Soil For Sustainable Agriculture Research Articles

Potentials of microbe-plant assisted bioremediation in reclaiming heavy metal polluted soil environments for sustainable agriculture

As human population growth drives the demand for food, crop intensification has increased. However, urbanization, industrialization, and contamination of soil by heavy metals (HM) have become significant challenges to agricultural production. Urbanization activities jeopardize and/or harm soil health, which is critical for the environment, ecosystems, sustainable agriculture, and the global economy. Smelting, mining, and other industrial activities that release toxic HMs into the environment significantly reduce soil health, with serious consequences for both plants and humans. Furthermore, the presence of HM in the soil severely hinders sustainable agriculture. Therefore, to counteract the subsequent decrease in crop yield due to HM contamination, we must involve plants and appropriate microbes in eliminating these pollutants. This will lead to a more productive agriculture, food safety, and food security realization. Therefore, this study explored the efficacy, advantages, and limitations of current conventional methods of soil HM remediation as well as the potential of plants and microbes like Pseudomonas aeruginosa, Vibrio parahaemolyticus, Alyxia rubricaulis, and Maytenus bureaviana in the reclamation of HM polluted soil for sustainable agriculture. Employing natural and non-hazardous methods to remove these contaminants, as highlighted in this review, would help to improve soil health and quality, increase crop production, and promote sustainable agriculture, as outlined in the United Nations' Sustainable Development Goals.

Tomato seed bio-priming with Pseudomonas aeruginosa strain PAR: a study on plant growth parameters under sodium fluoride stress.

The primary goal of this experiment is to examine the effectiveness of Pseudomonas aeruginosa strain PAR as a rhizobacterium that promotes plant growth in mitigating the negative effects of fluoride-induced stress in tomato (Lycopersicon esculentum Mill.) plants. A total of 16 rhizobacterial strains were tested for plant growth-promoting (PGP) attributes, with isolates S1, S2, and S3 exhibiting different characteristics. Furthermore, growth kinetics studies revealed that these isolates were resilient to fluoride stress (10, 20, 40, and 80 ppm), with isolate S2 exhibiting notable resilience compared to the other two strains. Phylogenetic analysis revealed isolate S2 as P. aeruginosa strain PAR. Physiological analyses demonstrated that P. aeruginosa strain PAR had a beneficial impact on plant properties under fluoride stress, comprising seed germination, root length, shoot height, relative water content, and leaf area, the strain also impacted the buildup of glycine betaine, soluble sugar, and proline, demonstrating its significance in enhancing plant stress tolerance. In P. aeruginosa strain PAR-treated plants, chlorophyll content increased while malondialdehyde (MDA) levels decreased, indicating enhanced photosynthetic efficiency and less oxidative stress. The strain modified antioxidant enzyme action (catalase, ascorbate, glutathione reductase, peroxidase, and superoxide dismutase), which contributed to improved stress resilience. Mineral analysis revealed a decrease in sodium and fluoride concentrations while increasing magnesium, potassium, phosphorus, and iron levels, emphasizing the strain's significance in nutrient management. Correlation and principal component analysis revealed extensive correlations between physiological and biochemical parameters, underscoring P. aeruginosa strain PAR's multifaceted impact on plant growth and stress response. This study offers valuable information on effectively utilizing PGPR, particularly P. aeruginosa strain PAR, in fluoride-contaminated soils for sustainable agriculture. It presents a promising biological strategy to enhance crop resilience and productivity.

European agricultural soil management: Towards climate‐smart and sustainability, knowledge needs and research approaches

AbstractCurrent soil‐ and land degradation seriously challenge our societies; it contributes to climate change, loss of biodiversity and loss of agricultural productions. Yet, soils are also seen as a major part of the solution, if maintained or restored to provide ecosystem services. Climate‐smart sustainable management of soils can provide options for soil health maintenance and restoration. In the European Union, the resource management and sustainability challenge are addressed in the Green Deal that, among other goals, aspires towards a healthy climate‐resilient agricultural sector that will produce sufficient products without damaging ecosystems and contribute to better biodiversity and mitigate climate change. The European Joint Programme (EJP) SOIL was set up to contribute to these goals by developing knowledge, tools and an integrated research community to foster climate‐smart sustainable agricultural soil management that provides a diversity of ecosystem service, such as adapting to and mitigating climate change, allowing sustainable food production, and sustaining soil biodiversity. This paper provides an overview of the potential of climate‐smart sustainable soil management research to the targets of the Green Deal that are related to soils most directly. The EJP SOIL EU‐wide consultation (interviews and questionnaires) and literature analysis (national and international reports and papers) done in the first year (2020–2021) generated a wealth of data. This data showed that there are specific manners to do research that are essential for it to be effective and efficient and that can actively contribute to the Green Deal targets. We concluded that research needs to be: (i) interdisciplinary, (ii) long‐term, (iii) multi‐scaled, from plot to landscape, (iv) evaluating trade‐offs of selected management options for ecosystem services and (v) co‐constructed with key stakeholders. Research on climate‐smart sustainable soil management should be developed (1) on plot scale when mobilizing soil processes and on landscape scale when addressing sediment and water connectivity and biodiversity management; and (2) address the enabling conditions through good governance, social acceptance and viable economic conditions.

Depth distribution of nano- and microplastics and their contribution to carbon storage in Chinese agricultural soils

The extensive and prolonged utilization of plastic materials in agriculture has primarily led to the accumulation of nano- and microplastics (NMPs, ≤5 mm) in farmland soils. The spatial-vertical distribution of NMPs mass concentrations and their impact on the national agricultural soil carbon reservoir remain unexamined. In this study, we quantified the residual mass concentrations of six prevalent plastic types in farmland soils around China using the double-shot model of thermal desorption/pyrolysis-gas chromatography–mass spectrometry (TD/Py-GC–MS). The results showed that median NMPs concentrations were 79.81 μg/g in the topsoil layer (0–15 cm), 57.17 μg/g in the middle soil layer (15–30 cm), and 32.90 μg/g in the bottom soil layer (30–45 cm). Overall, agricultural soil NMPs levels declined from the surface to deeper soil layers; however, some regions exhibit an opposite trend. Furthermore, our estimations indicate that carbon sourced from NMPs contributes to the agricultural soil carbon pool within a range from 0.004 % to 5.606 %, depending on the soil depth. As a hallmark of sustainable agricultural soil management, it is noteworthy that the concealed and continuously expanding carbon contribution of NMPs has an impact on soil carbon storage, albeit at a relatively low level. Our data serves as a foundational reference point and enables a precise evaluation of future contributions of NMPs to the storage of carbon in agricultural soils within China.

Quantifying the Influence of Enriched Urban Compost and Wastes on Soil Physico-chemical and Biological Parameters of Bettahalli Village, Bangalore North Taluk: A Quantitative Analysis

Enriched urban compost enhances soil for sustainable agriculture, improving structure, water dynamics, nutrient release, microbial life, and contributing to climate change mitigation. The present study was carried out in 2022 late winter to assess the impact of enriched urban compost and wastes on soil properties. Collected Soil samples were analyzed for physical, chemical, and biological properties pre and post-maize harvest. Enriched urban compost treatments showed a slight reduction in bulk density. Increased Moisture holding capacity, pH, electrical conductivity, organic carbon, and magnesium remained mostly unchanged.
 Nitrogen, phosphorus, and potassium increased significantly with enriched compost, promoting sustained nutrient release. Available sulfur rose with compost addition. DTPA-extractable Cu, Zn, Fe, Mn, and B were significantly higher with enriched compost. Chromium, nickel, lead, and cadmium remained below critical limits. Dehydrogenase and urease activities were significantly higher with enriched compost, indicating enhanced microbial action. Acid phosphatase activity increased, likely due to elevated phosphorus levels in organics, supporting P solubilizers.
 Enriched urban compost enhances soil properties, promoting agricultural sustainability through climate change mitigation, improved structure, and enhanced nutrient release. Advisably, incorporating enriched urban compost into agricultural practices optimizes soil health, fosters sustainable nutrient management, and supports microbial activities, thereby enhancing agricultural productivity.

The importance of biomass in sustainable agricultural soil management

The importance of biomass in sustainable agricultural soil management

Plant Growth-Promoting Rhizobacteria (PGPR) Assisted Bioremediation of Heavy Metal Toxicity.

Due to a variety of natural and anthropogenic processes, heavy metal toxicity of soil constitutes a substantial hazard to all living beings in the environment. The heavy metals alter the soil properties, which directly or indirectly influence the agriculture systems. Thus, plant growth-promoting rhizobacteria (PGPR)-assisted bioremediation is a promising, eco-friendly, and sustainable method for eradicating heavy metals. PGPR cleans up the heavy metal-contaminated environment using various approaches including efflux systems, siderophores and chelation, biotransformation, biosorption, bioaccumulation, precipitation, ACC deaminase activity, biodegradation, and biomineralization methods. These PGPRs have been found effective to bioremediate the heavy metal-contaminated soil through increased plant tolerance to metal stress, improved nutrient availability in soil, alteration of heavy metal pathways, and by producing some chemical compounds like siderophores and chelating ions. Many heavy metals are non-degradable; hence, another remediation approach with a broader scope of contamination removal is needed. This article also briefly emphasized the role of genetically modified PGPR strains which improve the soil's degradation rate of heavy metals. In this regard, genetic engineering, a molecular approach, could improve bioremediation efficiency and be helpful. Thus, the ability of PGPRs can aid in heavy metal bioremediation and promote a sustainable agricultural soil system.

Nanoparticle Mediated Plant Tolerance to Heavy Metal Stress: What We Know?

Nanoparticles (NPs) are playing an important role in addressing various environmental constraints by giving ingenious and successful resolutions. Heavy metal (HM) stress has gained significant importance in the last few years because of its speedy incorporation into agricultural sectors. Due to exclusive physiochemical properties, NPs can be effectively applied for stress mitigation strategies. NPs are highly effective over bulk scale parts owing to the control of the enhanced surface area and the possibility for specific properties to enhance nutrient uptake. In the present review, we explore the use of NPs as an environmentally sound practice to enhance plant growth when exposed to abiotic stress, particularly HM stress. Furthermore, we display an extensive summary of recent progress concerning the role of NPs in HM stress tolerance. This review paper will also be useful for comprehending phytoremediation of contaminated soils and indicates the prospective research required for the cooperative submission of NPs in the soil for sustainable agriculture.

Impacts of Co-application of Chemical Fertilizer Reduction and Organic Material Amendment on Fluvo-aquic Soil Microbial N-cycling Functional Gene Abundances and N-converting Genetic Potentials in Northern China

The emerging environment-associated issues due to the overuse of inorganic fertilizers in agricultural production are of global concern despite the benefit of high yields. Eco-friendly organic materials with the capability to fertilize soil are encouraged to partially replace mineral fertilizer. The N cycle conducted by soil microorganisms is the most important biogeochemical process, dictating the N bioavailability in farmland ecosystems; however, little is known about how organic material amendment affects soil microbial N cycling under chemical fertilizer reduction. Hence, a fixed field trial with five fertilization practices was implemented to experimentally alter microorganisms essential for the soil N cycle, including conventional chemical fertilization (NPK), reduced chemical fertilization (NPKR), reduced chemical fertilization plus straw (NPKRS), reduced chemical fertilization plus organic fertilizer (NPKRO), and reduced chemical fertilization plus organic fertilizer and straw (NPKROS). The microbial N-cycling gene abundances and associated N-converting genetic potentials were evaluated using real-time quantitative PCR. In comparison to conventional chemical fertilization (NPK), organic addition significantly increased the amounts of heterotrophic microbes involved in organic N decomposition, N fixation, and N reduction; however, it reduced autotrophic microbes performing ammonia oxidization. Consequently, the overall proportion of heterotrophic microbes was remarkably enhanced, and the autotrophic proportion was correspondingly lowered. The fertilization practice shift significantly improved N fixation and gaseous N emission potentials, whereas it suppressed NO3- leaching potential. A significant discrepancy among five fertilization treatments was observed based on functional gene abundances (PERMANOVA, P=0.002),as revealed by distance-based redundancy analysis (db-RDA), with NH4+ as the dominant factor. Organic fertilizer addition was beneficial for heterotrophic N functional microorganisms, with simultaneous input of straw augmenting such an effect. Pearson's correlation analysis revealed that N storage and gaseous N emission potentials were both substantially negatively correlated with NH4+; NO3- leaching potential was notably negatively associated with SOC and TN but significantly related to NH4+. In conclusion, chemical fertilizer reduction combined with organic material amendments, a main fertilization recommendation, may enhance soil N storage, diminish N loss by leaching, and mitigate the environmental risk of N2O emission. This deserves attention considering that healthy and sustainable agricultural soil environment can be cultivated from the view of microbial N-cycling.

Biosynthesis and chemical composition of nanomaterials in agricultural soil bioremediation: a review.

Nanomaterials (NMs) are currently being used in agricultural soils as part of a new bioremediation (BR) process. In this study, we reviewed the biosynthesis of NMs, as well as their chemical composition and prospective strategies for helpful and sustainable agricultural soil bioremediation (BR). Different types of NMs, such as nanoparticles, nanocomposites, nanocrystals, nano-powders, and nanotubes, are used in agricultural soil reclamation, and they reflect the toxicity of NMs to microorganisms. Plants (Sargassum muticum, Dodonaea viscose, Aloe Vera, Rosemarinus officinalis, Azadirachta indica, Green tea, and so on) and microorganisms (Escherichia coli, Shewanella oneidensis, Pleurotus sp., Klebsiella oxytoca, Aspergillus clavatus, and so on) are the primary sources for the biosynthesis of NMs. By using the BR process, microorganisms, such as bacteria and plants, can immobilize metals and change both inorganic and organic contaminants in the soil. Combining NMs with bioremediation techniques for agricultural soil remediation will be a valuable long-term solution.

Synergism of Beneficial Microbes Helps to Rejuvenate Flood and Landslide Affected Soils for Sustainable Agriculture – A Review

Climatic disasters, like floods and landslides, are the major causes for the decline in soil fertility or soilorganic matter. Soil organic matter influences the physical, chemical, and biological properties of soil; it isthe fundamental aspect that discloses soil health. Microorganisms in the soil environment participate acritical task in the enhancement of soil nutrients and soil fertility. Even though microbial bioinoculants arewidely studied for improving agriculture, the application of microbial consortium for the restoration oforganic matter or soil fertility in the flood and landslide depleted soils are yet to be exploited. The part ofliving biomass, i.e. soil microorganisms in restoring soil organic matter seems to be crucial, as microbes arethe major drivers in escalating organic matter in the soil. The living biomass recycles the nutrients in thesoil by utilizing the plant and animal litter in the soil and offers the crops adequate nutrients. Thus,microorganisms can force the accumulation of stable and chemically diverse soil organic matter in poorfertile soils. Exploring such vibrant, complex advantageous interactions among microorganisms seemsimperative to replenish organic matter exhausted soil. This article reviews the relevance of soil organicmatter, the role of soil microorganisms in improving soil organic matter and emphasizes the need forintensive research in raising beneficial microbiome for replenishing soil organic matter and thus to rejuvenatethe flood and landslide depleted soils to sustain agriculture.

Perspectives on Converting Keratin-Containing Wastes Into Biofertilizers for Sustainable Agriculture.

Keratin-containing wastes become pollution to the environment if they are not treated properly. On the other hand, these wastes can be converted into value-added products applicable to many fields. Organic fertilizers and biofertilizers are important for sustainable agriculture by providing nutrients to enhance the growth speed of the plant and production. Keratin-containing wastes, therefore, will be an important resource to produce organic fertilizers. Many microorganisms exhibit capabilities to degrade keratins making them attractive to convert keratin-containing wastes into valuable products. In this review, the progress in microbial degradation of keratins is summarized. In addition, perspectives in converting keratin into bio- and organic fertilizers for agriculture are described. With proper treatment, feather wastes which are rich in keratin can be converted into high-value fertilizers to serve as nutrients for plants, reduce environmental pressure and improve the quality of the soil for sustainable agriculture.

Fly ash application in soil for sustainable agriculture: an Indian overview

Fly ash application in soil for sustainable agriculture: an Indian overview

Proposal of a Nomenclature for Hydrogeological Instability Risks and Case Studies of Conservative Soil Tillage for Environmental Protection

In order to implement environmental protection, within the Soil Cadastre, previously proposed as a multipurpose inventory that aims to promote sustainable soil uses, the hydrogeological instability caused by human activities is the focus of this work. These activities can be aimed at sustainable agricultural soil use or the building of roads to allow the access to the fields. The soil’s hydrogeological instability causes the unsustainable use and management of a cadastral parcel. Therefore, the aim of this work is to propose a nomenclature for hydrogeological instability risks, as well as the best practices of conservative soil tillage in case studies, in order to reduce environmental impact. According to the proposed Soil Cadastre, the missing environmental sustainability of a parcel and the reason for this must be communicated to the field owner or manager. In a hilly area of inland Western Sicily, four main risk types of hydrogeological instability were identified: hydrogeological instability (caused only by natural factors); hydraulic-pedological farming instability (crop not suitable for the field for missing or insufficient soil drainage and landslides); hydraulic-infrastructural instability (built up infrastructures unsuitable for the site); hydraulic-infrastructural-pedological-management instability (field improvements changing the downflow line and crop operations not suitable for the soil and climate parameters). The farm owner or manager must be informed about the risk type affecting their fields in order to perform the best practices (i.e., conservative soil tillage), for implementing or restoring a sustainable soil use or management in each cadastral parcel.

A soil quality index using Vis-NIR and pXRF spectra of a soil profile

A soil quality index (SQI) can be used to manage the soil for potential uses and remediate limitations of soil for sustainable agriculture and ecology. The objectives of this study were to (i) characterize vertical and horizontal variations of some soil properties and SQI in a Fluventic Haploxerepts profile in Eskişehir, Turkey, (ii) compare interpolation methods for mapping the distribution of soil properties and SQI in the profile wall, and (iii) assess cubist model for predicting soil properties and SQI using individual and combined Vis-NIR and pXRF spectra in the profile. The soil profile wall (1 m deep × 1 m wide) was divided into a raster of 10 × 10 cm intervals for collecting a total of 100 soil samples. The soil samples were analyzed for soil physical, chemical properties, and elemental concentrations and scanned using Vis-NIR (350–2500 nm) and pXRF (0–8 and 0–45 kV) spectrometers. Standard scoring function was used for standardization of indicators. Weighted linear combination method was used to calculate SQI and F-AHP for assigning weights of indicators. The 100 samples were split into calibration (70%) and validation (30%) datasets. Individual or combined Vis-NIR and pXRF spectra were used in cubist model to evaluate the feasibility for predicting soil properties and SQI in the Inceptisol. Results suggested that the soil profile had a considerable variation of soil properties and SQI with depth and within horizons. The A horizon had the highest SQI. In addition, Vis-NIR had better prediction performances for pH, SOM, Fe, and Mn (R2 = 0.42–0.88), whereas pXRF had better prediction performances for EC, CaCO3, P, and Zn (R2 = 0.18–0.90). In addition, combining Vis-NIR, pXRF8, and pXRF45 had better prediction performance for sand, silt, clay, K, Cu, and SQI (R2 = 0.81–0.97). We concluded that Vis-NIR and pXRF spectra can be successfully used to predict SQI in Fluventic Haploxerepts. Combined Vis-NIR and pXRF spectra had better prediction performance for SQI.

Organic versus inorganic fertilizers: Response of soil properties and crop yield

<abstract> <p>The decrease in soil productivity and quality caused by the continuous and abusive use of mineral fertilizers makes necessary to adopt more sustainable agricultural soil management strategies that help to maintain soil edaphic fertility. In light of these considerations, we have evaluated the effect of organic vs. inorganic fertilization on soil microbial communities, soil quality, and crop yield in a melon crop. The following treatments were tested: i) aerobic sewage sludge from a conventional wastewater treatment plant (WWTP) using aerobic bacteria (SS); ii) aerobic sewage sludge from a WWTP using a bacteria-microalgae consortium (B); iii) N-P-K mineral fertilizer (M); iv) a treatment in which 50% of the N was contributed by SS and 50% by mineral fertilizer (M + SS); v) a treatment in which 50% of the N was contributed by B and 50% by mineral fertilizer (M + B); and vi) a no-fertilized control soil. Melon yield and fruit quality were determined in addition to several soil physical, chemical, biochemical and microbiological parameters. Organic fertilizers (SS and B) increased the percentage of soil water-stable aggregates (52 and 60% respectively) as well as the content of organic C (18 and 31%), water soluble C (21 and 41%), N (15 and 41%) and available P content (41 and 82%) compared to inorganic fertilization. They also stimulated bacterial and fungal abundance to a greater extent than mineral fertilizers (189 and 242% vs 85%, and 57 and 122% vs 29%, respectively), as well as soil respiration, and dehydrogenase, β-glucosidase, phosphatase, urease, and glycine aminopectidase activities. The analysis of principal components with parameters linked to soil quality clearly showed that organic fertilizers cause a greater improvement in soil characteristics and microbial community than mineral fertilizers. Results demonstrate that organic and combined fertilization could be used as substitutes for nitrogen mineral fertilizers in melon crop, since these treatments led to similar melon production and quality while improving soil characteristics and microbial population size and activity.</p> </abstract>

Application of Nanoparticles Alleviates Heavy Metals Stress and Promotes Plant Growth: An Overview.

Nanotechnology is playing a significant role in addressing a vast range of environmental challenges by providing innovative and effective solutions. Heavy metal (HM) contamination has gained considerable attention in recent years due their rapidly increasing concentrations in agricultural soil. Due to their unique physiochemical properties, nanoparticles (NPs) can be effectively applied for stress alleviation. In this review, we explore the current status of the literature regarding nano-enabled agriculture retrieved from the Web of Science databases and published from January 2010 to November 2020, with most of our sources spanning the past five years. We briefly discuss uptake and transport mechanisms, application methods (soil, hydroponic and foliar), exposure concentrations, and their impact on plant growth and development. The current literature contained sufficient information about NPs behavior in plants in the presence of pollutants, highlighting the alleviation mechanism to overcome the HM stress. Furthermore, we present a broad overview of recent advances regarding HM stress and the possible mechanism of interaction between NPs and HM in the agricultural system. Additionally, this review article will be supportive for the understanding of phytoremediation and micro-remediation of contaminated soils and also highlights the future research needs for the combined application of NPs in the soil for sustainable agriculture.

Cassava Leaf Compost Influences Growth, Yield and Nutrient Uptake of Rice

The application of compost as alternatives to reduce the use of synthetic fertilizers is considered a feasible agricultural practice to mitigate soil degradation caused by long term application of synthetic fertilizers. Therefore, the study aimed to investigate the effect of cassava leaf compost on growth, yield and nutrient uptake of rice. Six treatments of two rice varieties (BRRI dhan29 and BINA dhan5) and three sources of nitrogen (Control - no nitrogen applied but residual soil N was 0.123%, urea @ 200 kg ha-1 and Cassava Leaf Compost @ 10 t ha-1) were used in this study. Cassava Leaf Compost @ 10 t ha-1 and urea @ 200 kg ha-1 significantly increased effective tillers per hill, 1000-grain weight, and grain yield were 12.84 and 13.75, 25.00 g and 24.93 g, 5.57 t ha-1 and 6.047 t ha-1, respectively. Cassava Leaf Compost @ 10 t ha-1 and urea @ 200 kg ha-1 increased N uptake in root is 0.821% and 0.756%, and the residual effect of compost increased C, N, P, K and S availability in soil for the succeeding crop in Cassava Leaf Compost @ 10 t ha-1 applied plots. Carbon and N mineralization rates were higher than control and soils receiving recommended dose of inorganic fertilizers. Our findings suggested that compost could be used as biofertilizer to improve degraded cropland soils for sustainable agriculture.

Temporal and spatial variation of soil microorganisms and nutrient under white clover cover

Cover crops have been implemented for decades as sustainable agricultural soil management practice. However, knowledge about the temporal and spatial variation in soil nutrients and the succession of microorganisms during soil restoration under cover crops maintained for a different number of years are still poorly understood. Here, using the 16S and ITS rRNA gene sequencing techniques, we investigated the evolution of microbial community structure, and the pattern of nutrient accumulation was analyzed in a chronosequence of white clover used as a cover crop for 4, 8, and 13 years in a semiarid orchard on the Loess Plateau, China. Clean tillage was used as the control. We found that 4 years of cover crop had little effect on the soil nutrients, while 8- and 13-year-old cover crops contributed greatly to the soil nutrients. The use of cover crops for 13 years effectively increased the bacterial alpha diversity and the relative abundances of Actinobacteria, Firmicutes and Ascomycota in the 0−20 cm soil layer. These results indicated that long-term organic input stimulated transformation of the dominant population of microorganisms into a population conducive to the decomposition of plant residues. Furthermore, bacteria were more sensitive to the implementation of cover practices than fungi. Notably, on the genus level, the evolution of the bacterial community structure was more stable, while the evolution of the fungal community structure was more disordered with an increase in the years of cover crop. The nitrogen components were the best environmental predictors of the state of the microbial community. Overall, this study adds to our understanding of the patterns of nutrient accumulation and microbial succession under different years of cover crops and has implications for the formulation of a sustainable development strategy in semiarid agriculture systems.

Long‐term fertilization does not affect soil carbon/nitrogen/sulfur ratios or the proportion between labile and nonlabile fractions in Mollisols

AbstractAgricultural management practices such as fertilization may affect the overall soil quality and nutrient supply capacity. In this study, we hypothesized that long‐term fertilization promotes (a) an increase in the proportion of easily degradable soil organic C, N, and S fractions and (b) changes in the soil C, N, and S stoichiometric ratios in the direction of favoring the specific nutrient added to the soil. We included S in our study due to the increasing importance of S fertilization in many agricultural soils. A long‐term experiment involving six fertilization treatments and maize (Zea mays L.), soybean [Glycine max (L.) Merr.], and wheat (Triticum aestivum L.) as cash crops was conducted for 14 yr in an on‐farm network located in the Pampean region (Argentina). Long‐term fertilization did not have a central role in defining the C, N, and S distribution between soil organic fractions or their stoichiometric ratios since the particulate organic matter (POM)‐C/total C, POM‐S/total S, C/N, C/N, and N/S ratios were not affected by fertilization treatments and the mineralizable N/total N ratio varied in a very short range. Instead, long‐term fertilization increased residue C inputs to the soil (8.7–19 Mg ha−1 over the unfertilized control) and, in turn, increases in soil total C, N, and S followed a linear relationship with residue inputs. This relationship was not affected by fertilization or site factors. These data contribute to understanding of the effects of continued fertilization on soil properties such as the distribution of fast‐ and slow‐cycling organic matter and nutrient concentrations, which are essential for effectively managing soils for sustainable agriculture.