Effects of continuous straw and equivalent straw-derived biochar application on soil multifunctionality, crop productivity, and greenhouse gas emissions

Excessive nitrogen (N) fertilization accelerates agricultural greenhouse gas (GHG) emissions and leads to soil degradation, yet the potential of reduced N inputs to balance crop yield, GHG emissions, and soil multifunctionality—and the underlying mechanisms—remains unclear. Through a 2‐year field experiment, we found that a 25% reduction in N fertilizer (R25) reshaped the soil microbial co‐occurrence network, resulting in a topology with higher connectivity (avgK) and shorter path distances (GD) compared to conventional fertilization (CF, 200 kg ha −1 ). This restructuring increased the abundance of functional microbes associated with aromatic compound degradation, aerobic ammonia oxidation, and nitrification, thereby maintaining soil carbon and nitrogen cycling capacity and sustaining crop productivity. Mechanistically, the enhanced microbial network facilitated more efficient nutrient transformation and transfer, leading to a 30.66%–32.94% increase in nitrogen use efficiency (NUE) and a 13.87%–35.72% reduction in greenhouse gas intensity (GHGI). In contrast, a 50% N reduction (R50) restricted nutrient availability and decreased yield by 10.08%–11.10%. Partial least squares path modeling revealed that N‐induced changes in soil multifunctionality were primarily driven by microbial network topology. Our findings identify an optimal N reduction range of 22.50%–34.00% (132–155 kg ha −1 ) for sustaining maize yield and soil multifunctionality while reducing GHGI, highlighting the regulation of microbial network as a key strategy for sustainable maize production.

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

Continuous biochar application results in higher greenhouse gas emissions than a single biochar application in an upland agroecosystem.

Plant diversity is more important than soil microbial diversity in explaining soil multifunctionality in Qinghai-Tibetan plateau wetlands

Trade-offs between crop production and GHG emissions following organic material inputs in wheat-maize systems.

Balancing crop production and greenhouse gas (GHG) emissions from agriculture soil requires a better understanding and quantification of crop GHG emissions intensity, a measure of GHG emissions per unit crop production. Here we conduct a state-of-the-art estimate of the spatial-temporal variability of GHG emissions intensities for wheat, maize, and rice in China from 1949 to 2012 using an improved agricultural ecosystem model (Dynamic Land Ecosystem Model-Agriculture Version 2.0) and meta-analysis covering 172 field-GHG emissions experiments. The results show that the GHG emissions intensities of these croplands from 1949 to 2012, on average, were 0.10-1.31kgCO2 -eq/kg, with a significant increase rate of 1.84-3.58×10-3 kgCO2 -eqkg-1 year-1 . Nitrogen fertilizer was the dominant factor contributing to the increase in GHG emissions intensity in northern China and increased its impact in southern China in the 2000s. Increasing GHG emissions intensity implies that excessive fertilizer failed to markedly stimulate crop yield increase in China but still exacerbated soil GHG emissions. This study found that overfertilization of more than 60% was mainly located in the winter wheat-summer maize rotation systems in the North China Plain, the winter wheat-rice rotation systems in the middle and lower reaches of the Yangtze River and southwest China, and most of the double rice systems in the South. Our simulations suggest that roughly a one-third reduction in the current N fertilizer application level over these "overfertilization" regions would not significantly influence crop yield but decrease soil GHG emissions by 29.60%-32.50% and GHG emissions intensity by 0.13-0.25kgCO2 -eq/kg. This reduction is about 29% and 5% of total agricultural soil GHG emissions in China and the world, respectively. This study suggests that improving nitrogen use efficiency would be an effective strategy to mitigate GHG emissions and sustain China's food security.

The role of extractable pool of biochar in crop productivity and soil greenhouse gas (GHGs) emission is not yet clear. In this study, two biochars with and without extraction was added to a paddy before rice transplantation at 20 t·ha−1. Crop yield, plant traits and greenhouse gas emission monitored throughout a rice-wheat rotation. Between the biochar treatments, changes in bulk density and microbial biomass carbon were insignificant. However, the increase in organic carbon was similar between maize and wheat biochars while higher under bulk wheat biochar than extracted one. The increase in available P and K was higher under wheat than maize biochar regardless of extraction. Moreover, the increase in plant traits and grain yield, in rice season only, was higher under bulk than extracted biochars. Yet, there was no difference in changes in GHGs emission between bulk and extracted biochars regardless of feedstock. Nevertheless, increased methane emission for rice season was lower under extracted biochars than bulk ones. Overall, crop productivity rather than GHGs emission was affected by treatment of extraction of biochars. Thus, use of unextracted biochar is recommended for improving soil crop productivity in the paddy soils.

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.

Researchers have previously described the response of crop productivity and greenhouse gas (GHG) emissions to fertilizer nitrogen (N) additions, but they have not determined how to maximize yields while minimizing GHG emissions. We conducted an experiment at 2293 sites with four N levels to simulate both grain yield and yield-scaled GHG emissions in response to the N addition. The yield-scaled GHG emissions decreased by 16% as the N rate increased from treatments without the N addition to the minimum yield-scaled GHG emissions, which was comparable to the values associated with the maximum grain yields. The sites with both high soil productivity and high crop productivity had the highest yield and lowest yield-scaled GHG emissions, with 43% higher yield and 38% lower yield-scaled GHG emissions than sites with low soil and low crop productivity. These findings are expected to enhance evaluations of wheat production and GHG emissions in China, and thereby contribute to addressing disparities in the global food and GHG budget.

Conservation tillage is crucial for rehabilitating degraded cropland, securing crop production and lessening greenhouse gas (GHG) emissions. Yet, the optimal nitrogen (N) application level that balances crop productivity with environmental effects following long‐term conservation tillage remains unclear. Based on a 9‐year conservation tillage experiment of black soil in Northeast China, an in situ microplot experiment was conducted from 2021 to 2023, including six N fertilization levels: 240 (N240, conventional N fertilization level by local farmers), 210 (N210), 180 (N180), 150 (N150), 120 (N120) and 0 kg N ha −1 (N0, control). The systematic effects of N fertilization on crop production, N fertilizer agronomic efficiency (NAE), GHG emissions and N balance were evaluated by using TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution). N fertilization significantly enhanced crop production ( p < 0.05), especially maize grain yield was increased by 27.7%–36.2% in high N fertilization treatments (N180, N210 and N240) over that for N0. The NAE increased with the increase of N fertilization and exhibited a positive nonlinear correlation with the N fertilization level elevating ( R 2 = 0.61), whereas no notable variation in NAE was found across high N fertilization treatments. Moreover, global warming potential (GWP) showed an upward trend with the increase of N fertilization, while greenhouse gas intensity (GHGI) did not show a consistent trend. Analysis of the annual N balance suggested that, except for the N deficit observed in N0. Based on the TOPSIS method, the integrated evaluation showed that N180 ranked first with the total score of 0.61. Overall, from the perspective of crop production, nutrient utilization and the environment, an N fertilization level of 180 kg N ha −1 after long‐term conservation tillage is beneficial for ensuring food security while mitigating global change. This study provided scientific data for optimizing N management and promoting sustainable development of the black soil granary in Northeast China.

Climate-adaptive crop distribution can feed food demand, improve water scarcity, and reduce greenhouse gas emissions

Energy use and greenhouse gas emissions in organic and conventional farming systems in the Netherlands

Estimating energy consumption and GHG emissions in crop production: A machine learning approach

Dairy production systems represent a significant source of air pollutants such as greenhouse gases (GHG), that increase global warming, and ammonia (NH3), that leads to eutrophication and acidification of natural ecosystems. Greenhouse gases and ammonia are emitted both by conventional and organic dairy systems. Several studies have already been conducted to design practices that reduce greenhouse gas and ammonia emissions from dairy systems. However, those studies did not consider options specifically applied to organic farming, as well as the multiple trade-offs occurring between these air pollutants. This article reviews agricultural practices that mitigate greenhouse gas and ammonia emissions. Those practices can be applied to the most common organic dairy systems in northern Europe such as organic mixed crop-dairy systems. The following major points of mitigation options for animal production, crop production and grasslands are discussed. Animal production: the most promising options for reducing greenhouse gas emissions at the livestock management level involve either the improvement of animal production through dietary changes and genetic improvement or the reduction of the replacement rate. The control of the protein intake of animals is an effective means to reduce gaseous emissions of nitrogen, but it is difficult to implement in organic dairy farming systems. Considering the manure handling chain, mitigation options involve housing, storage and application. For housing, an increase in the amounts of straw used for bedding reduces NH3 emissions, while the limitation of CH4 emissions from deep litter is achieved by avoiding anaerobic conditions. During the storage of solid manure, composting could be an efficient mitigation option, depending on its management. Addition of straw to solid manure was shown to reduce CH4 and N2O emissions from the manure heaps. During the storage of liquid manure, emptying the slurry store before late spring is an efficient mitigation option to limit both CH4 and NH3 emissions. Addition of a wooden cover also reduces these emissions more efficiently than a natural surface crust alone, but may increase N2O emissions. Anaerobic digestion is the most promising way to reduce the overall greenhouse gas emissions from storage and land spreading, without increasing NH3 emissions. At the application stage, NH3 emissions may be reduced by spreading manure during the coolest part of the day, incorporating it quickly and in narrow bands. Crop production: the mitigation options for crop production focus on limiting CO2 and N2O emissions. The introduction of perennial crops or temporary leys of longer duration are promising options to limit CO2 emissions by storing carbon in plants or soils. Reduced tillage or no tillage as well as the incorporation of crop residues also favour carbon sequestration in soils, but these practices may enhance N2O emissions. Besides, the improvement of crop N-use efficiency through effective management of manure and slurry, by growing catch crops or by delaying the ploughing of leys, is of prime importance to reduce N2O emissions. Grassland: concerning grassland and grazing management, permanent conversion from arable to grassland provides high soil carbon sequestration while increasing or decreasing the livestock density seems not to be an appropriate mitigation option. From the study of the multiple interrelations between gases and between farm compartments, the following mitigation options are advised for organic mixed crop-dairy systems: (1) actions for increasing energy efficiency or fuel savings because they are beneficial in any case, (2) techniques improving efficiency of N management at field and farm levels because they affect not only N2O and NH3 emissions, but also nitrate leaching, and (3) biogas production through anaerobic digestion of manure because it is a promising efficient method to mitigate greenhouse gas emissions, even if the profitability of this expensive investment needs to be carefully studied. Finally, the way the farmer implements the mitigation options, i.e. his practices, will be a determining factor in the reduction of greenhouse gas and NH3 emissions.KeywordsAgricultureGreenhouse gasAmmoniaAbatementMixed crop-dairy systemsOrganicLivestockManureGrasslandCarbon storageSoil carbon sequestration

The Earth’s climate is rapidly changing largely due to increasing anthropogenic greenhouse gas (GHG) emissions. Agricultural practices during crop production, food processing, and product marketing all generate GHG, contributing to the global climate change. The general public and farmers are urging the development and adoption of effective measures to reduce GHG emissions from all agricultural activities and sectors. However, quantitative information is not available in regard to what strategies and practices should be adopted to reduce emission from agriculture and how crop productivity would affect the intensity of GHG emission. To provide the potential solution, we estimated the carbon footprint [i.e., the total amount of GHG associated with the production and distribution of a given food product expressed in carbon dioxide equivalence (CO2e)] for some of the major field crops grown on the Canadian prairie and assessed the effect of crop sequences on the carbon footprint of durum wheat. Key strategies for reducing the carbon footprint of various field crops grown in semiarid areas were identified. Carbon footprints were estimated using emissions from (1) the decomposition of crop straw and roots; (2) the manufacture of N and P fertilizers and their rates of application; (3) the production of herbicides and fungicides; and (4) miscellaneous farm field operations. Production and application of N fertilizers accounted for 57% to 65% of the total footprint, those from crop residue decomposition 16% to 30%, and the remaining portion of the footprint included CO2e from the production of P fertilizer and pesticides, and from miscellaneous field operations. Crops grown in the Brown soil zone had the lowest carbon footprint, averaging 0.46 kg CO2e kg−1 of grain, whereas crops grown in the Black soil zone had a larger average carbon footprint of 0.83 kg CO2e kg−1 of grain. The average carbon footprint for crops grown in the Dark Brown soil zone was intermediate to the other two at 0.61 kg CO2e kg−1 of grain. One kilogram of grain product emitted 0.80 kg CO2e for canola (Brassica napus L.), 0.59 for mustard (Brassica juncea L.) and flaxseed (Linum usitatissimum L.), 0.46 for spring wheat (Triticum aestivum L.), and 0.20 to 0.33 kg CO2e for chickpea (Cicer arietinum L.), dry pea (Pisum sativum L.), and lentil (Lens culinaris Medik.). Durum wheat (T. aestivum L.) preceded by an N-fixing crop (i.e., pulses) emitted total greenhouse gases of 673 kg CO2e, 20% lower than when the crop was preceded by a cereal crop. Similarly, durum wheat preceded by an oilseed emitted 744 kg CO2e, 11% lower than when preceded by a cereal. The carbon footprint for durum grown after a pulse was 0.25 kg CO2e per kg of the grain and 0.28 kg CO2e per kg of the grain when grown after an oilseed: a reduction in the carbon footprint of 24% to 32% than when grown after a cereal. The average carbon footprint can be lowered by as much as 24% for crops grown in the Black, 28% in the Dark Brown, and 37% in the Brown soil zones, through improved agronomic practices, increased N use efficiency, use of diversified cropping systems, adoption of crop cultivars with high harvest index, and the use of soil bioresources such as P-solublizers and arbuscular mycorrhizal fungi in crop production.