A global meta-analysis of greenhouse gases emission and crop yield under no-tillage as compared to conventional tillage

Effects of Conservation Agriculture on Soil N2O Emissions and Crop Yield in Global Cereal Cropping Systems

Conservation agriculture, which involves minimal soil disturbance, permanent soil cover, and crop rotation, has been widely adopted as a sustainable agricultural practice globally. However, the effects of conservation agriculture practices on soil N2O emissions and crop yield vary based on geography, management methods, and the duration of implementation, which has hindered its widespread scientific application. In this study, we assessed the impacts of no-tillage (NT), both individually and in combination with other conservation agriculture principles, on soil N2O emissions and crop yields worldwide, based on 1270 observations from 86 peer-reviewed articles. Our results showed that conservation agriculture practices significantly increased crop yield by 9.1% while significantly reducing soil N2O emissions by 6.8% compared to conventional tillage (CT). These mitigation effects were even greater when NT was combined with other conservation agriculture principles, such as crop residue retention and crop rotation, leading to reductions in N2O emissions of over 15% and yield increases of more than 30%. Additionally, conservation agriculture was more effective at mitigating soil N2O emissions in dry climates compared to humid regions. Long-term adoption of conservation agriculture practices was found to reduce soil N2O emissions by up to 26% without compromising crop yields. Smallholder farm in Central Asia, South Asia, and sub-Saharan Africa appear particularly suitable for the adoption of conservation agriculture, whereas, in humid climates, high nitrogen (N) input management and silt-clay loam soil should be applied with caution. Overall, conservation agriculture holds significant potential for mitigating soil N2O emissions while enhancing grain yields in cereal cropping systems.

The pivotal role of arbuscular mycorrhizal fungi in enhancing plant biomass and nutrient availability under drought stress conditions: A global meta-analysis

Drought is a serious threat to crop productivity and global food security. About 40 % of the worldwide land is considered arid dryland soil because of a lack of rainfall, high solar radiation, and temperature fluctuations. Though rhizobacteria, particularly mycorrhizal fungi (MF), assist plants in coping with drought stress, an intensive quantitative assessment of their effects on plant growth and nutrient availability is still limited. We systematically carried out a global meta-analysis using 122 peer-reviewed publications comprising 3534 observations to investigate the effects of MF on plant biomass (PB) and nutrient availability (nitrogen: N and phosphorus: P) under drought-stress conditions. The results show that the MF inoculation significantly increased mycorrhizal colonization (MC), N and P uptakes, and plant biomass (PB) at a C:N ratio > 15 by 2171.44 %, 23.74 %, 135.61 %, and 220.91 %, respectively. The MF species Claroideoglomus etunicatum and Glomus significantly influenced the MC, N, and PB concentrations by 2541.68 %, 40.35 %, and 110.85 %, respectively. Moreover, the concentrations of MC, N, and PB were considerably affected by the soil texture categories, with the maximum levels of 4940.04 %, 127.05 %, and 84.04 % found in sandy, clay, and clay loam soils, respectively. In addition, soil pH, crop types, soil textural class, and MF species were identified as vital pedologic factors affecting plant growth and nutrient availability during fungal inoculation. Overall, this meta-analysis addresses gaps in understanding the effects of MF inoculation on plant development and nutrient availability under drought stress.

Reevaluating the Drivers of Fertilizer-Induced N2O Emission: Insights from Interpretable Machine Learning

Direct nitrous oxide (N2O) emissions from fertilizer application are the largest anthropogenic source of global N2O, but the factors influencing these emissions remain debated. Here, we compile 1134 observations of fertilizer-induced N2O emission factor (EF) from 229 publications, covering various regions and crops globally. We then employ an interpretable machine learning model to investigate the driving factors of fertilizer-induced N2O emissions. Our results reveal that pH, soil organic carbon, precipitation, and temperature are the most influential factors, overweighing the impacts of management practices. Nitrogen application rate has a positive impact on the EF, but the effect diminishes as nitrogen application rate increases, which has been overestimated in previous studies. Soil pH has three-stage influence on EF: positive when 7.3 ≤ pH ≤ 8.7, significantly negative between 6.8 and 7.3, and insignificant at lower pH levels (4.7 ≤ pH ≤ 6.8). Moreover, we confirm the nonlinear contributions of temperature and precipitation to EF, which may cause an unexpected increase in N2O emission under climate change. Our research provides crucial insights for global N2O modeling and mitigation strategies.

Mineral and organic fertilisation influence ammonia oxidisers and denitrifiers and nitrous oxide emissions in a long-term tillage experiment

Nitrous oxide (N2O) emissions from different agricultural systems have been studied extensively to understand the mechanisms underlying their formation. While a number of long-term field experiments have focused on individual agricultural practices in relation to N2O emissions, studies on the combined effects of multiple practices are lacking. This study evaluated the effect of different tillage [no-till (NT) vs. conventional plough tillage (CT)] in combination with fertilisation [mineral (MIN), compost (ORG), and unfertilised control (CON)] on seasonal N2O emissions and the underlying N-cycling microbial community in one maize growing season. Rainfall events after fertilisation, which resulted in increased soil water content, were the main triggers of the observed N2O emission peaks. The highest cumulative emissions were measured in MIN fertilisation, followed by ORG and CON fertilisation. In the period after the first fertilisation CT resulted in higher cumulative emissions than NT, while no significant effect of tillage was observed cumulatively across the entire season. A higher genetic potential for N2O emissions was observed under NT than CT, as indicated by an increased (nirK + nirS)/(nosZI + nosZII) ratio. The mentioned ratio under NT decreased in the order CON > MIN > ORG, indicating a higher N2O consumption potential in the NT-ORG treatment, which was confirmed in terms of cumulative emissions. The AOB/16S ratio was strongly affected by fertilisation and was higher in the MIN than in the ORG and CON treatments, regardless of the tillage system. Multiple regression has revealed that this ratio is one of the most important variables explaining cumulative N2O emissions, possibly reflecting the role of bacterial ammonia oxidisers in minerally fertilised soil. Although the AOB/16S ratio aligned well with the measured N2O emissions in our experimental field, the higher genetic potential for denitrification expressed by the (nirK + nirS)/(nosZI + nosZII) ratio in NT than CT was not realized in the form of increased emissions. Our results suggest that organic fertilisation in combination with NT shows a promising combination for mitigating N2O emissions; however, addressing the yield gap is necessary before incorporating it in recommendations for farmers.

Conservation tillage: a way to improve yield and soil properties and decrease global warming potential in spring wheat agroecosystems

Climate change is one of the main challenges, and it poses a tough challenge to the agriculture industry globally. Additionally, greenhouse gas (GHG) emissions are the main contributor to climate change; however, croplands are a prominent source of GHG emissions. Yet this complex challenge can be mitigated through climate-smart agricultural practices. Conservation tillage is commonly known to preserve soil and mitigate environmental change by reducing GHG emissions. Nonetheless, there is still a paucity of information on the influences of conservation tillage on wheat yield, soil properties, and GHG flux, particularly in the semi-arid Dingxi belt. Hence, in order to fill this gap, different tillage systems, namely conventional tillage (CT) control, straw incorporation with conventional tillage (CTS), no-tillage (NT), and stubble return with no-tillage (NTS), were laid at Dingxi, Gansu province of China, under a randomized complete block design with three replications to examine their impacts on yield, soil properties, and GHG fluxes. Results depicted that different conservative tillage systems (CTS, NTS, and NT) significantly (p < 0.05) increased the plant height, number of spikes per plant, seed number per meter square, root yield, aboveground biomass yield, thousand-grain weight, grain yield, and dry matter yield compared with CT. Moreover, these conservation tillage systems notably improved the soil properties (soil gravimetric water content, water-filled pore space, water storage, porosity, aggregates, saturated hydraulic conductivity, organic carbon, light fraction organic carbon, carbon storage, microbial biomass carbon, total nitrogen, available nitrogen storage, microbial biomass nitrogen, total phosphorous, available phosphorous, total potassium, available potassium, microbial counts, urease, alkaline phosphatase, invertase, cellulase, and catalase) while decreasing the soil temperature and bulk density over CT. However, CTS, NTS, and NT had non-significant effects on ECe, pH, and stoichiometric properties (C:N ratio, C:P ratio, and N:P ratio). Additionally, conservation-based tillage regimes NTS, NT, and CTS significantly (p < 0.05) reduced the emission and net global warming potential of greenhouse gases (carbon dioxide, methane, and nitrous oxide) by 23.44, 19.57, and 16.54%, respectively, and decreased the greenhouse gas intensity by 23.20, 29.96, and 18.72%, respectively, over CT. We conclude that NTS is the best approach to increasing yield, soil and water conservation, resilience, and mitigation of agroecosystem capacity.

Do Added Microplastics, Native Soil Properties, and Prevailing Climatic Conditions Have Consequences for Carbon and Nitrogen Contents in Soil? A Global Data Synthesis of Pot and Greenhouse Studies

Microplastics threaten soil ecosystems, strongly influencing carbon (C) and nitrogen (N) contents. Interactions between microplastic properties and climatic and edaphic factors are poorly understood. We conducted a meta-analysis to assess the interactive effects of microplastic properties (type, shape, size, and content), native soil properties (texture, pH, and dissolved organic carbon (DOC)) and climatic factors (precipitation and temperature) on C and N contents in soil. We found that low-density polyethylene reduced total nitrogen (TN) content, whereas biodegradable polylactic acid led to a decrease in soil organic carbon (SOC). Microplastic fragments especially depleted TN, reducing aggregate stability, increasing N-mineralization and leaching, and consequently increasing the soil C/N ratio. Microplastic size affected outcomes; those <200 μm reduced both TN and SOC contents. Mineralization-induced nutrient losses were greatest at microplastic contents between 1 and 2.5% of soil weight. Sandy soils suffered the highest microplastic contamination-induced nutrient depletion. Alkaline soils showed the greatest SOC depletion, suggesting high SOC degradability. In low-DOC soils, microplastic contamination caused 2-fold greater TN depletion than in soils with high DOC. Sites with high precipitation and temperature had greatest decrease in TN and SOC contents. In conclusion, there are complex interactions determining microplastic impacts on soil health. Microplastic contamination always risks soil C and N depletion, but the severity depends on microplastic characteristics, native soil properties, and climatic conditions, with potential exacerbation by greenhouse emission-induced climate change.

Horticulture crop under pressure: Unraveling the impact of climate change on nutrition and fruit cracking

Climate change is increasingly affecting the nutritional content and structural integrity of horticultural crops, leading to challenges such as diminished fruit quality and the exacerbation of fruit cracking. This manuscript systematically explores the multifaceted impacts of these changes, with a particular focus on the nutritional quality and increased incidence of fruit cracking. An exhaustive review of current research identifies the critical role of transcription factors in mediating plant responses to climatic stressors, such as drought, temperature extremes, and saline conditions. The significance of transcription factors, including bHLH, bZIP, DOF, MDP, HD-ZIP, MYB, and ERF4, is highlighted in the development of fruit cracking, underscoring the genetic underpinnings behind stress-related phenotypic outcomes. The effectiveness of greenhouse structures in mitigating adverse climatic effects is evaluated, offering a strategic approach to sustain crop productivity amidst CO2 fluctuations and water scarcity, which are shown to influence plant physiology and lead to changes in fruit development, nutrient dynamics, and a heightened risk of cracking. Moreover, the manuscript delves into advanced breeding strategies and genetic engineering techniques, such as genome editing, to enhance crop resilience against climatic challenges. It also discusses adaptation strategies vital for sustainable horticulture, emphasizing the need to integrate novel genetic insights with controlled environment horticulture to counteract climate change's detrimental effects. The synthesis presented here underscores the urgent need for innovative breeding strategies aimed at developing resilient crop varieties that can withstand climatic uncertainty while preserving nutritional integrity.

Effects of tillage and maturity stage on the yield, nutritive composition, and silage fermentation quality of whole-crop wheat

Whole-crop wheat (Triticum aestivum, WCW) has a high nutritional value and digestibility. No-tillage (NT) can reduces energy and labor inputs in the agricultural production process, thus decreasing production costs. There are many studies on planting techniques of WCW at present, few being on no-tillage planting. This study aimed to compare the effects of different tillage methods and maturity stages on the yield, nutritive value, and silage fermentation quality of WCW. The experiment included two tillage methods (NT; conventional tillage, CT), two maturity stages (flowering stage; milk stage), and three years (2016-2017; 2017-2018; 2018-2019). Years had a strong influence on the yield and nutritional composition of WCW. This was mainly related to the amount of rainfall, as it affects the seedling emergence rate of wheat. Although tillage methods showed no significant effects on the yield, plant height, and stem number per plant of WCW (P > 0.05), compared to CT, the dry matter (DM) and crude protein (CP) yields of NT decreased by 0.74 t/ha and 0.13 t/ha. Tillage methods showed no significant effects on the nutritive composition of WCW (P > 0.05). The WCW at the milk stage had greater DM (5.25 t/ha) and CP (0.60 t/ha) yields than that at the flowering stage (3.19 t/ha and 0.39 t/ha) (P< 0.05). The acid detergent fiber concentration of WCW decreased by 34.5% from the flowering to the milk stage, whereas water-soluble carbohydrates concentration increased by 50.6%. The CP concentration at the milk stage was lower than that at the flowering stage (P< 0.05). The lactic acid concentration of NT (17.1 g/kg DM) silage was lower than that of CT (26.6 g/kg DM) silage (P< 0.05). The WCW silage at the milk stage had a lower NH3-N concentration (125 g/kg TN) than that at the flowering stage (169 g/kg TN) (P< 0.05). Wheat sown by NT and CT was of similar yield and nutritional value, irrespective of harvest stages. WCW harvested at the milk stage had greater yield and better nutritional composition and silage fermentation quality than that at the flowering stage. Based upon the results of the membership function analysis, no-tillage sowing of wheat was feasible and harvesting at milk stage was recommended.

Does no-till crop management mitigate gaseous emissions and reduce yield disparities: An empirical US-China evaluation

Global agricultural systems face one of the greatest sustainability challenges: meeting the growing demand for food without leaving a negative environmental footprint. United States (US) and China are the two largest economies and account for 39 % of total global greenhouse gases (GHG) emissions into the atmosphere. No-till is a promising land management option that allows agriculture to better adapt and mitigate climate change effects compared to traditional tillage. However, the efficacy of no-till for mitigating GHG is still debatable. In this meta-analysis, we comprehensively assess the impact of no-till (relative to traditional tillage) on GHG mitigation potential and crop productivity in different agroecological systems and management regimes in the US and China. Overall, no-till in China did not change crop yields, although soil CO2 (8 %) and N2O (12 %) emissions decreased significantly, while soil CH4 emissions increased by 12 %. In contrast to Chinese no-till, a significant improvement in crop yields (up to 12 %) was recorded on US cropland under no-till. Moreover, significant decreases in soil N2O (21 %) and CH4 (12 %) emissions were observed. Of the three cropping systems, only wheat showed significant reduction in CO2, N2O and CH4 emissions in the Chinese no-till system. In the case of US, no-till soybean-rice and maize cropping systems demonstrated significant emission reductions for N2O and CO2, respectively. Interestingly, yields of no-till maize in China and rice in US exceeded those of other no-till cereals. In China, no-till on medium-texture soils resulted in significant reductions in GHG emissions and higher crop yields compared to other soil types. In both countries, the relatively higher crop yields under irrigated versus non-irrigated no-till and the significant yield differences on fine textured soils under US no-till are likely due to the substantial N2O reductions. In summary, crop yield disparities from no-till between China and the US were related to the insignificant effects on controlling CH4 emissions and successfully mitigating N2O, respectively. This study comprehensively demonstrates how cropping system and pedoclimatic conditions influence the relative effectiveness of no-till in both countries.

Alternatives to maize monocropping in Mediterranean irrigated conditions to reduce greenhouse gas emissions

Winter legume cover crops or double-cropping in high N-fertilizer maize-based sprinkler-irrigated systems enhance agroecosystem diversity and potentially increase yields. However, the effects on direct N2O emissions and global warming potential (GWP) have not been fully established. For two years, in the Ebro Valley (Spain), four maize-based systems consisted of: long-season maize (Zea mays) with winter fallow period (F-LSM) the reference system; or after a leguminous cover crop (common vetch, Vicia sativa) (CC-LSM); and short-season maize after a cereal crop (barley, Hordeum vulgare) (B-SSM) or after a leguminous crop (pea, Pisum sativum) (P-SSM). They were assessed in terms of productivity, direct greenhouse gasses emissions (GHG: N2O, CH4, CO2), and global warming potential (GWP). Direct GHG emissions were measured using the static chamber technique, while soil parameters were monitored. Crop yields and nitrogen uptake were also quantified. GHG emissions linked to management and inputs were calculated to obtain GWP and greenhouse gas intensity (GHGI). The most productive system (B-SSM) obtained the highest direct (79 %, 35 %, and 30 % higher than the F-LSM, P-SSM, and CC-SSM, respectively) and scaled N2O emissions. The P-SSM system had similar N-uptake-scaled emissions to the monocropping (MC) systems. Irrigation, fertilizer, and farm operations accounted for the 26 %, 31 %, and 27 % of the total indirect emissions, respectively. Fertilizer production-related emissions in B-SSM and F-LSM systems were 172 % and 45 % higher than the average emissions in the systems with legumes (461 kg CO2eq. ha-1). Diversified systems lead to slightly higher GHGI values than the reference system (F-LSM). However, no differences were found between the F-LSM and P-SSM systems in GWP (4521 and 5512 kg CO2-eq. ha-1, respectively) or GHGI (144 and 158 kg CO2-eq. ha-1, respectively). The P-SSM system may be a potential alternative for increasing the diversification of maize-based irrigated agrosystems without increasing GHG emissions.

Global N2O emissions from our planet: Which fluxes are affected by man, and can we reduce these?

In some places, N2O emissions have doubled during the last 2-3 decades. Therefore, it is crucial to identify N2O emission hotspots from terrestrial and aquatic systems. Large variation in N2O emissions occur in managed as well as in natural areas. Natural unmanaged tropical and subtropical wet forests are important N2O sources globally. Emission hotspots, often coupled to human activities, vary across climate zones, whereas N2O emissions are most often a few kg N ha-1 year-1 from arable soils, drained organic soils in the boreal and temperate zones often release 20-30 kg N ha-1 year-1. Similar high N2O emissions occur from some tropical crops like tea, palm oil and bamboo. This strong link between increased N2O emissions and human activities highlight the potential to mitigate large emissions. In contrast, water where oxic and anoxic conditions meet are N2O emission hotspots as well, but not possible to reduce.

Modification of the RothC model to evaluate the inconsistent effect of conservation tillage on SOC stock and a suggestion of a national-scale assessment framework

Simulation of conservation tillage effect on soil organic carbon (SOC) stock on the national scale is essential for Tier 3 level greenhouse gas inventory in the agricultural sector. However, the conservation tillage effects varied depending on different soil conditions, potentially leading to inaccurate national assessments. This study aimed to propose a framework for estimating the national scale impact of conservation tillage on SOC. As even in the most commonly used SOC dynamic model, the Rothamsted Carbon Model (RothC), does not reflect the conservation tillage effect in an explicit way, we modified it by developing the tillage rate modifiers (TRMs). First, we investigated the conditions for the inconsistent conservation tillage effects using the decision tree analysis based on 210 field experiment data from the mid-latitude region. The results highlighted that soil sand content and the existing SOC stock were the main factors driving the inconsistencies. After we categorized into four distinctive conditions, the TRMs for each condition were parameterized using a genetic algorithm. The average TRMs were 0.88 in the soils with sand content >37.6 % and 1.58 in the soils with sand content ≤37.6 %, indicating that conservation tillage is more effective in coarse-textured soil, and there is a risk of decreasing SOC stock in the latter condition. Using the modified RothC model, a three-step national-scale simulation framework was suggested: compiling country-specific data, establishing baseline and conservation tillage scenarios, and modeling conservation tillage effects with uncertainty analysis. Our approach also defined the maximum conservation tillage area, factoring in local cropping systems and soil conditions. Our refined RothC model with TRMs provides a nuanced understanding of conservation tillage effects, emphasizing the role of soil characteristics. The proposed national-scale simulation framework offers a reliable tool for evaluating conservation tillage impact on SOC, ensuring more accurate greenhouse gas inventories in agriculture.

Waste-derived nanobiochar: A new avenue towards sustainable agriculture, environment, and circular bioeconomy

The greatest challenge for the agriculture sector in the twenty-first century is to increase agricultural production to feed the burgeoning global population while maintaining soil health and the integrity of the agroecosystem. Currently, the application of biochar is widely implemented as an effective means for boosting sustainable agriculture while having a negligible influence on ecosystems and the environment. In comparison to traditional biochar, nano-biochar (nano-BC) boasts enhanced specific surface area, adsorption capacity, and mobility properties within soil, allowing it to promote soil properties, crop growth, and environmental remediation. Additionally, carbon sequestration and reduction of methane and nitrous oxide emissions from agriculture can be achieved with nano-BC applications, contributing to climate change mitigation. Nonetheless, due to cost-effectiveness, sustainability, and environmental friendliness, waste-derived nano-BC may emerge as the most viable alternative to conventional waste management strategies, contributing to the circular bioeconomy and the broader goal of achieving the Sustainable Development Goals (SDGs). However, it's important to note that research on nano-BC is still in its nascent stages. Potential risks, including toxicity in aquatic and terrestrial environments, necessitate extensive field investigations. This review delineates the potential of waste-derived nano-BC for sustainable agriculture and environmental applications, outlining current advancements, challenges, and possibilities in the realms from a sustainability and circular bioeconomy standpoint.

The impact of organic fertilizer replacement on greenhouse gas emissions and its influencing factors

Although organic fertilizers played an important role in enhancing crop yield and soil quality, the effects of organic fertilizers replacing chemical fertilizers on greenhouse gas (GHG) emissions remained inconsistent, and further impeding the widespread adoption of organic fertilizers. Therefore, a global meta-analysis used 568 comparisons from 137 publications was conducted to evaluate the responses of GHG emissions to organic fertilizers replacing chemical fertilizers. The results indicated that organic fertilizers replacing chemical fertilizers significantly decreased N2O emissions, but increasing global warming potential (GWP) by enhancing CH4 and CO2 emissions. When replacing chemical fertilizers with organic fertilizers, a variety of factors such as climate conditions, soil conditions, crop types and agricultural practices influenced the GHG emissions and GWP. Among these factors, fertilizer organic C and available N level were the main factors affecting GHG and GWP. However, considering the feasibility and ease of optimizing these factors, fertilizer organic C, C/N and N substitution rate showed a more favorable choice for GWP reduction, and their interactions significantly affecting GWP. Moreover, considering the distinct GHG emissions patterns in dryland and paddy field, the analysis of optimizing GWP based on fertilizer organic C, C/N and N substitution rate was separately conducted. According to the simulation optimization, the optimal combination of fertilizer organic C (137.2-228.8 g·kg-1), C/N (6.9-52.0) and N substitution rate (20.0-22.5 %) effectively suppressed the extent of increase in GWP in paddy field compared with chemical fertilizers. In dryland, optimizing fertilizer organic C (100-278 g·kg-1), C/N (70.7-76.6) and N substitution rate (10.2-16.0 %) led to a reduction in GWP compared with chemical fertilizers, indicating that dryland are more suitable for promoting organic fertilizer application. In conclusion, this meta-analysis study quantitatively assessed the GHG emissions when organic fertilizers replacing chemical fertilizers, and also provided a scientific basis for the mitigation of GHG emissions by organic fertilizers management.

Advancements in technology and innovation for sustainable agriculture: Understanding and mitigating greenhouse gas emissions from agricultural soils

In recent decades, Technology and Innovation (TI) have shown tremendous potential for improving agricultural productivity and environmental sustainability. However, the adoption and implementation of TI in the agricultural sector and its impact on the environment remain limited. To gain deeper insights into the significance of TI in enhancing agricultural productivity while maintaining environmental balance, this study investigates 21 agriculture-dependent Asian countries. Two machine learning techniques, LASSO (Least Absolute Shrinkage and Selection Operator) and Elastic-Net, are employed to analyze the data, which is categorized into three regional groups: ASEAN (Association of Southeast Asian Nations), SAARC (South Asian Association for Regional Cooperation), and GCC (Gulf Cooperation Council). The findings of this study highlight the heterogeneous nature of technology adoption and its environmental implications across the three country groups. ASEAN countries emerge as proactive adopters of relevant technologies, effectively enhancing agricultural production while simultaneously upholding environmental quality. Conversely, SAARC countries exhibit weaker technology adoption, leading to significant fluctuations in environmental quality, which in turn impact agricultural productivity. Notably, agricultural emissions of N2O (nitrous oxide) and CO2 (carbon dioxide) in SAARC countries show a positive association with agricultural production, while CH4 (methane) emissions have an adverse effect. In contrast, the study reveals a lack of evidence regarding technological adoption in agriculture among GCC countries. Surprisingly, higher agricultural productivity in these countries is correlated with increased N2O emissions. Moreover, the results indicate that deforestation and expansion of cropland contribute to increased agricultural production; however, this expansion is accompanied by higher emissions related to agricultural activities. This research represents a pioneering empirical analysis of the impact of TI and environmental emission gases on agricultural productivity in the three aforementioned country groups. It underscores the imperative of embracing relevant technologies to enhance agricultural output while concurrently ensuring environmental sustainability. The findings of this study provide valuable insights for policymakers and stakeholders in formulating strategies to promote sustainable agriculture and technological advancement in the context of diverse regional dynamics.

Global evaluation of key factors influencing nitrogen fertilization efficiency in wheat: a recent meta-analysis (2000-2022)

Improving nitrogen use efficiency (NUE) without compromising yield remains a crucial agroecological challenge in theory and practice. Some meta-analyses conducted in recent years investigated the impact of nitrogen (N) fertilizer on crop yield and gaseous emissions, but most are region-specific and focused on N sources and application methods. However, various factors affecting yield and N fertilizer efficiency in wheat crops on a global scale are not extensively studied, thus highlighting the need for a comprehensive meta-analysis. Using 109 peer-reviewed research studies (published between 2000 and 2022) from 156 experimental sites (covering 36.8, 38.6 and 24.6% of coarse, medium, and fine texture soils, respectively), we conducted a global meta-analysis to elucidate suitable N management practices and the key factors influencing N fertilization efficiency in wheat as a function of yield and recovery efficiency and also explained future perspectives for efficient N management in wheat crop. Overall, N fertilization had a significant impact on wheat yield. A curvilinear relationship was found between N rates and grain yield, whereas maximum yield improvement was illustrated at 150-300 kg N ha-1. In addition, N increased yield by 92.18% under direct soil incorporation, 87.55% under combined chemical and organic fertilizers application, and 72.86% under split application. Site-specific covariates (climatic conditions and soil properties) had a pronounced impact on N fertilization efficiency. A significantly higher yield response was observed in regions with MAP > 800 mm, and where MAT remained < 15 °C. Additionally, the highest yield response was observed with initial AN, AP and AK concentrations at < 20, < 10 and 100-150 mg kg-1, respectively, and yield response considerably declined with increasing these threshold values. Nevertheless, regression analysis revealed a declining trend in N recovery efficiency (REN) and the addition of N in already fertile soils may affect plant uptake and RE. Global REN in wheat remained at 49.78% and followed a negative trend with the further increase of N supply and improvement in soil properties. Finally, an advanced N management approach such as "root zone targeted fertilization" is suggested to reduce fertilizer application rate and save time and labor costs while achieving high yield and NUE.

New evidence on the impact of No-tillage management on agricultural carbon emissions

Controlling agricultural carbon emissions contributes to achieving peak carbon emissions and carbon neutrality. However, as a conservation management practice of farmland, the impact of No-tillage management (NTM) on agricultural carbon emissions needs to be further discussed. The main purpose of this paper is to assess the direct effect and spatial spillover effect of NTM on agricultural carbon emissions, revealing the regulating mechanism of NTM on agricultural carbon emissions and the combined application of NTM. Results indicate that NTM reduces agricultural carbon emissions, which is significant in the central and western regions, along with the primary grain, corn, and rice production areas, as well as the northern regions of the Huai River. Furthermore, the spatial spillover analysis reveals that the implementation of NTM increases agricultural carbon emissions in neighboring regions, but financial support and cross-regional services can negatively regulate the relationship between NTM and space agricultural carbon emissions. This paper also finds that combining straw-returning technology and NTM reduces agricultural carbon emissions. Building a cross-regional coordination mechanism, an incentive mechanism, and innovating the conservation tillage model is essential for promoting the NTM and achieving agricultural carbon reduction.

No-tillage with straw mulching promotes the utilization of soil nitrogen by rice under wheat-rice and oilseed rape-rice cropping systems

Introduction

To investigate the effects of no-tillage with straw mulching on the absorption and utilization of soil nitrogen (N), fertilizer N, and straw N by rice under paddy-upland rotations.

Methods

A field experiment with three cropping systems: fallow-rice rotation without straw mulching (FRN), wheat-rice rotation with wheat mulching in rice season (WRS), and oilseed rape-rice rotation with oilseed rape straw mulching in rice season (ORS) was conducted from 2015 to 2017, along with a mini-plot experiment with ¹⁵N-labeled urea and straws, which was conducted in 2017.

Results

No-tillage with straw reduced rice N uptake up to 20 days after transplanting, the total amount of fertilizer N uptake of WRS and ORS rice plants was 46.33 and 61.67 kg/ha, respectively, which was 9.02 and 45.10% higher than that of FRN plants. Soil N was the main source for rice growth, followed by fertilizer N. Soil N uptake by WRS and ORS rice plants was 21.75 and 26.82% higher than that of FRN plants, accounting for 72.37 and 65.47%, respectively, of the total N accumulated in rice plants. Straw mulching increased the N utilization efficiency of tillering, panicle, and total fertilizer by 2.84-25.30%; however, base fertilizer was dependent on straw mulching. The total amount of N released from WRS and ORS straw mulching in the rice season was 34.97 and 24.82 kg/ha, respectively; however, only 3.04 and 4.82% of it was absorbed by the rice plants, accounting for only 0.62 and 0.66% of the total accumulated N.

Discussion

No-tillage with straw mulching under paddy-upland rotations increased the N utilization of rice, especially for the absorption of soil N. These results provide theoretical information for the effective utilization of straw and rational N application practices in rice-based cropping systems.

A 40 % paddy surface soil organic carbon increase after 5-year no-tillage is linked with shifts in soil bacterial composition and functions

Soil organic carbon (SOC) is related to soil fertility, crop yield, and climate change mitigation. Paddy soil is a significant carbon (C) sink, but its C sequestration potential has not been realized as the various driving factors are still not fully understood. We performed a 5-year paddy field experiment in southern China to estimate tillage effects on SOC accumulation and its relation with soil bacteria. The C input from rice residue, SOC content, CO₂ flux, soil bacterial community composition, and predicted functions were analyzed. No-tillage (NT) increased (p < 0.05) rice residue C inputs (by 12.6 %-15.9 %), SOC (by 40 % at the surface soil layer compared with conventional tillage, CT), and CO₂ fluxes compared with reduced tillage (RT) and CT. Also, NT significantly altered the soil bacterial community. The random forest model showed that the predicted bacterial functions of "Degradation/Utilization/Assimilation Other", "C1 Compound Assimilation", and "Amin and Polyamine Degradation" were the most important functions associated with SOC accumulation. Analysis of metabolic pathway differences indicated that NT significantly decreased the BENZCOA-PWY (anaerobic aromatic compound degradation) and the AST-PWY (L-arginine degradation II). Therefore, the rapid paddy SOC increase is associated with both residue C input (from higher rice yields) and the degradation functions regulated by soil bacteria.

Herbicide Use in the Era of Farm to Fork: Strengths, Weaknesses, and Future Implications

Climate change mitigation is a major concern of the European Union (EU). In 2019, the EU presented the European Green Deal (EGD), a new environmental strategy that aimed to neutralize climate change by 2050. Within its policy areas, the EGD included the Farm to Fork (F2F) Strategy that aims to reduce pesticide use by 50%, by 2030. This reduction was proposed due to the supposed negative effects of pesticides on the environment and its biota. Among the different pesticide groups (herbicides, fungicides, insecticides, etc.) though, herbicides are perhaps the hardest to reduce. This review aimed to shed light to any factors that might hinder the reduction of herbicide use; thus, the implementation of the Farm to Fork Strategy underlines some of its weaknesses and highlights key points of a viable herbicide reduction-related policy framework. The literature suggests that integrated weed management (IWM) consists perhaps the most suitable approach for the reduction of herbicides in the EU. Even though it is too soon to conclusively assess F2F, its success is not impossible.

Manure properties, soil conditions and managerial factors regulate greenhouse vegetable yield with organic fertilizer application across China

To better understand the responses of vegetable yields in a greenhouse system to organic fertilizer through a quantitative evaluation based on peer-reviewed journal articles and in consideration of environmental managerial factors. We conducted a meta-analysis of 453 paired observations from 68 peer-reviewed journal articles to assess the response of vegetable yields in greenhouse vegetable systems in China to organic fertilization. Compared with the control (no organic fertilizer), organic fertilization significantly increased the yields of vegetables by 44.11% on average. The response of vegetable yields to organic fertilizer tended to increase with the increasing experimental duration. Organic fertilizer application had the greatest potential for leafy vegetables (+76.44%), in loamy soils (+53.94%), at moderate organic fertilizer carbon input levels (+54.13%), and in soils with moderate initial soil total nitrogen levels (+50.89%). Aggregated boosted tree analysis indicated that organic fertilizer carbon inputs, vegetable type and experimental duration were the predominant factors that manipulated the response of vegetable yields to organic fertilizer application. The rational application of farmyard manure would be a promising strategy for increasing vegetable yields in greenhouse vegetable systems in China. Factoring in vegetable type, carbon and nitrogen inputs of organic fertilizer, and soil texture would benefit vegetable yields with the application of organic fertilizer.

Current status of carbon neutrality in Chinese rice fields (2002-2017) and strategies for its achievement

China has pledged to achieve carbon neutrality by 2060 to address global climate change, and achieving carbon neutrality in rice fields is a vital component of this commitment. However, the current status of carbon neutrality in rice fields in China is unclear, and there are few feasible strategies to achieve its successful implementation. Therefore, this study calculated the net carbon sequestration rate (NCSR, i.e., carbon sequestration minus carbon emissions) of rice fields in China from 2002 to 2017 to clarify the carbon neutrality status of Chinese rice fields. Furthermore, the effects of field management measures, rice sown area, and rice yield on NCSR were analyzed to identify suitable carbon neutralization pathways in Chinese rice fields. Our findings indicated that the annual carbon sequestration rate in rice fields was lower than the carbon emissions, resulting in continuous net emissions of 195.49 Tg CO₂-eq yr^-1. The NCSR of paddy fields increased first and then decreased with increases in rice sown area and yield. Meta-analysis indicated that management measures such as water conservation and biochar significantly increased NCSR by ~5766.50 kg CO₂-eq ha^-1 yr^-1 and 22,296.62 kg CO₂-eq ha^-1 yr^-1, respectively. Our findings suggests that proper control of rice sown area and the adoption of reasonable field management measures (water conservation and biochar) can promote carbon neutrality in Chinese rice fields.

Soil Nitrogen Transformation Process Influenced by Litterfall Manipulation in Two Subtropical Forest Types

Nitrogen (N) is often recognized as the primary limiting nutrient element for the growth and production of forests worldwide. Litterfall represents a significant pathway for returning nutrients from aboveground parts of trees to the soils and plays an essential role in N availability in different forest ecosystems. This study explores the N transformation processes under litterfall manipulation treatments in a Masson pine pure forest (MPPF), and Masson pine and Camphor tree mixed forest (MCMF) stands in subtropical southern China. The litterfall manipulation included litterfall addition (LA), litterfall removal (LR), and litterfall control (LC) treatments. The project aimed to examine how litterfall inputs affect the soil N process in different forest types in the study region. Results showed that soil ammonium N (NH₄ ⁺-N) and nitrate N (NO₃ ^--N) content increased under LA treatment and decreased under LR treatment compared to LC treatment. LA treatment significantly increased soil total inorganic N (TIN) content by 41.86 and 22.19% in MPPF and MCMF, respectively. In contrast, LR treatment decreased the TIN content by 10 and 24% in MPPF and MCMF compared to LC treatment. Overall, the soil net ammonification, nitrification, and N mineralization rates were higher in MCMF than in MPPF; however, values in both forests were not significantly different. LA treatment significantly increased annual net ammonification, nitrification, and mineralization in both forest types (p < 0.05) compared to LC treatment. LR treatment significantly decreased the values (p < 0.05), except for ammonification, where LR treatment did not differ substantially compared to LC treatment. Our results suggested that changes in litterfall inputs would significantly alter soil N dynamics in studied forests of sub-tropical region. Moreover, mixed forest stands have higher nutrient returns due to mixed litter and higher decomposition compared to pure forest stands.

Estimating Nitrogen Use Efficiency, Profitability, and Greenhouse Gas Emission Using Different Methods of Fertilization

Fertilization is a way to better use nitrogen fertilizers and increase productivity, but in another way, fertilization is also a source of anthropogenic greenhouse gas emissions. The study was carried out to measure the profitability ratio, technical efficiency, and CO₂ from the top dressing (TD) and deep placement (DP) fertilization. The study was based on primary data, which were collected from different respondents and areas through a well-designed questionnaire. The study finds that DP fertilization is more profitable, least costly, and more efficient than TD fertilization. The finding observed that the yield of the TD growers is 727.82 kg/ha more than that of TD respondents. The efficiency score shows that to reach the 90% efficiency level, the farmers of TD need to use DP fertilization. The farmers of TD and DP can still increase their efficiency up to 12% and 9% by using the same inputs. The findings also clarify that manufacturing of synthetic nitrogen (N), direct use of N, Yield, and Area-Scaled greenhouse gas (GHG) emissions from the use of synthetic N through TD fertilization are greater than that of the DP group. The farming community needs to be aware of greenhouse gas emissions and how they can be reduced. It is also suggested that farmers need to shift toward DP fertilization to increase yield, profit, efficiency, food security, and reduce GHG emissions.

Soil carbon sequestration, greenhouse gas emissions, and water pollution under different tillage practices

Tillage is a common agricultural practice and a critical component of agricultural systems that is frequently employed worldwide in croplands to reduce climatic and soil restrictions while also sustaining various ecosystem services. Tillage can affect a variety of soil-mediated processes, e.g., soil carbon sequestration (SCS) or depletion, greenhouse gas (GHG) (CO2, CH4, and N2O) emission, and water pollution. Several tillage practices are in vogue globally, and they exhibit varied impacts on these processes. Hence, there is a dire need to synthesize, collate and comprehensively present these interlinked phenomena to facilitate future researches. This study deals with the co-benefits and trade-offs produced by several tillage practices on SCS and related soil properties, GHG emissions, and water quality. We hypothesized that improved tillage practices could enable agriculture to contribute to SCS and mitigate GHG emissions and leaching of nutrients and pesticides. Based on our current understanding, we conclude that sustainable soil moisture level and soil temperature management is crucial under different tillage practices to offset leaching loss of soil stored nutrients/pesticides, GHG emissions and ensuring SCS. For instance, higher carbon dioxide (CO2) and nitrous oxide (N2O) emissions from conventional tillage (CT) and no-tillage (NT) could be attributed to the fluctuations in soil moisture and temperature regimes. In addition, NT may enhance nitrate (NO3-) leaching over CT because of improved soil structure, infiltration capacity, and greater water flux, however, suggesting that the eutrophication potential of NT is high. Our study indicates that the evaluation of the eutrophication potential of different tillage practices is still overlooked. Our study suggests that improving tillage practices in terms of mitigation of N2O emission and preventing NO3- pollution may be sustainable if nitrification inhibitors are applied.

Energy budgeting, carbon budgeting, and carbon footprints of straw and plastic film management for environmentally clean of wheat-maize intercropping system in northwestern China

Modern agricultural production is an energy- and carbon-intensive system. Enhancing energy and carbon efficiencies and reducing carbon footprints are important issues of sustainable development in modern agriculture. This study aimed to comprehensively assess energy and carbon budgeting and carbon footprints in wheat-maize intercropping, monoculture maize, and monoculture wheat with straw and plastic film management approaches, as based on a field experiment conducted in northwestern China. The results showed that intercropping had a greater grain yield by 12.8% and 131.0% than monoculture maize and wheat, respectively. Intercropping decreased energy and carbon inputs, increased energy and carbon outputs, thus improving energy and carbon efficiency, compared to monoculture maize. Intercropping reduced carbon footprint (CF) and yield-scale on the carbon footprint (CFy) via decreasing soil CO₂ equivalent emissions over monoculture maize. For the intercropping treatments, NTSMw/NTm (no-tillage with straw mulching and residual plastic film re-mulching) and NTSSw/NTm (no-tillage with straw standing and residual plastic film re-mulching) treatments increased grain yields by 14.9% and 13.8% over CTw/CTm (conventional tillage with no straw returning and annual new plastic film mulching). The lower energy inputs and higher energy outputs were observed in NTSMw/NTm and NTSSw/NTm treatments, thus, NTSMw/NTm and NTSSw/NTm had greater energy use efficiency by 36.9% and 34.9% than CTw/CTm. NTSMw/NTm and NTSSw/NTm treatments decreased carbon inputs and increased carbon outputs, thus improving carbon efficiency by 56.6% and 53.1%, compared to CTw/CTm. NTSMw/NTm and NTSSw/NTm treatments decreased CF by 16.8% and 14.3%, and decreased CFy by 27.6% and 24.8% compared to CTw/CTm, respectively, because of the decrease in soil CO₂ equivalent emissions. Our study indicated that system productivity, as well as energy and carbon efficiencies were enhanced, and carbon footprints were reduced by NTSMw/NTm and NTSSw/NTm treatments, and NTSMw/NTm had a more robust effect, indicating this treatment is the most sustainable cropping system in arid areas.

Evaluation of no-tillage impacts on soil respiration by 13C-isotopic signature in North China Plain

It is a challenge to characterize soil respiration of crop residue return systems in the North China Plain (NCP) under no-tillage (NT) and conventional tillage (CT) practices. In this study, we addressed the "hot spot" research challenge of impacts of tillage practices on soil carbon storage and soil CO₂ emissions in the NCP by ¹³C-isotopic signature. A short-term (2018-2020) field experiment was conducted with two tillage practices: NT and CT. The results showed that in the tested area, NT had advantages of lower CO₂ emissions compared to CT with average reduced CO₂ emissions by 10.82%-19.14%. The results of this study suggested that the NT facilitated enhanced soil carbon storage by 2.80%, which was evidenced by the δ¹³C data. Based on the path analysis model, the main line of soil respiration reduced by NT was attributed to the increased of soil microbial carbon and nitrogen as well as soil moisture in NT, which further increased δ¹³C and eventually inhibited soil respiration. Overall, adopting NT in NCP is an effective means to improve soil carbon pool and decrease soil CO₂ emissions in agriculture practices.

Management Strategies to Mitigate N2O Emissions in Agriculture

The concentration of greenhouse gases (GHGs) in the atmosphere has been increasing since the beginning of the industrial revolution. Nitrous oxide (N2O) is one of the mightiest GHGs, and agriculture is one of the main sources of N2O emissions. In this paper, we reviewed the mechanisms triggering N2O emissions and the role of agricultural practices in their mitigation. The amount of N2O produced from the soil through the combined processes of nitrification and denitrification is profoundly influenced by temperature, moisture, carbon, nitrogen and oxygen contents. These factors can be manipulated to a significant extent through field management practices, influencing N2O emission. The relationships between N2O occurrence and factors regulating it are an important premise for devising mitigation strategies. Here, we evaluated various options in the literature and found that N2O emissions can be effectively reduced by intervening on time and through the method of N supply (30–40%, with peaks up to 80%), tillage and irrigation practices (both in non-univocal way), use of amendments, such as biochar and lime (up to 80%), use of slow-release fertilizers and/or nitrification inhibitors (up to 50%), plant treatment with arbuscular mycorrhizal fungi (up to 75%), appropriate crop rotations and schemes (up to 50%), and integrated nutrient management (in a non-univocal way). In conclusion, acting on N supply (fertilizer type, dose, time, method, etc.) is the most straightforward way to achieve significant N2O reductions without compromising crop yields. However, tuning the rest of crop management (tillage, irrigation, rotation, etc.) to principles of good agricultural practices is also advisable, as it can fetch significant N2O abatement vs. the risk of unexpected rise, which can be incurred by unwary management.

A global meta-analysis of animal manure application and soil microbial ecology based on random control treatments

The processes involved in soil domestication have altered the soil microbial ecology. We examined the question of whether animal manure application affects the soil microbial ecology of farmlands. The effects of global animal manure application on soil microorganisms were subjected to a meta-analysis based on randomized controlled treatments. A total of 2303 studies conducted in the last 30 years were incorporated into the analysis, and an additional 45 soil samples were collected and sequenced to obtain 16S rRNA and 18S rRNA data. The results revealed that manure application increased soil microbial biomass. Manure application alone increased bacterial diversity (M-Z: 7.546 and M-I: 8.68) and inhibited and reduced fungal diversity (M-Z: -1.15 and M-I: -1.03). Inorganic fertilizer replaced cattle and swine manure and provided nutrients to soil microorganisms. The soil samples of the experimental base were analyzed, and the relative abundances of bacteria and fungi were altered compared with no manure application. Manure increased bacterial diversity and reduced fungal diversity. Mrakia frigida and Betaproteobacteriales, which inhibit other microorganisms, increased significantly in the domesticated soil. Moreover, farm sewage treatments resulted in a bottleneck in the manure recovery rate that should be the focus of future research. Our results suggest that the potential risks of restructuring the microbial ecology of cultivated land must be considered.

Spatial distribution of carbon dynamics and nutrient enrichment capacity in different layers and tree tissues of Castanopsis eyeri natural forest ecosystem

Forest ecosystem carbon (C) storage primarily includes vegetation layers C storage, litter C storage, and soil C storage. The precise assessment of forest ecosystem C storage is a major concern that has drawn widespread attention in global climate change worldwide. This study explored the C storage of different layers of the forest ecosystem and the nutrient enrichment capacity of the vegetation layer to the soil in the Castanopsis eyeri natural forest ecosystem (CEF) present in the northeastern Hunan province, central China. The direct field measurements were used for the estimations. Results illustrate that trunk biomass distribution was 48.42% and 62.32% in younger and over-mature trees, respectively. The combined biomass of the understory shrub, herb, and litter layers was 10.46 t·hm^-2, accounting for only 2.72% of the total forest biomass. On average, C content increased with the tree age increment. The C content of tree, shrub, and herb layers was 45.68%, 43.08%, and 35.76%, respectively. Litter C content was higher in the undecomposed litter (44.07 %). Soil C content continually decreased as the soil depth increased, and almost half of soil C was stored in the upper soil layer. Total C stored in CEF was 329.70 t·hm^-2 and it follows the order: tree layer > soil layer > litter layer > shrub layer > herb layer, with C storage distribution of 51.07%, 47.80%, 0.78%, 0.25%, and 0.10%, respectively. Macronutrient enrichment capacity from vegetation layers to soil was highest in the herb layer and lowest in the tree layer, whereas no consistent patterns were observed for trace elements. This study will help understand the production mechanism and ecological process of the C. eyeri natural forest ecosystem and provide the basics for future research on climate mitigation, nutrient cycling, and energy exchange in developing and utilizing sub-tropical vegetation.

Conversion of alpine pastureland to artificial grassland altered CO2 and N2O emissions by decreasing C and N in different soil aggregates

BACKGROUND

The impacts of land use on greenhouse gases (GHGs) emissions have been extensively studied. However, the underlying mechanisms on how soil aggregate structure, soil organic carbon (SOC) and total N (TN) distributions in different soil aggregate sizes influencing carbon dioxide (CO₂), and nitrous oxide (N₂O) emissions from alpine grassland ecosystems remain largely unexplored.

METHODS

A microcosm experiment was conducted to investigate the effect of land use change on CO₂and N₂O emissions from different soil aggregate fractions. Soil samples were collected from three land use types, i.e., non-grazing natural grassland (CK), grazing grassland (GG), and artificial grassland (GC) in the Bayinbuluk alpine pastureland. Soil aggregate fractionation was performed using a wet-sieving method. The variations of soil aggregate structure, SOC, and TN in different soil aggregates were measured. The fluxes of CO₂ and N₂O were measured by a gas chromatograph.

RESULTS

Compared to CK and GG, GC treatment significantly decreased SOC (by 24.9-45.2%) and TN (by 20.6-41.6%) across all soil aggregate sizes, and altered their distributions among soil aggregate fractions. The cumulative emissions of CO₂ and N₂O in soil aggregate fractions in the treatments of CK and GG were 39.5-76.1% and 92.7-96.7% higher than in the GC treatment, respectively. Moreover, cumulative CO₂emissions from different soil aggregate sizes in the treatments of CK and GG followed the order of small macroaggregates (2-0.25 mm) > large macroaggregates (> 2 mm) > micro aggregates (0.25-0.053 mm) > clay +silt (< 0.053 mm), whereas it decreased with aggregate sizes decreasing in the GC treatment. Additionally, soil CO₂ emissions were positively correlated with SOC and TN contents. The highest cumulative N₂O emission occurred in micro aggregates under the treatments of CK and GG, and N₂O emissions among different aggregate sizes almost no significant difference under the GC treatment.

CONCLUSIONS

Conversion of natural grassland to artificial grassland changed the pattern of CO₂ emissions from different soil aggregate fractions by deteriorating soil aggregate structure and altering soil SOC and TN distributions. Our findings will be helpful to develop a pragmatic management strategy for mitigating GHGs emissions from alpine grassland.

Do soil conservation practices exceed their relevance as a countermeasure to greenhouse gases emissions and increase crop productivity in agriculture?

Globally, agriculture sector is the significant source of greenhouse gases (GHGs) emissions into the atmosphere. To achieve the goal of limiting or mitigating these emissions, a rigorous abatement strategy with an additional focus on improving crop productivity is now imperative. Replacing traditional agriculture with soil conservation-based farming can have numerous ecological benefits. However, most assessments only consider improvements in soil properties and crop productivity, and often preclude the quantitative impact analysis on GHGs emissions. Here, we conducted a meta-analysis to evaluate crop productivity (i.e., biomass, grain, total yield) and GHGs emissions (i.e., CO₂, N₂O, CH₄) for three major soil conservation practices i.e., no-tillage, manures, and biochar. We also examined the yield potential of three major cereal crops (i.e., wheat, rice, maize) and their significance in mitigating GHGs emissions. None of the manures were able to reduce GHGs emissions, with poultry manure being the largest contributor to all GHGs emissions. However, pig-manure had the greatest impact on crop yield while emitting the least CO₂ emissions_. Use of biochar showed a strong coupling effect between reduction of GHGs (i.e., CH₄ by -37%; N₂O by -25%; CO₂ by -5%) and the increase in crop productivity. In contrast, no-tillage resulted in higher GHGs emissions with only a marginal increase in grain yield. Depending on crop type, all cereal crops showed varied degrees of GHGs mitigation under biochar application, with wheat responding most strongly due to the additional yield increment. The addition of biochar significantly reduced CO₂ and N₂O emissions under both rainfed and irrigated conditions, although CH₄ reductions were identical in both agroecosystems. Interestingly, the use of biochar resulted in a greater yield benefit in rainfed than in irrigated agriculture. Despite significant GHGs emissions, manure application contributed to higher crop yields, regardless of soil type or agroecosystem. Moreover, no-tillage showed a significant reduction in CH₄ and N₂O emissions under rainfed and irrigated conditions. Notably , biochar application in coarse while no-till in fine textured soils contributed to N₂O mitigation. Most importantly, effectiveness of no-tillage as a countermeasure to GHGs emissions while providing yield benefits is inconsistent. Overall, the decision to use farm manures should be reconsidered due to higher GHGs emissions. We conclude that the use of biochar could be an ideal way to reduce GHGs emissions. However, further understanding of the underlying mechanisms and processes affecting GHGs emissions is needed to better understand the feedback effects in conservation agriculture.

Reinvigorating the role of clean energy transition for achieving a low-carbon economy: evidence from Bangladesh

Achieving carbon-neutrality has become a global agenda following the ratification of the Paris Agreement. For the developing countries, in particular, attaining a low-carbon economy is particularly important since these economies are predominantly fossil-fuel dependent, to which Bangladesh is no exception. Therefore, this study specifically aimed at evaluating the environmental impacts associated with energy consumption and other key macroeconomic variables in the context of Bangladesh over the 1975-2016 period. As opposed to the conventional practice of using carbon dioxide emissions to proxy environmental quality, this study makes a novel attempt to use the carbon footprints to measure environmental welfare in Bangldesh. The outcomes from this study are expected to facilitate the carbon-neutrality objective of Bangladesh and, therefore, enable the nation to comply with its commitments concerning the attainment of the targets enlisted under the Paris Agreement and the United Nations Sustainable Development Goals declarations. The econometric analysis involved the application of methods that are suitable for handling the structural break issues in the data. The overall findings from empirical exercises reveal that aggregate energy consumption, fossil fuel consumption, and natural gas consumption boost the carbon footprint figures of Bangladesh. In contrast, nonfossil fuel consumption and hydroelectricity consumption are witnessed to abate the carbon footprint levels. Besides, economic growth and international trade are also evidenced to further increase the carbon footprints. Hence, these findings suggest that a clean energy transition within the Bangladesh economy can be the panacea to the nation's persitently aggravating environmental hardships. Furthermore, the causality analysis confirmed the presence of unidirectional causalities stemming from total energy consumption, fossil fuel consumption, natural gas consumption, hydroelectricity consumption, economic growth, and international trade to the carbon footprints. On the other hand, nonfossil fuel consumption is found to be bidirectionally associated with carbon footprints. In line with these aforementioned findings, several key policy suggestions are put forward regarding the facilitation of the carbon-neutrality agenda in Bangladesh.

Net effects of conservation agriculture principles on sustainable land use: A synthesis

Despite the strong recommendations from scientists, to till or not to till remains a confusing question for many farmers around the world due to the worries of crop yield decline and negative impacts on soils and environment. A confused understanding of the role of the individual principles of conservation agriculture significantly limits the effectiveness and applicability of soil conservation strategies and frameworks to achieve sustainable agriculture. By distinguishing clearly between the different principles of conservation agriculture, the net effects of no-tillage on improving and sustaining agro-ecosystems are analyzed based on 49 recent meta-analyses in this study. The review shows that no-tillage leads to a significant decline of crop yield (-8.0% to 10.0%, median: -1.9%), whereas residue retention represents the key driver for improving crop production (4.0%-28.0%, median: 8.2%). The efficacy of no-tillage for water erosion control, especially runoff (-24.0% to -0.7%, median: -10.0%), is often insignificant and otherwise lower compared to residue retention (-87.0% to -14.0%, median: -45.5%). Soil carbon sequestration potential under conservation tillage is quite limited or even close to zero, and if any, it can likely be attributed to the associated residue retention (-0.1% to 12.8%, median: 9.7%) rather than no-tillage (-2.0% to 10.0%, median: 4.8%). Our analysis illustrates that in conservation agriculture, no-tillage as the original and central principle of soil management is often less effective than associated supplementary measures, in particular residue retention. Residue retention may therefore play a key role for achieving sustainable land use. An additional benefit of residue retention is the less dramatic change of farming practices compared to no-tillage. The results of this review illustrate that a new framework for assessing the benefits of conservation practices has to be developed. To till, or not to till, is not the question: residue retention seems more critical.

Does biochar accelerate the mitigation of greenhouse gaseous emissions from agricultural soil? - A global meta-analysis

Greenhouse gaseous (GHGs) emissions from cropland soils are one of the major contributors to global warming. However, the extent and pattern of these climatic breakdowns are usally determined by the management practices in-place. The use of biochar on cropland soils holds a great promise for increasing the overall crop productivity. Nevertheless, biochar application to agricultural soils has grown in popularity as a strategy to off-set the negative feedback associated with agriculture GHGs emissions, i.e., CO₂ (carbon dioxide), CH₄ (methane), and N₂O (nitrous oxide). Despite increasing efforts to uncover the potential of biochar to mitigate the farmland GHGs effects, there has been little synthesis of how different types of biochar affect GHGs fluxes from cropland soils under varied experimental conditions. Here, we presented a meta-analysis of the interactions between biochar and GHGs emissions across global cropland soils, with field experiments showing the strongest GHG mitigation potential, i.e. CO₂ (RR = -0.108) and CH₄ (RR = -0.399). The biochar pyrolysis temperature, feedstock, C: N ratio, and pH were also found to be important factors influencing GHGs emissions. A prominent reduction in N₂O (RR = -0.13) and CH₄ (RR = -1.035) emissions was observed in neutral soils (pH = 6.6-7.3), whereas acidic soils (pH ≤ 6.5) accounted for the strongest mitigation effect on CO₂ compared to N₂O and CH₄ emissions. We also found that a biochar application rate of 30 t ha^-1 was best for mitigating GHGs emissions while achieving optimal crop yield. According to our meta-analysis, maize crop receiving biochar amendment showed a significant mitigation potential for CO₂, N₂O, and CH₄ emissions. On the other hand, the use of biochar had shown significant impact on the global warming potential (GWP) of total GHGs emissions. The current data synthesis takes the lead in analyzing emissions status and mitigation potential for three of the most common GHGs from cropland soils and demonstrates that biochar application can significantly reduce the emissions budget from agriculture.

A review of carbon farming impacts on nitrogen cycling, retention, and loss

Soil carbon (C) sequestration in agricultural working lands via soil amendments and management practices is considered a relatively well-tested and affordable approach for removing CO₂ from the atmosphere. Carbon farming provides useful benefits for soil health, biomass production, and crop resilience, but the effects of different soil C sequestration approaches on the nitrogen (N) cycle remain controversial. While some C farming practices have been shown to reduce N fertilizer use in some cases, C farming could also impose an unwanted "N penalty" through which soil C gains can only be maintained with additional N inputs, thereby increasing N losses to the environment. We systematically reviewed meta-analysis studies on the impacts of C farming on N cycling in agroecosystems and estimated the cumulative effect of several C farming practices on N cycling. We found that, on average, combined C farming practices significantly reduced nitrous oxide emissions and nitrate leaching from soils, thus inferring both N cycling and climate change benefits. In addition to more widely studied C farming practices that generate organic C, we also discuss silicate rock additions, which offer a pathway to inorganic C sequestration that does not require additional N inputs, framing important questions for future research.

Influence of Intraspecific Competition Stress on Soil Fungal Diversity and Composition in Relation to Tree Growth and Soil Fertility in Sub-Tropical Soils under Chinese Fir Monoculture

Soil microorganisms provide valuable ecosystem services, such as nutrient cycling, soil remediation, and biotic and abiotic stress resistance. There is increasing interest in exploring total belowground biodiversity across ecological scales to understand better how different ecological aspects, such as stand density, soil properties, soil depth, and plant growth parameters, influence belowground communities. In various environments, microbial components of belowground communities, such as soil fungi, respond differently to soil features; however, little is known about their response to standing density and vertical soil profiles in a Chinese fir monoculture plantation. This research examined the assemblage of soil fungal communities in different density stands (high, intermediate, and low) and soil depth profiles (0–20 cm and 20–40 cm). This research also looked into the relationship between soil fungi and tree canopy characteristics (mean tilt angle of the leaf (MTA), leaf area index (LAI), and canopy openness index (DIFN)), and general growth parameters, such as diameter, height, and biomass. The results showed that low-density stand soil had higher fungal alpha diversity than intermediate- and high-density stand soils. Ascomycota, Basidiomycota, Mucromycota, and Mortierellomycota were the most common phyla of the soil fungal communities, in that order. Saitozyma, Penicillium, Umbelopsis, and Talaromyces were the most abundant fungal genera. Stand density composition was the dominant factor in changing fungal community structure compared to soil properties and soil depth profiles. The most significant soil elements in soil fungal community alterations were macronutrients. In addition, the canopy openness index and fungal community structure have a positive association in the low-density stand. Soil biota is a nutrient cycling driver that can promote better plant growth in forest ecosystems by supporting nutrient cycling. Hence, this research will be critical in understanding soil fungal dynamics, improving stand growth and productivity, and improving soil quality in intensively managed Chinese fir plantations.

Unraveling the Influence of Land-Use Change on δ13C, δ15N, and Soil Nutritional Status in Coniferous, Broadleaved, and Mixed Forests in Southern China: A Field Investigation

Natural isotopic abundance in soil and foliar can provide integrated information related to the long-term alterations of carbon (C) and nitrogen (N) cycles in forest ecosystems. We evaluated total carbon (TC), total nitrogen (TN), and isotopic natural abundance of C (δ¹³C) and N (δ¹⁵N) in soil and foliar of coniferous plantation (CPF), natural broadleaved forest (NBF), and mixed forest stands at three different soil depths (i.e., 0–10, 10–20, and 20–40 cm). This study also explored how soil available nutrients are affected by different forest types. Lutou forest research station, located in Hunan Province, central China, was used as the study area. Results demonstrated that the topsoil layer had higher TC and TN content in the mixed forest stand, resulting in a better quality of organic materials in the topsoil layer in the mixed forest than NBF and CPF. In general, soil TC, TN, and δ¹⁵N varied significantly in different soil depths and forest types. However, the forest type did not exhibit any significant effect on δ¹³C. Overall, soil δ¹³C was significantly enriched in CPF, and δ¹⁵N values were enriched in mixed forest. Foliar C content varied significantly among forest types, whereas foliar N content was not significantly different. No big differences were observed for foliar δ¹⁵N and δ¹³C across forest types. However, foliar δ¹³C and δ¹⁵N were positively related to soil δ¹³C and δ¹⁵N, respectively. Foliar N, soil and foliar C:N ratio, soil moisture content (SMC), and forest type were observed as the major influential factors affecting isotopic natural abundance, whereas soil pH was not significantly correlated. In addition, forest type change and soil depth increment had a significant effect on soil nutrient availability. In general, soil nutrient availability was higher in mixed forest. Our findings implied that forest type and soil depth alter TC, TN, and soil δ¹⁵N, whereas δ¹³C was only driven by soil depth. Moreover, plantations led to a decline in soil available nutrient content compared with NBF and mixed forest stands.

Nitrous oxide emission from agricultural soils: Application of animal manure or biochar? A global meta-analysis

Organic amendments (animal manure and biochar) to agricultural soils may enhance soil organic carbon (SOC) contents, improve soil fertility and crop productivity but also contribute to global warming through nitrous oxide (N₂O) emission. However, the effects of organic amendments on N₂O emissions from agricultural soils seem variable among numerous research studies and remains uncertain. Here, eighty-five publications (peer-reviewed) were selected to perform a meta-analysis study. The results of this meta-analysis study show that the application of animal manure enhanced N₂O emissions by 17.7%, whereas, biochar amendment significantly mitigated N₂O emissions by 19.7%. Moreover, coarse textured soils increased [lnRR‾ = 182.6%, 95% confidence interval (CI) = 151.4%, 217.7%] N₂O emission after animal manure, in contrast, N₂O emission mitigated by 7.0% from coarse textured soils after biochar amendment. In addition, this study found that 121-320 kg N ha^-1 and ⩽ 30 T ha^-1 application rates of animal manure and biochar mitigated N₂O emissions by 72.3% and 22.5%, respectively. Soil pH also played a vital role in regulating the N₂O emissions after organic amendments. Furthermore, > 10 soil C: N ratios increased N₂O emissions by 121.4% and 27.6% after animal and biochar amendments, respectively. Overall, animal manure C: N ratios significantly enhanced N₂O emissions, while, biochar C: N ratio had not shown any effect on N₂O emissions. Overall, average N₂O emission factors (EFs) for animal manure and biochar amendments were 0.46% and -0.08%, respectively. Thus, the results of this meta-analysis study provide scientific evidence about how organic amendments such as animal manure and biochar regulating the N₂O emission from agricultural soils.

Intercropping of Peanut-Tea Enhances Soil Enzymatic Activity and Soil Nutrient Status at Different Soil Profiles in Subtropical Southern China

Intercropping is one of the most widely used agroforestry techniques, reducing the harmful impacts of external inputs such as fertilizers. It also controls soil erosion, increases soil nutrients availability, and reduces weed growth. In this study, the intercropping of peanut (Arachishypogaea L.) was done with tea plants (Camellia oleifera), and it was compared with the mono-cropping of tea and peanut. Soil health and fertility were examined by analyzing the variability in soil enzymatic activity and soil nutrients availability at different soil depths (0-10 cm, 10-20 cm, 20-30 cm, and 30-40 cm). Results showed that the peanut-tea intercropping considerably impacted the soil organic carbon (SOC), soil nutrient availability, and soil enzymatic responses at different soil depths. The activity of protease, sucrase, and acid phosphatase was higher in intercropping, while the activity of urease and catalase was higher in peanut monoculture. In intercropping, total phosphorus (TP) was 14.2%, 34.2%, 77.7%, 61.9%; total potassium (TK) was 13.4%, 20%, 27.4%, 20%; available phosphorus (AP) was 52.9%, 26.56%, 61.1%; 146.15% and available potassium (AK) was 11.1%, 43.06%, 46.79% higher than the mono-cropping of tea in respective soil layers. Additionally, available nitrogen (AN) was 51.78%, 5.92%, and 15.32% lower in the 10-20 cm, 20-30 cm, and 30-40 cm layers of the intercropping system than in the mono-cropping system of peanut. Moreover, the soil enzymatic activity was significantly correlated with SOC and total nitrogen (TN) content across all soil depths and cropping systems. The depth and path analysis effect revealed that SOC directly affected sucrase, protease, urease, and catalase enzymes in an intercropping system. It was concluded that an increase in the soil enzymatic activity in the intercropping pattern improved the reaction rate at which organic matter decomposed and released nutrients into the soil environment. Enzyme activity in the decomposition process plays a vital role in forest soil morphology and function. For efficient land use in the cropping system, it is necessary to develop coherent agroforestry practices. The results in this study revealed that intercropping certainly enhance soil nutrients status and positively impacts soil conservation.

Defining the wheat microbiome: Towards microbiome-facilitated crop production

Wheat is one of the world's most important crops, but its production relies heavily on agrochemical inputs which can be harmful to the environment when used excessively. It is well known that a multitude of microbes interact with eukaryotic organisms, including plants, and the sum of microbes and their functions associated with a given host is termed the microbiome. Plant-microbe interactions can be beneficial, neutral or harmful to the host plant. Over the last decade, with the development of next generation DNA sequencing technology, our understanding of the plant microbiome structure has dramatically increased. Considering that defining the wheat microbiome is key to leverage crop production in a sustainable way, here we describe how different factors drive microbiome assembly in wheat, including crop management, edaphic-environmental conditions and host selection. In addition, we highlight the benefits to take a multidisciplinary approach to define and explore the wheat core microbiome to generate solutions based on microbial (synthetic) communities or single inoculants. Advances in plant microbiome research will facilitate the development of microbial strategies to guarantee a sustainable intensification of crop production.