Organic amendment additions to rangelands: A meta-analysis of multiple ecosystem outcomes

Multiple targeted grassland restoration interventions enhance ecosystem service multifunctionality

The need to combat widespread degradation of grassland ecosystem services makes grassland restoration a global sustainability priority. However, simultaneously enhancing multiple ecosystem services (i.e. ecosystem service multifunctionality) is a major challenge for grassland restoration due to trade-offs among services. We use a long-term multifactor grassland restoration experiment established in 1989 on agriculturally improved, species-poor grassland in northern England, to assess how increasing the number of restoration treatments, including addition of manure, inorganic fertiliser, a seed mixture, and promotion of a nitrogen-fixing legume (Trifolium pratense), affects ecosystem service multifunctionality, based on 26 ecosystem service indicators measured between 2011 and 2014. We find that single interventions usually lead to trade-offs among services and thus have few positive effects on ecosystem service multifunctionality. However, ecosystem service multifunctionality increases with the number of restoration interventions, as trade-offs are reduced. Our findings highlight the significant potential for combined use of multiple targeted interventions to aid the restoration of ecosystem service multifunctionality in degraded grasslands, and potentially, other ecosystems.

Dung predicts the global distribution of herbivore grazing pressure in drylands

Dryland grazing sustains millions of people worldwide but, when poorly managed, threatens food security. Here we combine livestock and wild herbivore dung mass data from surveys at 760 dryland sites worldwide, representing independent measurements of herbivory, to generate high-resolution maps. We show that livestock and wild herbivore grazing is globally disconnected, and identify hotspots of herbivore activity across Africa, the Eurasian grasslands, India, Australia and the United States. Wild herbivore dung mass was negatively correlated with total organic nitrogen, yet strong site-level correlations exist between our livestock dung estimates and total soil organic nitrogen. Using dung mass as a proxy of herbivore abundance enables standardized, field-based measures of grazing pressure that account for different herbivore types. This can improve herbivore density modelling and guide better management practices for populations that rely on dryland-grazing livestock for food.

Soil moisture determines effects of climates and soil properties on nitrogen cycling: Examination of arid and humid soils

While soil moisture has a significant effect on nitrogen (N) cycling, how it influences the dependence of this important biological process on environmental factors is unknown. Specifically, it is unclear how the relationships of net N mineralization (Nm) and soil moisture vary with soil properties and climates. In turn, how the relationships of Nm vs. soil properties and climates vary with soil moisture is also unknown. Therefore, soil samples from the 26 sites were collected within two climatic regions (i.e., arid and humid) across China. Then a four-week microcosmic incubation experiment was conducted at five soil moisture levels (20, 40, 60, 80, and 100% field water holding capacity (FWHC)) at 25 °C to measure the dynamics of Nm. The results showed that increasing soil moisture significantly increased Nm (+212%) and the N mineralization rate constant (k) (+0.26%), and that the effects of soil moisture were greater in humid soils (+250%) than arid soils (+178%). The slopes of the relationship between Nm vs. soil moisture increased with soil organic carbon (SOC) (+50.6%) and total N (TN) (+65.3%) concentrations, and decreased with pH (-43.0%) and clay content (-0.09%), especially in arid regions. Additionally, Nm was significantly correlated with soil properties and mean annual precipitation (MAP), and the slopes of most of these relationships increased with soil moisture in arid soils (+59.2-3805%), but decreased in humid soils (-1.96-140%). The results indicated that increasing soil moisture strengthened the dependence of Nm on soil properties and climates in arid soils, and that increasing soil pH and clay content reduced, but SOC and TN concentrations enhanced the dependence of Nm on soil moisture. Therefore, with changes in rainfall distribution patterns and an increase in extreme rainfall events, there is enormous potential for Nm in agricultural soils in arid regions, which is regulated by soil moisture and properties. On the contrary, in humid regions, the decoupling of the effects of soil moisture and soil properties on N mineralization could be due to microbial adaptation. Moreover, the coupled effects of soil environment and properties on N cycling in different climatic regions merit great consideration in experimental research as well as in biogeochemical model development and prediction.

The application of shrub willow chip organic amendments impacts soil microbial community dynamics

Incorporating shrub willow chips into soil may improve the chemical, physical, and biological properties of soils with low organic matter but the impact on soil microbial communities and their dynamics is not known. We assessed changes in the soil microbial communities in response to willow chip applied at increasing rates (0, 20, 40, and 60 Mg ha-1) in a potato-barley cropping system. Bacterial and fungal community diversity, relative abundance, and potential functions were assessed using amplicon sequencing of 16S and ITS rRNA genes at six time points. High rates (40 and 60 Mg ha-1) of willow chips had no effect on bacterial alpha diversity but significantly decreased fungal alpha diversity (Shannon) while increasing fungal richness (Chao-1). At rates of 40 Mg ha-1 and higher, the relative abundance of copiotrophic bacterial groups increased, while that of copiotrophic fungal groups decreased. The relative abundance of the most dominant microbial phyla and genera varied over time, with copiotrophic groups declining and oligotrophic groups increasing. High willow chip application rates increased bacterial molecular markers related to carbon fixation and degradation, nitrogen fixation, and phosphorus solubilization, while decreasing markers related to cellobiose transport and denitrification. This study demonstrates the ability of willow chips to influence the microbial community composition and potential function over time.

Impact of nature-based solutions on sustainable development goals in Mediterranean agroecosystems: A meta-analysis

Mediterranean agroecosystems' vulnerability to hydroclimatic extremes threatens their resilience and sustainability. Nature-based Solutions present a sustainable strategy to address global challenges. This meta-analysis of 70 studies developed in Mediterranean climates identified solutions to improve soil health and water quality in agroecosystems by estimating their effects on soil organic matter, organic carbon, water, erosion, and Kjeldahl nitrogen, total nitrogen, nitrate, total phosphorus, phosphate, and suspended solids, respectively. Using meta-regression, we analysed how the interaction with biophysical conditions (e.g., soil texture and irrigation practices for soil health and macrophyte species and temperature for water quality) drives the effects of Nature-based Solutions. The results indicate that these solutions can improve soil health and water quality, supporting the achievement of land and water Sustainable Development Goals. Among all the options considered for rehabilitating land ecosystems, afforestation led to significant increases in soil organic carbon up to 137%. Of all tillage practices tested, eliminating soil disturbance combined with using cover crops and mulching revealed the potential to counteract agricultural land degradation, showing significant reductions in erosion as high as 98%. The individual application of organic inputs showed the potential to reverse ongoing agricultural soil degradation trends. Applying olive mill wastewater was associated with a significant increase of 249\% in soil organic matter. However, applying manure compost in no-tilled plots with herbaceous cover reduced the soil water content at field capacity by 46\%.Constructed wetlands have shown the most significant results in improving water quality by reducing pollutants and contributing to protecting and restoring aquatic ecosystems. Polycultural systems with horizontal subsurface flow reduced Kjeldahl nitrogen by 9%, nitrates and phosphorus by 3%, and total suspended solids by 10%. However, in continuous aerated systems, nitrate levels increased by 36%. The reduction in total nitrogen in subsurface vertical flow systems was 11%, while surface flow wetlands with two macrophyte species reduced total suspended solids by 6%. Implementing Nature-based Solutions in Mediterranean agroecosystems depended on biophysical conditions, highlighting the need for site-specific adaptation based on local conditions and objectives. In a global change scenario, mainstreaming these solutions as sustainable land and water management practices is vital for enhancing the resilience and sustainability of Mediterranean agroecosystems, providing ecosystem services beyond soil health and water quality, including climate change mitigation, biodiversity protection and human well-being.

Climate mitigation potential of natural climate solutions and clean energy on The Nature Conservancy properties in California, USA

Natural climate solutions (NCS) and transitioning to clean energy can reduce greenhouse gases and contribute to mitigating climate change. Private landowners with large holdings, such as conservation organizations like The Nature Conservancy, have set ambitious goals to reduce net emissions and increase sequestration on their lands by implementing NCS. We assessed the potential carbon dioxide-equivalent (CO2e) reduction from feasible NCS, specifically implementing new restoration and agricultural management activities, and transitions to clean energy on The Nature Conservancy, California chapter's fee-owned and conservation easement properties. We compared the total CO2e reduction from potential new NCS activities to the impact from ongoing NCS activities, the chapter's 2030 goal, and the state's reduction goal for natural and working lands to understand how the organization can contribute to climate mitigation. We found that implementing NCS on 37 fee-owned properties (63,175 MTCO2e year -1) and clean energy on 10 fee-owned properties (488 MTCO2e year -1) combined would not reach the chapter's 2030 goal (72,000 MTCO2e year -1), and there can be tradeoffs between maximizing CO2e reduction and protecting conservation values. However, ongoing changes to forest management on a single conservation easement property, where another non-profit harvests timber and sells carbon credits, currently contributes 147,749 MTCO2e year -1, more than two times the 2030 goal and representing 7.4% of the state's annual goal. Our results suggest that The Nature Conservancy, California chapter would need to implement NCS on some of the conservation easements or consider future land protection deals with carbon rich ecosystems or high impact NCS to reach their CO2e reduction goal.

Emerging technology effects on combined agricultural and eco-vermicompost

This study focused on the waste management of livestock manure and wetland plant residues and their increasing effect on terrestrial and aquatic ecosystems. The benefits of nutrient-rich plants and manures are often overlooked. By conducting a soil column experiment with a fully factorial design, this work found that adding the vermicompost amendments of wetland plants [combination of Canna indica (CiV), Cyperus alternifollius (CaV), Acorus calamus (AcV), and Hydrocotyle vulgaris (HvV) vermicompost] to agricultural wastes affected maize growth throughout its growing season. The results demonstrated that the use of combined AcV and HvV wetland plant-based vermicompost as an organic fertilizer increased the plant total nitrogen (TN: 92% increase) and soil organic matter (SOM: 192% increase) compared with those in control CK. Meanwhile, the combination of CaV with HvV increased the shoot biomass by 3.4 and 4.6 folds compared with that in NPK and CK, respectively. Overall, a new approach for transforming ecological wastes into organic fertilizers was proposed.

Decarbonization of Agriculture: The Greenhouse Gas Impacts and Economics of Existing and Emerging Climate-Smart Practices

The worldwide emphasis on reducing greenhouse gas (GHG) emissions has increased focus on the potential to mitigate emissions through climate-smart agricultural practices, including regenerative, digital, and controlled environment farming systems. The effectiveness of these solutions largely depends on their ability to address environmental concerns, generate economic returns, and meet supply chain needs. In this Review, we summarize the state of knowledge on the GHG impacts and profitability of these three existing and emerging farming systems. Although we find potential for CO2 mitigation in all three approaches (depending on site-specific and climatic factors), we point to the greater level of research covering the efficacy of regenerative and digital agriculture in tackling non-CO2 emissions (i.e., N2O and CH4), which account for the majority of agriculture's GHG footprint. Despite this greater research coverage, we still find significant methodological and data limitations in accounting for the major GHG fluxes of these practices, especially the lifetime CH4 footprint of more nascent climate-smart regenerative agriculture practices. Across the approaches explored, uncertainties remain about the overall efficacy and persistence of mitigation-particularly with respect to the offsetting of soil carbon sequestration gains by N2O emissions and the lifecycle emissions of controlled environment agriculture systems compared to traditional systems. We find that the economic feasibility of these practices is also system-specific, although regenerative agriculture is generally the most accessible climate-smart approach. Robust incentives (including carbon credit considerations), investments, and policy changes would make these practices more financially accessible to farmers.

Positive Effects of Organic Amendments on Soil Microbes and Their Functionality in Agro-Ecosystems

Soil microbial characteristics are considered to be an index for soil quality evaluation. It is generally believed that organic amendments replacing chemical fertilizers have positive effects on changing microbial activity and community structure. However, their effects on different agro-ecosystems on a global scale and their differences in different environmental conditions and experimental durations are unclear. This study performed a meta-analysis based on 94 studies with 204 observations to evaluate the overall effects and their differences in different experimental conditions and duration. The results indicated that compared to chemical fertilizer, organic amendments significantly increased total microbial biomass, bacterial biomass, fungal biomass, Gram-positive bacterial biomass and Gram-negative bacterial biomass, and had no effect on the ratio of fungi to bacteria and ratio of Gram-positive bacteria to Gram-negative bacteria. Meanwhile, land use type, mean annual precipitation and soil initial pH are essential factors affecting microbial activity response. Organic-amendment-induced shifts in microbial biomass can be predominantly explained by soil C and nutrient availability changes. Additionally, we observed positive relationships between microbial functionality and microbial biomass, suggesting that organic-amendment-induced changes in microbial activities improved soil microbial functionality.

Co-application of biochar and organic amendments on soil greenhouse gas emissions: A meta-analysis

Biochar has been shown to reduce soil greenhouse gas (GHG) and increase nutrient retention in soil; however, the interaction between biochar and organic amendments on GHG emissions remain largely unclear. In this study, we collected 162 two-factor observations to explore how biochar and organic amendments jointly affect soil GHG emissions. Our results showed that biochar addition significantly increased soil CO2 emission by 8.62 %, but reduced CH4 and N2O emissions by 27.0 % and 23.9 %, respectively. Meanwhile, organic amendments and the co-application with biochar resulted in an increase of global warming potential based on the 100-year time horizon (GWP100) by an average of 18.3 % and 26.1 %. More importantly, the interactive effect of biochar and organic amendments on CO2 emission was antagonistic (the combined effect was weaker than the sum of their individual effects), while additive on CH4 and N2O emissions. Additionally, our results suggested that when biochar is co-applied with organic amendments, soil GHG emissions were largely influenced by soil initial total carbon, soil texture, and biochar feedstocks. Our work highlights the important interactive effects of biochar and organic amendments on soil GHG emissions, and provides new insights for promoting ecosystem sustainability as well as mitigating future climate change.

A systematic review on whether regenerative agriculture improves animal welfare: A qualitative analysis with a One Welfare perspective

The welfare of animals in food-production systems is a cause of concern to the public. Regenerative agriculture was first used by the Rodale Institute and proposes to regenerate degraded components of ecosystems, aiming to be more than just sustainable. However, despite animal welfare being pushed to be part of the SDG agenda for 2030, there is no clarity on how regenerative agriculture impacts animal welfare. It is challenging to determine regenerative agriculture impacts on animal welfare, since it is not entirely defined. One Welfare could help define entry points for future research by studying animal welfare in connection with human welfare and environmental conservation. We aimed to analyse the extent to which positive animal welfare outcomes characterise regenerative agriculture systems in peer-reviewed articles and whether the narratives of such articles support that regenerative agriculture promotes animal welfare directly or indirectly by improving human welfare and environmental conservation. We searched papers including 'regenerative agriculture' using PRISMA-P, selecting animal welfare, human welfare, environment conservation terms, developed themes, and carried out analysis using Atlas.Ti8 and Causal Loop Diagram. We found that papers mainly linked animal welfare to animal health, human welfare to financial farm status and farmer's self-awareness, and environmental conservation to soil improvement. Causal Loop Diagram indicated that regenerative agriculture had the potential to improve the health and nutrition components of animal welfare by enhancing financial farmers' status/self-awareness (human welfare), and the soil (environmental conservation), reflecting that the processes that affect human welfare and environmental conservation could also affect animal welfare. However, information in papers remains insufficient to determine how regenerative agriculture impacts on animal welfare and research into regenerative agriculture needs to extend its focus on animal welfare and elucidate the regenerative agriculture principles leading to animal welfare.

Effects of the Ratio of Substituting Mineral Fertilizers with Manure Nitrogen on Soil Properties and Vegetable Yields in China: A Meta-Analysis

Substituting mineral fertilizers (MFs) with manure nitrogen (N) can not only reduce environmental pollution, but also improve soil quality. However, the effects of various manure N substitution ratios (SRs, the ratio of manure N over total N applied) on soil properties and vegetable yields in China are poorly studied. Here, through a meta-analysis of 667 observations, we assessed the effects of three manure N SRs (low (SR ≤ 35%), medium (35% < SR ≤ 70%), and high (SR > 70%)) on vegetable yields and soil properties (soil organic carbon, SOC; soil total nitrogen, STN; microbial biomass carbon (C) and nitrogen (N), MBC/N; and available phosphorus and potassium, (AP/AK)) in the 0-20 cm soil under different climatic conditions, initial soil properties, and management practices. The results show that the SOC and STN contents increased by 28.5% and 21.9%, respectively, under the medium SRs compared to the MF, which were the highest among the three SRs. Both soil MBC and MBN increased with the increase in the SRs, and the increased ratios in the high SRs reached 203.4% and 119.3%, respectively. In addition, the AP also increased with the increase in the SR, but the AK was not significantly changed with the low and medium SRs compared with the MF. Overall, the medium SR produced the highest vegetable yield among the three SRs with an increase of 18.6%. Additionally, a random forest analysis indicated that the N application rate, planting years, and mean annual precipitation were the most important factors influencing vegetable yield. In conclusion, the SR of 35-70% is more conducive to increasing soil nutrient contents significantly and improves vegetable yields in Chinese vegetable fields.

Impacts of vermicompost application on crop yield, ammonia volatilization and greenhouse gases emission on upland in Southwest China

Ammonia (NH₃) volatilization and greenhouse gas (GHG) emission are important environment pollution sources in upland agro-ecosystems. Vermicompost was used for amending purple soil and comparing NH₃ and GHG emissions. A field experiment was conducted with a comparison of organic and inorganic fertilizers in a wheat-maize rotation system in the Sichuan Basin, China. The five treatments were conventional inorganic fertilizers, NPK as control; vermicompost prepared with cow dung (VCM); and pig manure (VPM); cow dung and pig manure vermicompost, respectively (VCMNPK, VPMNPK). Total nitrogen rates of all treatments were the same. Soil NH₃ volatilization and GHG emissions were monitored with the static chamber method. The results showed that NH₃ volatilization occurred in the first two weeks following nitrogen (N) fertilization. The cumulative fluxes of NH₃ recorded in the NPK, VCM, VPM, VCMNPK, and VPMNPK treatments were 15.4, 5.7, 6.3, 10.32, and 10.29 kg N ha^-1 yr^-1, respectively, in the winter and 4.8, 5.5, 19.83, 12.8, and 11.9 kg N ha^-1 yr^-1 respectively, in the summer. The global warming potential (GWP) 773.6 and 803.9 g CO₂-eq m^-2 in VCM and VPM, respectively, during the wheat season 540.6 and 576.2 g CO₂-eq m^-2, respectively, during the maize season. The GWPs in NPK treatment were 1032.4 and 570.7 g CO₂-eq m^-2 during the wheat and maize seasons, respectively. The increasing effects of nutrient loops, particularly 18 % soil total nitrogen (TN) and 31 % soil organic carbon (SOC) in VCM, and crop productivity of vermicompost treatments during the wheat-maize rotation had been evaluated. This study recommends that VCM can be considered as a better organic amendment, promoting plant growth while decreasing the environmental costs of gas emissions.

The climate change mitigation potential of annual grasslands under future climates

Composted manure and green waste amendments have been shown to increase net carbon (C) sequestration in rangeland soils and have been proposed as a means to help lower atmospheric CO₂ concentrations. However, the effect of climate change on soil organic C (SOC) stocks and greenhouse gas emissions in rangelands is not well understood, and the viability of climate change mitigation strategies under future conditions is even less certain. We used a process-based biogeochemical model (DayCent) at a daily time step to explore the long-term effects of potential future climate changes on C and greenhouse gas dynamics in annual grassland ecosystems. We then used the model to explore how the same ecosystems might respond to climate change following compost amendments to soils and determined the long-term viability of net SOC sequestration under changing climates. We simulated net primary productivity (NPP), SOC, and greenhouse gas fluxes across seven California annual grasslands with and without compost amendments. We drove the DayCent simulations with field data and with site-specific daily climate data from two Earth system models (CanESM2 and HadGEM-ES) and two representative concentration pathways (RCP4.5 and RCP8.5) through 2100. NPP and SOC stocks in unamended and amended ecosystems were surprisingly insensitive to projected climate changes. A one-time amendment of compost to rangeland acted as a slow-release organic fertilizer and increased NPP by up to 390-814 kg C ha^-1  year^-1 across sites. The amendment effect on NPP was not sensitive to Earth system model or emissions scenario and endured through the end of the century. Net SOC sequestration amounted to 1.96 ± 0.02 Mg C ha^-1 relative to unamended soils at the maximum amendment effect. Averaged across sites and scenarios, SOC sequestration peaked 22 ± 1 years after amendment and declined but remained positive throughout the century. Though compost stimulated nitrous oxide (N₂ O) emissions, the cumulative net emissions (in CO₂ equivalents) due to compost were far less than the amount of SOC sequestered. Compost amendments resulted in a net climate benefit of 69.6 ± 0.5 Tg CO₂ e 20 ± 1 years after amendment if applied to similar ecosystems across the state, amounting to 39% of California's rangeland. These results suggest that the biogeochemical benefits of a single amendment of compost to rangelands in California are insensitive to climate change and could contribute to decadal-scale climate change mitigation goals alongside emissions reductions.

Grassland soil carbon sequestration: Current understanding, challenges, and solutions

Grasslands store approximately one third of the global terrestrial carbon stocks and can act as an important soil carbon sink. Recent studies show that plant diversity increases soil organic carbon (SOC) storage by elevating carbon inputs to belowground biomass and promoting microbial necromass contribution to SOC storage. Climate change affects grassland SOC storage by modifying the processes of plant carbon inputs and microbial catabolism and anabolism. Improved grazing management and biodiversity restoration can provide low-cost and/or high-carbon-gain options for natural climate solutions in global grasslands. The achievable SOC sequestration potential in global grasslands is 2.3 to 7.3 billion tons of carbon dioxide equivalents per year (CO₂e year^-1) for biodiversity restoration, 148 to 699 megatons of CO₂e year^-1 for improved grazing management, and 147 megatons of CO₂e year^-1 for sown legumes in pasturelands.

Organic amendments enhance soil microbial diversity, microbial functionality and crop yields: A meta-analysis

Fertilization plays an important role in changing soil microbial diversity, which is essential for determining crop yields. Yet, the influence of organic amendments on microbial diversity remains uncertain, and few studies have addressed the relative importance of microbial diversity versus other drivers of crop yields. Here, we synthesize 219 studies worldwide and found that organic amendments significantly increased microbial diversity components (i.e., Shannon, richness, and phylogenetic diversity) and shifted microbial community structure compared to mineral-only fertilization. The performance of microbial alpha diversity varied substantially with organic amendment types, microbial groups and changes in soil pH. Both microbial diversity and community structure exhibited significantly positive relationships with microbial functionality and crop yields. In addition, soil abiotic properties and microbial functionality had a much stronger impact on crop yields than microbial diversity and climate factors. Partial least squares path modeling showed that soil microbial diversity was an important underlying factor driving crop yields via boosting soil microbial functionality. Overall, our findings provide robust evidence for the positive diversity-functions relationships, emphasizing that substituting mineral fertilizers with organic amendments is a promising way to conserve microbial diversity and promote soil microbial functions and crop yields.

Land use change and collaborative manureshed management in New Mexico

Agricultural communities of New Mexico regularly redistribute manure nutrients from dairies to nearby croplands to fulfill agronomic nutrient needs and protect water quality. Yet competition for water resources can result in land use change that affects these cooperative manure transfers. Focusing on three clusters of New Mexico dairy farms and their surrounding lands (three manuresheds), we calculated the magnitude of land use changes in 2008-2019 and the balance between manure nutrient supply and crop demand in 2019 to assess how past change may predict future prospects for sustainable management. The overall magnitude of change was small, with each manureshed experiencing a different complement: an exchange of cropland and rangeland in the Roosevelt manureshed (7,975 ha rangeland to cropland; 7,624 ha cropland to rangeland), a 464-ha gain in cropland but a 1,187-ha loss of "spreadable" land (cropland, rangeland, fallow) to developed land in the Doña Ana manureshed, and relatively minor changes in the Chaves manureshed. Nutrient supply and demand were mainly in balance, but a surplus of manure phosphorus (P) in the Chaves manureshed and a thin margin of P assimilation by croplands in the Roosevelt manureshed point to the need for preserving existing croplands and understanding of effects of dairy manure on shortgrass rangeland. Our assessment suggests that an ideal scenario would entail manure being generated in landscapes with portfolios of productive lands that can sustainably use the manure nutrients to minimize environmental quality concerns and agronomic tradeoffs. Coordinated, participatory, and interdisciplinary research and planning are needed.

Effect of Polymer Mixtures on Physical-Chemical Properties of Sandy Soil and Plant Growth

Serious desertification problems were found in alpine grassland of the Qinghai-Tibet Plateau, China. The rehabilitation progress of degraded grassland is slow under natural conditions that have low rainfall and large evaporation. Organic agent-solidified soil is one of the most important measurements that limit desertification and grassland conservation-restoration. However, the characteristics of vegetation growth and development in solidified soil need to be studied in depth. This research is based on the modified carboxymethyl cellulose (MCMC) of independent development. Based on the sand soil taken from moving sandy land of Zoige, potted plants were tested in the environmental chamber at the laboratory. The physical, chemical, and biological characteristics of root soil were monitored for more than 7 months. As a result, the plant biomass in the experimental group increased, lodging rate decreased, drought tolerance and survival rate increased, and the number of plant roots and root surface area index, root cross-sectional area ratio, and root volume ratio increased compared with the matched group. It is shown that MCMC can effectively promote plant root development and improve plant drought tolerance and lodging resistance. We also found that, compared with the matched group, the values of the rhizosphere soil mass, root soil mass, and soil crust layer thickness of the experimental group were much higher, meaning that MCMC has strengthened the root soil-fixation ability and soil-crusting ability of plants. The soil nutrient indexes and bioactivity of the experimental group were higher than the matched group, indicating that MCMC has a positive influence on soil maturation. The quantitative description model of soil aging enhancement of MCMC material during root growth and development was established to explore the soil-fixation mechanism of MCMC plant root succession and provided an important scientific basis and technical support for the conservation and restoration of alpine grassland desertification grassland.

Agricultural Use of Sewage Sludge as a Threat of Microplastic (MP) Spread in the Environment and the Role of Governance

Sewage sludge from wastewater treatment plants is commonly used as a soil amendment on agricultural land. Unfortunately, more and more research indicates that large amounts of microplastic (MP) are re-introduced to soil with sludge. This study aims to present the impact MP has on soil ecosystems, global trends in agricultural sludge management resulting from a high concentration of micropollutants in sludge, and finally propose a high-level strategy for sustainable sludge management. This strategy is mostly dedicated to the European Union and involves multiple stakeholders and the links between each of them to achieve appropriate sludge management to avoid soil pollution with MP. Governance, Technology, Consumer Acceptance, and Economy and Commercial Viability is explored in depth. To the author’s knowledge, this is the first paper to discuss these topics in the context of a changing agricultural scene and identifies ways of which sewage sludge can limit MP pollution whilst still fitting into a circular economy. As total elimination of agriculturally used sludge is not a viable option, more stringent regulation on sludge quality before its use is necessary, especially on contaminant concentrations. This includes MPs limits, to improve sludge quality, in turn improving soil health. More alternative management options for sludge that does not meet land usage requirements are necessary and will be explored in this study. Overall, the combination of factors discussed will inevitably lead to more emphasis on sewage sludge management, therefore it can be expected that the information presented in this review will be of high demand and importance for sludge producers and serves as a comprehensive foundation for researchers to build off.

Responses of soil organic carbon stock to animal manure application: A new global synthesis integrating the impacts of agricultural managements and environmental conditions

Enhancing soil organic carbon (SOC) through applying animal manure is of interest for both sustaining cereal production and mitigating greenhouse gas (GHG) emissions. Previous syntheses showed that manuring-induced SOC changes varied substantially with agricultural managements and environmental conditions, while their significance and relative importance to such variability are still largely uncertain. Here, we presented a new synthesis using an updated and balanced database integrating the manuring-induced SOC stock changes and their plausible explanatory factors in 250 observations at global 120 sites. Manure application increased SOC stock by 7.41 ± 1.14 (95% confidence interval, CI) and 8.96 ± 1.83 (95% CI) Mg C ha^-1 , respectively, compared to their mineral fertilized (REF-min) and unfertilized (REF-zero) references. Of which approx. 72% and 34% were directly contributed by manure-C input, respectively. Following the IPCC (Intergovernmental Panel on Climate Change) approach, these changes corresponded to the manuring-induced SOC change factors of 1.27 ± 0.04 (95% CI) and 1.40 ± 0.08 (95% CI), respectively. Basing on a balanced database, we identified the amount of manure-C input as the most important factor to the global variations in the resultant SOC stock changes. More importantly, our integrative analysis distinguished the significance of soil properties (e.g., soil pH and initial SOC content) in regulating the efficiency of manure application in enhancing SOC stock. These results indicate that, at the similar rate, applying manure could sequestrate much more carbon in alkaline soils than in neutral and acidic soils. By integrating the impacts of agricultural managements and environmental conditions, our findings would help to develop region-specific tailor-made manure application measures in agriculture and to refine the SOC change factors for regional GHG inventories.

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.

Soil amendments from recycled waste differently affect CO₂ soil emissions in restored mining soils under semiarid conditions

Drylands affected by serious disturbances such as mining activities lose their vegetation cover and organic soil horizons, becoming CO₂ emissions sources. Applications of organic amendments could be a good restoration solution that favours vegetation establishment and soil carbon sequestration; however, they are also associated with CO₂ emissions. Experimental plots with different organic amendments (sewage sludge, garden and greenhouse vegetable composts, and mixtures of both) and unamended soils were installed in a quarry in southeast Spain. The aim of this study was: i) to evaluate the magnitude and changes of in situ CO₂ emission from each experimental plot during a year and a half, and ii) to assess the effects of several physical-chemical (total organic carbon, total nitrogen, water retention, pH and electrical conductivity) and environmental parameters (moisture and temperature) in CO₂ emissions. The results showed an initial CO₂ emission (priming effect), produced from all restored plots just after the application of the organic amendment, which was significantly higher (P < 0.05) in soils with sewage sludge and their mixtures in comparison to vegetable compost. Garden compost had low emission rates, similar to soils without amendment and showed lower CO₂ emission rates than the rest of the restoration treatments. Nevertheless, CO₂ emissions decreased in each field campaign over time, showing that all restored soils had lower emissions than natural soils at the end of the sampled period. The different composition of organic amendments had a different effect on soil CO₂ emissions. DistLM analysis showed that soil properties such as total organic carbon, total nitrogen, pH and soil moisture, associated with rainfall periods, strongly influenced CO₂ emissions, whereas temperature did not affect the CO₂ flow. In conclusion, the compost from plant remains could serve better as treatment to restore degraded soils in drylands than sewage sludge because of its lower CO₂ emissions and concomitant effect on climate warming and carbon balance.

Incorporating Biogeochemistry into Dryland Restoration

Dryland degradation is a persistent and accelerating global problem. Although the mechanisms initiating and maintaining dryland degradation are largely understood, returning productivity and function through ecological restoration remains difficult. Water limitation commonly drives slow recovery rates within drylands; however, the altered biogeochemical cycles that accompany degradation also play key roles in limiting restoration outcomes. Addressing biogeochemical changes and resource limitations may help improve restoration efforts within this difficult-to-restore biome. In the present article, we present a synthesis of restoration literature that identifies multiple ways biogeochemical understandings might augment dryland restoration outcomes, including timing restoration around resource cycling and uptake, connecting heterogeneous landscapes, manipulating resource pools, and using organismal functional traits to a restoration advantage. We conclude by suggesting ways to incorporate biogeochemistry into existing restoration frameworks and discuss research directions that may help improve restoration outcomes in the world's highly altered dryland landscapes.

Soil carbon response to long-term biosolids application

Astudy was conducted in three agroecosystems in California (Sacramento, Solano, and Merced counties) that received biosolids applications for 20 yr. Management varied in application rates and frequencies, resulting in average cumulative amount of biosolids applied of 74 (Solano), 105 (Merced), and 359 (Sacramento) Mg biosolids_dry ha^-1 , resulting in the addition of 26 (Solano), 36 (Merced), and 125 (Sacramento) Mg biosolids-C ha^-1 . Measurements included soil organic carbon (SOC) and total nitrogen (N) concentrations from 0 to 100 cm and microbial biomass C (MBC) and microbial biomass N (MBN) from 0 to 30 cm in biosolids-amended and control sites. Biosolids treatments had greater amounts of SOC and total N at all sites, and MBC and MBN were greatest at Sacramento and Solano. The largest increases in SOC were at the site that received the lowest cumulative loading rate of biosolids (Solano), where SOC content to 100 cm was 50% greater in amended soils (p < .001). Net changes in soil C stocks to 30 cm were 0.4 ± 0.1 (Solano), -0.04 ± 0.1 (Merced), and 0.3 ± 0.2 (Sacramento) Mg C ha^-1 yr^-1 . These values change when considering deeper soil depths (0-100 cm) to 0.5 ± 0.1 (Solano), 0.2 ± 0.2 (Merced), and 0.216 ± 0.2 (Sacramento) Mg C ha^-1 yr^-1 , reflecting differences in C stocks changes in surface and subsurface soils across sites. Rates of C storage per dry Mg of biosolids per year applied were 1 ± 0.2 (Solano), 0.5 ± 0.4 (Merced), and 0.04 ± 0.1 (Sacramento). Our results suggest that local controls on soil C stabilization are more important than amendment application amount at predicting climate benefits and that accounting for soil C changes below 30 cm can provide insight for sequestering C in agroecosystems.

Reducing climate impacts of beef production: A synthesis of life cycle assessments across management systems and global regions

The global demand for beef is rapidly increasing (FAO, 2019), raising concern about climate change impacts (Clark et al., 2020; Leip et al., 2015; Springmann et al., 2018). Beef and dairy contribute over 70% of livestock greenhouse gas emissions (GHG), which collectively contribute ~6.3 Gt CO₂ -eq/year (Gerber et al., 2013; Herrero et al., 2016) and account for 14%-18% of human GHG emissions (Friedlingstein et al., 2019; Gerber et al., 2013). The utility of beef GHG mitigation strategies, such as land-based carbon (C) sequestration and increased production efficiency, are actively debated (Garnett et al., 2017). We compiled 292 local comparisons of "improved" versus "conventional" beef production systems across global regions, assessing net GHG emission data from Life Cycle Assessment (LCA) studies. Our results indicate that net beef GHG emissions could be reduced substantially via changes in management. Overall, a 46 % reduction in net GHG emissions per unit of beef was achieved at sites using carbon (C) sequestration management strategies on grazed lands, and an 8% reduction in net GHGs was achieved at sites using growth efficiency strategies. However, net-zero emissions were only achieved in 2% of studies. Among regions, studies from Brazil had the greatest improvement, with management strategies for C sequestration and efficiency reducing beef GHG emissions by 57%. In the United States, C sequestration strategies reduced beef GHG emissions by over 100% (net-zero emissions) in a few grazing systems, whereas efficiency strategies were not successful at reducing GHGs, possibly because of high baseline efficiency in the region. This meta-analysis offers insight into pathways to substantially reduce beef production's global GHG emissions. Nonetheless, even if these improved land-based and efficiency management strategies could be fully applied globally, the trajectory of growth in beef demand will likely more than offset GHG emissions reductions and lead to further warming unless there is also reduced beef consumption.

Integrated Crop-Livestock Systems for Nitrogen Management: A Multi-Scale Spatial Analysis

Simple Summary

Manure disposal is a growing problem as agricultural specialization leads to ever-larger concentrations of farm animals. Animals and crops were once grown on the same farm, creating an easy path for manure disposal on cropland in a cycle from animals to feed crops and back. Increasing specialization today means that concentrated animal operations are no longer linked to adjacent cropland on which animal waste can be disposed, leading to significant off-farm externalities in the form of risks of air and water contamination. Using an arid lands case study of dairies and crop and grass land in New Mexico, USA, we explore the possibility of reintegration through the analysis of available crop and range land in the scale of counties and watersheds surrounding the state’s concentrated dairies. We find that there is often available land to make productive use of the waste. However, in developing the policy tools to reintegrate the animal waste-crop cycle among independent farms and ranches, it is critical to consider the appropriate geographic scale.

Abstract

The size and productivity of the livestock operations have increased over the past several decades, serving the needs of the growing human population. This growth however has come at the expense of broken connection between croplands and livestock operations. As a result, there is a huge disconnect between the nutrient needs of croplands and the availability of nutrients from livestock operations, leading to a range of environmental and public health issues. This study develops a theoretical framework for multi-scale spatial analysis of integrated crop-livestock systems. Using New Mexico, USA as a case study, we quantify the amount of nitrogen produced by dairy farms in the state and examine if the available nitrogen can be assimilated by the croplands and grasslands across spatial scales. The farm-level assessment identifies that all the farms under study do not have adequate onsite croplands to assimilate the nitrogen produced therein. The successive assessments at county and watershed levels suggest that the among-farm integration across operations could be an effective mechanism to assimilate the excess nitrogen. Our study hints towards the multi-spatial characteristic of the problem that can be pivotal in designing successful policy instruments.

A meta-analysis contrasting active versus passive restoration practices in dryland agricultural ecosystems

Restoration of agricultural drylands globally, here farmlands and grazing lands, is a priority for ecosystem function and biodiversity preservation. Natural areas in drylands are recognized as biodiversity hotspots and face continued human impacts. Global water shortages are driving increased agricultural land retirement providing the opportunity to reclaim some of these lands for natural habitat. We used meta-analysis to contrast different classes of dryland restoration practices. All interventions were categorized as active and passive for the analyses of efficacy in dryland agricultural ecosystems. We evaluated the impact of 19 specific restoration practices from 42 studies on soil, plant, animal, and general habitat targets across 16 countries, for a total of 1,427 independent observations. Passive vegetation restoration and grazing exclusion led to net positive restoration outcomes. Passive restoration practices were more variable and less effective than active restoration practices. Furthermore, passive soil restoration led to net negative restoration outcomes. Active restoration practices consistently led to positive outcomes for soil, plant, and habitat targets. Water supplementation was the most effective restoration practice. These findings suggest that active interventions are necessary and critical in most instances for dryland agricultural ecosystems likely because of severe anthropogenic pressures and concurrent environmental stressors-both past and present.