Cumulative CH4 Emissions Research Articles

An appropriate amount of straw replaced chemical fertilizers returning reduced net greenhouse gas emissions and improved net ecological economic benefits

With the increasing application of crop straw, the greenhouse gas emissions caused due to crop straw have received increasing attention. However, the current studies have not explored the greenhouse gas emissions from on-farmland consumption of returned straw. Based on a long-term positioning experiment, three treatments were set up in double-cropping rice fields: chemical fertilizer (CF), straw replacing 1/3 nitrogen fertilizer (MS), and straw replacing 2/3 nitrogen fertilizer (HS). We measured the biomass, soil properties, and greenhouse gas emissions of double-cropping rice and then comprehensively evaluated the global warming potential, carbon footprint, and net ecological and economic benefits. The straw treatments (MS and HS) increased the cumulative annual emissions of CH4 (98.44% and 261.23%), CO2 (30.85% and 122.29%), and N2O (7.37% and 52.50%), the cumulative annual global warming potential (74.15% and 206.12%), average GHG intensity (43.26% and 138.07%), and the annual cumulative net ecosystem carbon budget (52.96% and 100.97%) in the early and late rice growing seasons, respectively. We observed that the real-time greenhouse gas emissions were significantly correlated to the soil microbial functional genes and total carbon, NH4+-N, and NO3−-N. The results of the random forest model showed that total carbon (13.87%) and nirK abundance (9.80%) were the highest predictors of global warming potential at the booting and maturity stages, respectively during rice growing season. Combining the resource inputs for agricultural production and the greenhouse gas emission potential of the returned straw on its own, MS showed the lowest net greenhouse gas emission, and MS and HS showed significantly increased annual cumulative net ecological economic benefits (38.08% and 34.30%). Overall, MS showed the lowest net greenhouse gas emission and the highest net ecological economic benefits, which is a straw-returning measure with low environmental impact and high economic returns.

Alternative fertilization practices lead to improvements in yield-scaled global warming potential in almond orchards

This study investigates the impact of alternative fertilization practices on the yield-scaled global warming potential (YS-GWP) in almond orchards. Almond production is a contributor to greenhouse gas emissions, primarily due to nitrogen-based mineral fertilizers. This research aims to identify strategies that reduce the environmental footprint of almond cultivation while maintaining yield. Field experiments were conducted in an almond orchard using three alternative fertigation practices: Advance Grower Practice (AGP), Pump and Fertilize (P&F), and High Frequency Low Concentration (HFLC). AGP is the current practice used by producers to meet annual N demand for almond tree growth; P&F is a reduction in applied N rate in response to measured N concentrations in the groundwater so that the added N and groundwater N reach the same total N applied; HFLC is a practice of applying smaller N rates per individual event. HFLC uses a greater number of fertigation events to reach similar total annual N load as other treatments. Cumulative N2O and CH4 emissions were used to determine GWP by converting the emissions to carbon dioxide equivalents (CO2eq) within a 100-year horizon. Nitrous oxide emissions were multiplied by a radiative forcing potential CO2eq of 298 and CH4 by 25 (UNFCCC, 2007). The results revealed that both P&F and HFLC reduced the YS-GWP compared to AGP. HFLC demonstrated 52% to 78% decrease in GWP per unit of almond yield compared to AGP, while P&F showed 48% to 58% decrease over AGP. These reductions were attributed to the reduced nitrous oxide emissions associated with P&F and HFLC. Further, P&F and HFLC tended to have higher N use efficiency than AGP. We demonstrate that adopting alternative fertilization practices can effectively mitigate the environmental footprint of almond orchards while maintaining crop yields. These practices offer viable options for almond growers to reduce greenhouse gas emissions, enhance sustainability, and contribute to climate change mitigation.

Evaluating greenhouse gas mitigation through alternate wetting and drying irrigation in Colombian rice production

Rice demand in Latin America is increasing rapidly, but few studies have identified management practices to reduce water demand and soil greenhouse gas (GHG) emissions for irrigated rice systems in this region. Therefore, we tested the hypothesis that alternate wetting and drying (AWD) irrigation could maintain crop yields while mitigating global warming potential (GWP) compared to a conventional system with recommended irrigation and nutrient management practices for tropical rice in Colombia. Over four consecutive growing seasons, we monitored CH4 and N2O emissions, grain yield, and water consumption for two AWD treatments (AWD5 cm and AWD10 cm - where water drained to depths of 5 and 10 cm below the soil surface, respectively) and a control, in which the field was drained multiple times during fertilizer applications and then continuously flooded until harvest. The control had the highest water use across all rice seasons, with values ranging from 9260 to 16559 m3 ha−1 harvest−1. Implementation of AWD reduced cumulative water use by 19–56%, especially in dry seasons. Both AWD treatments significantly reduced cumulative CH4 emissions by 72–100%, which is consistent with previous research. A new finding is that AWD also decreased N2O emissions by 12–70%, which was attributed to management of soil moisture during fertilizer application events. In total, AWD reduced GWP by 25–73% compared to the control, with minimal impacts on crop productivity. Rice yields ranged from 5.2 to 8.2 Mg ha−1, with no significant difference among treatments in three of four seasons. This study shows that AWD saves irrigation water while greatly reducing GWP with little agronomic penalty, suggesting this technology could be a promising strategy for GHG mitigation in tropical rice in Colombia. Because there are important barriers to AWD adoption, future work should explore challenges at the farm-level as well as changes in policy, irrigation infrastructure, and institutional arrangements to understand the potential for broader implementation.

Impact of Water Management on Methane Emission Dynamics in Sri Lankan Paddy Ecosystems

Paddy ecosystems constitute a dominant source of greenhouse gases, particularly of methane (CH4), due to the continuous flooding (CF) practiced under conventional paddy cultivation. A new management method, namely alternative wetting and draining (AWD) (i.e., flooding whenever surface water levels decline to 15 cm below the soil surface), is an emerging practice developed to mitigate CH4 emissions while providing an optimal solution for freshwater scarcity. Despite extensive paddy cultivation in Sri Lanka, no systematic research study has been conducted to investigate CH4 emissions under different water management practices. Thus, field experiments were conducted in Sri Lanka to investigate the feedback of controlled water management on seasonal and diel variation of CH4 emission, water consumption, and crop productivity. Adopting the same rice variety, two water management methods, continuous flooding (CF) and alternative wetting and draining (AWD), were compared with plants (W/P) and without plants (N/P) present. The emission of CH4 was measured using the static closed chamber method. The results show a 32% reduction in cumulative CH4 emission, on average, under AWD when compared to CF. The yield under the AWD was slightly higher than that of CF. Although it was not statistically significant (p > 0.05) there was not any reduction in yield in AWD than in CF. The total water saving under AWD ranged between 27–35% when compared to CF. Thus, the results support (without considering the effect of nitrous oxide) AWD as a promising method for mitigating CH4 emissions while preserving freshwater and maintaining grain yield in paddy systems.

Adding Corbicula fluminea altered the effect of plant species diversity on greenhouse gas emissions and nitrogen removal from constructed wetlands in the low-temperature season

Plant species diversity is crucial in greenhouse gas emissions and nitrogen removal from constructed wetlands (CWs). However, previous studies have overlooked the impact of benthos on cumulative greenhouse gas emissions during the low-temperature season in CWs. In this study, we established 66 vertical flow CWs with three levels of species richness (1, 2, and 4 species) and eleven species compositions. The Corbicula fluminea was added or not added at each diversity level and monitored greenhouse gas emissions and effluent nitrogen concentration. Our findings indicated that (1) in microcosms without C. fluminea, high species richness significantly increased effluent nitrogen concentrations (NO3−-N, NH4+-N, and TIN), but plant species richness did not affect cumulative CH4, N2O, and CO2 emissions. The presence of Hemerocallis fulva significantly increased cumulative CO2 emissions, while the presence of Iris tectorum significantly increased effluent nitrogen (NO3−-N and TIN) concentrations and cumulative N2O emissions; (2) in microcosms with C. fluminea, the lowest cumulative CH4 emissions occurred when there were two species, but plant species richness did not affect cumulative CO2 and N2O emissions. The presence of H. fulva significantly increased cumulative CH4 emissions, while the presence of Reineckea carnea significantly increased effluent nitrogen (NO3−-N, NH4+- N, TIN) concentrations; (3) at the same diversity level, the addition of C. fluminea significantly increased cumulative CH4 and N2O emissions, as well as effluent nitrogen concentrations. These results demonstrate that C. fluminea alters the effect of plant species diversity on cumulative greenhouse gas emissions and nitrogen removal from CWs during the low-temperature season. We recommend using a two-species mixture to reduce greenhouse gas emissions. However, we caution against using plant compositions with H. fulva or I. tectorum for effective wastewater treatment and greenhouse gas reduction in CWs.

Double-cropping, tillage and nitrogen fertilization effects on soil CO2 and CH4 emissions

Double-cropping is increasingly embraced for its economic advantages in irrigated crops within the Ebro Valley region. However, the implications of this practice for soil carbon dioxide (CO2) and methane (CH4) emissions remain poorly understood. This study aimed to assess the impact of legume-maize double-cropping on soil CO2 and CH4 emissions and to identify optimal tillage systems and nitrogen fertilization rates for enhancing soil carbon budget. Conducted in Agramunt (NE Spain), the research transformed a long-term tillage and nitrogen fertilization field experiment initiated in 1996 under rainfed conditions. It transitioned into a maize monocrop system in 2015 and a diversification experiment in 2018. Maize monocrop was compared to a legume-maize double-cropping with two tillage systems (conventional tillage and no-tillage) and three mineral nitrogen fertilization rates (zero, medium and high). The legumes used were pea for grain (2019), vetch for green manure (2020) and vetch for forage (2021). The use of legumes in the double-cropping system had a significant impact on CO2 fluxes. CO2 emissions in the double-cropping ranged from 250 to 8070 mg CO2-C m−2 day−1, while in the monocropping, the fluxes were in the range of 150–5790 mg CO2-C m−2 day−1. Due to the higher biomass production and extended crop cycle in the double-cropping, along with increased residue decomposition due to the higher amount of residue provided, the cumulative CO2 emissions were higher in the double-cropping. Within the double-cropping, the response of cumulative soil CO2 emissions to tillage depended on the legume used and residue management. For legumes with a low nitrogen content, conventional tillage resulted in lower cumulative CO2 emissions, while for legumes with a high nitrogen content, the lowest emissions were observed in the no-tillage system. The increased incorporation of crop residues in the combined approach of double-cropping and no-tillage led to a greater net ecosystem carbon budget, reaching 1960 kg C ha−1. However, the use of high or medium nitrogen fertilization rates did not have a significant impact on CO2 emissions or the net ecosystem carbon budget. Cumulative soil CH4 emissions were only affected by soil tillage in 2019 and 2021, with greater net CH4 uptake under no-tillage compared with conventional tillage. This work underlines the importance of using legume-maize double-cropping together with no-tillage and N fertilization reduction to control the soil CO2 and CH4 emission yields, while maintaining crop yields under Mediterranean conditions.

Optimizing delayed sowing date decreases methane emissions from paddies and ensures the comprehensive benefits of rice production

Adjusting the sowing date presents a cost-effective and advantageous practice to mitigate the adverse effects of climate change on agricultural cultivation. However, its impact on the comprehensive benefits of rice production in terms of methane (CH4) emissions remains uncertain. During the 2019–2021 rice growing season, field studies with different sowing dates were carried out, including a conventional sowing date (CS) and a delayed sowing date of 10 days (DS1) and 20 days (DS2) from the conventional sowing date. CH4 fluxes were monitored using a transparent box-high precision greenhouse gas analyzer (LGR). During the crucial growth stage of rice, the physicochemical properties and enzyme activities of the soils were assessed, while both atmospheric and soil temperatures were recorded. Changes in rice yields were analyzed, and the comprehensive benefits of rice production were calculated. The results demonstrated a significant decrease in the peak of CH4 flux with the delayed sowing date, and the growth stages of rice characterized by high cumulative CH4 emissions were observed to be delayed. Compared to CS, DS1 and DS2 exhibited reductions in cumulative CH4 emissions by 29.98 % and 56.61 %, respectively (three-year average). Atmospheric and soil temperatures showed significant increasing exponential correlations with CH4 fluxes, and temperature sensitivity decreased with the delay of sowing date. The delayed sowing date resulted in more stable changes in soil carbon and nitrogen levels, elevated soil pH, and diminished soil enzyme activity, which could potentially serve as a mechanism for mitigating CH4 flux. DS1 improved the solar radiation and heat utilization efficiency of rice and promoted the growth of panicles and grains, so the yield increased by 20.16 % compared with CS. However, the growth period of DS2 was insufficient for photosynthetic product formation and posed a risk of yield reduction, with an average decrease of 6.46 % over the three-year average. Relative to CS, DS1 effectively reduced cumulative CH4 emissions while ensuring an increase in production, resulting in a 28.90 % increase in comprehensive benefits. Although DS2 achieved greater reductions in cumulative CH4 emissions, the decline in yield resulted in a 7.73 % decrease in comprehensive benefits. In summary, optimizing delayed sowing (delayed sowing for 10 days) is conducive to achieving rice yield and CH4 emission reduction, and this finding provides important and novel insights for eco-efficient rice planting.

Ratoon Rice Cropping Mitigates the Greenhouse Effect by Reducing CH4 Emissions through Reduction of Biomass during the Ratoon Season.

The ratoon rice cropping system (RR) is developing rapidly in China due to its comparable annual yield and lower agricultural and labor inputs than the double rice cropping system (DR). Here, to further compare the greenhouse effects of RR and DR, a two-year field experiment was carried out in Hubei Province, central China. The ratoon season showed significantly lower cumulative CH4 emissions than the main season of RR, the early season and late season of DR. RR led to significantly lower annual cumulative CH4 emissions, but no significant difference in cumulative annual N2O emissions compared with DR. In RR, the main and ratoon seasons had significantly higher and lower grain yields than the early and late seasons of DR, respectively, resulting in comparable annual grain yields between the two systems. In addition, the ratoon season had significantly lower global warming potential (GWP) and greenhouse gas intensity-based grain yield (GHGI) than the main and late seasons. The annual GWP and GHGI of RR were significantly lower than those of DR. In general, the differences in annual CH4 emissions, GWP, and GHGI could be primarily attributed to the differences between the ratoon season and the late season. Moreover, GWP and GHGI exhibited significant positive correlations with cumulative emissions of CH4 rather than N2O. The leaf area index (LAI) and biomass accumulation in the ratoon season were significantly lower than those in the main season and late season, and CH4 emissions, GWP, and GHGI showed significant positive correlations with LAI, biomass accumulation and grain yield in the ratoon and late season. Finally, RR had significantly higher net ecosystem economic benefits (NEEB) than DR. Overall, this study indicates that RR is a green cropping system with lower annual CH4 emissions, GWP, and GHGI as well as higher NEEB.

Assessment of the straw and biochar application on greenhouse gas emissions and yield in paddy fields under intermittent and controlled irrigation patterns

Water-saving irrigation and straw and biochar application are common agronomic practices in rice production, and their profound impact on greenhouse gas (GHG) emissions from paddy soils cannot be ignored. A three-year field experiment was conducted in typical paddy fields in the subtropical region of eastern China. The methane (CH4) and nitrous oxide (N2O) emissions with straw or biochar application under intermittent irrigation (II) and controlled irrigation (CI) patterns were systematically assessed, and relevant soil physicochemical properties were measured to clarify the internal linking mechanisms. Five treatments were established: conventional flooding as the control group (CG), intermittent irrigation + straw (II + S), intermittent irrigation + biochar (II + B), controlled irrigation + straw (CI + S), and controlled irrigation + biochar (CI + B). The cumulative CH4 emissions with II + S, II + B, CI + S, and CI + B were reduced by 11.2%, 33.2%, 14.1%, and 40.3%, respectively； while the cumulative N2O emissions increased by 20.2%, 5.8%, 13.6%, and 1.2%, respectively (three-year average). Each treatment significantly reduced the global warming potential (GWP) by 10.1–44.8%, and increased rice grain yield by 7.9–13.3%, significantly reducing the greenhouse gas emission intensity (GHGI) by 16.7–46.7%. With II and CI, straw or biochar application increased the soil pH, ground temperature at 5 cm depth, and soil nitrogen levels and regulated the SOM and DOC contents, which may be closely related to greenhouse gas emission regulation and improvements to soil fertility. Notably, the decrease in the soil mcrA/pmoA gene abundance ratio was a dominant factor in CH4 reduction. Overall, each treatment has the potential to reduce GHG emissions and increase crop productivity in paddy fields, and CI + B achieved the best results. These practices facilitate the development of optimal management strategies for rice cultivation.

Biochar combined with different nitrogen fertilization rates increased crop yield and greenhouse gas emissions in a rapeseed-soybean rotation system

Biochar as agricultural soil amendment has been extensively investigated for its potential to sequester carbon, to mitigate greenhouse gases (GHGs) emissions, to enhance soil fertility and enhance crop yields. In this study, we investigated the impact of varying N fertilization rates in conjunction with biochar on soil properties, crop yield, and GHGs emissions in a rapeseed (Brassica napus L.)-soybean (Glycine max (L.) Merrill) rotation system for one year. Biochar and N fertilizer were applied following a factorial combination design of three biochar (B0: 0 t hm−2, B1: 15 t hm−2, and B2: 60 t hm−2) and three N fertilizer application rates (H: 100%, M: 75%, and L: 50% of the conventional application rates). In general, there was no significant effect of N fertilizer and its interaction with biochar application on soil water content, pH, and total carbon content, but the addition of biochar significantly increased these parameters (P < 0.05). The yield of both crops were significantly augmented by biochar up to 75% compared to using N fertilization alone, potentially due to enhanced N use efficiency. However, biochar significantly increased the cumulative N2O and CH4 emissions by as much as 2.2 times and 19 times, respectively, during the rapeseed season, thereby elevating the global warming potential (GWP) and the yield-scaled GWP. Nevertheless, the significantly increased soil carbon content following biochar addition might boost soil carbon sequestration, which could counterbalance the escalating GWP induced by GHGs. Therefore, we recommend a comprehensive and long-term evaluation of biochar's impact by considering crop yield, GHGs emissions, and carbon sequestration in agricultural systems to ensure sustainable agricultural management.

Impacts and mechanism of biodegradable microplastics on lake sediment properties, bacterial dynamics, and greenhouse gasses emissions

The accumulation of microplastics (MPs) in freshwater ecosystems plays a vital role in greenhouse gases (GHGs) emissions from lake sediment by altering sediment properties and microbial communities. Thus, a short-term microcosm experiment was performed to explore the effect of conventional polyethylene (PE) and biodegradable Poly (butylene-adipate-co-terephtalate) (PBAT) MPs on carbon dioxide (CO2) and methane (CH4) emissions from lake sediment and associated microbial community. The results indicated that at 1.0 % concentration, the cumulative CO2 emissions were increased by 16.8 % and the cumulative CH4 emissions were increased more than four times following the addition of biodegradable MPs compared to conventional MPs, which was due to the more dissolved organic carbon (DOC) provided by biodegradable MPs for microbial respiration. Furthermore, the cumulative CO2 and CH4 emissions significantly (p < 0.05) increased with the increasing concentrations of biodegradable MPs. Notably, the accumulation of MPs could weaken the microbial stress from requirements of energy and substrate, and increase the microbial biomass carbon (MBC) value, thus eventually improving the respiratory capacity of microbes. In addition, the biodegradable MPs significantly increased the abundance of microbes, such as Firmicutes, Myxococcota and Actinobacteriota, which were related to the function of anaerobic respiration. Overall, we concluded that the abundant DOC provided by biodegradable MPs could promote the growth of microbes in lake sediment, and they could change the structure and diversity of the microbial community, which would eventually enhance the anaerobic respiration of microbes and aggravate the GHGs emissions.

Microbial resistance stability of rice straw biochar with vermiculite modification: A novel insight into persistent free radicals and pore structure

Biochar is considered a promising material for carbon sequestration owing to its high stability. However, the effects of biochar properties, especially pore structure and persistent free radical (PFR) content, on its microbial resistance stability (MRS) remain unclear. Incubation experiments were conducted to investigate the anaerobic and aerobic MRS of rice straw biochar produced at 300–700 °C, with and without vermiculite modification, and to evaluate the relationship between key biochar properties and MRS. The results showed that PFR signal intensity in biochar was much higher under anaerobic conditions than that under aerobic conditions, increasing with production temperatures of 300–600 °C, but sharply decreasing at 700 °C. Anaerobic MRS of biochar produced at 700 °C was lower than that of biochar produced at 300–600 °C, as indicated by higher CH4 emission. Redundancy analysis revealed a negative correlation between PFR concentration and cumulative CH4 emission with a correlation coefficient of –0.467, and a positive correlation between cumulative CH4 emission and pore volume and specific surface area with correlation coefficients of 0.405 and 0.281, respectively. Biochar dissolved organic carbon content and pH were the two most important factors affecting aerobic MRS as reflected by their high correlation coefficients (0.933 and –0.848) with cumulative CO2 emission. Vermiculite modification enhanced MRS and accordingly lowered the global warming potential of biochar produced at low temperature (300–500 °C) by 4.59–20.2 % and 15.3–42.9 % under anaerobic and aerobic conditions, respectively. However, it had a contrasting effect on biochar produced at 700 °C. Biochar would be more effective at mitigating global warming in paddy fields than in dry lands.

Effects of biochar produced from distiller grains on agronomic performances of sorghum (Sorghum bicolor L.) and greenhouse gas emissions from soil

Aromatic liquor breweries produce massive distiller grains containing a high percentage of rice husks that necessitate harmless treatment and resource utilization. These husk-rich distiller grains can be pyrolyzed in the Ni-based catalyst system at a relatively low temperature (480 °C) into combustible gas, which is used in liquor distillation, and biochar (BDG) with high mineral nutrients and good surface properties. A 3-year field experiment (2018–2020) was established to understand the effects of BDG on sorghum agronomic performances and greenhouse gas emissions from the soil. The results showed that BDG had higher mineral nutrient (N, P, K, and S) contents, larger cation exchange capacity, and better surface structure than those prepared using the traditional method at 400 and 600 °C. Compared with sole chemical fertilizer (CF), the combination of CF and BDG (CF+BDG) increased sorghum nutrient (N, P, and K) uptake, yield, fertilizer use efficiency, and economic benefit. Cumulative CO2 emission from the soil changed little between with and without BDG, indicating the microbial stability of BDG. The effective adsorption of NH3 or NH4+ by BDG upon N application may reduce N loss through NH3 and N2O emissions and increase the efficiency of fertilizer N use. Cumulative CH4 emission ranged from 32.45 to 44.86 g ha-1, which could be overlooked as a greenhouse gas in the sorghum field. Moreover, CF+BDG significantly decreased NH3 and N2O emissions for the production of each unit of sorghum grains and the CO2 emission from the land for the production of a certain amount of sorghum grains. Therefore, CF+BDG exhibited better agronomic and environmental performances in sorghum cultivation.

Subsurface drip irrigation reduces CH4 emissions and ecosystem respiration compared to surface drip irrigation

Sustainable irrigation expansion is pivotal to guarantee global food security. Fertigation techniques with surface or subsurface drip lines are among the most promising irrigation practices. Yet, the effect of surface versus subsurface drip fertigation on ecosystem respiration (CO2) fluxes remains largely unknown while there is not available information regarding CH4 emissions, even though this knowledge is essential to obtain a comprehensive overview of the carbon (C) footprint of these practices. To address this knowledge gap, a field experiment was set up in a maize (Zea mays L.) crop comparing surface and subsurface drip (buried at 30 cm depth) in combination with four fertilization treatments (unfertilized control, calcium nitrate and ammonium sulphate with or without the nitrification inhibitor DMPP). Our results showed that all fertilized treatments (except the unfertilized control) were net CH4 sources (135–208 g C ha−1). Subsurface irrigation reduced cumulative CH4 emissions compared to surface irrigation by 80% (P < 0.05). Moreover, subsurface irrigation also abated ecosystem respiration fluxes (by 41%, P < 0.05) relative to surface irrigation. Emission peaks of both C fluxes were observed after fertigation events. Our results demonstrate that subsurface irrigation is a water-saving strategy that can contribute to decreasing the net greenhouse gas emissions of irrigated croplands through the abatement of CH4 and respiration fluxes.

The impacts of soil tillage combined with plastic film management practices on soil quality, carbon footprint, and peanut yield

Soil tillage and plastic film management practices are essential agricultural production strategies for improving crop yield. Furthermore, they can also play important roles in affecting soil quality, greenhouse gas (GHG) emissions, and carbon footprint (CF), and the overall impacts of tillage and plastic film management on these indicators and the potential links among them are rarely assessed. A 4-year-long field experiment was performed under the winter wheat–summer peanut rotation pattern to investigate how the tillage (plow tillage and rotary tillage) and plastic film management practices (plastic film mulching and no plastic film mulching) affected the summer peanut fields' soil quality (soil carbon (C) stock, enzyme activity, and nutrients concentration), soil GHG (N2O and CH4) emissions, CF components, and peanut yield. The present results showed that plow tillage management improved peanut yield and decreased seasonal cumulative soil N2O and CH4 emissions and CF relative to rotary tillage management. However, the seasonal cumulative emissions of soil N2O and CH4 under plastic film mulching were higher than those under no mulching. The application of plastic film mulching also increased soil TOC stock, soil enzymes (invertase, unease, and catalase) activities, and soil nutrients (microbial biomass C, microbial biomass nitrogen (N), ammonium N, and nitrate N) concentrations. The mulching-induced improvements in soil quality can promote an increase in crop productivity; thus, plastic film mulching showed increased peanut yield and decreased yield-scaled CF. In conclusion, plow tillage combined with plastic film mulching (PTM) treatment maintained higher peanut productivity and produced lower CF while generating suitable soil conditions and therefore may be a more high-yielding, eco-friendly, and sustainable development management strategy for summer peanut production.

Optimized tillage methods increase mechanically transplanted rice yield and reduce the greenhouse gas emissions

Biaxial rotary tillage in dryland (DBRT) can complete biaxial rotary tillage with straw incorporation, secondary suppression, and ditching, and it has been previously studied in direct-seeded rice and wheat. However, the effects of DBRT on the mechanically transplanted rice yield and greenhouse gas emissions remain unclear. To evaluate the effects of DBRT on improving the food security of mechanically transplanted rice and reducing the greenhouse gas emissions, we conducted an experiment for two years with wheat straw incorporation. Three tillage methods were set up: DBRT, uniaxial rotary tillage in dryland and paddy (DPURT), and uniaxial rotary tillage in paddy (PURT). The results showed that compared with DPURT and PURT, DBRT increased the yield of machine-transplanted rice by 7.5–11.0% and 13.3–26.7%, respectively, while the seasonal cumulative CH4 emissions were reduced by 13.9–21.2% and 30.2–37.0%, respectively, and the seasonal cumulative N2O emissions were increased by 13.5–28.6% and 50.0–73.1%, respectively. Consequently, DBRT reduced the global warming potential by 10.7–15.5% and 23.7–28.6%, respectively, and the yield-scaled global warming potential by 18.2–21.8% and 36.4–39.3%, respectively, compared to DPURT and PURT. These results were mainly related to the fact that DBRT significantly reduced soil bulk density and increased soil redox potential (Eh). Therefore, implementing DBRT in machine-transplanted rice fields is feasible, which cannot only increase the rice yield, but also reduce the greenhouse gas emissions.

Effects of Irrigation Regimes and Rice Varieties on Methane Emissions and Yield of Dry Season Rice in Bangladesh

Adoption of the right rice variety and water-saving irrigation method could reduce greenhouse gas (GHG) emissions in lowland rice cultivation. A study was conducted at the research farm of Bangladesh Agricultural University, Mymensingh, Bangladesh, in 2019 during the Boro (dry) season to determine the impacts of different rice varieties (BRRI dhan29, BRRI dhan47, BRRI dhan69, Binadhan-8, Binadhan-10, and Binadhan-17) on methane (CH4) emissions under two irrigation methods, i.e., alternate wetting and drying (AWD) and continuous flooding (CF). The treatments were laid out in a split-plot design, considering water regime as the main plots and rice variety as the sub-plots. The emission rates of CH4 were determined by collecting air samples using the closed chamber technique and measuring the concentrations using a gas chromatograph. CH4 emission rates varied with the growth and development of the rice varieties. The lowest cumulative CH4 emission rate was observed in Binadhan-17, particularly under AWD irrigation. Across the rice varieties, AWD irrigation significantly reduced the cumulative CH4 emissions by about 35% compared with CF. No significant variation in rice yield was observed between AWD (5.38 t ha−1) and CF (5.16 t ha−1). This study suggests that the cultivation of Binadhan-17 under AWD irrigation could be effective at reducing the carbon footprint of lowland rice fields.

Combined Effects of Biochar and Inhibitors on Greenhouse Gas Emissions, Global Warming Potential, and Nitrogen Use Efficiency in the Tobacco Field

Biochar (BC), nitrification inhibitors (methyl 3-(4-hydroxyphenyl) propionate, MHPP), and urease inhibitors (n-butyl phosphorothioate triamine, NBPT) have emerged as effective soil greenhouse gas (GHG) mitigation strategies in agroecosystems. However, the combined use of BC and inhibitors in karst areas has no available data. Therefore, the combined effects of BC, MHPP, and NBPT on GHG emissions, global warming potential (GWP) and nitrogen use efficiency (NUE) in roasted tobacco cropping systems were studied to improve the understanding in climate mitigation. CO2, CH4, and N2O emissions from soils were measured using static chamber-gas chromatography. Results showed that the combined use of BC and inhibitors significantly increased soil total nitrogen, available potassium, electric conductivity, pH, and soil organic matter compared to the control. The combined use of BC and MHPP or NBPT significantly increased cumulative soil CO2 emissions by 33.95% and 34.25%, respectively. The exponential–exponential function of soil CO2 fluxes with soil moisture and temperature demonstrated good fit (R2: 0.506–0.836). The combination of BC and NBPT increased the cumulative soil CH4 emissions by 14.28% but not significantly compared to the fertiliser treatment. However, the combination of BC and MHPP resulted in a significant reduction in cumulative soil CH4 emissions by 80.26%. In addition, the combined use of BC and MHPP or NBPT significantly reduced the cumulative soil N2O emissions by 26.55% and 40.67%, respectively. The inhibition effect of NBPT was better than MHPP. Overall, the combined use of BC and inhibitors significantly reduced the yield-scaled GWP, markedly increased crop yield and NUE, and mitigated climate change in the southwest karst region.

Rice Yield and Greenhouse Gas Emissions Due to Biochar and Straw Application under Optimal Reduced N Fertilizers in a Double Season Rice Cropping System

This study aimed to investigate the impacts of straw and biochar on greenhouse gas (GHG) emissions and grain yield in a double rice cropping system under optimal N fertilizer reduction. Conventional fertilization (CF) was used as the control group, and treatments included optimal fertilization and 15% less nitrogen (OF), together with straw (S) or biochar (B) applied under different fertilization conditions, namely CF + S, CF + B, OF + S, and OF + B. The effects of treatments on soil CH4 and N2O emissions were studied, and changes in soil physicochemical properties were analyzed. The results showed that relative to CF, CF + S and OF + S increased the cumulative CH4 emissions by 11.80% and 2.35%, respectively, while CF + B and OF + B resulted in significant reductions in cumulative CH4 emissions by 27.80% and 28.46%, respectively. Biochar was effective in reducing N2O emissions, and OF further increased the potential, with CF + B and OF + B achieving the best N2O reductions of 30.56% and 32.21%, respectively. Although OF reduced yields by 0.16%, this difference was within reasonable limits; the remaining treatments increased grain yields by 2.55% to 3.47%. CF + B and OF + B reduced the global warming potential (GWP) by 27.93% and 28.63%, respectively, and ultimately reduced the greenhouse gas emission intensity (GHGI) by 30.42% and 30.97%. Both straw and biochar increased the soil organic matter, NH4+-N, and NO3−-N contents, and biochar increased the soil pH, which may be the potential mechanism regulating soil GHG emissions. Overall, OF + B is beneficial for reducing GHG emissions and may be a better agronomic cropping pattern in double season rice growing areas.

Multiyear methane and nitrous oxide emissions in different irrigation management under long-term continuous rice rotation in Arkansas.

Rice paddies are one of the major sources of anthropogenic methane (CH4 ) emissions. The alternate wetting and drying (AWD) irrigation management has been shown to reduce CH4 emissions and total global warming potential (GWP) (CH4 and nitrous oxide [N2 O]). However, there is limited information about utilizing AWD management to reduce greenhouse gas (GHG) emissions from commercial-scale continuous rice fields. This study was conducted for five consecutive growing seasons (2015-2019) on a pair of adjacent fields in a commercial farm in Arkansas under long-term continuous rice rotation irrigated with either continuously flooded (CF) or AWD conditions. The cumulative CH4 emissions in the growing season across the two fields and 5 years ranged from 41 to 123kg CH4 -C ha-1 for CF and 1 to 73kg CH4 -C ha-1 for AWD. On average, AWD reduced CH4 emissions by 73% relative to CH4 emissions in CF fields. Compared to N2 O emissions, CH4 emissions dominated the GWP with an average contribution of 91% in both irrigation treatments. There was no significant variation in grain yield (7.3-11.9 Mg ha-1 ) or growing season N2 O emissions (-0.02 to 0.51kg N2 O-N ha-1 ) between the irrigation treatments. The yield-scaled GWP was 368 and 173kg CO2 eq. Mg-1 season-1 for CF and AWD, respectively, showing the feasibility of AWD on a commercial farm to reduce the total GHG emissions while sustaining grain yield. Seasonal variations of GHG emissions observed within fields showed total GHG emissions were predominantly influenced by weather (precipitation) and crop and irrigation management. The influence of air temperature and floodwater heights on GHG emissions had high degree of variability among years and fields. These findings demonstrate that the use of multiyear GHG emission datasets could better capture variability of GHG emissions associated with rice production and could improve field verification of GHG emission models and scaling factors for commercial rice farms.