Aug 2026· Journal of Soils and Sediments· Vol 26· 0 citations· 139 references
Abstract
Greenhouse gasses emission, depletion of nutrients and soil degradation are major factors that are deteriorating soil health. A global challenge to agriculture is the production of enough crops while reducing the impact of intensive chemical inputs on the environment. Humic acids (HA), a main fraction of humic substances produced through humification of organic matter, are considered as multi-functional biostimulants playing an important role in sustainable and climate-smart crop production systems. Recent developments in molecular spectroscopy, humeomics, and soil–plant systems biology have significantly changed our understanding of HA; from inert recalcitrant macropolymers to supramolecular assemblies that are dynamic and govern soil physicochemical properties, microbial activity and plant physiological responses. This review critically synthesizes the available evidence on structure–function relationships of HA with soil fertility restoration, nutrient-use efficiency, crop productivity and environmental sustainability. Emphasis is placed on mechanisms involved in humic acid-mediated soil aggregation, cation exchange capacity improvement, nutrient chelation and modification of root architecture, hormonal signaling and stress tolerance. Nutrient-use efficiency can be improved through HA applications and lower synthetic fertilizer inputs, as well as long-term stabilization of soil carbon and immobilization of heavy metals through the formation of stable organo-mineral complexes. Despite these benefits, substantial variability in HA sources, extraction protocols and molecular composition as well as adoption methodologies continue to limit their reproducibility and widespread application. Knowledge gaps, such as the standardization of molecular characterization, omics-level validation of the plant and microbial responses, long-term field-scale assessment for carbon (C) permanence and agronomic performance of HA are discussed in this review. It also proposes future research and policy needs to develop humic-based amendments for resilient low-input agricultural systems.
Humic substances (HS) are an essential component of soil organic matter and are
considered a promising basis for the development of environmentally safe bioproducts used in
sustainable agriculture. In the context of global soil degradation and the increasing demand for
enhanced productivity of agroecosystems, interest in natural compounds capable of improving soil
fertility and stimulating plant growth is steadily growing. This review summarizes current scientific
data on the origin, structure, physical and chemical properties, as well as biological activity of humic
substances, as well as their role in the functioning of soil ecosystems. It is shown that humic
substances are formed during the humification of organic residues and are characterized by a complex
molecular structure containing various functional groups that ensure their high chemical and biological
activity. Due to their ability to participate in complexation, ion exchange, and electron transfer
processes, humic substances regulate key soil processes, including nutrient cycling, carbon
sequestration, soil structure formation, and detoxification of pollutants. Particular attention is given to
the physiological effects of humic substances on plants. It is demonstrated that they exhibit hormonelike properties, stimulating root system development, activating metabolic processes, and increasing
plant resistance to abiotic stress. In addition, humic substances enhance the bioavailability of macroand micronutrients, improve soil water retention capacity, and promote the activity of soil microbiota.
The review also examines modern methods for obtaining humic acids from natural carbon-containing
materials, including chemical, mechanochemical, hydrothermal, biochemical methods, as well as
process intensification techniques using ultrasound, microwaves, and electromagnetic fields. The
advantages and limitations of various technologies, as well as their environmental aspects, are
discussed. Thus, humic substances are considered multifunctional natural compounds with significant
potential for improving soil fertility, enhancing the sustainability of agroecosystems, and developing
biologically active products for agriculture. Their use opens new opportunities for the advancement of
environmentally oriented agricultural technologies and for addressing current challenges in food
security and environmental protection.
G.A. Yerekeshova, S. Kabdrakhmanova, A. Kabdrakhmanova et al.· Bulletin of Korkyt Ata Kyzyl...· 0 citations
Soil humus and its operationally defined fractions, humic acid, fulvic acid and humin, have re-entered the centre of debate on sustainable crop production as natural farming systems expand across smallholder and commercial agriculture. This review synthesises evidence on the formation, chemistry and agronomic functions of humic substances, with particular attention to their integration into natural farming practices that avoid synthetic fertilisers and pesticides. The chemical architecture of humic substances, dominated by carboxylic and phenolic functional groups arranged around aliphatic and aromatic cores, underlies their capacity to buffer soil pH, increase cation exchange capacity, chelate micronutrients and stimulate root architecture through auxin- and cytokinin-like signalling. Field and greenhouse trials across cereals, pulses, oilseeds and horticultural crops show that humic acid and vermicompost-derived humic fractions frequently increase nutrient use efficiency, microbial diversity and yield, although the magnitude and even direction of these effects depend strongly on humic source, application rate, soil type and crop. Within natural farming systems such as Zero Budget Natural Farming, farm-generated inputs including Jeevamrita and vermicompost function partly through their humic content, contributing to soil organic carbon accumulation, improved water-holding capacity and enhanced biological activity, while large-scale evaluations report comparable yields and higher farm profitability relative to conventional systems. Evidence on heavy metal immobilisation and drought and salinity tolerance further extends the relevance of humic substances beyond fertility management into environmental remediation and climate resilience. Nonetheless, mechanistic inconsistencies, a scarcity of long-term multi-site field trials and weak standardisation of humic product characterisation constrain firm agronomic recommendations. This review concludes that humic substances represent a scientifically credible, though imperfectly characterised, component of natural farming, and it outlines priority research directions for reconciling laboratory-derived mechanistic insight with field-scale reliability.
C. Panchal, G. D. Vadodariya, B. L. Raghunandan et al.· Journal of Experimental Agri...· 0 citations
Microplastics (MPs) pollution caused by agricultural film residues, organic fertilizer application, sewage irrigation, and atmospheric deposition has gradually become an unignorable interference factor to the sustainable development of the rhizosphere soil and crop in farmland. However, their specific impacts on the rhizosphere and crops remain unclear. Therefore, this review focuses on the current knowledge on the response mechanisms of rhizosphere soil and crops to MP contamination. The density of MPs is generally lower than that of soil mineral particles. Their substantial accumulation in soil can significantly reduce both the bulk density (by increasing total porosity) and the particle density (by diluting the heavy solid phase with light plastic components). The introduction of MPs disrupts the normal metabolism of soil bacterial communities; a disruption directly reflected in functional genes associated with carbon cycling. MPs can interfere with the activity of key metabolic enzymes involved in fungal nutrient cycling, thereby disrupting normal energy allocation and material metabolism. Viruses can regulate the turnover and metabolism of microbial communities through lytic and lysogenic cycles, consequently influencing the carbon fate of MPs. The toxicity and underlying mechanisms of MPs on soil fauna primarily manifest in aspects such as feeding behavior, growth and development, oxidative stress, intestinal toxicity, and reproductive toxicity. The direct effects of MPs on plants include physical barriers and mechanical damage, induction of oxidative stress, interference with nutrient uptake, disruption of photosynthesis and carbon metabolism, and disruption of plant hormone networks. This review identifies critical knowledge gaps, particularly regarding crop quality, field-based soil faunal studies, virus-microbe interactions, and degradation products, and proposes future research directions to better understand the risks MPs pose to agricultural sustainability and food safety.
The growing pressure exerted by global food demand, combined with the excessive use of chemical and synthetic inputs, is prompting the agricultural sector to seek innovative and sustainable solutions to improve, or at least maintain, crop yields in a context of increased abiotic stress linked to climate change. Among the promising approaches, biostimulants are attracting growing interest, particularly those derived from natural sources such as seaweed extracts, humic acids, and beneficial microorganisms. These products work through various mechanisms, including osmotic regulation, activation of antioxidant systems, stimulation of root growth, and improvement of nutrient absorption. Many recent research and review articles have explored the optimal combinations of raw materials, formulation processes, target crops, and environmental conditions to maximize beneficial effects on plant growth, soil health, and tolerance to abiotic stresses. As a result, a growing range of commercial products is emerging, with diverse chemical compositions, formulations, and modes of application. However, the precise relationships between the biochemical composition of biostimulants and their physiological effects remain poorly understood, suggesting a key role for molecular synergies. This review provides a concise overview of recent advances in biostimulant research and their potential to enhance food security by improving crop resilience in the context of climate change.
Boujemaa Fassih, Raja Ben-Laouane, Abdessamad Fakhech et al.· Sustainability· 2 citations
Cover crops are increasingly promoted as a pillar of climate-smart agriculture due to their potential to improve soil organic carbon (SOC) sequestration, improve soil health, and regulate agroecosystem resilience. However, reported gains in SOC are inconsistent, and a fragmented understanding of the underlying mechanisms has hindered a clear evaluation of their long-term stabilization potential. This review summarizes the recent literature on the various functions of cover crops in the soil carbon cycle, nutrient cycling, and ecological processes. Cover crops can enhance SOC sequestration in numerous ways, such as through above- and belowground biomass inputs, root protein exudation, and microbial necromass. They also help in carbon stabilization by improving soil aggregation and physical protection of soil organic matter. Cover cropping leads to an average of 7–8% increase in SOC stocks and 15% increase in water-stable aggregates, with these effects differing based on climate, soil properties, cover crop species, and management approach. Biologically, cover crops contribute to soil biodiversity, microbial activity, and habitats of useful organisms that facilitate natural pest control and weed control. Notwithstanding these advantages, there are certain drawbacks, such as possible water use trade-offs and inconsistent effects across agroecosystems. This review emphasizes the diverse benefits of cover crops for sustainable agricultural production, climate change mitigation, and ecosystem resilience. The future studies should focus on long-term, system-based, and region-specific studies to quantify the carbon stabilization mechanisms and optimize cover cropping management in different agroecosystems. Cover crops increase global soil organic carbon stocks by 7–8%. Water-stable aggregates increase by 15% under cover crop management systems. Soil organic carbon sequestration rate ranges from 0.24–0.32 Mg C ha⁻¹ yr⁻¹ Cover crops enhance microbiomes (up to +24%) and soil biodiversity. Cover crops enhance soil structure, water storage, and decrease soil erosion. Legumes also fix nitrogen, reducing synthetic N fertilizer by 30–50%. Cover crops increase global soil organic carbon stocks by 7–8%. Water-stable aggregates increase by 15% under cover crop management systems. Soil organic carbon sequestration rate ranges from 0.24–0.32 Mg C ha⁻¹ yr⁻¹ Cover crops enhance microbiomes (up to +24%) and soil biodiversity. Cover crops enhance soil structure, water storage, and decrease soil erosion. Legumes also fix nitrogen, reducing synthetic N fertilizer by 30–50%.
S. Demissie, Genetu Fekadu, G. Tiruneh· Ecological Processes· 0 citations
Micronutrient deficiencies, collectively known as hidden hunger, affect more than two billion people worldwide and remain a major challenge for sustainable agriculture, global food security and human nutrition. Crop biofortification has emerged as a sustainable agricultural strategy to enhance the concentration and bioavailability of essential micronutrients in edible plant tissues while reducing reliance on post-harvest fortification and dietary supplementation. This review provides an integrated analysis of the soil, plant physiological, agronomic and molecular processes governing biofortification efficiency in agricultural systems. Particular emphasis is placed on how soil formation, mineralogy, nutrient speciation, organic matter and rhizosphere interactions regulate micronutrient availability, root uptake, translocation and accumulation in crops. The review further examines plant physiological mechanisms involved in nutrient acquisition and partitioning, together with the contribution of beneficial microorganisms, precision agriculture and digital technologies to improving nutrient-use efficiency under diverse agricultural conditions. Conventional breeding, agronomic biofortification, transgenic approaches and genome-editing technologies are critically evaluated as complementary strategies for developing nutrient-enriched and climate-resilient crop varieties. Particular attention is also given to nutrient bioavailability, post-harvest stability and consumer acceptance, which ultimately determine the nutritional effectiveness of biofortified crops. Furthermore, the review discusses how climate change modifies soil properties, plant physiology and crop productivity, thereby influencing micronutrient availability, nutrient accumulation and the long-term effectiveness of biofortification programmes. By integrating advances in soil science, plant physiology, agronomy and molecular biology, this review identifies current challenges, knowledge gaps and future research priorities for developing resilient biofortification strategies capable of supporting sustainable agricultural systems and improving global nutritional security.
C. Pessoa, D. Daccak, I. Luís et al.· The Scientist· 0 citations
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