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Journal ArticleDOI

Stimulation of N2O emission by manure application to agricultural soils may largely offset carbon benefits: a global meta-analysis

01 Oct 2017-Global Change Biology (Glob Chang Biol)-Vol. 23, Iss: 10, pp 4068-4083
TL;DR: A global meta-analysis using field experimental data published in peer-reviewed journals prior to December 2015 suggested that the benefit of increasing SOC stocks as GHG sinks could be largely offset by stimulation of soil N2 O emissions and aggravated byCH4 emissions if, particularly for rice paddy soils, the stimulation of CH4 emissions by manure application was taken into account.
Abstract: Animal manure application as organic fertilizer does not only sustain agricultural productivity and increase soil organic carbon (SOC) stocks, but also affects soil nitrogen cycling and nitrous oxide (N2O) emissions. However, given that the sign and magnitude of manure effects on soil N2O emissions is uncertain, the net climatic impact of manure application in arable land is unknown. Here, we performed a global meta-analysis using field experimental data published in peer-reviewed journals prior to December 2015. In this meta-analysis, we quantified the responses of N2O emissions to manure application relative to synthetic N fertilizer application from individual studies and analyzed manure characteristics, experimental duration, climate, and soil properties as explanatory factors. Manure application significantly increased N2O emissions by an average 32.7% (95% confidence interval: 5.1-58.2%) compared to application of synthetic N fertilizer alone. The significant stimulation of N2O emissions occurred following cattle and poultry manure applications, subsurface manure application, and raw manure application. Furthermore, the significant stimulatory effects on N2O emissions were also observed for warm temperate climate, acid soils (pH < 6.5), and soil texture classes of sandy loam and clay loam. Average direct N2O emission factors (EFs) of 1.87% and 0.24% were estimated for upland soils and rice paddy soils receiving manure application, respectively. Although manure application increased SOC stocks, our study suggested that the benefit of increasing SOC stocks as GHG sinks could be largely offset by stimulation of soil N2O emissions and aggravated by CH4 emissions if, particularly for rice paddy soils, the stimulation of CH4 emissions by manure application was taken into account.
Citations
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Journal ArticleDOI
TL;DR: Testing biochar's impact on cumulative N2O emissions, soil NO3- concentrations and leaching in temperate, semi-arid, sub-tropical, and tropical climate provided a valuable starting point for future biochar-based N loss mitigation studies.

292 citations

Journal ArticleDOI
TL;DR: It is suggested it is more realistic to promote practices for increasing SOC based on improving soil quality and functioning as small increases can have disproportionately large beneficial impacts, though not necessarily translating into increased crop yield.
Abstract: We evaluated the "4 per 1000" initiative for increasing soil organic carbon (SOC) by analysing rates of SOC increase in treatments in 16 long-term experiments in southeast United Kingdom. The initiative sets a goal for SOC stock to increase by 4‰ per year in the 0-40 cm soil depth, continued over 20 years. Our experiments, on three soil types, provided 114 treatment comparisons over 7-157 years. Treatments included organic additions (incorporated by inversion ploughing), N fertilizers, introducing pasture leys into continuous arable systems, and converting arable land to woodland. In 65% of cases, SOC increases occurred at >7‰ per year in the 0-23 cm depth, approximately equivalent to 4‰ per year in the 0-40 cm depth. In the two longest running experiments (>150 years), annual farmyard manure (FYM) applications at 35 t fresh material per hectare (equivalent to approx. 3.2 t organic C/ha/year) gave SOC increases of 18‰ and 43‰ per year in the 23 cm depth during the first 20 years. Increases exceeding 7‰ per year continued for 40-60 years. In other experiments, with FYM applied at lower rates or not every year, there were increases of 3‰-8‰ per year over several decades. Other treatments gave increases between zero and 19‰ per year over various periods. We conclude that there are severe limitations to achieving the "4 per 1000" goal in practical agriculture over large areas. The reasons include (1) farmers not having the necessary resources (e.g. insufficient manure); (2) some, though not all, practices favouring SOC already widely adopted; (3) practices uneconomic for farmers-potentially overcome by changes in regulations or subsidies; (4) practices undesirable for global food security. We suggest it is more realistic to promote practices for increasing SOC based on improving soil quality and functioning as small increases can have disproportionately large beneficial impacts, though not necessarily translating into increased crop yield.

229 citations


Cites background from "Stimulation of N2O emission by manu..."

  • ...For example, a recent global meta-analysis of experiments with manure showed that, on average, manure addition increased N2O emission by 33% compared to inorganic N fertilizer and this could largely offset the benefit of increased SOC stock (Zhou et al., 2017)....

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  • ...…not necessarily the key issue when considering the success of climate change mitigation through land management practices: the impacts of management changes on emissions of trace greenhouse gases, especially N2O, must be given equal weight (Smith et al., 2008; Zhou et al., 2017; Tian et al., 2016)....

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Journal ArticleDOI
TL;DR: In this paper, the authors synthesized 20 years of research to explain the interrelated processes that determine soil and plant responses to biochar and found that biochar can catalyze biotic and abiotic reactions, particularly in the rhizosphere, that increase nutrient supply and uptake by plants.
Abstract: We synthesized 20 years of research to explain the interrelated processes that determine soil and plant responses to biochar. The properties of biochar and its effects within agricultural ecosystems largely depend on feedstock and pyrolysis conditions. We describe three stages of reactions of biochar in soil: dissolution (1–3 weeks); reactive surface development (1–6 months); and aging (beyond 6 months). As biochar ages, it is incorporated into soil aggregates, protecting the biochar carbon and promoting the stabilization of rhizodeposits and microbial products. Biochar carbon persists in soil for hundreds to thousands of years. By increasing pH, porosity, and water availability, biochars can create favorable conditions for root development and microbial functions. Biochars can catalyze biotic and abiotic reactions, particularly in the rhizosphere, that increase nutrient supply and uptake by plants, reduce phytotoxins, stimulate plant development, and increase resilience to disease and environmental stressors. Meta-analyses found that, on average, biochars increase P availability by a factor of 4.6; decrease plant tissue concentration of heavy metals by 17%–39%; build soil organic carbon through negative priming by 3.8% (range −21% to +20%); and reduce non-CO2 greenhouse gas emissions from soil by 12%–50%. Meta-analyses show average crop yield increases of 10%–42% with biochar addition, with greatest increases in low-nutrient P-sorbing acidic soils (common in the tropics), and in sandy soils in drylands due to increase in nutrient retention and water holding capacity. Studies report a wide range of plant responses to biochars due to the diversity of biochars and contexts in which biochars have been applied. Crop yields increase strongly if site-specific soil constraints and nutrient and water limitations are mitigated by appropriate biochar formulations. Biochars can be tailored to address site constraints through feedstock selection, by modifying pyrolysis conditions, through pre- or post-production treatments, or co-application with organic or mineral fertilizers. We demonstrate how, when used wisely, biochar mitigates climate change and supports food security and the circular economy.

181 citations

Journal ArticleDOI
TL;DR: It is shown that partial substitution of fertilizer by manure can increase crop yields, and decrease emissions of NH3 and N2 O, but depending on site-specific conditions.
Abstract: Recycling of livestock manure to agricultural land may reduce the use of synthetic fertilizer and thereby enhance the sustainability of food production. However, the effects of substitution of fertilizer by manure on crop yield, nitrogen use efficiency (NUE), and emissions of ammonia (NH3 ), nitrous oxide (N2 O) and methane (CH4 ) as function of soil and manure properties, experimental duration and application strategies have not been quantified systematically and convincingly yet. Here, we present a meta-analysis of these effects using results of 143 published studies in China. Results indicate that the partial substitution of synthetic fertilizers by manure significantly increased the yield by 6.6% and 3.3% for upland crop and paddy rice, respectively, but full substitution significantly decreased yields (by 9.6% and 4.1%). The response of crop yields to manure substitution varied with soil pH and experimental durations, with relatively large positive responses in acidic soils and long-term experiments. NUE increased significantly at a moderate ratio (<40%) of substitution. NH3 emissions were significantly lower with full substitution (62%-77%), but not with partial substitution. Emissions of CH4 from paddy rice significantly increased with substitution ratio (SR), and varied by application rates and manure types, but N2 O emissions decreased. The SR did not significantly influence N2 O emissions from upland soils, and a relative scarcity of data on certain manure characteristic was found to hamper identification of the mechanisms. We derived overall mean N2 O emission factors (EF) of 0.56% and 0.17%, as well as NH3 EFs of 11.1% and 6.5% for the manure N applied to upland and paddy soils, respectively. Our study shows that partial substitution of fertilizer by manure can increase crop yields, and decrease emissions of NH3 and N2 O, but depending on site-specific conditions. Manure addition to paddy rice soils is recommended only if abatement strategies for CH4 emissions are also implemented.

167 citations


Cites background or methods or result from "Stimulation of N2O emission by manu..."

  • ...In addition to the effects of manure properties, the responses of N2O emissions following substitution of N fertilizer by manure is affected also by climate con‐ dition and soil properties (Zhou et al., 2017)....

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  • ...However, manure characteristics can have a strong impact on nitrification and denitrification rates and sub‐ sequently on N2O emissions (Charles et al., 2017; Hou et al., 2015; Zhou et al., 2017)....

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  • ...However, our estimates are lower than the mean of 1.87% for manure‐amended upland (143 observations in 17 countries) and the mean of 0.24% for manure amended paddy soil (Zhou et al., 2017)....

    [...]

  • ...…meta‐analyses were either weighted by the number of replications (Guo et al., 2017; Xia et al., 2017), or by the inverse of the pooled variance (Zhou et al., 2017), or were unweighted (Wang et al., 2017; Yu, Stomph, Makowski, & Van Der Werf, 2015), depending on the integrity of the reported…...

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  • ...Another recent meta‐ analysis solely addressed the response of N2O emissions to manure application relative to fertilizer use (Zhou et al., 2017), but did not address other gaseous emissions (e.g. CH4 and NH3) and crop yield, which hampers the evaluation of agronomic perspective and envi‐ ronmental…...

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Book ChapterDOI
TL;DR: In this paper, the effects of mulching and nitrogen (N) fertilizer on the soil environment and crop yield to inform food security are discussed. But, the use of mulch in agriculture provides many benefits to the soil by reducing evaporation, improving temperatures, adjusting the microbial biomass, maintaining the soil organic carbon balance, increasing nutrient cycling, promoting soil enzyme activity, enhancing soil aggregate stability and suppressing weed infestation.
Abstract: The demand for food is expected to significantly increase with continued population growth over the next 50 years, indicating that agricultural efficiency should be simultaneously stabilized and enhanced. Here, we discuss the effects of mulching and nitrogen (N) fertilizer on the soil environment and crop yield to inform food security. The use of mulch in agriculture provides many benefits to the soil by reducing evaporation, improving temperatures, adjusting the microbial biomass, maintaining the soil organic carbon balance, increasing nutrient cycling, promoting soil enzyme activity, enhancing soil aggregate stability and suppressing weed infestation. Nitrogen fertilization can markedly improve soil fertility and crop yield. However, nitrogen use efficiency (NUE) and the environment may be negatively affected by the improper application of N fertilizers. The improvement of NUE has been an important focus in field management for the more sustainable use of valuable N fertilizers. A better understanding of the interaction between N and mulch may improve NUE and crop yields. Inorganic mulches more efficiently alter the soil environment to enhance the NUE and crop yield, while organic mulching materials are more environmentally friendly and inexpensive. The selection of appropriate mulching materials should be combined with effective N management strategies, crop species, crop management practices and climatic conditions. In the future, precise nitrogen fertilizer management on farms and the development of relatively high-NUE and high-yielding crops will be highly feasible.

164 citations

References
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Journal ArticleDOI
TL;DR: The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models as discussed by the authors.
Abstract: The relationship between soil structure and the ability of soil to stabilize soil organic matter (SOM) is a key element in soil C dynamics that has either been overlooked or treated in a cursory fashion when developing SOM models. The purpose of this paper is to review current knowledge of SOM dynamics within the framework of a newly proposed soil C saturation concept. Initially, we distinguish SOM that is protected against decomposition by various mechanisms from that which is not protected from decomposition. Methods of quantification and characteristics of three SOM pools defined as protected are discussed. Soil organic matter can be: (1) physically stabilized, or protected from decomposition, through microaggregation, or (2) intimate association with silt and clay particles, and (3) can be biochemically stabilized through the formation of recalcitrant SOM compounds. In addition to behavior of each SOM pool, we discuss implications of changes in land management on processes by which SOM compounds undergo protection and release. The characteristics and responses to changes in land use or land management are described for the light fraction (LF) and particulate organic matter (POM). We defined the LF and POM not occluded within microaggregates (53–250 μm sized aggregates as unprotected. Our conclusions are illustrated in a new conceptual SOM model that differs from most SOM models in that the model state variables are measurable SOM pools. We suggest that physicochemical characteristics inherent to soils define the maximum protective capacity of these pools, which limits increases in SOM (i.e. C sequestration) with increased organic residue inputs.

3,301 citations

Journal ArticleDOI
TL;DR: In this article, the economic potential of agricultural practices, such as water and rice management, set-aside, land use change and agroforestry, livestock management and manure management, is estimated.
Abstract: Agricultural lands occupy 37% of the earth's land surface. Agriculture accounts for 52 and 84% of global anthropogenic methane and nitrous oxide emissions. Agricultural soils may also act as a sink or source for CO2, but the net flux is small. Many agricultural practices can potentially mitigate greenhouse gas (GHG) emissions, the most prominent of which are improved cropland and grazing land management and restoration of degraded lands and cultivated organic soils. Lower, but still significant mitigation potential is provided by water and rice management, set-aside, land use change and agroforestry, livestock management and manure management. The global technical mitigation potential from agriculture (excluding fossil fuel offsets from biomass) by 2030, considering all gases, is estimated to be approximately 5500–6000 Mt CO2-eq. yr−1, with economic potentials of approximately 1500–1600, 2500–2700 and 4000–4300 Mt CO2-eq. yr−1 at carbon prices of up to 20, up to 50 and up to 100 US$ t CO2-eq.−1, respectively. In addition, GHG emissions could be reduced by substitution of fossil fuels for energy production by agricultural feedstocks (e.g. crop residues, dung and dedicated energy crops). The economic mitigation potential of biomass energy from agriculture is estimated to be 640, 2240 and 16 000 Mt CO2-eq. yr−1 at 0–20, 0–50 and 0–100 US$ t CO2-eq.−1, respectively.

2,002 citations

Journal ArticleDOI
TL;DR: Improved process understanding, building on the increased use of isotope tracing techniques and metagenomics, needs to go along with improvements in measurement techniques for N2O (and N2) emission in order to obtain robust field and laboratory datasets for different ecosystem types.
Abstract: Although it is well established that soils are the dominating source for atmospheric nitrous oxide (N2O), we are still struggling to fully understand the complexity of the underlying microbial production and consumption processes and the links to biotic (e.g. inter- and intraspecies competition, food webs, plant–microbe interaction) and abiotic (e.g. soil climate, physics and chemistry) factors. Recent work shows that a better understanding of the composition and diversity of the microbial community across a variety of soils in different climates and under different land use, as well as plant–microbe interactions in the rhizosphere, may provide a key to better understand the variability of N2O fluxes at the soil–atmosphere interface. Moreover, recent insights into the regulation of the reduction of N2O to dinitrogen (N2) have increased our understanding of N2O exchange. This improved process understanding, building on the increased use of isotope tracing techniques and metagenomics, needs to go along with improvements in measurement techniques for N2O (and N2) emission in order to obtain robust field and laboratory datasets for different ecosystem types. Advances in both fields are currently used to improve process descriptions in biogeochemical models, which may eventually be used not only to test our current process understanding from the microsite to the field level, but also used as tools for up-scaling emissions to landscapes and regions and to explore feedbacks of soil N2O emissions to changes in environmental conditions, land management and land use.

1,871 citations

Journal ArticleDOI
TL;DR: The basic concepts of the composting process and how manure characteristics can influence its performance are explained and a summary of those factors such as nitrogen losses, organic matter humification and compost maturity which affect the quality of composts produced by manure composting is presented.

1,795 citations

Journal ArticleDOI
TL;DR: The effects of lime, fertilizer and manure applications on soil organic matter status and soil physical properties are of importance to agricultural sustainability as mentioned in this paper, and there is a need to study these relationships on existing long-term liming trials.
Abstract: The effects of lime, fertilizer and manure applications on soil organic matter status and soil physical properties are of importance to agricultural sustainability. Their effects are complex and many interactions can occur. In the short-term, liming can result in dispersion of clay colloids and formation of surface crusts. As pH is increased the surface negative charge on clay colloids increases and repulsive forces between particles dominate. However, at higher lime rates, Ca2+ concentrations and ionic strength in soil solution increase causing compression of the electrical double layer and renewed flocculation. When present in sufficient quantities, both lime and hydroxy-Al polymers formed by precipitation of exchangeable Al, can act as cementing agents bonding soil particles together and improving soil structure. Liming often causes a temporary flush of soil microbial activity but the effect of this on soil aggregation is unclear. It is suggested that, in the long-term, liming will increase crop yields, organic matter returns, soil organic matter content and thus soil aggregation. There is a need to study these relationships on existing long-term liming trials. Fertilizers are applied to soils in order to maintain or improve crop yields. In the long-term, increased crop yields and organic matter returns with regular fertilizer applications result in a higher soil organic matter content and biological activity being attained than where no fertilizers are applied. As a result, long-term fertilizer applications have been reported, in a number of cases, to cause increases in water stable aggregation, porosity, infiltration capacity and hydraulic conductivity and decreases in bulk density. Fertilizer additions can also have physico-chemical effects which influence soil aggregation. Phosphatic fertilizers and phosphoric acid can favour aggregation by the formation of Al or Ca phosphate binding agents whilst where fertilizer NH4 + accumulates in the soil at high concentrations, dispersion of clay colloids can be favoured. Additions of organic manures result in increased soil organic matter content. Many reports have shown that this results in increased water holding capacity, porosity, infiltration capacity, hydraulic conductivity and water stable aggregation and decreased bulk density and surface crusting. Problems associated with large applications of manure include dispersion caused by accumulated K+, Na+ and NH4 + in the soil and production of water-repellant substances by decomposer fungi.

1,278 citations