Global food security increasingly depends on sustained soil fertility while meeting the rising demand for agricultural production under increasing climatic and environmental pressures. However, the intensive application of synthetic fertilizers over recent decades has created a paradox: short-term yield gains are offset by the long-term degradation of the very resource base on which crop production depends. Chemical fertilizers are energy-intensive to manufacture and contribute to soil acidification, nutrient imbalances, declining soil biological activity and physical deterioration that accelerates erosion [1]-[3]. These challenges have renewed global interest in sustainable soil management practices that improve productivity while maintaining ecosystem functions.

In tropical regions, these pressures are compounded by highly weathered soils particularly Ferric Acrisols and Ferralsols which are characterized by low organic matter, weak aggregate stability, and limited cation exchange capacity, poor nutrient retention, and high susceptibility to nutrient depletion [4][5]. Furthermore, the high cost and intermittent availability of mineral inputs further constrain their adoption by smallholder farmers across sub-Saharan Africa, where local organic resources remain the primary means of fertility management.

Among organic amendments, poultry manure (PM) occupies a distinct position because of its high nutrient density and relatively rapid mineralization. Comparative analyses consistently show that PM contains higher concentrations of nitrogen (N), phosphorus (P), calcium (Ca), magnesium (Mg) and potassium (K), than most other livestock manures, and a significant fraction of these nutrients is rapidly available for plant uptake [6]-[9]. In addition to supplying essential nutrients, PM improves soil physical structure, stimulates microbial activity, and promotes soil organic carbon (SOC) sequestration [3][10][11]. These multifunctional properties make PM an attractive cornerstone of integrated soil fertility management (ISFM) and climate-smart agricultural systems.

Concurrently, the rapid expansion of global poultry production is generating increasing volumes of manure that may exceed local land-application capacity in intensive production regions. This biomass represents an important renewable nutrient resource, but it also poses significant environmental management challenges when poorly handled or indiscriminately applied [8][12]. Uncontrolled land disposal of PM may introduce heavy metals, human pathogens, veterinary antibiotic residues, and antibiotic resistance genes (ARGs) into agricultural soils and waterways [8][13][14]. Furthermore, inadequate storage and handling may generate methane (CH₄), nitrous oxide (N₂O), and ammonia (NH₃), contributing to both climate change and local air quality degradation.

Existing reviews generally focus on nutrient supply, composting technologies, or environmental pollution separately, whereas few integrate manure composition, soil physicochemical and biological responses, carbon sequestration, greenhouse gas emissions, valorisation pathways, and environmental risks within a single systems-oriented framework. Such an integrated perspective is increasingly needed to support sustainable nutrient management and evidence-based decision-making across agricultural systems. Sustainable management of poultry manure also contributes to several Sustainable Development Goals (SDGs), particularly SDG 2 (Zero Hunger), SDG 12 (Responsible Consumption and Production), SDG 13 (Climate Action), and SDG 15 (Life on Land), through improved food security, resource efficiency, climate change mitigation, and land restoration.

This review therefore structures its synthesis around the key decision nodes that a researcher, agronomist, or policy-maker must navigate:

i) understanding the composition and variability of PM;

ii) quantifying its effects on the physical, chemical, and biological dimensions of soil functioning;

iii) characterising the balance between SOC sequestration potential and greenhouse gas trade-offs;

iv) evaluating bio-energy and circular-economy valorisation alternatives;

v) identifying and managing environmental and health risks; and

vi) integrated management strategies that maximize agronomic benefits while minimizing environmental impacts.

By synthesizing evidence across these interconnected themes, this review aims to provide a comprehensive scientific basis for the sustainable management of poultry manure in both tropical and temperate agroecosystems, with particular emphasis on tropical and subtropical regions where soil fertility constraints are most severe and research needs remain greatest.

This manuscript follows a structured narrative review methodology. Peer-reviewed literature was identified through major scientific databases, including Web of Science, Scopus, PubMed, and Google Scholar. Search terms combined “poultry manure” with sub-topics including “soil physical properties”, “soil chemical properties”, “microbial community”, “soil organic carbon”, “greenhouse gas emissions”, “biogas”, “heavy metals”, “antibiotic resistance genes”, and “pathogen contamination”. Priority was given to studies published within the last decade; seminal earlier studies were included where they established mechanistic or conceptual foundations.

Review articles and high-quality laboratory, greenhouse, and experimental field studies were integrated to ensure both breadth and depth. Additional relevant publications were identified through citation tracking of key review papers and highly cited original research articles to improve the comprehensiveness of the review. Studies from tropical and subtropical agroecosystems were given greater emphasis, reflecting the focus on contexts where degraded soils and resource-constrained farmers represent the primary target audience.

The poultry manure (PM) used here as a generic term for excreta-derived poultry waste, whereas poultry litter refers specifically to excreta mixed with bedding material, feathers, spilled feed and other residues generated during poultry production [8][15]. Broiler is generally bedding-rich and may contain variable amounts of feed residues and feathers; cage-layer manure is dominated by excreta and usually contains little or no bedding; high-rise manure accumulates beneath caged birds; and poultry slurry refers to manure mixed with water. Distinguishing these forms is essential because nutrient concentration, moisture content, mineralisation rate, salt load and contaminant risk differ substantially among manure types and production systems [5][16]. Unless otherwise specified, the composition values discussed below are reported on a dry-matter basis and as elemental nutrients, not oxide equivalents.

Poultry litter typically contains approximately 2.9% - 4.4% N, 3.2% - 5.5% P, 3.2% - 5.5%, and 2.2% - 3.8% K on a dry-matter basis although these ranges vary substantially with production system, bedding material, diet, manure age and storage history [8][15][17][18]. It also supplies calcium (Ca), magnesium (Mg), sulfur (S) and trace elements such as copper (Cu), iron (Fe), manganese (Mn), chlorine (Cl), boron (B), molybdenum (Mo), cobalt (Co), and zinc (Zn), which may contribute to crop nutrition but may also create contaminant-loading risks when manure is repeatedly applied at high rates [2][3][11][17]-[19]. Broiler litter typically contains higher bedding-derived organic matter, while layer manure generally contains higher Ca because of eggshell production. The C:N ratio of PM is generally low (6 - 15), promoting rapid microbial mineralisation, accelerated nutrient cycling, and early nutrient release compared with crop residues or compost.

Compositional variability is substantial and must be acknowledged in any management recommendation (Figure 1). The concentrations of macro- and micronutrients in PM are governed by the breeding system (cage, deep litter, free range), bird species and age, feed formulation, moisture content, manure age, bedding type and quantity, and storage and handling practices [8]. This variability is agronomically significant: N availability in the first growing season can range from as little as 25% to over 70% of total N, depending on manure management history and soil conditions. Variability in heavy metal content notably Zn, Cu, and As also depends on feed additives and management practices, creating site-specific environmental risks that require local assessment and continuous monitoring [19].

Overall, the high nutrient density, relatively low C:N ratio, and variable physicochemical composition of poultry manure highlight both its agronomic value and the importance of site-specific management strategies to optimize nutrient use efficiency while minimizing environmental risks.

Figure 1.Agronomic benefits and environmental risk pathways associated with poultry manure recycling.

Conceptual framework illustrating of poultry manure (PM) as both a nutrient-rich organic amendment and a potential source of environmental and health risks. The diagram links PM application to improved soil properties, enhanced nutrient availability, increased soil organic carbon sequestration and crop yield, while highlighting parallel pathways of greenhouse-gas emissions, pathogen exposure, heavy-metal dissemination, crop-quality risks, runoff losses and farmer-health concerns. This dual agronomic environmental framework underscores the need for appropriate application rates, manure pre-treatment (e.g., composting or anaerobic digestion), and continuous environmental monitoring to maximize agronomic benefits while minimizing environmental impacts.

PM application can improve these physical constraints through organic matter inputs that promote aggregation and increase the proportion of mesopores and macropores available for water storage and gas exchange (Figure 2). However, the magnitude and persistence of the response depend on manure type and maturity, application rate and duration, soil texture and mineralogy, antecedent degradation status, climate, tillage and crop management. These improvements may enhance soil physical quality and crop production when PM is applied within a site-specific nutrient-management framework.

Soil biological activity mediates a wide range of nutrient transformation and cycling processes; it is therefore both a target and an indicator of soil health. PM provides readily available carbon and nitrogen substrates, organic compounds, micronutrients, vitamins, and enzyme precursors that stimulate microbial biomass production and enzymatic activity.

The addition of poultry manure modifies soil microbial communities through both direct and indirect mechanisms. Direct effects result from the supply of organic substrates and nutrients, whereas indirect effects occur through improvements in soil pH, moisture availability, aggregation, and nutrient status. Incorporation of poultry litter into soil induces marked changes in bacterial community composition as well as soil chemical properties [11]. These findings are in agreement with long-term fertilisation studies showing that repeated PM application restructures edaphic microbial communities through modifications of soil chemical attributes [33][34]. A meta-analysis by [35] documented significant increases in microbial carbon and nitrogen following manure application across diverse soil types, attributing the effect to improved substrate availability and physical soil conditions created by PM-induced structural improvements. Increased microbial biomass following PM addition reflects enhanced microbial growth potential and greater nutrient turnover capacity, particularly in nutrient-depleted soils. Similar trends have been reported by [36], who noted that the composition of the microbial community also shifts qualitatively, with changes in microbial diversity, functional groups, and ecological interactions that may influence nutrient cycling, pathogen suppression and soil disease dynamics.

The stimulation of microbial activity by PM has important dual significance: it accelerates nutrient cycling beneficial to crops, but it may also temporarily increase CO₂ efflux and, under anaerobic microsites, methane and nitrous oxide production (Section 7). These responses depend strongly on manure application rate, moisture conditions, soil aeration status, temperature, and manure decomposition stage. Managing the balance between these outcomes maximising nutrient availability while limiting net greenhouse gas (GHG) emissions is a central challenge in PM-based soil fertility management. Overall, poultry manure acts as a biological catalyst that enhances microbial activity, nutrient cycling, and soil functional capacity. However, its effects are context-dependent and require integrated management approaches that consider both agronomic benefits and potential environmental consequences.

The rapid expansion of the global poultry sector has generated large biomass that in some intensive production regions exceed local soil nutrient demand and land application capacity. This accumulation creates environmental challenges related to nutrient losses, greenhouse gas emissions, pathogen dissemination, and odour generation. Consequently, alternative valorisation strategies based on circular economy principles are increasingly being explored to transform poultry manure from an agricultural waste stream into a source of renewable energy, recovered nutrients, and value-added soil amendments.

The evidence reviewed above supports a coherent set of management recommendations for integrating PM into sustainable soil fertility systems, while also identifying research gaps that still constrain confident implementation across contrasting agroecological contexts.

Nutrient-budgeting, rather than a fixed application rate, should be the primary management lever for PM use. Application rates of around 10 t∙ha⁻¹ have h improve in soil physical condition, nutrient availability and crop performance in tropical and subtropical field studies [79][80], but these values should be treated only as examples from specific soil-crop contexts. Operational recommendations should instead be based on crop nutrient demand, manure nutrient analysis, soil-test phosphorus, background salinity, soil texture and mineralogy, and cumulative contaminant loading. Site-specific calibration is essential because PM composition varies strongly with bird type, feed formulation, bedding material, manure age, storage conditions and farm-management practices [5][16]. Farmers, researchers and extension services would therefore benefit from rapid, low-cost analytical tools for PM characterisation at the point of use. Near-infrared spectroscopy has shown promise for rapid manure nutrient assessment, but operational reliability still depends on calibration quality, sample preparation and locally representative manure databases [81].

Pre-treatment, particularly composting and anaerobic digestion, should be considered a central component of safe PM recycling rather than an optional step. Composting can stabilise organic matter, improve nutrient handling and reduce the bioavailability of some contaminants, whereas anaerobic digestion converts manure into biogas and digestate while reducing odour, pathogen pressure and greenhouse-gas risks associated with unmanaged manure storage or direct application [16][53][82]. Nevertheless, the successful implementation of these technologies depends on technical expertise, financial investment, infrastructure availability, and institutional support. These requirements may exceed the capacity of many individual smallholder farmers in sub-Saharan Africa and other resource-constrained regions. Consequently, policy incentives supporting cooperative composting facilities, community-scale anaerobic digesters, and locally adapted co-digestion systems could substantially improve technology adoption while reducing environmental pollution [83][84].

Complementary amendment strategies also show promise. Combining PM with biochar or converting PM into biochar-based fertilisers can enhance nutrient retention, improve soil physical and chemical functioning, and potentially increase the persistence of manure-derived carbon in soil [30][85]. Similarly, integrated nutrient management strategies that combine PM with reduced or targeted mineral fertiliser inputs can improve nutrient synchrony with crop demand, maintain productivity and reduce dependence on mineral fertilisers alone [86]. These integrated approaches also contribute to improved nutrient-use efficiency while reducing cumulative loading of phosphorus, soluble salts, heavy metals, and other potential contaminants, particularly in regions where repeated manure application is common.

Monitoring protocols for heavy metals, veterinary antibiotics, pathogens and antibiotic-resistance genes (ARGs) should be institutionalised for any land-application programme involving repeated or high-rate PM inputs. Recent evidence shows that manure application can enrich soil resistomes, increase the abundance of ARG subtypes and interact with heavy-metal contamination through co-selection processes [36][87]-[89]. This is particularly important in intensively managed poultry landscapes where repeated manure use may generate cumulative contaminant and resistance pressures. Regulatory guidance comparable to European and North American frameworks could be adapted to tropical contexts, but such adaptation must account for differences in soil texture, rainfall intensity, organic-matter turnover, crop systems and monitoring capacity.

On the research agenda, three priority gaps stand out. First, integrated life-cycle assessments spanning manure generation, storage, processing, field application, crop response, fertiliser substitution and soil carbon dynamics remain limited for tropical agroecosystems. Existing assessments increasingly quantify individual pathways such as broiler-manure treatment, composted or pelletised poultry litter, and manure-derived organic composts, but they rarely close the full manure–soil–crop–carbon accounting boundary [58][59][61][90]. The integration of contaminant monitoring within a One Health framework would strengthen links between agricultural productivity, environmental quality, animal health, and human health.

Regulatory guidance comparable to European and North American frameworks could be adapted for tropical regions; however, such adaptations should account for local differences in soil properties, rainfall regimes, climate, cropping systems, nutrient-use practices, and institutional monitoring capacity.

Poultry manure is a nutrient-dense and widely available organic amendment whose relevance extends beyond simple fertiliser substitution. Its value lies in the simultaneous supply of nitrogen, phosphorus, potassium, calcium, magnesium and organic carbon, together with a low C:N ratio that favours rapid mineralisation and early nutrient release. Yet poultry manure is not a uniform input. Its chemical composition, nutrient-release dynamics and contaminant load vary strongly with bird type, feed formulation, bedding material, moisture content, manure age, storage conditions and handling practices. Recognizing and managing this variability is fundamental to maximizing agronomic benefits while minimizing environmental risks.

The evidence reviewed throughout this study demonstrates that poultry manure can improve multiple dimensions of soil functioning. Physically, it reduces bulk density, promotes aggregation, enhances porosity and increases water-retention capacity, particularly in structurally degraded tropical soils. Chemically, it contributes to pH amelioration, organic-matter enrichment, nutrient replenishment and increased exchangeable-base availability. Biologically, it stimulates microbial biomass, enzymatic activity and nutrient-cycling processes, thereby strengthening the coupling between organic inputs, microbial transformation and plant nutrient supply. Collectively, these improvements enhance soil health, increase nutrient-use efficiency, and contribute to more resilient and productive agroecosystems. These interacting effects position poultry manure as a relevant component of integrated soil fertility management, especially in smallholder systems where mineral fertilisers are costly, intermittently available or environmentally problematic.

The role of poultry manure in carbon cycling is equally important but more ambivalent. Through the addition of carbonaceous residues and the formation of organo-mineral associations, poultry manure can contribute to soil organic carbon accumulation and the recovery of degraded soils. However, its carbon-sequestration potential cannot be evaluated independently from greenhouse-gas emissions generated during manure storage, treatment and field application. Methane, nitrous oxide, ammonia and carbon dioxide emissions depend on moisture, aeration, temperature, nitrogen availability and the management pathway adopted. Consequently, the net climate benefit of poultry manure depends not only on its capacity to build soil carbon but also on the effectiveness of management practices that minimize greenhouse-gas emissions throughout the manure management chain.

Valorisation pathways offer a means of shifting poultry manure from a waste-management constraint toward a circular bioresource. Composting stabilises organic matter, reduces pathogen pressure, improves handling and produces a slower-release amendment. Anaerobic digestion generates biogas while retaining much of the nutrient value in the digestate. Thermochemical conversion, including pyrolysis, gasification and fluidised-bed combustion, can produce renewable energy and biochar-based fertilisers with potential benefits for nutrient retention and long-term carbon stabilization. These technologies demonstrate that appropriately managed poultry manure can simultaneously contribute to renewable energy generation, nutrient recycling, waste reduction, and climate-change mitigation.

Nevertheless, the sustainable recycling of poultry manure depends on rigorous management of environmental and human-health risks. Repeated or high-rate applications may lead to the accumulation of heavy metals, salts, veterinary antibiotic residues, pathogens and antibiotic-resistance genes in soil–plant–water systems. These risks define the boundary between beneficial nutrient recycling and environmental contamination. Safe use therefore requires site-specific rate calibration, appropriate pre-treatment, monitoring of contaminant and pathogen loads, and regulatory guidance adapted to soil texture, rainfall regime, crop system, organic-matter turnover and local analytical capacity. Adopting a One Health perspective that integrates soil, environmental, animal, and human health considerations will further strengthen the sustainability of poultry manure management.

Overall, poultry manure should be managed not as a simple organic fertiliser, but as a multifunctional resource embedded in a manure–soil–crop–climate continuum. Its successful integration into sustainable soil fertility strategies requires a shift from opportunistic disposal to evidence-based recycling. Priority should be given to rapid manure characterisation, locally calibrated application rates, cooperative composting or anaerobic-digestion facilities, combined use with biochar or targeted mineral fertilisers, and long-term monitoring of nutrients, carbon and contaminants. Future research should move beyond short-term agronomic trials toward integrated life-cycle assessments that link manure generation, storage, processing, field application, crop response, greenhouse-gas emissions, soil organic carbon stabilisation and socioeconomic feasibility. Such an integrated framework is essential for poultry manure to contribute simultaneously to soil restoration, food security, waste valorisation and climate-smart agriculture.

Future research should increasingly adopt multidisciplinary approaches integrating agronomy, soil science, microbiology, environmental chemistry, climate science, engineering, economics, and policy analysis. Comprehensive life-cycle assessments linking manure generation, storage, processing, field application, crop productivity, greenhouse-gas emissions, soil carbon stabilization, and socioeconomic performance remain particularly needed, especially in tropical and subtropical agroecosystems.

Ultimately, the sustainable management of poultry manure represents far more than an agricultural practice; it constitutes an important pathway toward regenerative agriculture, circular bioeconomy development, climate-smart food production, and long-term soil restoration. By integrating scientific knowledge, technological innovation, and evidence-based policies, poultry manure can become a strategic resource for enhancing food security while simultaneously advancing environmental sustainability and supporting the achievement of Sustainable Development Goals, particularly SDGs 2 (Zero Hunger), 12 (Responsible Consumption and Production), 13 (Climate Action), and 15 (Life on Land).

Mabicka Obame Rolf Gael: Conception design and drafting the full paper; Neil-Yohan Musadji data cleaning and analysis, Urlain Gael Yakouya-moubamba: formal analysis, Elie Fosso Menkem methodology: Maurice Ognalaga: project administration, Dieu-Donne Mouketou-Tarazewicz5 revising the paper critically for intellectual content. All authors consent to publish.