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Chapter 20 - Effect of biochar on the emission of greenhouse gas in farmland

Maize ethanol feedstock production and net energy value as affected by climate variability and crop management practices

This review paper synthesizes the current understanding of greenhouse gas (GHG) emissions from field cropping systems. It examines the key factors influencing GHG emissions, including crop type, management practices, and soil conditions. The review highlights the variability in GHG emissions across different cropping systems. Conventional tillage systems generally emit higher levels of carbon dioxide (CO2) and nitrous oxide (N2O) than no-till or reduced tillage systems. Crop rotation, cover cropping, and residue management can significantly reduce GHG emissions by improving soil carbon sequestration and reducing nitrogen fertilizer requirements. The paper also discusses the challenges and opportunities for mitigating GHG emissions in field cropping systems. Precision agriculture techniques, such as variable rate application of fertilizers and water, can optimize crop production while minimizing environmental impacts. Agroforestry systems, which integrate trees and crops, offer the potential for carbon sequestration and reducing N2O emissions. This review provides insights into the latest research on GHG emissions from field cropping systems and identifies areas for further study. It emphasizes the importance of adopting sustainable management practices to reduce GHG emissions and enhance the environmental sustainability of agricultural systems.

Cover crops are increasingly promoted as a management strategy to enhance soil carbon (C) stocks and soil health, but their effects on greenhouse gas (GHG) emissions remain uncertain, particularly in flooded rice systems where anaerobic conditions prevail. In these systems, organic inputs such as green manures have been widely reported to stimulate methane (CH₄) emissions, raising concerns about their net climate impact.Here, we evaluated the impacts of contrasting rice rotational strategies, i.e., winter fallow, hairy vetch (Vicia villosa Roth), and Italian ryegrass (Lolium multiflorum Lam.), on soil health, C dynamics, and GHG emissions in a Mediterranean rice system located in the Ebro Delta (NE Spain). The field experiment was established in 2021, and the results presented here cover the period from February 2024 to October 2025.Soil biological health was assessed by integrating weekly measurements of CH₄ and nitrous oxide (N₂O) emissions with microbial biomass C and nitrogen (N) and litter decomposition of cover crop shoots and roots assessed at key stages of the rice growing cycle. These indicators were complemented by measurements of soil organic carbon (SOC) stocks and soil aggregation to evaluate links between biological activity, soil structure, and C storage. Ongoing analyses of microbial necromass and SOC fractionation into particulate and mineral-associated pools will provide further mechanistic insight into C stabilization processes under different cover crop strategies.Cover crop identity strongly influenced biogeochemical dynamics. CH₄ emissions peaked under vetch during the flooded cultivation phase, whereas no significant treatment effects were detected for N₂O emissions, despite a tendency towards lower emissions under vetch. Consequently, no net differences in global warming potential were observed among treatments. Shoot litter decomposition was significantly slower for vetch than for ryegrass, a pattern not mirrored in roots, and consistent with differences in residue lignin content. However, rapid mass loss occurred for both residue types under anaerobic conditions, suggesting an important role of solubilization processes. SOC stocks did not differ among treatments in the most superficial soil layer, but ryegrass was associated with significantly lower stocks in the 10–30 cm soil layer. Cover cropping tended to promote macroaggregate formation, suggesting potential improvements in soil structure and physical protection of organic matter. Microbial biomass C and N were marginally higher under vetch in autumn, indicating enhanced soil biological activity. At the agronomic level, rice grain yield showed a marginal increase under vetch.Overall, our results suggest that vetch represents a promising cover crop option in Mediterranean rice paddies, enhancing soil biological functioning and rice productivity while not leading to clear increases in total GHG emissions. AcknowledgementsThis study was funded by The Government of Catalonia through the projects AgriCarboniCat and Carboni al Sòl.

<p>Cover crop mixtures of legumes and non-legumes have multiple advantages compared to bare soil like reducing erosion by covering the soil, fixing nitrogen from the air and reducing nitrate leaching, adding organic matter to the soil, increasing soil biological activity and improving soil structure. The advantages and disadvantages of a winter-hardy vs. a freeze-killed cover crop (CC) mixture were studied on an organic farm in Raipoltenbach in Lower Austria (10.5 °C, 760 mm) with non-inverting soil cultivation since 2008. Effects on soil inorganic nitrogen contents and the yield of a following maize crop were assessed. On an orthic Luvisol with a silty clay to silty loam texture, two field experiments (FE1 and FE2) were laid out in a randomized complete block design in four replicates in two consecutive years. The winter-hardy CC mixture was “Landsberger Gemenge” consisting of winter vetch, crimson clover and Italian ryegrass. The freeze-killed CC mixture consisted of fodder pea, common vetch, chickling vetch, buckwheat, phacelia and fodder radish. The winter-hardy catch crop mixture was terminated with a rotary cultivator and the freeze-killed CC was worked into the soil with a chisel on 4 April 2017 / 19 April 2018. After chiseling the soil (only in FE1), maize, cv “Connexxion RZ 340”, was sown on 4 May 2017 / 7 May 2018. In both treatments, soil was harrowed once in May and hoed twice in June. Soil inorganic nitrogen (N<sub>in</sub>) was analysed in 0.0125 M CaCl<sub>2</sub> extracts. The winter-hardy CC had a biomass of 2.8 t ha<sup>-1</sup> on average when terminated in April, the freeze-killed CC reached on average 3.1 t ha<sup>-1</sup> in November. The N<sub>in</sub> values in 0-90 cm soil depth in spring (2017 FE1 / 2018 FE2) were almost doubled in the freeze-killed CC treatment compared to the winter-hardy CC treatment. The winter-hardy CC mixture in took up soil nitrogen until termination in April, thus reducing N<sub>in</sub> contents after winter and the risk of nitrate leaching during winter, saving nitrogen for the following main crop. An assessment in June (FE1) and May (FE2) showed no differences in the number of maize plants per m<sup>2</sup>. Maize grain dry matter yield was 7.8 t ha<sup>-1</sup> in FE1 and 7.0 t ha<sup>-1</sup> in FE2 on average and did not differ between treatments. Also maize nitrogen yield did not differ. Sowing maize without inverting soil cultivation was more difficult in the winter-hardy CC treatment than in the treatment where the CC mixture was freeze-killed. But mainly due to the effective CC termination with the rotary cultivator, weed density was not higher in this treatment (except for one assessment date in July 2018 in FE2). In our study, both freeze-killed and winter-hardy CC mixtures consisted of a legume-dominated legume-non-legume mixture. This resulted in a narrow C-to-N ratio (10 to 13) in the CC biomass as a basis for a swift N mineralization from the CC residues in both treatments. Accordingly, maize grain DM yield and maize grain N yield did not differ between the CC treatments.</p>

No-tillage with mulching improves maize yield in dryland farming through regulating soil temperature, water and nitrate-N

Deep rooted apple trees decrease groundwater recharge in the highland region of the Loess Plateau, China

The response of broadacre mixed crop-livestock farmers to agricultural greenhouse gas abatement incentives

Benefits of biochar, compost and biochar–compost for soil quality, maize yield and greenhouse gas emissions in a tropical agricultural soil

Summary Corn‐ethanol production is expanding rapidly with the adoption of improved technologies to increase energy efficiency and profitability in crop production, ethanol conversion, and coproduct use. Life cycle assessment can evaluate the impact of these changes on environmental performance metrics. To this end, we analyzed the life cycles of corn‐ethanol systems accounting for the majority of U.S. capacity to estimate greenhouse gas (GHG) emissions and energy efficiencies on the basis of updated values for crop management and yields, biorefinery operation, and coproduct utilization. Direct‐effect GHG emissions were estimated to be equivalent to a 48% to 59% reduction compared to gasoline, a twofold to threefold greater reduction than reported in previous studies. Ethanol‐to‐petroleum output/input ratios ranged from 10:1 to 13:1 but could be increased to 19:1 if farmers adopted high‐yield progressive crop and soil management practices. An advanced closed‐loop biorefinery with anaerobic digestion reduced GHG emissions by 67% and increased the net energy ratio to 2.2, from 1.5 to 1.8 for the most common systems. Such improved technologies have the potential to move corn‐ethanol closer to the hypothetical performance of cellulosic biofuels. Likewise, the larger GHG reductions estimated in this study allow a greater buffer for inclusion of indirect‐effect land‐use change emissions while still meeting regulatory GHG reduction targets. These results suggest that corn‐ethanol systems have substantially greater potential to mitigate GHG emissions and reduce dependence on imported petroleum for transportation fuels than reported previously.

Under European and International policies, organic soil amendments are highly promoted as a cost-efficient solution to improve soil C, quality, and agrosystem sustainability. Inorganic N application is an essential agronomic practice to increase and secure crop yields, however, its long-term application has led to serious environmental problems including deterioration of soil organic C, enhanced greenhouse gas emissions, and an overall decline in environmental quality. Consequently, the co-application of organic and inorganic fertilizers is advocated as a more effective and environmentally friendly fertilization regime. This study aims, to decipher the short-term N kinetics in agricultural soils amended with organic, inorganic, and a combined application of N fertilizer, with and without biochar, and to assess the trade-off balance of soil C and greenhouse gas emissions. Therefore, we investigated the short-term (90 d) soil N dynamics of sandy soil mesocosms (2 Kg) receiving municipal sewage sludge (MSS) amendments (50 t/ha), urea-N fertilization (U; 200 kg/ha), a combined application (MSS+U), without and with biochar (1.5% w/w). An unamended soil mesocosm was included as a control. The addition of urea-N (U), municipal sewage sludge (MSS), and their combined application (MSS+U) increased the availability of soil NH4+ by 3x, 5x and 12x times, relative to the control, respectively. Interestingly, we observed a tremendous release of soil NO2- only in the urea treatment (U; 128 mg kg-1), and not in the other remaining treatments. Throughout the incubation approx. 12.7x, 13.4x, and 19.7x more soil NO3- was observed for the U, MSS, and MSS+U treatment, relative to the control, respectively. Where biochar was applied, an approx. 40% reduction in soil available NO2- andNO3- was observed. Considering the gaseous emissions of CO2 and N2O, that are generally products of soil respiration, nitrification, and denitrification, the addition of MSS and its co-application (MSS+U), enhanced soil CO2 by 2.4x and 2.4x, and by 13.6x and 16.9x for soil N2O emissions, respectively. Though biochar addition reduced cumulative CO2 emissions by 24%, for all treatments except the control. Although biochar addition decreased cumulative N2O emission by 65% in the U, it had no effect on cumulative N2O emission for MSS and the combined treatment (MSS+U). Fertilization by U did not affect much soil CO2 (526 mg CO2-C kg-1) and N2O (1258 μg N2O-N kg-1) emissions when compared to the unamended soil treatment (C). The MSS+U reduced the N2O emission factor, by 5x when compared to MSS treatment, however, it was well above the IPPC emission factor of 1%. Municipal sewage sludge is a source of C, though we observed that MSS (74%) and the combined treatment (MSS+U, 96%) enhanced the CO2-equivalent emissions, indicating a complete loss of the added organic C through greenhouse gas emissions. Considering our key question, whether co-application of inorganic, and organic fertilizer with biochar is a double-edged sword, we conclude that co-application should be carefully evaluated case per case, as it affects several key soil parameters differently, and therefore we should seek new ways to minimize gaseous losses thus to improve sustainability in agrosystems.

A modeling analysis of runoff and ground-water recharge for the arid and semiarid southwestern United States was performed to investigate the interactions of climate and other controlling factors and to place the eight study-site investigations into a regional context. A distributed-parameter water-balance model (the Basin Characterization Model, or BCM) was used in the analysis. Data requirements of the BCM included digital representations of topography, soils, geology, and vegetation, together with monthly time-series of precipitation and airtemperature data. Time-series of potential evapotranspiration were generated by using a submodel for solar radiation, taking into account topographic shading, cloudiness, and vegetation density. Snowpack accumulation and melting were modeled using precipitation and air-temperature data. Amounts of water available for runoff and ground-water recharge were calculated on the basis of water-budget considerations by using measured-and generated-meteorologic time series together with estimates of soil-water storage and saturated hydraulic conductivity of subsoil geologic units. Calculations were made on a computational grid with a horizontal resolution of about 270 meters for the entire 1,033,840 square-kilometer study area. The modeling analysis was composed of 194 basins, including the eight basins containing ground-water recharge-site investigations. For each grid cell, the BCM computed monthly values of potential evapotranspiration, soil-water storage, in-place ground-water recharge, and runoff (potential stream flow). A fixed percentage of runoff was assumed to become recharge beneath channels operating at a finer resolution than the computational grid of the BCM. Monthly precipitation and temperature data from 1941 to 2004 were used to explore climatic variability in runoff and ground-water recharge.

Agronomy JournalVolume 48, Issue 8 p. 379-381 Note Influence of Half-height Sieves and of Incomplete Sieve Nests on Wet Sieve Aggregate Analyses1 R. W. Wengel, R. W. Wengel University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this authorD. S. McIntyre, D. S. McIntyre University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this authorC. B. Tanner, C. B. Tanner Associate Professor of Soils University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this author R. W. Wengel, R. W. Wengel University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this authorD. S. McIntyre, D. S. McIntyre University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this authorC. B. Tanner, C. B. Tanner Associate Professor of Soils University of Wisconsin. The authors are indebted to J. H. Torrie, Professor of Agronomy, for his advice on statistical procedure and interpretation.Search for more papers by this author First published: 01 August 1956 https://doi.org/10.2134/agronj1956.00021962004800080013x 1 Contribution from the Department of Soils, University of Wisconsin, Madison, Wis. Published with the permission of the Director of Wisconsin Agr. Exp. Sta. This work was supported in part by Regional Cooperative Research Project NC-17, entitled “The Value of organic matter and of various soil and crop management practices in improving soil structure and other factors affecting productivity.”. AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume48, Issue8August 1956Pages 379-381 RelatedInformation

We compared 4 tillage practices (traditional, stubble mulch, reduced, no tillage) during 10 years under rainfed conditions on an alluvial soil in the semi-arid subtropics of central Queensland. In the final 4 years, responses to applied fertiliser nitrogen (N), sulfur (S), and zinc (Zn) were determined. We measured soil water storage, soil nitrate accumulation, grain yield (sorghum, wheat), grain protein content, and populations of soil macrofauna, with the aim of identifying soil-conserving practices that also produce high yields of high quality grain. Stubble mulch, reduced tillage, and no tillage all outyielded traditional tillage when soil fertility was adequate. With applied N, S, and Zn, the mean wheat yields from traditional, stubble mulch, reduced, and no tillage were 2.44, 3.32, 3.46, and 3.64 t/ha, respectively. The yield responses to tillage practices were due to increases in storage of soil water or efficiency of crop water use or both. Populations of soil macrofauna averaged (per m2) 19 (traditional tillage), 21 (stubble mulch), 33 (reduced tillage), and 44 (no tillage). The effect of the tillage practices on soil animal populations may be a factor contributing to the measured differences in soil water storage and water use efficiency. We conclude that conservation tillage practices can greatly increase grain yields, provided crop and fallow management practices are appropriate. Potential yield advantages are realised if crop establishment, crop nutrition; and control of weeds, bests, and diseases ark adequate.

Agricultural soils are the primary source of nitrous oxide (N2O) emissions into the atmosphere, contributing 78% of total N2O emissions. These emissions are influenced by different tillage practices and types of plant cover that are left after harvest. Cover crops (CC) are widely used in agriculture to take up excess nitrogen from the fields, thereby reducing nitrate leaching and increasing soil carbon accrual. However, despite these benefits, agricultural soils containing cover crops have often resulted in high N2O emissions.A two-year field study with measurement of N2O emissions was conducted in Denmark using a long-term conservation agriculture experiment, including cover cropping, no tillage and crop rotation. The study focused on the influence of soil tillage and cover cropping on soil physical properties and N2O emissions. The tillage systems included no tillage (direct seeding) and conventional ploughing; CC management included paired subplots with oil-seed radish (Raphanus sativus L.), where (i) the cover crop residues were terminated and removed in autumn (CC-rem), and (ii) the cover crop residues were killed by the frost and left in the field (CC-left). Bare soil treatment (i.e., without CC) is included as a reference. Spring oats (Avena sativa L.) grew as the main crop during the first year followed by spring barley (Hordeum vulgare L.) in the second year.The first-year results for N2O fluxes showed that there were no significant differences in N2O emissions between the tillage practices. However, emissions varied significantly among CC treatments. Compared to the reference without CC, peak emissions (up to 74 µg N2O-N m-2 h-1) were observed for both cover crop treatments. During the cropping season, most of the emissions occurred after fertilization. Especially, +CC-left emitted more N2O than CC-rem during the main cropping season. Before establishing the main crop, CC-rem emitted more N2O than CC-left. Volume-effective porosity, air permeability, bulk density and gas diffusivity are critical soil physical properties that influenced N2O emissions among the cover crop treatments.