Carbon footprint of grain production in China

Combining slow-release fertilizer and plastic film mulching reduced the carbon footprint and enhanced maize yield on the Loess Plateau

Agricultural practices significantly contribute to greenhouse gas (GHG) emissions, necessitating cleaner production technologies to reduce environmental pressure and achieve sustainable maize production. Plastic film mulching is commonly used in the Loess Plateau region. Incorporating slow-release fertilizers as a replacement for urea within this practice can reduce nitrogen losses and enhance crop productivity. Combining these techniques represents a novel agricultural approach in semi-arid areas. However, the impact of this integration on soil carbon storage (SOCS), carbon footprint (CF), and economic benefits has received limited research attention. Therefore, we conducted an eight-year study (2015-2022) in the semi-arid northwestern region to quantify the effects of four treatments [urea supplied without plastic film mulching (CK-U), slow-release fertilizer supplied without plastic film mulching (CK-S), urea supplied with plastic film mulching (PM-U), and slow-release fertilizer supplied with plastic film mulching (PM-S)] on soil fertility, economic and environmental benefits. The results revealed that nitrogen fertilizer was the primary contributor to total GHG emissions (≥71.97%). Compared to other treatments, PM-S increased average grain yield by 12.01%-37.89%, water use efficiency by 9.19%-23.33%, nitrogen accumulation by 27.07%-66.19%, and net return by 6.21%-29.57%. Furthermore, PM-S decreased CF by 12.87%-44.31% and CF per net return by 14.25%-41.16%. After eight years, PM-S increased SOCS (0-40 cm) by 2.46%, while PM-U decreased it by 7.09%. These findings highlight the positive effects of PM-S on surface soil fertility, economic gains, and environmental benefits in spring maize production on the Loess Plateau, underscoring its potential for widespread adoption and application.

Quantification and mapping of regulating ecosystem services in canola agroecosystems (case study: Gorgan County, Iran)

Regulating services are the advantages that humans receive from regulating ecosystem processes. These services include, but are not limited to pollination, climate regulation, water purification, carbon sequestration, and erosion control. Quantifying and mapping ecosystem services in agroecosystems is one of the main effective actions to increase pay attention to these services and adopt suitable approaches to direct sustainability. The purpose of the study was quantification, and mapping of regulating ecosystem services in canola agroecosystems of Gorgan County, north of Iran. For this purpose, some regulating services such as carbon sequestration, climate regulation, soil microbial respiration, soil aggregate stability, and pollination by insects were evaluated based on the Common International Classification of Ecosystem Services framework. The information and data required for each of these services were collected through field measurements, laboratory experiments, and field surveys. After quantifying, the surveyed services in canola agroecosystems were presented on geospatial maps generated by ArcGIS software, version 10.3. Results showed that agroecosystems in the west and north of the studied region provided the more regulating services. Also, the results of the pollination showed that pollinating insects belonged to four orders and 13 families. The majority of the pollinators were Hymenoptera (44.74%), especially honey bees (Apis mellifera L.), Diptera (5.26%), Butterflies (Lepidoptera; 25%), and the beetles (Coleoptera; 25%), and Anthophora sp. and Andrena sp. were the second and the third most abundant pollinating species after honey bees. Generally, the canola agroecosystems close to the rivers and the natural ecosystems provided more services than other regions.

Assessing agricultural greenhouse gas emission mitigation by scaling up farm size: An empirical analysis based on rural household survey data

Agriculture is a major contributor to greenhouse gas (GHG) emissions. Farm size affects agricultural production inputs and thus has impacts on agricultural GHG emissions. However, the effects and mechanisms behind this are still unclear. In this paper, we identified the effects and mechanisms of farm size on agricultural GHG emissions, based on survey data about over 20,000 rural households in China from 2009 to 2016. Firstly, we calculated the agricultural CO2, CH4, and N2O emissions using the life-cycle analysis (LCA). Secondly, the impacts of farm size on GHG emissions intensity were explored with a fixed effect model, based on the long-term rural household survey data. Finally, the mechanisms were tested by the mediation effect model. The results showed that a 1 % increase in farm size, on average, could reduce the GHG emissions intensity of rural households by 0.245 % from 2009 to 2016. The mechanism analysis showed that the larger farm size reduced GHG emissions intensity mainly by reducing the non-fixed input intensity and raising fixed input investment. By identifying the impacts and mechanisms of farm size on agricultural GHG emissions, this paper aims to provide insights for policymakers to achieve China's goal of reaching carbon neutrality by 2060.

Global needs for nitrogen fertilizer to improve wheat yield under climate change

Increasing global food demand will require more food production1 without further exceeding the planetary boundaries2 while simultaneously adapting to climate change3. We used an ensemble of wheat simulation models with improved sink and source traits from the highest-yielding wheat genotypes4 to quantify potential yield gains and associated nitrogen requirements. This was explored for current and climate change scenarios across representative sites of major world wheat producing regions. The improved sink and source traits increased yield by 16% with current nitrogen fertilizer applications under both current climate and mid-century climate change scenarios. To achieve the full yield potential-a 52% increase in global average yield under a mid-century high warming climate scenario (RCP8.5), fertilizer use would need to increase fourfold over current use, which would unavoidably lead to higher environmental impacts from wheat production. Our results show the need to improve soil nitrogen availability and nitrogen use efficiency, along with yield potential.

Carbon footprint of maize-wheat cropping system after 40-year fertilization

Two main challenges which human society faces for sustainable development goals are the maintenance of food security and mitigation of greenhouse gas (GHG) emissions. Here, we examined the impacts of six fertilization treatments including unfertilized control (CK), mineral nitrogen (N, 90 kg N ha-1), mineral N plus 30 kg P ha-1 phosphorus (NP), NP combined with 3.75 Mg ha-1 straw (NP + Str), farmyard manure (Man, 75 Mg ha-1), and NP combined with manure (NP + Man) on crop productivity and carbon emissions (soil GHG emission; GHGI, yield-based GHG intensity; NGHGB, net GHG balance; carbon footprint, CF) in a maize-wheat cropping system during two years (April 2018-June 2020) in a semi-arid continental climate after 40 years of fertilization in the Northwest China. Manure and straw increased total GHG by 38-60 % compared to the mineral fertilizers alone, which was mainly due to the 49-80 % higher direct emissions of carbon dioxide (CO2) rather than nitrous oxide (N2O). Compared to the N fertilizer alone, organic amendments and NP increased cumulative energy yield by 134-202 % but decreased GHGI by 38-55 %, indicating that organic fertilizers increased crop productivity at the cost of higher GHG emissions. When the soil organic carbon changes (ΔSOC) were accounted for in the C emission balance, manure application acted as a net C sink due to the NGHGB recorded with -123 kg CO2-eq ha-1 year-1. When producing the same yield and economic benefits, the manure and straw addition decreased the CF by 59-85 % compared to N fertilization alone. Overall, the transition from mineral to organic fertilization in the semi-arid regions is a two-way independent solution to increase agricultural productivity along with the reduction of C emissions.

Predicting environmental impacts of smallholder wheat production by coupling life cycle assessment and machine learning

Wheat grain production is a vital component of the food supply produced by smallholder farms but faces significant threats from climate change. This study evaluated eight environmental impacts of wheat production using life cycle assessment based on survey data from 274 households, then built random forest models with 21 input features to contrast the environmental responses of different farming practices across three shared socioeconomic pathways (SSPs), spanning from 2024 to 2100. The results indicate significant environmental repercussions. Compared to the baseline period of 2018-2020, a similar upward trend in environmental impacts is observed, showing an average annual growth rate of 5.88 % (ranging from 0.45 to 18.56 %) under the sustainable pathway (SSP119) scenario; 5.90 % (ranging from 1.00 to 18.15 %) for the intermediate development pathway (SSP245); and 6.22 % (ranging from 1.16 to 17.74 %) under the rapid economic development pathway (SSP585). Variation in rainfall is identified as the primary driving factor of the increased environmental impacts, whereas its relationship with rising temperatures is not significant. The results suggest adopting farming practices as a vital strategy for smallholder farms to mitigate climate change impacts. Emphasizing appropriate fertilizer application and straw recycling can significantly reduce the environmental footprint of wheat production. Standardized fertilization could reduce the environmental impact index by 11.10 to 47.83 %, while straw recycling might decrease respiratory inorganics and photochemical oxidant formation potential by over 40 %. Combined, these approaches could lower the impact index by 12.31 to 63.38 %. The findings highlight the importance of adopting enhanced farming practices within smallholder farming systems in the context of climate change. SPOTLIGHTS.

Toward Low-Carbon Rice Production in China: Historical Changes, Driving Factors, and Mitigation Potential

Under the "Double Carbon" target, the development of low-carbon agriculture requires a holistic comprehension of spatially and temporally explicit greenhouse gas (GHG) emissions associated with agricultural products. However, the lack of systematic evaluation at a fine scale presents considerable challenges in guiding localized strategies for mitigating GHG emissions from crop production. Here, we analyzed the county-level carbon footprint (CF) of China's rice production from 2007 to 2018 by coupling life cycle assessment and the DNDC model. Results revealed a significant annual increase of 74.3 kg CO2-eq ha-1 in the average farm-based CF (FCF), while it remained stable for the product-based CF (PCF). The CF exhibited considerable variations among counties, ranging from 2324 to 20,768 kg CO2-eq ha-1 for FCF and from 0.36 to 3.81 kg CO2-eq kg-1 for PCF in 2018. The spatiotemporal heterogeneities of FCF were predominantly influenced by field CH4 emissions, followed by diesel consumption and soil organic carbon sequestration. Scenario analysis elucidates that the national total GHG emissions from rice production could be significantly reduced through optimized irrigation (48.5%) and straw-based biogas production (18.0%). Moreover, integrating additional strategies (e.g., advanced crop management, optimized fertilization, and biodiesel application) could amplify the overall emission reduction to 76.7% while concurrently boosting the rice yield by 11.8%. Our county-level research provides valuable insights for the formulation of targeted GHG mitigation policies in rice production, thereby advancing the pursuit of carbon-neutral agricultural practices.

Spatial autocorrelation and driving factors of carbon emission density of crop production in China

Mitigating carbon emissions from crop production is essential for addressing global warming. At a macro-level, existing studies have often relied on the calculation of carbon emission intensity of crop production to understand comparable carbon effects between regions. However, this approach obscures the differences in crop planting scale and natural attributes across regions, leaving room for improvement in the methods and scope of analysis. To extend the existing research, we proposed an idea for calculating the carbon emission density of crop production based on planting area. Additionally, we developed an analytical framework for driving factors of carbon emission density of crop production from a spatial interaction perspective. The provincial carbon emission density of crop production in mainland China between 2000 and 2020 was calculated, and spatial econometric models were utilized to investigate the spatial autocorrelation and driving factors. The results indicate that the national average carbon emission density of crop production was 1.462 t/hm2 annually. Over 21 years, the carbon emission density of agricultural materials, rice cultivation, soil management, and straw burning evolved from 0.384 to 0.470 t/hm2, 0.409 to 0.367 t/hm2, 0.171 to 0.169 t/hm2, and 0.317 to 0.448 t/hm2, respectively. The global Moran's index indicated a positive spatial autocorrelation of carbon emission density of crop production and the subdivided carbon sources among provinces. Regarding direct effects, an increase in the proportion of paddy fields in cropland composition and irrigation efficiency would significantly promote the carbon emission density, while factors such as cropland area, multiple cropping, agricultural personnel numbers, departmental proportion, and disaster degree would decrease the local carbon emission density. Certain factors, such as cropland area and agricultural disasters, had a spatial spillover effect on carbon emission density between provinces. The study suggests harnessing key drivers and spatial spillover effects to achieve regional low-carbon crop production.

Carbon footprint of farming practices in farmland ecosystems on the North and Northeast China plains

Fast development of farming practices in China is projected to result in additional carbon emissions and thus affect farmland ecosystems' environmental performance. Based on 454 farm surveys on the North and Northeast China Plain, the carbon footprint (CF) of two farmland ecosystems (irrigated system for wheat and maize on the North China Plain and rainfed system for maize on the Northeast Plain) were assessed and emission reduction pathways explored by quantifying greenhouse gas emissions of agricultural inputs and farm practices during the entire crop growing seasons with an agricultural footprint model. The results demonstrated that the GHG emissions from wheat and maize rotation in the irrigated system were 7.63 t CO2 eq ha-1 and 3.17 t CO2 eq ha-1 for single season maize in the rainfed system. While energy consumption accounted for 12.5%-21.3% of the carbon footprint in both systems, the group assessment found that the largest difference in GHG emissions between the high and low emission groups came from mechanical energy consumption. Approximately 50.6% and 39.2% of the mechanical carbon footprint of wheat and maize, respectively, were caused by irrigation practices in the irrigated system. Regarding the rainfed system, where 46.6% of mechanical carbon emissions were generated by maize tillage operations. In addition, scenario analysis indicated that the mechanical carbon footprint could be reduced to 56 kg CO2 eq t-1 for NCP-wheat and 26 kg CO2 eq t-1 for NCP-maize, respectively, by optimizing yields and irrigation practices in irrigated systems and that the mechanical carbon footprint of NEP-maize could be reduced to 25 kg CO2 eq t-1 by optimizing yields and tillage practices in rainfed systems. Therefore, improvement in mechanization in irrigation and tillage practices can contribute to reduce GHG emissions in China. Water-saving irrigation technology is recommended in irrigated area and conservation tillage is recommended in rainfed agricultural area to reduce carbon footprints.

Spatio-temporal evolution and its policy influencing factors of agricultural land-use efficiency under carbon emission constraint in mainland China

In the context of the vision to reach peak carbon dioxide emissions before 2030 and achieve carbon neutrality before 2060, Mainland China's agricultural development will face strict carbon constraints. This paper analyzes the agricultural land-use efficiency of Mainland China's agriculture under carbon emission constraint from 1996 to 2020, based on the unexpected super SBM (Slack-based measure)-Undesirable DEA, Malmquist index model, and quartile division-GIS method. The results show that: from 1996 to 2020, the agricultural output value per land and grain output per land show an upward trend, and the agricultural carbon emissions per land of most provinces show an increasing trend and larger emissions. The agricultural land-use efficiency in Mainland China rises first and then decreases, and technological progress is the decisive path to improving the agricultural land-use efficiency in Mainland China. The average MI in the prominent grain-selling area during 1996-2020 was as high as 1.071, which was significantly higher than that in the prominent grain-producing area (1.039) and the balance area (1.030). The improvement of agricultural land-use efficiency is mostly due to technological progress, but the instability of technical input and management in land use. To improve agricultural land-use efficiency in Mainland China, we should pay attention to the precise policy formulation of low-carbon and high-quality development and strengthen government investment in the difference between space resource endowment and development status.

Decoupling effect and driving factors of carbon footprint in megacity Wuhan, Central China

Background

China's 35 largest cities, including Wuhan, are inhabited by approximately 18% of the Chinese population, and account for 40% energy consumption and greenhouse gas emissions. Wuhan is the only sub-provincial city in Central China and, as the eighth largest economy nationwide, has experienced a notable increase in energy consumption. However, major knowledge gaps exist in understanding the nexus of economic development and carbon footprint and their drivers in Wuhan.

Methods

We studied Wuhan for the evolutionary characteristics of its carbon footprint (CF), the decoupling relationship between economic development and CF, and the essential drivers of CF. Based on the CF model, we quantified the dynamic trends of CF, carbon carrying capacity, carbon deficit, and carbon deficit pressure index from 2001 to 2020. We also adopted a decoupling model to clarify the coupled dynamics among total CF, its accounts, and economic development. We used the partial least squares method to analyze the influencing factors of Wuhan's CF and determine the main drivers.

Results

The CF of Wuhan increased from 36.01 million t CO2eq in 2001 to 70.07 million t CO2eq in 2020, a growth rate of 94.61%, which was much faster than that of the carbon carrying capacity. The energy consumption account (84.15%) far exceeded other accounts, and was mostly contributed by raw coal, coke, and crude oil. The carbon deficit pressure index fluctuated in the range of 8.44-6.74%, indicating that Wuhan was in the relief zone and the mild enhancement zone during 2001-2020. Around the same time, Wuhan was in a transition stage between weak and strong CF decoupling and economic growth. The main driving factor of CF growth was the urban per capita residential building area, while energy consumption per unit of GDP was responsible for the CF decline.

Conclusions

Our research highlights the interaction of urban ecological and economic systems, and that Wuhan's CF changes were mainly affected by four factors: city size, economic development, social consumption, and technological progress. The findings are of realistic significance in promoting low-carbon urban development and improving the city's sustainability, and the related policies can offer an excellent benchmark for other cities with similar challenges.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13717-023-00435-y.

Yield, water, and carbon footprint of rainfed rice production under the lens of mid-century climate change: a case study in the eastern coastal agro-climatic zone, Odisha, India

Water and carbon footprint assessment can be a good indicator of sustainable agricultural production. The present research quantifies the potential impact of near-future (2026-2050) climate change on water footprint (WF) and carbon footprint (CF) of farm-level kharif rice production of three locally grown varieties (Khandagiri, Lalat, and Swarna) in Odisha, India, under the two RCP scenarios of 4.5 and 8.5. The crop yield, water resources utilization, and greenhouse gas (GHG) emissions were estimated using the calibrated and validated DSSAT crop simulation model. The precipitation and temperature estimates from three regional climate models (RCM), namely HadGEM3-RA, RegCM4, and YSU-RSM were downscaled using the quantile mapping method. The results revealed a considerably high increase in the total WF of the Khandagiri, Lalat, and Swarna rice varieties elevating up to 101.9%, 80.7%, and 71.8% respectively during the mid-century for RCP 4.5 scenario, and 67.3%, 66.6%, and 67.2% respectively for RCP 8.5 scenario relative to the baseline WF. Moreover, compared to the green WF, the blue WF was projected to increase significantly (~ 250-450%) in the future time scales. This could be attributed to increasing minimum temperature (~ 1.7 °C) and maximum temperature (~ 1.5 °C) and reduced precipitation during the rice-growing periods. Rice yield was projected to continually decline in the future period (2050) with respect to the baseline (1980-2015) by 18.8% and 20% under RCP 4.5 and 8.5 scenarios respectively. The maximum CF of Swarna, Lalat, and Khandagiri rice were estimated to be 3.2, 2.8, and 1.3 t CO₂eq/t respectively under RCP 4.5 and 2.7, 2.4, and 1.3 t CO₂eq/t respectively under RCP 8.5 scenario. Fertilizer application (40%) followed by irrigation-energy use (30%) and farmyard manure incorporation (26%) were the three major contributors to the CF of rice production. Subsequently, management of N-fertilizer dose was identified as the major mitigation hotspot, simultaneously reducing carbon footprint and grey water footprint in the crop production process.

Impact of Digital Village Construction on Agricultural Carbon Emissions: Evidence from Mainland China

Reducing agricultural carbon emissions is required to reach the goal of carbon neutrality and mitigate the effects of climate change. With the advent of the digital economy, we aimed to determine if digital village construction can achieve carbon reduction in agriculture. As such, in this study, we used balanced panel data for 30 provinces in China from 2011 to 2020 to conduct an empirical analysis based on measuring the digital village construction level in each province. We found the following: Firstly, digital village construction is conducive to reducing the carbon emitted from agriculture, and the results of further tests showed that the carbon reduction effect of digital villages is mainly based on the reduction in carbon emissions from chemical fertilisers and pesticides. Secondly, the digital village construction has a stronger inhibiting effect on agricultural carbon emissions in major grain-producing areas than in non-major grain-producing areas. The level of rural human capital is the limiting condition for digital village construction to enable green agricultural development; in areas with higher levels of human capital, digital village construction has a significant inhibiting effect on agricultural carbon emissions. The above conclusions are valuable for the future promotion of digital village construction and the design of a green development model for agriculture.

The impact of irrigation modes on agricultural water-energy‑carbon nexus

Despite the tremendous contribution of irrigated agriculture in addressing global food security, there is still confusion for farmers and governments about the choice of irrigation mode owing to the drastic environmental impacts of irrigation, including water shortage, energy crisis, and global warming. Exploring the agricultural water-energy‑carbon (WEC) nexus under different irrigation modes helps to accomplish the multi-objective of water & energy saving and carbon emission reduction. In this paper, a conceptual framework was nominated to evaluate the water & energy consumption and carbon emissions for winter wheat irrigation at township level and quantitatively discuss the complex interaction by the coupling coordination degree (CCD) of the WEC system under different irrigation modes in Henan Province, China. We discovered that irrigation modes profoundly affect water and energy consumption and carbon emissions in agriculture, as well as the spatial distribution of CCD from WEC system. Townships under irrigation mode with diversion and irrigation projects as the primary method (WDI) clustered together in the north and east with highest water consumption and carbon emissions, while townships under irrigation mode with rain-fed agriculture as the primary method (PI) accumulated in the west and south with lower water consumption and carbon emissions. Meanwhile, the CCD of the WEC nexus system was in basic coordination (0.40) and showed an unbalanced spatial distribution pattern with high in the southeast and low in the northwest. By comparing four irrigation modes, the coupling level of the WEC nexus system under irrigation mode with groundwater irrigation as the primary method (GI) was better and PI mode was the least ideal. This study helps to further understand agricultural WEC nexus under different irrigation modes and provide references for local governments in selecting appropriate irrigation modes to realize water-energy saving and carbon emission reduction in agricultural activities.

LCA of Barley Production: A Case Study from Cyprus

Greenhouse gas emissions (i.e., carbon dioxide, methane, nitrous oxide) produced by agriculture contribute to global warming and climate change. Various practices followed by farmers in different environmental conditions contribute to the increase in the phenomena, and there is a need for immediate measures. The current study examines the environmental impact of barley production under rain-fed conditions in Cyprus. For this, four different nutrient management scenarios were investigated in order to evaluate the environmental performance of crop production, namely: (1) Nitrogen (20%), Phosphorous (20%), Potassium (10%); (2) Nitrogen (20%), Phosphorous (20%), Potassium (10%) and manure; (3) Nitrogen (25%), Phosphorous (10%), Potassium (0%); and (4) Nitrogen (25%), Phosphorous (10%), Potassium (0%) and manure. Data were collected from two different areas of Cyprus (Nicosia and Larnaca) through on-site visits and questionnaires. Life Cycle Assessment (LCA) was used as a method to quantify environmental impacts which were categorized into six impact categories: (i) acidification potential (AP), (ii) eutrophication potential (EP), (iii) global warming potential (GWP), (iv) ozone depletion potential (ODP), (v) photochemical, ozone creation potential (POCP), and (vi) terrestrial ecotoxicity (TAETP). LCA was used with system boundaries from field to harvest and a functional unit (FU) of one bale of hay. Research results showed that the addition of manure increased values in all impact categories. Comparing scenarios without manure (1 and 3) and with manure (2 and 4), the main process which contributed to GWP was field preparation, which resulted in 3 t CO₂-Eq∙FU^-1 and 46.96 t CO₂-Eq∙FU^-1, respectively. Furthermore, the highest contribution of sub-processes to GWP (kg CO₂-Eq∙FU^-1) was machinery maintenance (scenarios 2 and 4). The potential to reduce environmental impacts from barley and moreover, to mitigate the footprint of the agriculture sector in Cyprus is proposed by changing existing practices such as decreasing fuel consumption by agricultural machinery, and monitoring fertilizing and seeding. Conclusively, the carbon footprint of barley can be decreased through the improvement of nutrient management and cropping practices.

Do changes in land use, water bodies, and grazing pastures have a detrimental influence on environmental quality? Opportunities and threats to long-term growth

Land use activities mainly for economic and agricultural purposes have converted one third to one half of our planet's land surface into urban expansion and agricultural practice, which has had significant impacts on natural ecosystems, food production, and environmental quality, attracting the attention of researchers and policymakers. Consequently, land use is emerging as a fundamental issue in global environmental change and sustainable development. This study represents an addition to the prevailing literature by investigating the asymmetric impacts of land-use and land-cover changes on environmental quality in Pakistan using time series data from 1961 to 2016. Carbon dioxide (CO2) emissions were deemed a dependent variable (a proxy for environmental quality), whereas built-up land, cropland, water bodies, and grazing land were considered independent. A nonlinear ARDL bound testing technique (NARDL) was used to investigate dynamic cointegration among the study variables. Moreover, this study used the BDS test and structural break unit root test to confirm nonlinearity and stationarity of the data set. The results confirm that the variables exhibit asymmetrical co-integration. There is a symmetric unidirectional causation, running from built-up land and grazing land towards CO2 emissions with coefficients of 10.570 and 17.045, respectively. Furthermore, asymmetric causality shows that any positive shocks to built-up land (6.134) and water bodies (20.335) significantly cause CO2 emissions. Similarly, a negative shock to grazing land (16.470) also causes CO2 emissions. By contrast, a neutral effect was found between cropland and CO2 emissions.

Decreased carbon footprint and increased grain yield under ridge-furrow plastic film mulch with ditch-buried straw returning: A sustainable option for spring maize production in China

Ditch-buried straw returning with ridge-furrow plastic film mulch (RP+S) is a novel tillage measure in semiarid regions, but it is unclear whether RP+S can increase maize yield while reducing the carbon footprint (CF). Therefore, a six-year continuous experiment was conducted from 2016 to 2021 to quantify the effect of four straw returning and film mulching measures [conventional flat cultivation (CK), conventional flat cultivation with ditch-buried straw returning (CK+S), ridge-furrow plastic film mulch (RP), and RP+S] on soil organic carbon sequestration (SOC_S), greenhouse gas (GHG) emissions, CF, and economic benefits. Straw returning and film mulching measures significantly increased total GHG emissions across the six seasons. For all treatments, nitrogen fertilizer was the most important source of GHG emissions (≥73%), followed by diesel (8-11%) and plastic film (8%, RP and RP+S only). RP+S significantly increased yield and partial factor productivity of nitrogen fertilizer by 8.7-59.1%, and net economic benefit by 7.37-57.76%, but decreased CF by 34-61% and CF per net return by 33-61% relative to the other treatments. RP+S had the highest GHG emissions, increasing by 6.11-16.47% relative to the other treatments. However, compared with the initial 0-40 cm SOC_S in 2016, RP+S had the highest carbon sequestration rate (678.17 kg·ha^-1·yr^-1), increasing by 2.29% after six years, followed by CK+S (1.78%), CK (0.89%), and RP (-0.49%). Thus, RP+S had the lowest CF and CF per net return in four treatments. This comprehensive analysis of agronomic and environmental benefits revealed that RP+S is a high-yielding, economically and environmentally friendly measure in semiarid areas.

Seasonal Variations in Grain Yield, Greenhouse Gas Emissions and Carbon Sequestration for Maize Cultivation in Bangladesh

Rationale: Greenhouse gas (GHG) emissions from crop agriculture are of great concern in the context of changing climatic conditions; however, in most cases, data based on lifecycle assessments are not available for grain yield variations or the carbon footprint of maize. The current study aimed to determine net carbon emissions and sequestration for maize grown in Bangladesh. Methods: The static closed-chamber technique was used to determine total GHG emissions using data on GHG emissions from maize fields and secondary sources for inputs. A secondary source for regional yield data was used in the current study. GHG emission intensity is defined as the ratio of total emissions to grain yield. The net GHG emission/carbon sequestration was determined by subtracting total GHG emissions (CO2 eq.) from net primary production (NPP). Results: Grain yields varied from 1590 to 9300 kg ha−1 in the wet season and from 680 to 11,820 kg ha−1 in the dry season. GHG emission intensities were 0.53–2.21 and 0.37–1.70 kg CO2 eq. kg−1 grain in the wet and dry seasons, respectively. In Bangladesh, the total estimated GHG emissions were 1.66–4.09 million tonnes (MT) CO2 eq. from 2015 to 2020, whereas the net total CO2 sequestration was 1.51–3.91 MT. The net CO2 sequestration rates were 984.3–5757.4 kg ha−1 in the wet season and 1188.62–5757.39 kg ha−1 in the dry season. This study observed spatial variations in carbon emissions and sequestration depending on growing seasons. In the rice–maize pattern, maize sequestered about 1.23 MT CO2 eq. per year−1, but rice emitted about 0.16 MT CO2 eq. per year−1. This study showed potential spatiotemporal variations in carbon footprints. Recommendation: Special care is needed to improve maize grain yields in the wet season. Fertiliser and water use efficiencies need to be improved to minimise GHG emissions under changing climatic conditions. Efforts to increase the area under cultivation with rice–maize or other non-rice crop-based cropping systems are needed to augment CO2 sequestration. The generation of a regional data bank on carbon footprints would be beneficial for combating the impact of climate change.

Research on the Eco-Efficiency of Rice Production and Its Improvement Path: A Case Study from China

The eco-efficiency of rice production is an important indicator in the measurement of sustainable rice development. Scientific evaluation of the eco-efficiency of rice production facilitates accurate evaluation of the real level of rice ecosystems to realize efficient utilization of agricultural resources. This paper measured the eco-efficiency of farms growing rice using both the life cycle assessment (LCA) and the data envelopment analysis (DEA) methods based on survey data from 370 farms mainly growing rice conducted in 2020 in the Hubei Province, the middle reaches of the Yangtze River in China. Then, sensitivity analysis and scenario analysis were carried out on the comprehensive index of the rice environmental impact and eco-efficiency of rice production, respectively. The results indicate that the comprehensive index of the rice environmental impact was 2.0971. Water toxicity, soil toxicity and eutrophication were the main influencing factors. The mean value of the eco-efficiency reached 0.51. More specifically, the proportion of farms in the low-, middle- and high-efficiency groups was 87.03%, 1.89% and 11.08%, respectively, with mean values up to 0.42, 0.86 and 1.14, respectively. A sensitivity analysis revealed that the pesticide sensitivity was higher than the fertilizer sensitivity in terms of the environmental impact sensitivity of rice systems. When comprehensively considering environmental and economic benefits, the fertilizer sensitivity was higher than that of pesticides. Moreover, reducing the application of both fertilizers and pesticides by 50% could promote the eco-efficiency of rice production systems by 6%, and the value could reach 0.54. Thus, reducing the application of fertilizers and pesticides and improving the utilization efficiency are effective ways to improve green rice production.

Pomelo Green Production on Acidic Soil: Reduce Traditional Fertilizers, but Do Not Ignore Magnesium

Orchards in acid soils are at risk of magnesium (Mg) deficiency which negatively affects the plant growth, yield, and quality. However, the impacts of Mg supplementation on fruit yield, quality, and environmental and economic benefits have only been rarely addressed. We conducted 15 pomelo (Citrus grandis L.) orchard trials in South China to assess more efficient integrated nutrient management (INM) practices, including local farmer fertilization practices (FP; average application rate of nitrogen, phosphorus, and potassium were 1,075 kg N ha−1, 826 kg P2O5 ha−1, and 948 kg K2O ha−1, respectively), optimum fertilization practice (OPT; average application rate of nitrogen, phosphorus, and potassium were 550 kg N ha−1, 295 kg P2O5 ha−1, and 498 kg K2O ha−1, respectively) and optimum fertilization supplemented with Mg (OPT+Mg; average application rate of Mg was 196 kg MgO ha−1). The results showed that the yield, total soluble solid-to-titratable acidity ratio, and economic benefits under OPT practice were not significantly different from those of FP, while those of OPT+Mg were significantly higher than those of FP, by 8.76, 8.79, and 15.00%, respectively, while titratable acidity contents were significantly lower by 7.35%. In addition, compared with those from FP, the energy inputs and greenhouse gas (GHG) emissions from OPT were 31.00 and 26.48% lower, and those from OPT+Mg were 26.71 and 23.40% lower, respectively. Compared with those of OPT, the marginal efficiency of energy, GHG emissions, and capital of Mg under OPT+Mg were reduced by 62.30, 44.19, and 21.07%, respectively. Overall, adopting OPT+Mg for pomelo production could further enhance yield, fruit quality, and economic benefits while reducing the environmental burdens.

Closing Greenhouse Gas Emission Gaps of Staple Crops in China

China is facing the dual challenge of achieving food security and agricultural carbon neutrality. Developing spatially explicit crop emission profiles can help inform policy to mitigate agricultural greenhouse gases (GHGs), but previous life-cycle studies were conducted mostly at national and provincial levels. Here, we estimate county-level carbon footprint of China's wheat and maize production based on a nationwide survey and determine the contribution of different strategies to closing regional emission gaps. Results show that crop carbon footprint varies widely between regions, from 0.07 to 3.00 kg CO₂e kg^-1 for wheat and from 0.09 to 2.30 kg CO₂e kg^-1 for maize, with inter-county variation generally much higher than interprovince variation. Hotspots are mainly concentrated in Xinjiang and Gansu provinces, owing to intensive irrigation and high plastic mulch and fertilizer inputs. Closing the regional emission gaps would benefit mostly from increasing crop yields and nitrogen use efficiency, but increasing manure use (e.g., in Northeast, East, and Central China) and energy use efficiency (e.g., in North and Northwest China) can also make important contributions. Our county-level carbon footprint estimates improve upon previous broad-scale results and will be valuable for detailed spatial analysis and the design of localized GHG mitigation strategies in China.

Comparing rice production systems in China: Economic output and carbon footprint

In recent years, many rotational and integrated rice production systems coupled with several greenhouse gas (GHG) emissions mitigation practices have been developed and adopted for demand of low carbon production. However, there have been only few studies about comparisons on the balance between high production and mitigation of GHG emissions in different rice production systems. We therefore aimed to evaluate economic output and carbon footprint of different rice production systems, based on several long-term experiments conducted by our lab. CH₄ and N₂O emission were measured by the same static chamber/gas chromatogram measurement procedure in different rice production systems, including rice-fallow, rice-rapeseed, rice-wheat, double rice, and integrated rice-crayfish production system. Then, we applied the DeNitrification DeComposition model to simulate CH₄ and N₂O emission over different years under the same condition for comparison. Carbon footprint was calculated following the process-based life cycle assessment (PLCA) methodology. The economic benefit of rice production systems was assessed by cost-benefit analysis. According to the analysis, the double-rice production system exhibited the highest intensity of carbon footprint (ICF = 4.14 kg CO₂-eq yuan^-1), rain-fed treatment in the rice-rapeseed system had the lowest (ICF = 0.68 kg CO₂-eq yuan^-1). The intensity of carbon footprint in different treatments in the integrated rice-crayfish production system was around 0.8 kg CO₂-eq yuan^-1. Overall, the results of this case study suggest: (1) the proposed practices in different rice production systems are no straw returning (rice-fallow), no-tillage without straw returning (rice-wheat), rain-fed farming (rice-rapeseed), no insect and no inoculation (double rice), and feeding with straw returning (rice-crayfish); (2) rotational and integrated systems can achieve high net output with low carbon emission; (3) reducing the amount of nitrogenous fertilizer application is the most important and effective GHG mitigation practice for rotational systems.

Comparative analysis of carbon footprint between conventional smallholder operation and innovative largescale farming of urban agriculture in Beijing, China

The sustainable development of agriculture is one of the key issues of ensuring food security and mitigating climate change. Since innovative large-scale agriculture is gaining popularity in cities in China, where the agricultural landscape is dominated by conventional smallholder farming, it is necessary to investigate the difference in carbon emissions between conventional smallholder operation and innovative largescale agriculture. This study evaluated the carbon footprint (CF) of conventional and innovative urban agriculture in Beijing using the cradle-to-consumption Life Cycle Assessment (LCA). Two modes of greenhouse vegetable and fruit production were analyzed and compared respectively: conventional smallholder operated vegetable farms that sell in local markets versus largescale home-delivery agriculture (HDA) that deliver vegetables to consumers' home directly, conventional smallholder operated fruit farms that sell in farm shops versus largescale pick-your-own (PYO) initiatives. Results showed that HDA and PYO can reduce CF per area in on-farm cultivation compared to smallholder operation, while may bring an increase in CF per product weight unit and the gap was wider if the supply chain was considered. This is mainly because innovative large-scale farming consumes fewer agricultural inputs (e.g., fertilizer, pesticides) and obtains lower yields than conventional smallholder operations. Plastic materials with high carbon emission, fossil energy dependence and transportation efficiency are CF hotspots of both modes and therefore can be prioritized and targeted for carbon reduction adjustment. The results of this work further advance understanding of how innovative largescale agriculture and conventional smallholder operation compare and which particular inputs and activities should be prioritized to effectively reduce the CF in China during agricultural transformation.

Managing the trade-offs among yield, economic benefits and carbon and nitrogen footprints of wheat cropping in a semi-arid region of China

It is critical to understand how farming practices affect the carbon and nitrogen footprints of agricultural production. Grain yield, economic return, and carbon and nitrogen footprints of spring wheat (Triticum aestivum L.) were examined under different tillage-mulch practices. Wheat was grown over 15 years (2002-2016) in the semi-arid region of the western Loess Plateau of China under six tillage-mulch practices: traditional plough with no straw mulching (T), no-till without straw mulching (NT), traditional plough with straw mulching (TS), no-till without straw mulching (NTS), traditional plough with plastic mulching (TP), no-till with plastic mulching (NTP). Average wheat yield over 15 years under NTS, NTP, TP and TS was increased by 28, 24, 22, and 13%, respectively, compared to T. Average net return was greatest under NTS and lowest under TP. The soils under all six tillage-mulch practices gained a considerably large amount of soil organic carbon (SOC) over the 15 yr. The increase in SOC in the 0-30 cm soil layer was greatest under NTS and lowest under T. When changes in soil C were included in the calculations, treatments of NT, TS, NTS, and NTP sharply reduced total greenhouse gas (GHG) emission compared to T. Compared to T, the carbon footprint was decreased by 180, 44, and 123% under NTS, NT, and TS, respectively, but was increased by 153% under TP. Compared to T, the nitrogen footprint was 24-26% lower in TP and NTP, but was not significantly different under NTS, NT, and TS. Therefore, NTS enhanced yield and net return, and reduced GHG and the carbon footprint without increasing the nitrogen footprint, and should be adopted to mitigate the environmental impacts of wheat production in the semiarid Loess Plateau.

Wheat Grain Protein Content under Mediterranean Conditions Measured with Chlorophyll Meter

Adequate N fertilisation is crucial to increase the grain protein content (GPC) values in wheat. The recommended level of GPC needed to achieve high-quality bread-making flour should be higher than 12.5%. However, it is difficult to ensure the GPC values that the crop will achieve because N in grain is derived from two different sources: N remobilized into the grain from N accumulated in the pre-anthesis period, and N absorbed from the soil in the post-anthesis period. This study aimed to (i) evaluate the effect of the application of N on the rate of stem elongation (GS30) when farmyard manures are applied as initial fertilisers on GPC and on the chlorophyll meter (CM) values at mid-anthesis (GS65), (ii) establish a relationship between the CM values at GS65 and GPC, and (iii) determine a minimum CM value at GS65 to obtain GPC values above 12.5%. Three field trials were performed in three consecutive growing seasons, and different N fertilisation doses were applied. Readings using the CM Yara N-Tester^TM were taken at GS65. The type of initial fertiliser did not affect the GPC and CM values. Generally, the greater the N application at GS30 is, the higher the GPC and CM values are. CM values can help to estimate GPC values only when yields are below 8000 kg ha⁻¹. Additionally, CM values at GS65 should be higher than 700 to achieve high-quality bread-making flour (12.5%) at such yield levels. These results will allow farmers and cooperatives to make better decisions regarding late-nitrogen fertilisation and wheat sales.

Effects of straw returning levels on carbon footprint and net ecosystem economic benefits from rice-wheat rotation in central China

Straw returning usually gives rise to greenhouse gas (GHG) emissions from the soil, and thus negatively affects carbon footprint (CF) of crop production. Numerous studies reported the effects of straw returning on the CF from single crop production. However, little is known about the integrated effects of different levels of straw returning on the CF and net ecosystem economic benefits (NEEB) from rice-wheat rotation. Here, we investigated the effects of different amounts of straw returning on soil CH₄ and N₂O emissions, GHG emissions from agricultural inputs (AIGHG), CF, and NEEB from a 2-year cycle of rice-wheat rotation. The CF was determined based on the total GHG emissions associated with crop production inputs and services. Overall, straw returning significantly increased annual CH₄ emissions by 5.4-72.2% and reduced annual N₂O emissions by 3.3-31.4% compared with straw removal. Straw returning remarkably increased rice grain yields by 8.1-9.9% and wheat grain yields by 10.2-21.1% compared with straw removal. The average annual AIGHG from rice-wheat rotation ranged from 3579 to 4987 kg CO₂-eq ha^-1. Diesel consumption played a dominant role in the AIGHG. The annual CF ranged from 0.96 to 1.31 kg CO₂-eq kg^-1 and increased with increasing straw returning amounts. The NEEB, which ranged from 14161 to 17413 CNY ha^-1, was significantly affected by the levels of straw returning. The treatment with returning of 1/3 of preceding crop straw to the field (2.19-2.47 kg ha^-1 year^-1 of rice straw in the wheat season and 1.38-1.68 kg ha^-1 year^-1 of wheat straw in the rice season) resulted in relatively higher grain yield, the lowest CF, and the highest NEEB among all treatments, and thus can reduce CF, and increase grain yields and NEEB, and thus can be recommended as a sustainable approach to mitigate GHG emissions and increase economic benefits from rice-wheat rotation.

Nutrition-Oriented Reformulation of Extruded Cereals and Associated Environmental Footprint: A Case Study

The global food system faces a dual challenge for the decades ahead: to (re)formulate foods capable to feed a growing population while reducing their environmental footprint. In this analysis, nutritional composition, recipe, and sourcing data were analyzed alongside five environmental indicators: climate change (CC), freshwater consumption scarcity (FWCS), abiotic resource depletion (ARD), land use impacts on biodiversity (LUIB), and impacts on ecosphere/ecosystems quality (IEEQ) to assess improvement after three reformulation cycles (2003, 2010, 2018) in three extruded breakfast cereals. A life cycle assessment (LCA) was performed using life cycle inventory (LCI) composed by both primary data from the manufacturer and secondary data from usual third-party LCI datasets. Reformulation led to improved nutritional quality for all three products. In terms of environmental impact, improvements were observed for the CC, ARD, and IEEQ indicators, with average reductions of 12%, 14%, and 2% between 2003 and 2018, respectively. Conversely, the FWCS and LUIB indicators were increased by 57% and 70%, respectively. For all indicators but ARD, ingredients contributed most to the environmental impact. This study highlights the need for further focus on the selection of less demanding ingredients and improvements in agricultural practices in order to achieve environmental and nutritional improvements.

Optimizing Nitrogen and Residue Management to Reduce GHG Emissions while Maintaining Crop Yield: A Case Study in a Mono-Cropping System of Northeast China

Reducing the use of nitrogen fertilizers and returning straw to field are being promoted in northeast China (NEC). In this paper, the agricultural production system model (APSIM) was applied to assess the long-term variations of crop yield and soil GHG emissions in a maize mono-cropping system of NEC, and the simulation results were combined with lifecycle assessment to estimate annual GHG emissions (GHGL) and GHG emission intensity (GHGI, GHG emissions per unit yield) of different agricultural practices. Under current farmers’ practice, emissions due to machinery input (including production, transportation, repair, and maintenance) and soil organic carbon (SOC) decline accounted for 15% of GHGL, while emissions from nitrogen fertilizer input (production and transportation) and direct N2O emissions from soil accounted for the majority (~60% of GHGL). Current farmers’ practice in terms of N application and residue management are nearly optimal for crop production but not for climate change mitigation. Reducing N input by 13% and increasing straw retention by 20% can maintain crop yield and SOC, and also reduce GHGL and GHGI by 13% and 11%, respectively. However, it is not feasible to incorporate the straw used as household fuel into soil, which could incur substantial fossil CO2 emissions of 3.98 Mg CO2-eq ha−1 resulting from the substitution of coal for straw. APSIM was successful in simulating crop yield, N2O emissions, and SOC change in NEC, and our results highlight opportunities to further optimize management strategies (especially for the nitrogen and straw management) to reduce GHG emissions while maintaining crop yield.

Crop Production Pushes Up Greenhouse Gases Emissions in China: Evidence from Carbon Footprint Analysis based on National Statistics Data

The rapid growth of crop yield in China was maintained by more fossil fuel inputs in the past years, causing concern about the greenhouse gas (GHG) emissions related to crop production. Therefore, this study analyzed historical dynamics of carbon footprint (CF) of 11 major crops in China during 2000–2016 and estimated possible GHG emissions of the system in 2020 under different scenarios. Results indicated that the GHG emissions of the Chinese crop system increased by 20.07% from 2000 to 2016, in which the grain crops contributed to more than 80% of the total emissions. The GHG emissions from grain crops including maize, wheat, and rice as well as sugar crops including sugarcane and sugar beet were increased by 28.07% and 14.27% in the study period, respectively, making up the primary factor of increased GHG emissions of crop system in China. Moreover, if the cropping pattern and agricultural practices is not improved in the future, the GHG emissions from Chinese crop system are estimated to increase by 346.19 million tons in 2020. If advanced agricultural policies and practices are implemented, the GHGs emissions of crop system in China in 2020 are estimated to be 2.92–12.62% lower than that in 2016. Overall, this study illustrated that the crop system in China contributed to the growth of GHG emissions in China over the past decades. Improving utilization efficiency of fertilizers and crop structure in China are the most important ways to reduce GHG emissions from the Chinese crop system.

Evaluating the Coordination of Industrial-Economic Development Based on Anthropogenic Carbon Emissions in Henan Province, China

The mechanism of interaction between economic development, industrial structure and anthropogenic carbon emissions has become one of the focuses of climate change research. In this investigation, Henan Province was studied as an example, wherein the calculation model of carbon emissions in the primary, secondary and tertiary economic sectors was built using the ArcGIS 10.1 software. The spatiotemporal difference of carbon emissions between 2006 and 2015 from the three sectors was studied. The relation between economic development and environmental protection is discussed, based on the construction of a coordination degree model. Conclusions drawn from this analysis are: (1) In 2015, China's total carbon emissions reached 10,291.93 × 10⁷ t and Henan's carbon emissions accounted for 1.96% of China's total carbon emissions. The total carbon emissions in Henan Province increased more than 25.00% between 2006 and 2015. (2) Carbon emissions from different economic sectors demonstrated varied patterns. The primary sector presented a gradual decreasing trend in carbon emission, while the secondary sector showed a fluctuating pattern and the tertiary sector had an inclining trend in carbon emission. (3) There are also disparities in the spatial distribution of carbon emissions from different economic sectors. The primary and tertiary sectors had higher emissions in the southeast and lower emissions in the northwest regions, while the secondary sector showed higher emissions in the northwest and lower emissions in the southeast Between cities at different prefecture levels, differences do not only lie on the quantity of carbon emissions from the three sectors of economy but also a larger variation with regards to the change in quantity of carbon emissions. (4) The coordination degree of economic development was low among different prefecture-level cities. The economic and environmental development appeared coordinated among cities at the same prefecture level; however, coordination degrees among different prefecture-level cities varies significantly.