nitrogen forms (ammonium- and nitrate-nitrogen), which caused N2O and NH3 peaks regardless of treatment type. Leachate chemistry was more affected by irrigation strategies than application techniques. Our study highlights the importance of soil conditions at the time of application, rather than the application technique for fertilization using pig slurry.

Cover crop residue influence on soil N2O and CO2 emissions under wetting‐drying intensities: An incubation study

AbstractUnder increasing frequency and intensity of extreme weather events, the natural wet‐dry cycles of different intensities can induce soil carbon (C) and nitrogen (N) transformation and may contribute to increased nitrous oxide (N2O) and carbon dioxide (CO2) emissions from cultivated soils. While cover crop residue addition is a viable strategy to improve soil health, their impacts on soil greenhouse gas (GHG) emissions, especially N2O emissions, in response to wetting‐drying intensities have received limited attention. A 3‐factorial laboratory incubation was conducted using soils from a long‐term experiment to examine cover crop residue roles on N2O and CO2 emissions when exposed to different intensities of wetting‐drying cycles. These factors included (i) cover crop residue (3 levels): no cover crop, winter wheat (Triticum aestivum L.), and crimson clover (Trifolium incarnatum L.), (ii) wetting intensity (2 levels): 70% and 90% water‐filled pore space (WFPS), and (iii) drying intensity (2 levels): 10% and 40% WFPS. All treatments received the same amount of N fertiliser as urea equivalent to 100 kg N ha−1. We measured N2O and CO2 fluxes, N2O isotopomer composition, as well as dynamics of soil WFPS and biogeochemical changes after wetting. While cover crop residue addition generally exhibited higher CO2 emissions than the no cover crop treatment under all wetting‐drying intensities, their impact on N2O was more nuanced and contingent on cover crop residue type and wetting‐drying intensity. When wetted to 70% WFPS, crimson clover amended soils produced the largest daily and cumulative N2O emissions, whereas soil amended with winter wheat residues had comparable emissions to the no cover crop treatment. In contrast, cover crop residues, especially winter wheat, significantly decreased N2O emissions under extreme wetting to 90% WFPS which was often dominated by denitrification and nitrifier denitrification processes (except in winter wheat when wetted from 10% WFPS). Our results suggest that winter wheat cover crop residues mixed with N fertiliser could provide reliable N2O mitigation benefits under variable soil moisture conditions.Highlights Cover crop effects on N2O emissions from soil with varied wetting‐drying intensities were studied Increased risks of N2O emissions with increasing intensity of wetting of dry soils Crimson clover produced higher N2O emissions than no cover crop when wetted to 70% WFPS Cover crops mixed with N fertiliser reduced N2O emissions than no cover crop when wetted to 90% WFPS

Straw return and nitrogen fertilization regulate soil greenhouse gas emissions and global warming potential in dual maize cropping system

Abundant nitrogen (N) fertilization is needed for maize (Zea mays L.) production in China because of its huge residual biomass return. However, excessive N fertilization has a negative impact on the soil ecosystem and environment, which contributes to climate change. Soil incorporation of maize residues is a well-known practice for reducing chemical N fertilization without compromising maize yield and soil fertility. Thus, residues incorporation has the capacity to minimize N fertilization uses and hence mitigate soil greenhouse gas emissions by improving plant N uptake and use efficiency. There is still a research gap regarding the effects of maize residues incorporation on maize yield, soil fertility, greenhouse gas emissions, and plant N and carbon (C) contents. Therefore, we conducted a field experiment during spring and autumn involving four different N fertilization rates (N0, N200, N250, and N300 kg N ha−1), with and without maize residues incorporation, to evaluate grain yield, soil fertility, plant N and C contents, and greenhouse gas emissions (GHGs). Compared to N0, N fertilizer application at 300 kg N ha−1 with residues incorporation significantly increased area-scaled global warming potential (GWP) compared to other N fertilization rates in both spring and autumn seasons, but soil nutrient contents and plant N and C contents were not statistically different from the N250 treatment. In contrast, the N recovery use efficiency (NRUE), physiological N use efficiency (PNUE), and agronomic N use efficiency (ANUE) were significantly lower in the N300 treatment than in the lower N treatment groups. Nitrous oxide (N2O) and carbon dioxide (CO2) fluxes, area-scaled GWP, and greenhouse gas intensity (GHGI) were significantly lower in the N200 treatment with straw incorporation than the N250 and N300 treatments of the traditional planting system. Thus, we concluded that N200 treatment with residues incorporation is optimal for improving grain yield, soil fertility, plant N uptake, and mitigating greenhouse gas emissions.

Soil greenhouse gas fluxes from tropical vegetable farms, using forest as a reference

Field-based quantification of soil greenhouse gas emissions from the Philippines’ agriculture sector is missing for vegetable production systems, despite its substantial contribution to agricultural production. We quantified soil N2O emission, CH4 uptake, and CO2 efflux in vegetable farms and compared these to the secondary forest. Measurements were conducted for 13 months in 10 smallholder farms and nine forest plots on Andosol soil in Leyte, Philippines using static chambers. Soil N2O and CO2 emissions were higher, whereas CH4 uptake was lower in the vegetable farms than in the forest. Vegetable farms had annual fluxes of 12.7 ± 2.6 kg N2O-N ha−1 yr−1, −1.1 ± 0.2 kg CH4-C ha−1 yr−1, and 11.7 ± 0.7 Mg CO2-C ha−1 yr−1, whereas the forest had 0.10 ± 0.02 kg N2O-N ha ha−1 yr−1, −2.0 ± 0.2 kg CH4-C ha−1 yr−1, and 8.2 ± 0.7 Mg CO2-C ha−1 yr−1. Long-term high N fertilization rates in vegetable farms resulted in large soil mineral N levels, dominated by NO3– in the topsoil and down to 1-m depth, leading to high soil N2O emissions. Increased soil bulk density in the vegetable farms probably increased anaerobic microsites during the wet season and reduced CH4 diffusion from the atmosphere into the soil, resulting in decreased soil CH4 uptake. High soil CO2 emissions from the vegetable farms suggested decomposition of labile organic matter, possibly facilitated by plowing and large N fertilization rates. The global warming potential of these vegetable farms was 31 ± 2.7 Mg CO2-eq ha−1 yr−1 (100-year time frame).

Responses of soil greenhouse gas emissions to land use conversion and reversion-A global meta-analysis.

Exploring the responses of greenhouse gas (GHG) emissions to land use conversion or reversion is significant for taking effective land use measures to alleviate global warming. A global meta-analysis was conducted to analyze the responses of carbon dioxide (CO2 ), methane (CH4 ), and nitrous oxide (N2 O) emissions to land use conversion or reversion, and determine their temporal evolution, driving factors, and potential mechanisms. Our results showed that CH4 and N2 O responded positively to land use conversion while CO2 responded negatively to the changes from natural herb and secondary forest to plantation. By comparison, CH4 responded negatively to land use reversion and N2 O also showed negative response to the reversion from agricultural land to forest. The conversion of land use weakened the function of natural forest and grassland as CH4 sink and the artificial nitrogen (N) addition for plantation increased N source for N2 O release from soil, while the reversion of land use could alleviate them to some degree. Besides, soil carbon would impact CO2 emission for a long time after land use conversion, and secondary forest reached the CH4 uptake level similar to that of primary forest after over 40 years. N2 O responses had negative relationships with time interval under the conversions from forest to plantation, secondary forest, and pasture. In addition, meta-regression indicated that CH4 had correlations with several environmental variables, and carbon-nitrogen ratio had contrary relationships with N2 O emission responses to land use conversion and reversion. And the importance of driving factors displayed that CO2 , CH4 , and N2 O response to land use conversion and reversion was easily affected by NH4 + and soil moisture, mean annual temperature and NO3 - , total nitrogen and mean annual temperature, respectively. This study would provide enlightenments for scientific land management and reduction of GHG emissions.

Soil Greenhouse Gas Emissions and Nitrogen Change for Wheat Field Application of Composted Sewage Sludge

This study aimed at assessing the character of greenhouse emissions under different rates of composted sewage sludge as a nitrogen fertilization substitute, founding the characteristic of soil nitrogen change and, ultimately, providing a theoretical basis for the rational utilization of composted sewage sludge in calcareous soil. Compost sludge as a nitrogen fertilizer substitute has emission reduction effects on N2O, CH4 and CO2. Compared with that of the single fertilizer application, the GHGI under the 20% sludge replacement treatment was significantly reduced by 20.15%, and the global warming potential was significantly reduced by 11.53%, while the wheat yield was increased by 4.78%. Compost sludge as a nitrogen substitute significantly increased the soil organic carbon at the jointing stage and reached a 100% replacement ratio at the maturity stage. During the jointing and mature stages, the total nitrogen content of the soil increased significantly at the 100% replacement ratio, while the soil nitrate nitrogen content only increased significantly at the 50% and 100% replacement ratio. Our findings highlight the impact of sludge compost on greenhouse gas emissions and soil nitrogen and guide the use of sludge compost in wheat fields.

Linking eutrophication to carbon dioxide and methane emissions from exposed mangrove soils along an urban gradient

Mangroves are one of the most important but threatened blue carbon ecosystems globally. Rapid urban growth has resulted in nutrient inputs and subsequent coastal eutrophication, associated with an enrichment in organic matter (OM) from algal and sewage sources and substantial changes in greenhouse gas (GHG) emissions. However, the effects of nitrogen (N) and phosphorus (P) enrichment on mangrove soil OM composition and GHG emissions, such as methane (CH4) and carbon dioxide (CO2), are still poorly understood. Here, we aim to evaluate the relationships between CO2 and CH4 efflux with OM composition in exposed soils from three mangrove areas along watersheds with different urbanization levels (Rio de Janeiro State, Brazil). To assess spatial (lower vs. upper intertidal zones) and seasonal (summer vs. winter) variability, we measured soil-air CO2 and CH4 fluxes at low spring tide, analyzing elementary (C, N, and P), isotopic (δ13C and δ15N), and the molecular (n-alkanes and sterols) composition of surface soil OM. A general trend of OM composition was found with increasing urban influence, with higher δ15N (proxy of anthropogenic N enrichment), less negative δ13C, more short-chain n-alkanes, lower C:N ratio (proxies of algal biomass), and higher epicoprostanol content (proxies of sewage-derived OM). The CO2 efflux from exposed soils increased greatly in median (25/75 % interquartile range) from 4.6 (2.9/8.3) to 24.0 (21.5/32.7) mmol m−2 h−1 from more pristine to more urbanized watersheds, independent of intertidal zone and seasonality. The CO2 fluxes at the most eutrophicated site were among the highest reported worldwide for mangrove soils. Conversely, CH4 emissions were relatively low (three orders of magnitude lower than CO2 fluxes), with high peaks in the lower intertidal zone during the rainy summer. Thus, our findings demonstrate the influence of coastal eutrophication on global warming potentials related to enhanced heterotrophic remineralization of blue carbon within mangrove soils.

Emissions of Greenhouse Gases and NO from Rice Fields and a Peach Orchard as Affected by N Input and Land-Use Conversion

Nitrogen (N) inputs and land-use conversion are management practices that affect soil greenhouse gas (GHG) and nitric oxide (NO) emissions. Here, we measured soil methane (CH4), nitrous oxide (N2O), and NO fluxes from rice fields and a peach orchard that converted from paddies to assess the impacts of nitrogen (N) inputs and land-use conversion on their emissions. Treatments included four paddy field treatments (PN0, PN160, PN220, and PN280) and one peach orchard treatment (ON280) with number indicating the N-input rate of kg N ha−1. The results showed that cumulative emissions of CH4, N2O and NO ranged from 28.6 to 85.3 kg C ha−1, 0.5 to 4.0 kg N ha−1 and 0.2 to 0.3 kg N ha−1 during the rice-growing season, respectively. In terms of greenhouse gas intensity, the PN280 treatment is the recommended N application rate. Land-use conversion significantly reduced the global warming potential from croplands. The conversion shifted soils from an essential source of CH4 to a small net sink. In addition, N2O emissions from the rice–wheat rotation system were 1.8 times higher than from the orchard, mainly due to the difference in the N application rate. In summary, to reduce agriculture-induced GHG emissions, future research needs to focus on the effects of N inputs on rice-upland crop rotation systems.

Conservation Agricultural Practices Impact on Soil Organic Carbon, Soil Aggregation and Greenhouse Gas Emission in a Vertisol

Conservation agriculture (CA), comprising of minimum soil disturbance and crop residue retention (&gt;30%), with a diversified cropping system, has become increasingly popular around the world. It is recognized as a sustainable practice to improve soil health by augmenting key soil properties. However, scanty information exists about the effect of CA practices on soil organic carbon (SOC), aggregation and greenhouse gas emissions (GHG) in a vertisol. Thus, this study investigated the effect of CA practices on SOC, soil aggregation and GHG emission under soybean-wheat and maize-chickpea cropping systems in a vertisol in Central India. Treatment consisted of three different tillage practices, being conventional tillage (CT), reduced tillage (RT), and no tillage (NT) under four cropping systems viz., Soybean–Wheat, Soybean + Pigeon pea (2:1), Maize–Chickpea and Maize + Pigeon pea (1:1). Regardless of cropping system, the soil under NT and RT exhibited better aggregation (20.77 to 25.97% increase), and SOC (12.9 to 19.4% increase) compared to the CT practice in surface layers. The aggregate-associated C concentration increased with aggregate size, and it was highest with large macroaggregates and lowest with silt and clay fractions across different tillage and cropping systems. Higher SOC stock was recorded under NT (4.22 ± 0.133 Mg C/ha) compared to RT (3.84 ± 0.123 Mg C/ha) and CT (3.65 ± 0.04 Mg C/ha) practices at 0 to 5 cm depth. Thus, the adoption of CA practices reduced CO2 emissions, while also contributing to increases in SOC as well as improvement in soil structure.

Effects of water allocation process on greenhouse gas emissions in drip-irrigated apple orchards on the Loess Plateau, China

Apple tree (Malus pumila Mill.) is a perennial and deciduous tree with large water demand in the growth period. Drip irrigation, as a mature and high-efficiency water-saving irrigation technology, has been widely used in apples, grapes and other economic crops around the world, achieving huge economic benefits. However, studies addressing the effects of drip irrigation on soil greenhouse gas emissions from apple orchards on the Loess Plateau in China are limited, and little is known about the potential drivers of the global warming potential based on the water allocation processes in apple orchards under drip irrigation technology. Hence, the goal of this study was to evaluate the impact of water allocation processes on soil greenhouse gas emissions and potential drivers of the global warming potential in apple orchards based on different irrigation water treatments under drip irrigation technology for a two-year consecutive field experiment in 2019 and 2020. The results showed that soil water-filled pore space, daily mean soil surface evaporation and plant transpiration were all significantly increased by drip irrigation. The peaks of carbon dioxide and nitrous oxide fluxes showed a lagged effect, with fluxes proportional to irrigation amount (with emissions occurring throughout the growth period) while methane fluxes were consumptive. Overall, using higher drip irrigation water in apple orchards increased the growth-period mean emissions of carbon dioxide and nitrous oxide and decreased the growth-period mean uptake of methane. Therefore, optimization of drip irrigation water is needed in practice to mitigate greenhouse gas emissions from apple orchard production. Furthermore, the global warming potential was directly driven by soil water-filled pore space, soil surface evaporation, plant transpiration and indirectly driven by rainfall and drip irrigation. The different water allocation processes were closely linked and interacted with each other, thereby affecting the global warming potential directly or indirectly.

Prediction of greenhouse gas emissions from agricultural fields with and without cover crops

AbstractThe significant contribution of greenhouse gas (GHG) emissions to global climate change and stratospheric ozone depletion has been calling the attention to assess the effect of agricultural management on them. Although machine learning (ML) methods have been widely used for the quantification of various inherent and dynamic soil properties, the accuracy of these techniques in the prediction of agricultural soil GHG emissions remains unclear. Therefore, this study aims at evaluating the performance of six different ML methods including simple linear regression, Cubist, support vector machines (SVM) with three different kernel functions, and random forest (RF) for the prediction of CO2 and N2O fluxes from plots managed with and without cover cropping. The input parameters include typical meteorological data as well as soil temperature and soil water content. Results show that the daily flux of CO2 is positively correlated with soil temperature and solar radiation and negatively with soil water content, whereas daily N2O flux is positively correlated with soil water content. For plots without cover cropping, Cubist and SVM with polynomial kernel function outperformed in the prediction of the testing dataset with RMSE of 14.18 kg ha–1 d–1 and 11.52 g ha–1 d–1 for daily CO2 and N2O emissions, respectively. Where cover cropping was considered, SVM with radial basis function and Cubist were the best models in the prediction of daily CO2 and N2O fluxes with respective RMSE values of 15.71 kg ha–1 d–1 and 14.12 g ha–1 d–1. Considering the ranking of the models for all scenarios and both GHGs, SVM with nonlinear kernel functions and Cubist method surpassed other ML techniques.

Soil greenhouse gas emissions from an animal excrement-based forage cropping system

Soil greenhouse gas emissions from an animal excrement-based forage cropping system

Biochar Amendments Facilitate Methane Production by Regulating the Abundances of Methanogens and Methanotrophs in Flooded Paddy Soil

The application of biochar in conjunction with fertilizer in agricultural production is one of the most promising types of management to improve soil quality. However, the effects on the soil microbial community and methane (CH4) emissions from the interactive mechanisms of biochar combined with fertilizer are unclear. In this study, soil column trial was conducted to monitor the surface water nitrogen, dissolved organic carbon (DOC) and CH4 emission dynamics during the process of leaching. Additionally, bacterial and archaeal communities of the soil (0-10 cm) amended with biochar derived from different pyrolysis temperatures (300°C, 500°C, and 700°C) were also analyzed. High-throughput sequencing revealed that the soil archaeal and bacterial community diversities increased under the biochar amendments. The CH4 emission flux of all the treatments in the whole leaching period ranged from 0.0001 to 2.04 μg m-2 h-1, and the DOC ranged from 1.86 to 24.4 mg L-1. Our results showed that biochar amendments significantly increase the soil pH, total nitrogen (TN), and DOC contents, while inhibiting the loss of NO3− N during leaching. In addition, biochar addition increased the paddy soil CH4 emissions, which ascribed to the increasing ratio of the abundances of methanogens to methanotrophs. Consequently, the higher CH4 emissions were probably caused by the stimulation of methanogenic archaea under the biochar amendments. Thus, the results obtained in this study can be applied to guide the application of biochar on greenhouse gas emissions in paddy soil.

Soil CO2 Efflux Response to Combined Application of Adaptation Technologies, Nitrogen Fertilization, and External Carbon Amendment in Wheat and Barley Field

Agricultural practices applied to increase crop production and secure future food demands can have a large negative impact on the environmental quality. They should be, therefore, also evaluated in terms of an impact on soil organic carbon (C) content and greenhouse gas emissions. In this study, we investigated the combined effects of adaptation technology (AT) based on no-till crop sowing into cover crop mulch, nitrogen (N) fertilization, and external C supply in the form of biochar, compost, and composted biochar on soil CO2 efflux (Rs). Rs was measured using a closed gas-exchange system in biweekly to monthly intervals during 2 consecutive years when winter wheat (first year) and spring barley (second year) were cultivated. Biochar, compost, and composted biochar had no significant effects on Rs. N fertilization with the medium fertilizer dose tended to increase Rs compared to the control at the beginning of the growing season, followed by Rs decrease later in the season. On the other hand, fertilization with the maximum fertilizer dose mostly decreased Rs throughout the whole growing season. AT affected the dynamics of Rs substantially, depending on the year, site, and N fertilization, resulting in significant interactions between technology and date of measurement and also between site and technology. However, the mean effect of AT across the whole season was insignificant. The results show that the C increase in the soil that occurs after the application of compost and the combination of composted biochar application with AT is not accompanied by an increase in Rs and, thus, leads to at least short-term C storage in the soil. The reduction in CO2 emissions from soil to the atmosphere under AT represents a positive aspect of such management practice for mitigating climate change.

Soil, vine, climate change; the challenge of predicting soil carbon changes and greenhouse gas emissions in vineyards and is the 4 per 1000 goal realistic?

The evaluation of the current and future impact of climate change on viticulture requires an integrated view on a complex interacting system within the soil-plant-atmospheric continuum under continuous change. Aside of the globally observed increase in temperature in almost all viticulture regions for at least four decades, we observe several clear trends at the regional level in the ratio of precipitation to potential evapotranspiration. Additionally the recently published 6th assessment report of the IPCC (The physical science basis) shows case-dependent further expected shifts in climate patterns which will have substantial impacts on the way we will conduct viticulture in the decades to come.Looking beyond climate developments, we observe rising temperatures in the upper soil layers which will have an impact on the distribution of microbial populations, the decay rate of organic matter or the storage capacity for soil organic carbon (SOC). All this influences the emission of greenhouse gases (GHGs) and the viscosity of water in the soil-plant pathway, altering the transport of water. Interactions between micro-organisms in the rhizosphere, the grapevine root system, degradation and fixation processes of SOC are complex and poorly understood but respond to environmental factors (such as increased soil temperatures), the plant material (rootstock for instance), and the cultivation system (for example bio-organic versus conventional, cover crop use versus open tillage). Increasing SOC stocks is discussed as a measure to reduce soil GHG emissions with the potential to improve the balance between GHG emissions and carbon removal from the atmosphere. Yet it is difficult to deduct the impact of climatic changes and cultivation practices on patterns of carbon storage or losses from soils. This paper presents a first attempt to quantify these potential impacts on SOC for a vineyard location using the RothC-model (Coleman and Jenkinson, 2005) in combination with the Geisenheim long-term (&gt; 100-year) soil temperature record and climate predictions by the STAR II-model of the Potsdam Institute of Climate Impact using a medium realization run (Orlowsky et al., 2008).It is shown that retaining pruning wood and using a full cover crop yielded a SOC increase of 16.2 t C ha-1 over time. However, CO2 emissions over the simulated time span were only slightly less than C-storage in the soil. It is concluded that cover crops in vineyards helps to achieve CO2-neutrality but additional measures are required to make vineyards a significant C-sink.

To what extent can soil moisture and soil Cu contamination stresses affect nitrous species emissions? Estimation through calibration of a nitrification–denitrification model

Abstract. Continental biogeochemical models are commonly used to predict the effect of land use, exogenous organic matter input or climate change on soil greenhouse gas emission. However, they cannot be used for this purpose to investigate the effect of soil contamination, while contamination affects several soil processes and concerns a large fraction of land surface. For that, in this study we implemented a commonly used model estimating soil nitrogen (N) emissions, the DeNitrification DeCompostion (DNDC) model, with a function taking into account soil copper (Cu) contamination in nitrate production control. Then, we aimed at using this model to predict N2O-N, NO2-N, NO-N and NH4-N emissions in the presence of contamination and in the context of changes in precipitations. Initial incubations of soils were performed at different soil moisture levels in order to mimic expected rainfall patterns during the next decades and in particular drought and excess of water. Then, a bioassay was used in the absence or presence of Cu to assess the effect of the single (moisture) or double stress (moisture and Cu) on soil nitrate production. Data of nitrate production obtained through a gradient of Cu under each initial moisture incubation were used to parameterise the DNDC model and to estimate soil N emission considering the various effects of Cu. Whatever the initial moisture incubation, experimental results showed a NO3-N decreasing production when Cu was added but depending on soil moisture. The DNDC-Cu version we proposed was able to reproduce these observed Cu effects on soil nitrate concentration with r2 &gt; 0.99 and RMSE &lt; 10 % for all treatments in the DNDC-Cu calibration range (&gt; 40 % of the water holding capacity) but showed poor performances for the dry treatments. We modelled a Cu effect inducing an increase in NH4-N soil concentration and emissions due to a reduced nitrification activity and therefore a decrease in NO3-N, N2O-N and NOx-N concentrations and emissions. The effect of added Cu predicted by the model was larger on N2-N and N2O-N emissions than on the other N species and larger for the soils incubated under constant than variable moisture. Our work shows that soil contamination can be considered in continental biogeochemical models to better predict soil greenhouse gas emissions.