Context Composite compost (CC), an advanced form of composting that integrates diverse organic feedstocks, has emerged as a sustainable solution for enhancing soil health and crop productivity. Unlike traditional single-feedstock compost, CC optimizes nutrient profiles, accelerates decomposition, and improves microbial diversity, resulting in higher humic content and reduced phytotoxicity. Aims This review paper synthesizes current knowledge on the composition, benefits, and challenges of CC, emphasizing its role in sustainable agriculture. Methods This comprehensive review was developed following PRISMA guidelines and synthesizes existing literature to assess the formulation, benefits, and challenges of CC. Key results Our study demonstrated that CC enhances structure, texture, water retention capacity, and nutrient profile of soils, while promoting beneficial microbial activity. Conclusions Application of CC has been shown to increase crop yields by 10–40%, improve crop quality, and enhance crop resistance to pests and diseases. However, challenges such as feedstock variability, seasonal variability, immature compost risks, and nutrient imbalance must be addressed through standardized production protocols. Implications The study indicates enormous potential of CC as a key element in sustainable soil management strategies, thus providing valuable directions to researchers, policymakers, and practitioners for promoting its use and setting standards. By bridging gaps in research and practice, CC offers a viable pathway toward soil restoration, climate resilience, and food security.
Context Wheat is a globally important cereal crop, and enhancing its root system through microbial interactions is a promising approach to improve nutrient uptake and reduce dependence on chemical fertilizers. Aim The objective of this study was to evaluate the effects of two Azospirillum brasilense strains, AbV5/6 (commercial) and HM053 (ammonia-excreting mutant), on the root morphology and architecture of wheat genotypes under in vitro conditions. Methods Eight commercial wheat cultivars were assessed in vitro for root morphological responses, including biomass, length, area, and perimeter, to bacterial inoculation and nitrogen availability. Key results Two contrasting wheat genotypes, G5 (responsive) and G6 (non-responsive), were selected for a subsequent experiment comparing the effects of the two bacterial strains. Results revealed genotype-dependent responses to A. brasilense, with G5 exhibiting enhanced root growth traits under AbV5/6 inoculation, including a 11% increase in root length and a 10% increase in root area compared to the control. In contrast, G6 exhibited reductions in root traits following inoculation. Both strains colonized root tissues and formed endophytic biofilms near xylem vessels, as confirmed by scanning electron microscopy, but only AbV5/6 significantly increased root perimeter in G5. Conclusions Overall, root area and perimeter were more reliable indicators of bacterial responsiveness than biomass or total nitrogen content. Strain AbV5/6 was able to significantly increase root area and perimeter in wheat cultivars. Implications This study underscores the importance of genotype–strain compatibility in plant–microbe interactions and indicates the potential of AbV5/6 to promote wheat root development, particularly in genotypes with favorable traits.
Context Soil aggregation is crucial for soil organic carbon (SOC) stabilisation, yet its response to climate warming in minimally managed systems is not fully understood. Aims This study was conducted to evaluate impacts of short-term (2 years) and long-term (10-years) warming on SOC dynamics in organic soils. Methods We employed open-top chambers to achieve a 2°C warming effect in a subalpine meadow in Tasmania, Australia (mean SOC, 0.14 kg kg−1; mean pH, 5). Soil samples were analysed seasonally for water-stable aggregates (WSA) and aggregate-associated SOC content across three size fractions: large macroaggregates (>2.00–5.6 mm), small macroaggregates (0.25–2 mm) and microaggregates (0.053–0.25 mm). Linear models were fitted to assess the effect of warming duration and sampling season. Key results Aggregate mean weight diameter, whole soil WSA and distribution of WSA across size fractions were all stable after 2 and 10 years of warming. Accordingly, no significant changes in response to warming were observed in whole soil SOC content or aggregate-associated SOC content. However, aggregate stability varied between sampling seasons and there was a significant effect of sampling season on aggregate-associated SOC content that increased with warming duration. Conclusions This study demonstrated that, despite apparent stability, warming affected the dynamics of aggregate-associated SOC by altering the amplitude of the seasonal variation. Implications Seasonal reconfiguration of carbon pools can have implications for long-term maintenance of SOC stocks, and we suggest future studies focus on this aspect across organic soils from other regions under similar conditions.
Context p-Nitrophenol (PNP) is a key intermediate in pesticides, pharmaceuticals, and dye industries, and can significantly disrupt soil ecosystem functions and pose risks to human health through bioaccumulation. The biodegradation behaviour of PNP under natural attenuation and its microbial response mechanisms remain inadequately understood. Aims This study investigated PNP degradation kinetics, coupled dynamics of soil properties and microbial communities, and key functional taxa/genes under natural attenuation. Methods A 168-day experiment in a sand box was conducted using PNP-contaminated soil. Concentrations, physico-chemical properties, enzyme activities, microbial communities (16S rRNA/ITS sequencing), and C/N cycling genes (KEGG annotation) were analyzed at multiple time points. Key results PNP with an initial concentration of 10–40 mg kg−1 degraded to the safe threshold (2 mg kg−1) within 126 days. The degradation process followed first-order or biphasic first-order kinetic models and was significantly correlated with changes in soil physico-chemical properties, with ammonium nitrogen, nitrate nitrogen, and organic matter being key environmental factors. Microbial diversity, reduced in high-contamination zones, gradually recovered as PNP degraded, peaking on Day 126. Bacillus and Penicillium dominated the early degradation stage, while Sphingomonas and Arthrobacter became predominant in later stages. Key functional genes involved in carbon and nitrogen cycling showed peak expression on Day 84. Conclusion PNP natural attenuation involves rate-limited degradation phases driven by successional shifts in degrading communities and functional gene expression. These findings confirm that biodegradation proceeds through distinct phases corresponding to community succession and functional gene dynamics. Implications Regulating soil moisture, aeration, and nutrient conditions can enrich functional degraders, providing a theoretical basis for in situ bioremediation of PNP-contaminated soils.
Context It is widely recognized that contaminants in urban topsoil can present substantial threats to ecosystems and human health. Mercury (Hg) is a persistent pollutant arising from both anthropogenic (industrial and transport emissions) and natural (e.g. biomass burning, weathering, and volcanism) sources, and can reach toxic levels in urban soils. Aims These threats highlight the need to better understand the dynamics of Hg contamination across human-modified and urbanized landscapes, particularly in regions where studies remain scarce. Methods Here, we conducted a topsoil (0–15 cm) survey involving 14 urbanized counties (eight sampling sites per county) in the Hengduan Mountains at the eastern margin of the Qinghai-Tibet Plateau (QTP), traversing an elevational range of 360–3380 m (a.s.l.). Key results Topsoil total Hg (THg) content range was 9.9–773.4 ng/g with an average of 100.7 ng/g across sites. Neither land use type (i.e. parkland, woodland, cropland, or vacant land) nor human population density had any significant effect on topsoil THg concentrations; however, THg levels were affected by climate (temperature, but not precipitation or UV-B), vegetation, and soil organic matter. Conclusions Our findings suggest that natural environmental factors exert stronger influences on topsoil THg concentrations than broad land-use categories across urbanized mosaic landscapes on the QTP. Implications Consideration of natural environmental drivers may improve the interpretation and monitoring of topsoil THg dynamics across broad urbanized landscapes.
