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

Could soil microplastic pollution exacerbate climate change? A meta-analysis of greenhouse gas emissions and global warming potential

Microplastics pollution and climate change are primarily investigated in isolation, despite their joint threat to the environment. Greenhouse gases (GHGs) are emitted during: the production of plastic and rubber, the use and degradation of plastic, and after contamination of environment. This is the first meta-analysis to assess underlying causal relationships and the influence of likely mediators. We included 60 peer-reviewed empirical studies; estimating GHGs emissions effect size and global warming potential (GWP), according to key microplastics properties and soil conditions. We investigated interrelationships with microbe functional gene expression. Overall, microplastics contamination was associated with increased GHGs emissions, with the strongest effect (60%) on CH4 emissions. Polylactic-acid caused 32% higher CO2 emissions, but only 1% of total GWP. Phenol-formaldehyde had the greatest (175%) GWP via 182% increased N2O emissions. Only polystyrene resulted in reduced GWP by 50%, due to N2O mitigation. Polyethylene caused the maximum (60%) CH4 emissions. Shapes of microplastics differed in GWP: fiber had the greatest GWP (66%) whereas beads reduced GWP by 53%. Films substantially increased emissions of all GHGs: 14% CO2, 10% N2O and 60% CH4. Larger-sized microplastics had higher GWP (125%) due to their 9% CO2 and 63% N2O emissions. GWP rose sharply if soil microplastics content exceeded 0.5%. Higher CO2 emissions, ranging from 4% to 20%, arose from soil which was either fine, saturated or had high-carbon content. Higher N2O emissions, ranging from 10% to 95%, arose from soils that had either medium texture, saturated water content or low-carbon content. Both CO2 and N2O emissions were 43%-56% higher from soils with neutral pH. We conclude that microplastics contamination can cause raised GHGs emissions, posing a risk of exacerbating climate-change. We show clear links between GHGs emissions, microplastics properties, soil characteristics and soil microbe functional gene expression. Further research is needed regarding underlying mechanisms and processes.

Predicting Quercus gilva distribution dynamics and its response to climate change induced by GHGs emission through MaxEnt modeling

Quercus gilva, an evergreen tree species in Quercus section Cyclobalanopsis, is an ecologically and economically valuable species in subtropical regions of East Asia. Predicting the impact of climate change on potential distribution of Q. gilva can provide a scientific basis for the conservation and utilization of its genetic resources, as well as for afforestation. In this study, 74 distribution records of Q. gilva and nine climate variables were obtained after data collection and processing. Current climate data downloaded from WorldClim and future climate data predicted by four future climate scenarios (2040s SSP1-2.6, 2040s SSP5-8.5, 2060s SSP1-2.6, and 2060s SSP5-8.5) mainly based on greenhouse gases emissions of distribution sites were used in MaxEnt model with optimized parameters to predict distribution dynamics of Q. gilva and its response to climate change. The results showed that the predicted current distribution was consistent with natural distribution of Q. gilva, which was mainly located in Hunan, Jiangxi, Zhejiang, Fujian, Guizhou, and Taiwan provinces of China, as well as Japan and Jeju Island of South Korea. Under current climate conditions, precipitation factors played a more significant role than temperature factors on distribution of Q. gilva, and precipitation of driest quarter (BIO17) is the most important restriction factor for its current distribution (contribution rate of 57.35%). Under future climate conditions, mean temperature of driest quarter (BIO9) was the essential climate factor affecting future change in potential distribution of Q. gilva. As the degree of climatic anomaly increased in the future, the total area of predicted distribution of Q. gilva showed a shrinking trend (decreased by 12.24%-45.21%) and Q. gilva would migrate to high altitudes and latitudes. The research results illustrated potential distribution range and suitable climate conditions of Q. gilva, which can provide essential theoretical references for the conservation, development, and utilization of Q. gilva and other related species.

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.

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.

Glucose input profit soil organic carbon mineralization and nitrogen dynamics in relation to nitrogen amended soils

Exogenous carbon (C) inputs stimulate soil organic carbon (SOC) decomposition, strongly influencing atmospheric concentrations and climate dynamics. The direction and magnitude of C decomposition depend on the C and nitrogen (N) addition, types and pattern. Despite the importance of decomposition, it remains unclear whether organic C input affects the SOC decomposition under different N-types (Ammonium Nitrate; AN, Urea; U and Ammonium Sulfate; AS). Therefore, we conducted an incubation experiment to assess glucose impact on N-treated soils at various levels (High N; HN: 50 mg/m2, Low N; LN: 05 mg/m2). The glucose input increased SOC mineralization by 38% and 35% under HN and LN, respectively. Moreover, it suppressed the concentration of NO3--N by 35% and NH4+-N by 15% in response to HN and LN soils, respectively. Results indicated higher respiration in Urea-treated soils and elevated net total nitrogen content (TN) in AS-treated soils. AN-amended soil exhibited no notable rise in C mineralization and TN content compared to other N-type soils. Microbial biomass carbon (MBC) was higher in glucose treated soils under LN conditions than control. This could result that high N suppressed microbial N mining and enhancing SOM stability by directing microbes towards accessible C sources. Our results suggest that glucose accelerated SOC mineralization in urea-added soils and TN contents in AS-amended soils, while HN levels suppressed C release and increased TN contents in all soil types except glucose-treated soils. Thus, different N-types and levels play a key role in modulating the stability of SOC over C input.

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.

A global meta-analysis of crop yield and agricultural greenhouse gas emissions under nitrogen fertilizer application

Nitrogen fertilization (NF) is one of the common practices to increase crop production worldwide over the past several decades. Nevertheless, unreasonable NF results in massive greenhouse gas (GHG) emissions, leading to climate change and global warming. Many studies have already reported the impact of NF on crop yield, global warming potential (GWP) and greenhouse gas intensity (GHGI), but the studies were limited to only some parameters. In this study, a total of 174 studies from 16 countries were collected and then a regression analysis was conducted to obtain the appropriate N fertilization rates that enhance crop yield while reducing GWP and GHGI. After that, a meta-analysis was performed to evaluate the effects of NF on crop yield, GHGI, GWP and GHG emissions and identify NF management strategies that benefit crop yield and maintain GWP. The results showed that the suitable N fertilization rate was 180, 150, 130 and 200 kg ha^-1 for wheat, maize, rice and vegetables or industrial crops, respectively. Overall, NF resulted in positive effect size in crop yield (0.56) and negative effect size in GHGI (-0.14) compared to NNF. GWP showed positive effect size (0.37) due to an increase in N₂O emissions (0.91) relative to NNF, which is higher than the increase of CH₄ emissions (0.01) and CO₂ emissions (0.22). It was recommended that split and banded application of urea or urea plus manure is employed for cereals (especially wheat) in the arid and semi-arid regions with medium-textured and neutral or alkaline soil.

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.