Global Warming Potential Intensity Research Articles

Optimizing irrigation management sustained grain yield, crop water productivity, and mitigated greenhouse gas emissions from the winter wheat field in North China Plain

Climate change caused by increasing greenhouse gas (GHG) emissions has led to frequent extreme weather events, which seriously threaten sustainable agricultural production. Therefore, it is essential to optimize proper irrigation management to improve the grain yield, crop water productivity (WPc), economic crop water productivity (EWPc), and lower global warming potential (GWP) and GWP Intensity (GWPI). The effect of irrigation scheduling and irrigation methods on GHG emissions remains largely unknown, even though this knowledge is essential to optimize the irrigation management. To address this knowledge gap, a field experiment was carried out in the North China Plain (NCP) for three winter wheat seasons to measure the influence of different irrigation methods and irrigation scheduling on WPc, EWPc, GWP, and GWPI. Irrigation scheduling including 50%, 60%, and 70% of the field capacity (FC) were kept in the main plots and irrigation methods, including sprinkler, drip, and flood irrigation methods in the sub-plots. The results revealed that relative to sprinkler irrigation at 60% FC, drip irrigation at 60% FC significantly (p < 0.05) improved the yield 4.89–7.52%, WPc 1.0–5.4%, EWPc 1.1–5.49%, lower GWP 7.47–9.34%, and GWPI 10.92–15.23%. Compared with flood irrigation at 60% FC, drip irrigation at 60% FC increased grain yield 5.34–6.81%, WPc 5.65–15.1%, EWPc 5.73–15.12%, lower GWP 10.36–15.16%, and GWPI 16.22–19.40%. Technique for order preference by similarity to an ideal solution (TOPSIS) presented that compared with sprinkler and flood irrigation at 60% FC irrigation scheduling, drip irrigation at 60% FC irrigation scheduling provides the best results for improved the yield, WPc, and EWPc, and optimal balance in GWP and GWPI. Therefore, the irrigation scheduling of 60% FC combined with drip irrigation is suggested for sustained wheat yield, improved WPc and EWPc, and mitigated GWP in the NCP.

Is green manure a viable substitute for inorganic fertilizer to improve grain yields and advance carbon neutrality in paddy agriculture?

Green manure is a widely applied to increase grain yield, while it also attributes to greenhouse gas (GHG) emissions in agriculture ecosystems. Combining green manure with inorganic fertilizer inputs is a common practice that can influence soil GHG emissions and grain yield, however, its impacts on grain yield and global warming potential (GWP) under different initial soil conditions before rotating experiments and agronomic management in paddy fields remain unclear. We synthesized 508 data pairs to evaluate the responses of CO2 emissions, CH4 emissions, N2O emissions, and grain yield to combined inputs of green manure plus inorganic fertilizer compared with only inorganic fertilizer application. Our findings indicate that both inorganic fertilizer plus extra green manure (GM-E) and green manure substitutes for inorganic fertilizer (GM-S) could increase CO2 emissions (22.5 %−76.8 %), CH4 emissions (100 %−103 %), N2O emissions (29.8 %−50.9 %), and yield (2.21 %−19.6 %). Except for GM-E, which showed a non-significant increase in grain yield. The initial soil properties before rotating experiments, the types and timing of green manure application were key drivers of GHG emissions and yield, and extra green manure applied in areas with low initial soil pH and high C:N can increase GWP and yield. Overall, the mixed green manure application had greater impact than leguminous or non-leguminous green manure applied alone. The responses of GHG emissions and yield to GM-S were modulated by mean annual precipitation and initial soil properties before rotating experiments, and green manure substitutes for inorganic fertilizer in areas with high initial soil pH and low C:N can increase GWP and yield. Meanwhile, excessive precipitation caused a reduction in yield and a significant increase in GWP intensity. Our results showed that extra green manure applications of less than 68.1 kg N ha−1 would not significantly increase GWP. Therefore, an effective green manure strategy can achieve a win-win situation for the dual challenge of agricultural production and climate change mitigation.

Climate-smart agriculture practice promotes sustainable maize production in northeastern China: Higher grain yield while less carbon footprint

Maize production is facing multiple challenges toward increasing crop productivity, enhancing resource utilization, and mitigating climate change nowadays. Climate-smart agriculture (CSA) is an emerging concept, which pursues the synthesis of higher crop productivity, lower carbon emissions, and improved soil resilience to the climate change. However, few studies have been done to evaluate the productivity and environmental consequences following the CSA of maize production. Herein, the effects of CSA practice on maize yield, nitrogen use efficiency (partial factor productivity, PFPN), soil organic carbon (SOC) sequestration, and carbon footprint (CF) were evaluated based on a nine-year in-situ field experiment in northeastern China. The experiment followed a randomized block design with three treatments including in traditional farmers’ practices (FM), optimized agronomic practices (OPT, aiming to high grain yield and PFPN), and climate-smart agriculture practices (CSA, aiming to higher grain yield, PFPN, SOC stock, while lower CF). Compared with FM, OPT and CSA practices significantly increased grain yield and PFPN by 25.0%− 30.1% and 92.2%− 100.2% on average of experimental duration, respectively. CSA practice had significant higher global warming potential (GWP) but equivalent global warming potential intensity (GWPI) than these of FM and OPT practices during 2016 and 2017. Meanwhile, CSA practice also achieved the highest SOC sequestration in 0–40 cm soil depth compared to other treatments. Consequently, CF per hectare (CFa) of CSA significantly decreased by 41.4% on average than that of FM mainly due to higher SOC sequestration. Concerning the profit of cropping system, CSA had the highest net ecosystem economic budget (NEEB) of 2090.62 $ ha−1 among the treatments. Overall, CSA practice showed advantages in promoting maize yield while reducing carbon footprint by integrated agronomic management (e.g. dense planting, subsoiling tillage, manure amendments, nitrogen fertilizer optimization, and so on), which could be regarded as a promising practice towards food security and carbon emission mitigation.

Ratoon rice-duck co-culture maintains rice grain yield and decreases greenhouse gas emissions in central China

Both ratoon rice monoculture and rice-duck co-culture systems are gaining growing popularity in China. However, it remains unclear whether integration of ducks into ratoon rice field can reduce the inputs, and how it affects the crop productivity and greenhouse gas emissions amid resource scarcity and climate change. Here, a two-year field experiment was conducted in Hubei Province of central China in 2020 and 2021 to evaluate rice grain yield, global warming potential (GWP), and GWP intensity (GWPi) from both main and ratoon seasons of ratoon rice monoculture system and ratoon rice-duck co-culture system. The four treatments including ratoon rice monoculture system with traditional fertilizer and pesticide management (RR), ratoon rice-duck co-culture system with traditional fertilizer management and no pesticide application (RRD-P0), ratoon rice-duck co-culture system with traditional fertilizer management and reduced pesticide by 88% (RRD-P1), and ratoon rice-duck co-culture system with reduced fertilizer by 15% and pesticide by 88% (RRD-F1P1) were carried out with three replications under field conditions. On average, the treatments of RRD-P1 and RRD-F1P1 showed significantly lower emissions of CH4 and CO2, and therefore lower GWP than RR. Compared with RR, RRD-P1 and RRD-F1P1 significantly decreased GWP by 19–25% and GWPi by 22–32% without sacrificing rice grain yield on an annual basis while RRD-P0 caused a GWPi increase primarily due to rice grain yield reduction. Overall, ratoon rice-duck co-culture system with reduction of 88% pesticide could decrease the 15% fertilizer and reduce greenhouse gas emissions, while maintaining rice productivity in ratoon rice production. Our findings propose a feasible technical approach to balance rice grain yield and lower environmental cost using rice-duck co-culture farming system.

Drainage in paddy systems maintains rice yield and reduces total greenhouse gas emissions on the global scale

Rice sustains the survival of nearly half of humanity, meanwhile, paddy systems are also a significant source of greenhouse gas (GHG) emissions in agriculture. Drainage is widely accepted as a key agricultural management practice (AMP) to reduce CH4 emissions in paddy systems, however, its impact on rice yield and global warming potential (GWP) under different soil and APM conditions remains uncertain. Here, we performed a global meta-analysis of 519 samples from 74 fields in 64 peer-reviewed publications, including measurements of rice yield and at least one of GHG emissions (N2O, CH4, and CO2). Overall, the effects of implementing drainage in paddy systems on yield, N2O emissions, CH4 emissions, CO2 emissions, GWP, and GWP intensity (GWPI) were +0.3% (p = 0.85), +149.9% (p< 0.0001), −57.8% (p< 0.0001), +27.7% (p = 0.12), −44.9% (p< 0.0001), and 57.7% (p< 0.0001), respectively. Drainage in lower total N soils was more capable of maintaining yield (+0.9% vs. −1.4%), and drainage in higher pH and organic carbon soils resulted in greater reductions in CH4 emissions (−46.73% vs. −37.3%, −46.36% vs. −38.12%). Mid-season drainage was superior to early-season and fallow season drainage in CH4 emissions reduction. Extending the duration and increasing the events of drainage would increase N2O emissions but contribute to a better CH4 emissions reduction effect. Implementing drainage in paddy systems with organic amendment can achieve greater GHG emissions reduction (both N2O and CH4) than in that without organic amendment. The GWPI decreased by the installation of drainage system might disappear when the nitrogen fertilizer application rate (N rate) reached over 530 kg ha−1. As for different N rates, single drainage is more suitable for the N rate below 115 kg ha−1, while multi-drainage has more advantages on reducing GWPI in the high N rate (≥ 115 kg ha−1).

Impacts of Irrigation Managements on Soil CO2 Emission and Soil CH4 Uptake of Winter Wheat Field in the North China Plain

The North China Plain is an important irrigated agricultural area in China. However, the effects of irrigation management on carbon emission are not well documented in this region. Due to the uneven seasonal distribution of rainfall, irrigation is mainly concentrated in the winter wheat growing season in the North China Plain. In this study, we estimated CO2 emission and soil CH4 uptake from winter wheat fields with different irrigation methods and scheduling treatments using the static chamber-gas chromatography method from April to May 2017 and 2018. Treatments included three irrigation methods (surface drip, sprinkler, and border) and three irrigation scheduling levels that initiated as soon as the soil moisture drained to 50%, 60%, and 70% of the field capacity for a 0–100 cm soil profile were tested. The results showed that both the irrigation methods and scheduling significantly influenced (p &lt; 0.05) the cumulative CO2 and CH4 emission, grain yield, global warming potential (GWP), GWP Intensity (GWPI), GWPI per unit irrigation applied, and water use efficiency (WUE). Compared to 60% and 70% FC, 50% FC irrigation scheduling de-creased accumulated CH4 uptake 26.8–30.3% and 17.8–25.4%, and reduced accumulated CO2 emissions 7.0–15.3% and 12.6–19.4%, respectively. Conversely, 50% FC reduced GWP 6.5–13.3% and 12.5–19.4% and lower grain yield 10.4–19.7% and 8.5–16.6% compared to 60% and 70% FC irrigation scheduling in 2017 and 2018, respectively. Compared to sprinkler irrigation and border irrigation, drip irrigation at 60% FC increased the accumulated CH4 uptake 11.3–12.1% and 1.9–5.5%, while reduced the accumulated CO2 emissions from 7.5–8.8% and 10.1–12.1% in 2017 and 2018, respectively. Moreover, drip irrigation at 60% FC increased grain yield 5.2–7.5% and 6.3–6.8%, WUE 0.9–5.4% and 5.7–7.4%, and lowered GWP 8.0–9.8% and 10.1–12.0% compared to sprinkler and border irrigation in 2017 and 2018, respectively. The interaction of irrigation scheduling and irrigation methods significantly impacted accumulated CH4 uptake, cumulative CO2 amount, and GWP in 2018 only while grain yield and WUE in the entire study. Overall, drip irrigation at 60% FC is the optimal choice in terms of higher grain yield, WUE, and mitigating GWP and GWPI from winter wheat fields in North China Plain.

Identify the optimization strategy of nitrogen fertilization level based on trade-off analysis between rice production and greenhouse gas emission

Abstract Application of nitrogen (N) fertilizer increases grain yield and soil organic carbon (SOC) sequestration, but accompanied by the emission of greenhouse gas (GHG) especially nitrous oxide (N2O). To spatial-temporally analyze the trade-off between yield and GHG emissions under different N fertilization levels at regional scale, this study integrated geographic information system (GIS) and the DeNitrification-DeComposition (DNDC, Version 9.5) model to define the impacts of different N fertilization levels on rice production, SOC sequestration, and GHG emission in Fuyang District, a county-scale region in Eastern China. The whole region was divided into 28825 polygon-based modeling units based on heterogeneity of soil property, climate and agricultural management conditions. After validating the DNDC model by field observation data of the year 1979 and 2015, five N fertilization levels (0, 140, 210, 280 and 350 kg N ha−1) from the year 2016–2035 were designed for simulating the rice yield, SOC sequestration, N2O and methane (CH4) emissions. Validation results showed a good performance of the refined DNDC model. Simulation results indicated that yield and GHG emission increased with the growth of N fertilization rate, but the SOC sequestration change was not noticeable. Around 210 kg N ha−1 was recommended as optimal N fertilization level in Fuyang District, because its global warming potential intensity (GWPI) was the lowest among all the N fertilization levels. As excessive N input is a common problem across China, our results provide a case for a win-win scenario for both food security and environmental friendliness.

Agronomic improvements can make future cereal systems in South Asia far more productive and result in a lower environmental footprint.

South Asian countries will have to double their food production by 2050 while using resources more efficiently and minimizing environmental problems. Transformative management approaches and technology solutions will be required in the major grain-producing areas that provide the basis for future food and nutrition security. This study was conducted in four locations representing major food production systems of densely populated regions of South Asia. Novel production-scale research platforms were established to assess and optimize three futuristic cropping systems and management scenarios (S2, S3, S4) in comparison with current management (S1). With best agronomic management practices (BMPs), including conservation agriculture (CA) and cropping system diversification, the productivity of rice- and wheat-based cropping systems of South Asia increased substantially, whereas the global warming potential intensity (GWPi) decreased. Positive economic returns and less use of water, labor, nitrogen, and fossil fuel energy per unit food produced were achieved. In comparison with S1, S4, in which BMPs, CA and crop diversification were implemented in the most integrated manner, achieved 54% higher grain energy yield with a 104% increase in economic returns, 35% lower total water input, and a 43% lower GWPi. Conservation agriculture practices were most suitable for intensifying as well as diversifying wheat-rice rotations, but less so for rice-rice systems. This finding also highlights the need for characterizing areas suitable for CA and subsequent technology targeting. A comprehensive baseline dataset generated in this study will allow the prediction of extending benefits to a larger scale.

Life Cycle Assessment of Switchgrass Cellulosic Ethanol Production in the Wisconsin and Michigan Agricultural Contexts

Spatial variability in yields and greenhouse gas emissions from soils has been identified as a key source of variability in life cycle assessments (LCAs) of agricultural products such as cellulosic ethanol. This study aims to conduct an LCA of cellulosic ethanol production from switchgrass in a way that captures this spatial variability and tests results for sensitivity to using spatially averaged results. The Environment Policy Integrated Climate (EPIC) model was used to calculate switchgrass yields, greenhouse gas (GHG) emissions, and nitrogen and phosphorus emissions from crop production in southern Wisconsin and Michigan at the watershed scale. These data were combined with cellulosic ethanol production data via ammonia fiber expansion and dilute acid pretreatment methods and region-specific electricity production data into an LCA model of eight ethanol production scenarios. Standard deviations from the spatial mean yields and soil emissions were used to test the sensitivity of net energy ratio, global warming potential intensity, and eutrophication and acidification potential metrics to spatial variability. Substantial variation in the eutrophication potential was also observed when nitrogen and phosphorus emissions from soils were varied. This work illustrates the need for spatially explicit agricultural production data in the LCA of biofuels and other agricultural products.

Nitrous Oxide and Methane Fluxes During the Maize Season Under Optimized Management in Intensive Farming Systems of the North China Plain

Addressing concerns about mitigating greenhouse gas (GHG) emissions while maintaining high grain yield requires improved management practices that achieve sustainable intensification of cereal production systems. In the North China Plain, a field experiment was conducted to measure nitrous oxide (N2O) and methane (CH4) fluxes during the maize (Zea mays L.) season under various agricultural management regimes including conventional treatment (CONT) with high N fertilizer application at a rate of 300 kg N ha−1 and overuse of groundwater by flood irrigation, optimal fertilization 1 treatment (OPT1T), optimal fertilization 2 treatment (OPT2T), and controlled-release urea treatment (CRUT) with reduced N fertilizer application and irrigation, and a control (CK) with no N fertilizer. In contrast to CONT, balanced N fertilization treatments (OPT1T, OPT2T, and CRUT) and CK demonstrated a significant drop in cumulative N2O emission (1.70 v.s. 0.43–1.07 kg N ha−1), indicating that balanced N fertilization substantially reduced N2O emission. The values of the N2O emission factor were 0.42%, 0.29%, 0.32%, and 0.27% for CONT, OPT1T, OPT2T, and CRUT, respectively. Global warming potentials, which were predominantly determined by N2O emission, were estimated to be 188 kg CO2-eq ha−1 for CK and 419–765 kg CO2-eq ha−1 for the N fertilization treatments. Global warming potential intensity calculated by considering maize yield was significantly lower for OPT1T, OPT2T, CRUT, and CK than for CONT. Therefore, OPT1T, OPT2T, and CRUT were recommended as promising management practices for sustaining maize yield and reducing GHG emissions in the North China Plain.

Integrated management practices significantly affect N2O emissions and wheat–maize production at field scale in the North China Plain

In the North China Plain, a field experiment was conducted to measure nitrous oxide (N2O) and methane (CH4) fluxes from a typical winter wheat–summer maize rotation system under five integrated agricultural management practices: conventional regime [excessive nitrogen (N) fertilization, flood irrigation, and rotary tillage before wheat sowing; CON], recommended regime 1 (balanced N fertilization, decreased irrigation, and deep plowing before wheat sowing; REC-1), recommended regime 2 (balanced N fertilization, decreased irrigation, and no tillage; REC-2), recommended regime 3 (controlled release N fertilizer, decreased irrigation, and no tillage; REC-3), and no N fertilizer (CK). Field measurements indicated that pulse emissions after N fertilization and irrigation contributed 19–49 % of annual N2O emissions. In contrast to CON (2.21 kg N2O-N ha−1 year−1), the other treatments resulted in significant declines in cumulative N2O emissions, which ranged from 0.96 to 1.76 kg N2O-N ha−1 year−1, indicating that the recommended practices (e.g., balanced N fertilization, controlled release N fertilizer, and decreased irrigation) offered substantial benefits for both sustaining grain yield and reducing N2O emissions. Emission factors of N fertilizer were 0.21, 0.22, 0.23, and 0.37 % under CON, REC-1, REC-3, and REC-2, respectively. Emissions of N2O during the freeze–thaw cycle period and the winter freezing period accounted for 9.7 and 5.1 % of the annual N2O budget, respectively. Thus, we recommend that the monitoring frequency should be increased during the freeze–thaw cycle period to obtain a proper estimate of total emissions. Annual CH4 fluxes from the soil were low (−1.54 to −1.12 kg CH4-C ha−1 year−1), and N fertilizer application had no obvious effects on CH4 uptake. Values of global warming potential were predominantly determined by N2O emissions, which were 411 kg CO2-eq ha−1 year−1 in the CK and 694–982 kg CO2-eq ha−1 year−1 in the N fertilization regimes. When comprehensively considering grain yield, global warming potential intensity values in REC-1, REC-2, and REC-3 were significantly lower than in CON. Meanwhile, grain yield increased slightly under REC-1 and REC-3 compared to CON. Generally, REC-1 and REC-3 are recommended as promising management regimes to attain the dual objectives of sustaining grain yield and reducing greenhouse gas emissions in the North China Plain.