Acid Soils Research Articles

Linking phosphorus fertility to soil microbial diversity and network complexity in citrus orchards: Implications for sustainable agriculture

Continuous input of chemical fertilizers causes soil acidification, land degradation, and water eutrophication, but its impact on soil microbial communities and co-occurrence patterns of microboes is unclear. In this study, we evaluated the impact of chemical fertilizer on bacterial community diversity and ecological network at 75 citrus sites in a watershed where chemical fertilizer is continuously applied. In addition, 25 natural forest sites adjacent to citrus sites were used as references to compare the potential effects of land conversion from natural forests to citrus orchards on soil bacterial diversity and microbial network. The results showed that the cultivation of citrus results in soil phosphorus (P) accumulation, with significantly higher available and mineral-bound phosphate contents than those found in soils of natural forests. Citrus soil average soil available P was 73.2 mg/kg, which was 20 times higher than that in forest soils. As the P content accumulates, soil bacterial Shannon index linearly decreases from 7.06 to 5.93 and is significantly lower than that of adjacent natural forest soils (7.13). Low P fertility soils have higher microbial network complexity and stability, containing more microbial communities and tighter relationships between microbes compared to higher P fertility soils. Soil P content and soil pH regulates soil microbial network complexity and stability. In addition, soil bacterial community structure in soils of natural forests is significantly different from that in citrus soils, and the bacterial community structure in high P soils is different from that in medium and low P soils. Soil P fertility reduces the relative abundance of dominant communities including Proteobacteria, Bacteroidetes, and Gemmatimonadetes, and also changes the relative abundance of some functional microbial communities, such as some phosphorus cycling microorganisms, including Acetobacteraceae and Beijerinckiaceae. In conclusion, soil phosphate accumulation severely alters soil bacterial community diversity, complexity, stability, and functionality. This could have negative impacts on soil functional stability and the sustainability of citrus orchards.

Nickel iron mining slag and soil acidity correction

Soil acidity is one of the limiting factors of agricultural production most commonly reported in oxidic soils, such as Oxisols often found in the Brazilian Cerrado regions for example. The dredging is the most efficient management practice in the correction of soil acidity and increase of base saturation levels. The nickel iron mining scora is a residue that has relevant amounts of magnesium silicate, and may have neutralization capacity of soil acidity. Therefore, the objective of this work was to value the potential of magnesium silicate as a soil acidity corrective. The experimental design used was completely randomized, arranged in a 2x5x5 factorial scheme with twelve replications, where the 1st factor consisted of two hatching dates, 30 and 60 days, the 2nd factor consisted of five doses of mining slag: 0, 90, 120, 150 and 180 Mg ha-1, and the 3rd factor consisted of five doses of dolomític limestone: 0, 90, 120, 150 and 180 Mg ha-1. The mining slag did not present soil pH neutralization power under the evaluated conditions. However, it presented potential for neutralization under conditions of lower granulometry and greater solubilization.

Genomic fingerprints of the world's soil ecosystems.

Despite the explosion of soil metagenomic data, we lack a synthesized understanding of patterns in the distribution and functions of soil microorganisms. These patterns are critical to predictions of soil microbiome responses to climate change and resulting feedbacks that regulate greenhouse gas release from soils. To address this gap, we assay 1,512 manually curated soil metagenomes using complementary annotation databases, read-based taxonomy, and machine learning to extract multidimensional genomic fingerprints of global soil microbiomes. Our objective is to uncover novel biogeographical patterns of soil microbiomes across environmental factors and ecological biomes with high molecular resolution. We reveal shifts in the potential for (i) microbial nutrient acquisition across pH gradients; (ii) stress-, transport-, and redox-based processes across changes in soil bulk density; and (iii) greenhouse gas emissions across biomes. We also use an unsupervised approach to reveal a collection of soils with distinct genomic signatures, characterized by coordinated changes in soil organic carbon, nitrogen, and cation exchange capacity and in bulk density and clay content that may ultimately reflect soil environments with high microbial activity. Genomic fingerprints for these soils highlight the importance of resource scavenging, plant-microbe interactions, fungi, and heterotrophic metabolisms. Across all analyses, we observed phylogenetic coherence in soil microbiomes-more closely related microorganisms tended to move congruently in response to soil factors. Collectively, the genomic fingerprints uncovered here present a basis for global patterns in the microbial mechanisms underlying soil biogeochemistry and help beget tractable microbial reaction networks for incorporation into process-based models of soil carbon and nutrient cycling.IMPORTANCEWe address a critical gap in our understanding of soil microorganisms and their functions, which have a profound impact on our environment. We analyzed 1,512 global soils with advanced analytics to create detailed genetic profiles (fingerprints) of soil microbiomes. Our work reveals novel patterns in how microorganisms are distributed across different soil environments. For instance, we discovered shifts in microbial potential to acquire nutrients in relation to soil acidity, as well as changes in stress responses and potential greenhouse gas emissions linked to soil structure. We also identified soils with putative high activity that had unique genomic characteristics surrounding resource acquisition, plant-microbe interactions, and fungal activity. Finally, we observed that closely related microorganisms tend to respond in similar ways to changes in their surroundings. Our work is a significant step toward comprehending the intricate world of soil microorganisms and its role in the global climate.

Dolomitic lime and silicate in no‐till: Nutritional status, soil fertility, and soybean agronomic performance

AbstractLimestone is the most widely used agricultural input for soil acidity correction and calcium (Ca) and magnesium (Mg) fertilization. However, other materials have the potential to fulfill these purposes, such as steel slags, also known as silicates. Silicates have higher solubility than limestone, serving as agents for increase pH in no‐till, in addition to being a source of Ca, Mg, and silicon (Si). This study aimed to compare the effects of surface application of dolomitic lime and calcium magnesium silicate on soil chemical properties, soybean [Glycine max (L.) Merr.] nutritional status, and grain yield under no‐till. The experiment was installed in the northwest Paraná State, Brazil, on a Rhodic Eutrustox. Lime and silicate rates were applied by broadcasting before the sowing of soybean. Silicate treatment increases soil Ca2+, pH, and base saturation up to a depth of 0.10 m. By contrast, liming effects on soil chemistry were restricted to the 0.05 m top layer after 24 months of application. The acidity correction and Ca2+ supply to greater soil depths and the increased leaf Si as a beneficial element provided by silicate treatment contributed to increasing soybean yield in the 2018/2019 and 2019/2020 seasons. Lime application, regardless of the rate, did not improve soybean yield. Waste from the steel industry can be used as acidity correctives and source of Si, Ca, and Mg, improving the agronomic performance of soybean.

Decrease in fertility of typical chernozem due to long-term anthropogenic pressure in grain-beet crop rotations

The saturation of sugar beet rotations under different fertilizer application systems and long-term cultivation induces significant changes in soil properties, leading to decreases in humus content, mineral nitrogen, phosphorus, and potassium. The study was conducted in a stationary multifactorial experiment in grain-beet crop rotations: crop rotation, row-crop, and grain-row crop rotations with the application of 40 t/ha of manure under sugar beets + NPK 100:90:90 and a variant without fertilizers. The paper presents the results of monitoring changes in humus content during each rotation, reduction of humus reserves in the plow layer, and physicochemical and agrochemical soil indicators. In the variants without fertilizers, we observed 0.24–0.41% decline in humus content in all crop rotations during 3 rotations of ten-field crop rotations (30 years). Overall, there occurred 0.89–1.00% decrease over 50 years of anthropogenic influence, equivalent to 31.8–35.7 t/ha, or 23.1–26.1% of initial reserves per hectare. Despite application of 40 t/ha of manure + NPK 100:90:90 under sugar beets, humus loss was 27.5 t/ha in the row-crop rotation and 16.8 t/ha in the grain-row crop rotation. Fertilizer application led to increase in exchangeable and hydrolytic soil acidity. With the application of 6.7 t/ha of manure + NPK 53:42:42 per 1 ha of crop rotation area, there was a tendency towards increase in mineral nitrogen content, mobile phosphorus doubled to 280.1–302.8 mg/kg compared to the variant without fertilizers, and exchangeable potassium decreased regardless of the fertilization system, which was associated with its utilization by plants. Sugar-beet yield increased to 44.76 t/ha in the crop-rotation under the organo-mineral-fertilizer application system, exceeding the spring wheat rotation by 4.63 t/ha and the variants without fertilizers by 2.45–2.72 times. Therefore, the modern fertilizer application system under sugar beets did not ensure stabilization of humus content in the soil and increased its acidity. It is necessary to more broadly use cover crops in crop rotations, incorporate crop residues, and apply biological preparations to improve soil fertility.

PH selects for distinct N2O-reducing microbiomes in tropical soil microcosms

Abstract Nitrous oxide (N2O), a greenhouse gas with ozone destruction potential, is mitigated by the microbial reduction to dinitrogen catalyzed by N2O reductase (NosZ). Bacteria with NosZ activity have been studied at circumneutral pH but the microbiology of low pH N2O reduction has remained elusive. Acidic (pH < 5) tropical forest soils were collected in the Luquillo Experimental Forest in Puerto Rico, and microcosms maintained with low (0.02 mM) and high (2 mM) N2O assessed N2O reduction at pH 4.5 and 7.3. All microcosms consumed N2O, with lag times of up to 7 months observed in microcosms with 2 mM N2O. Comparative metagenome analysis revealed that Rhodocyclaceae dominated in circumneutral microcosms under both N2O feeding regimes. In pH 4.5 microcosms, Peptococcaceae dominated in high-N2O, and Hyphomicrobiaceae in low-N2O microcosms. Seventeen high-quality metagenome-assembled genomes (MAGs) recovered from the N2O-reducing microcosms harbored nos operons, with all eight MAGs derived from acidic microcosms carrying the clade II type nosZ and lacking nitrite reductase genes (nirS/K). Five of the 8 MAGs recovered from pH 4.5 microcosms represent novel taxa indicating an unexplored N2O-reducing diversity exists in acidic tropical soils. A survey of pH 3.5–5.7 soil metagenome datasets revealed that nosZ genes commonly occur, suggesting broad distribution of N2O reduction potential in acidic soils.

[Effects of Modified Distillers' Grains Biochar on Cadmium Forms in Purple Soil and Cadmium Uptake by Rice].

Biochar and modified biochar have been widely used as remediation materials in heavy metal-contaminated agricultural soils. In order to explore economical and effective materials for the remediation of cadmium (Cd)-contaminated acidic purple soil, distillers 'grains were converted into distillers' grains biochar (DGBC) and modified using nano-titanium dioxide (Nano-TiO2) to produce two types of modified DGBCs:TiO2/DGBC and Fe-TiO2/DGBC. A rice pot experiment was used to investigate the effects of different biochar types and application rates (1%, 3%, and 5%) on soil properties, nutrient content, Cd bioavailability, Cd forms, rice growth, and Cd accumulation. The results showed that:① DGBC application significantly increased soil pH, cation exchange capacity (CEC), and nutrient content, with TiO2/DGBC and Fe-TiO2/DGBC exhibiting better effects. ② DGBC and modified DGBCs transformed Cd from soluble to insoluble forms, increasing residual Cd by 1.22% to 18.46% compared to that in the control. Cd bioavailability in soil decreased significantly, with available cadmium being reduced by 11.81% to 23.67% for DGBC, 7.64% to 43.85% for TiO2/DGBC, and 19.75% to 55.82% for Fe-TiO2/DGBC. ③ DGBC and modified DGBCs increased rice grain yield, with the highest yields observed at a 3% application rate:30.60 g·pot-1 for DGBC, 37.85 g·pot-1 for TiO2/DGBC, and 39.10 g·pot-1 for Fe-TiO2/DGBC, representing 1.13, 1.40, and 1.44 times the control yield, respectively. Cd content in rice was significantly reduced, with grain Cd content ranging from 0.24 to 0.30 mg·kg-1 for DGBC, 0.16 to 0.26 mg·kg-1 for TiO2/DGBC, and 0.14 to 0.24 mg·kg-1 for Fe-TiO2/DGBC. Notably, Cd content in rice grains fell below the food safety limit of 0.2 mg·kg-1 (GB2762-2022) at 5% for TiO2/DGBC and 3% and 5% for Fe-TiO2/DGBC. In conclusion, Nano-TiO2 modified DGBC effectively reduced the bioavailability of soil Cd through its own adsorption and influence on soil Cd forms distribution, thus reducing the absorption of Cd by rice and simultaneously promoting rice growth and improving rice yield. It is a type of Cd-contaminated soil remediation material with a potential application prospect. The results can provide scientific basis for farmland restoration and agricultural safety production of Cd-contaminated acidic purple soil.

Enhancing the phytoextraction efficiency of heavy metals in acidic and alkaline soils by Sedum alfredii Hance: A study on the synergistic effect of plant growth regulator and plant growth-promoting bacteria

Plant growth regulators (PGR) and plant growth-promoting bacteria (PGPB) have the potential in phytoremediation of heavy metals (HMs) contaminated soils. However, their sole application may not yield the optimal results, thus necessitating the combined application. The present study aimed to enhance the phytoremediation efficiency of Sedum alfredii Hance (S. alfredii) in acidic and alkaline soils through the combination of PGR (Brassinolide, BR) and PGPB (Pseudomonas fluorescens, P. fluorescens). The combination of BR and P. fluorescens (BRB treatment) effectively increased the removal efficiency of S. alfredii for Cd, Pb, and Zn by 355.2 and 155.3 %, 470.1 and 128.9 %, and 408.4 and 209.6 %, in acidic and alkaline soils, respectively. Moreover, BRB treatment led to a substantial increase in photosynthetic pigments contents and antioxidant enzymes activities, resulting in a remarkable increase in biomass (86.71 and 47.22 %) and dry mass (101.49 and 42.29 %) of plants grown in acidic and alkaline soils, respectively. Similarly, BRB treatment significantly elevated the Cd (109.4 and 71.36 %), Pb (174.9 and 48.03 %), and Zn levels (142.8 and 104.3 %) in S. alfredii shoots, along with cumulative accumulation of Cd (122.7 and 79.47 %), Pb (183.8 and 60.49 %), and Zn (150.7 and 117.9 %), respectively. In addition, the BRB treatment lowered the soil pH and DTPA-HMs contents, while augmenting soil enzymatic activities, thereby contributing soil microecology and facilitating the HMs absorption and translocation by S. alfredii to over-ground tissues. Furthermore, the evaluation of microbial community structure in phyllosphere and rhizosphere after remediation revealed the shift in microbial abundance. The combined treatment altered the principal effects on S. alfredii HMs accumulation from bacterial diversity to the soil HMs availability. In summary, our findings demonstrated that synergistic application of BR and P. fluorescens represents a viable approach to strengthen the phytoextraction efficacy of S. alfredii in varying soils.

Mobility inhibition of arsenic in the soil: the role of green synthesized silica nanoparticles

The studies showed the effectiveness of green-synthesized SiO2NPs in mitigating the toxicity of Arsenic. Density Functional Theory (DFT) is a computational method used to determine electronic structure, energy gap, and toxicity prediction. Experimentally, silicon nanoparticles of 0 (S0) and 100% v/v (S100) were applied to the surface of the soil. 150 mL of Arsenic trioxide was applied twice at a rate of 0 (As0) and 3.2 g/mL (As3.2) at an interval of three weeks. Green synthesized SiO2NPs possessed a higher chemical potential (µ) and electrophilicity index; consequently, charges could be transferred and easily polarized. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels of the green synthesized SiO2NPs enable them to donate electrons and complex with arsenic, reducing their bioavailability and toxicity. Evidence from the studies further showed that SiO2NPs had buffered the soil acidity and electric conductivity, posing a high binding site and reactivity with exchangeable cations and micronutrients due to their smaller energy gap. Furthermore, the catalytic activities of the soil enzymes dehydrogenase (DHA) and peroxidase (POD) were greatly increased, which enhanced the electrostatic interaction between the SiO2NPs and As.

Root system architecture variation among barley (Hordeum vulgare L.) accessions at seedling stage under soil acidity condition.

Soil acidity in Ethiopian highlands impacts barley production, affecting root system architecture. Study on 300 accessions showed significant trait variability, with potential for breeding enhancement. Soil acidity poses a significant challenge to crop production in the highland regions of Ethiopia, particularly impacting barley, a crucial staple crop. This acidity serves as a key stressor affecting the root system architecture (RSA) of this crop. Hence, the objective of this study was to assess the RSA traits variability under acidic soil conditions using 300 barley accessions in a greenhouse experiment. The analysis of variance indicated substantial variations among the accessions across all traits studied. The phenotypic coefficient of variation ranged from 24.4% for shoot dry weight to 11.1% for root length, while the genotypic coefficient variation varied between 18.83 and 9.2% for shoot dry weight and root length, respectively. The broad-sense heritability ranged from 36.7% for leaf area to 69.9% for root length, highlighting considerable heritability among multiple traits. The genetic advances as a percent of the mean ranged from 13.63 to 29.9%, suggesting potential for enhancement of these traits through breeding efforts. Principal component analysis and cluster analysis grouped the genotypes into two major clusters, each containing varying numbers of genotypes with contrasting traits. This diversegrouppresents an opportunity to access a wide range ofpotential parentcandidates to enhance geneticvariablity in breeding programs. The Pearson correlation analysis revealed significant negative associations between root angle (RA) and other RSA traits. This helps indirect selection of accessions for further improvement in soil acidity. In conclusion, this study offers valuable insights into the RSA characteristics of barley in acidic soil conditions, aiding in the development of breeding strategies to enhance crop productivity in acidic soil environments.

Use of organo-mineral amendments and Lupinus angustifolius to enhance mine tailings rehabilitation

Uncontrolled mine waste disposal globally poses severe environmental and health risks due to high concentrations of toxic substances like heavy metals and organic pollutants. This jeopardizes soil fertility and ecological balance. In this study, we adopted a novel approach based on the use of low-cost amendments that can be used in small to tailing sites for better plant growth and reducing health risks. On a 37-ha-old abandoned pyrrhotite mine site (Kettara) which was operated for 34 years near Marrakesh a high amount of tailing material low in organic C, high in salt contents, and contaminated by various heavy metals still exists. This material is low in fertility and is only patchily discovered by vegetation which should hinder the material of aeolian erosion. To increase the fertility of the material and improve vegetation growth, the soil material has to be improved by different organo-mineral amendments and their combinations as Marble waste (Mw), Clay (Cy), and Compost (Cp). To determine the impact of these amendments on plant growth the fast-growing Lupinus angustifolius L. a legume plant found close to the mining site, identified with the Regional Herbarium 'MARK' code: MARK-14861. This plant serves as a pivotal component in the comprehensive approach aimed at rehabilitating the soils surrounding the mining site. To identify the most effective organo-mineral amendment, we examined 65 combinations by mixing mine tailing soils with varying proportions (2.5%, 5%, 7.5%, or 10%) of the three distinct amendments and its combinations (Com), to identify the optimal rate for effective seeds germination and plant growth. Preliminary results on the germination index of L. angustifolius seeds revealed that four combinations (Com1: Cy2.5-Cp2.5-Mw10; Com2: Cy2.5-Cp5-Mw5; Com3: Cy7.5-Cp2.5-Mw7.5; and Com4: Cy10-Cp10-Mw10) maintained a high index due to improved soil properties. These combinations were used as the soil substrate material for a greenhouse experiment where plant growth, heavy metals accumulation, soil characteristics, and available metal content were determined. Our findings demonstrated that incorporating these four organo-mineral soil amendments into Kettara mine tailings led to a significant enhancement in plant growth. Notably, L. angustifolius plants exhibited a preferential accumulation of heavy metals in the root’s biomass (Cu: 565.60, Zn: 433.52, and Pb: 301.44 mg kg−1) with limited translocation to shoot parts (Cu: 37.44, Zn: 28.40, and Pb: 19.36 mg kg−1), particularly following the application of Com4. Furthermore, the properties of the mine soil were improved, including both neutralization of acidic soil pH (3 to ∼ 7) and reduction of metal elements bioavailability. Specifically, Com1, Com3, and Com4 effectively decreased the mobile fraction of metals in the tested mine tailings to exceptionally low levels achieving a reduction of 99% for copper, lead, and zinc, and 95% for arsenic. Our findings from this study indicated that our amendment holds promising potential for enhancing both plant growth and soil fertility, while simultaneously mitigating the mobility of heavy metals in heavy metal-contaminated acidic mine soils.

Effect of phosphorus management on yield and economics under direct seeded rice (Oryza sativa) and blackgram (Vigna mungo) intercropping in a rainfed acidic upland soil

A field experiment was conducted during rainy (kharif) season of 2019 at ICAR-National Rice Research Institute (NRRI), Central Rainfed Upland Rice Research Station (CRURRS), Hazaribagh, Jharkhand to study the effect of phosphorus management on productivity and profitability under direct seeded rice (Oryza sativa L.) (DSR) and blackgram [Vigna mungo (L.) Hepper] intercropping in rainfed acidic upland soil. The experiment was laid-out in a split-plot design comprised 4 methods of cropping, viz. Sole DSR; Sole blackgram; DSR + blackgram (4:1); and DSR + blackgram (4:2) allotted to main-plots and 4 phosphorus management practices, viz. P control (P0 ); Recommended dose of phosphorus (RDP) @17.5 kg P/ha; 50% RDP + phosphate solubilizing bacteria (PSB) @500 g/ha + arbuscular mycorrhiza fungi (AMF) @12.5 kg/ha; and 25% lime requirement (LR) + PSB + AMF in sub-plots. Experiment consisted of 16 treatment combinations, replicated thrice. The rice variety ‘Sahabhagi’ and blackgram variety ‘Uttara’ were used. Among the cropping systems, the highest grain yield was recorded in sole rice (3.84 t/ha) and sole blackgram (1.14 t/ha) which was significantly higher than yields under intercropping in both the ratios. Gross (`96,879/ha) and net returns (`70,603/ha) of sole blackgram were significantly higher than other cropping systems and followed by DSR + blackgram (4:2). Net benefit:cost (B:C) of sole blackgram was maximum (`2.69) and lowest in sole rice (`1.01). Among phosphorus management treatments, 50% RDP + PSB + AMF gave significantly higher net return (`49,440) and net benefit:cost (`1.68). Application of 100% RDP and 25% LR + PSB + AMF gave at par returns and net benefit:cost. It may be suggested that under rainfed uplands of eastern India, farmers may adopt either sole blackgram or intercropping of rice and blackgram in 4:2 over sole DSR for higher productivity and monetary returns. For better phosphorus management in soil they should inoculate PSB and AM fungi along with 50% RDP at the time of sowing.

Comparative genomics of plant growth promoting phosphobacteria isolated from acidic soils.

Despite being one of the most abundant elements in soil, phosphorus (P) often becomes a limiting macronutrient for plants due to its low bioavailability, primarily locked away in insoluble organic and inorganic forms. Phosphate solubilizing and mineralizing bacteria, also called phosphobacteria, isolated from P-deficient soils have emerged as a promising biofertilizer alternative, capable of converting these recalcitrant P forms into plant-available phosphates. Three such phosphobacteria strains-Serratia sp. RJAL6, Klebsiella sp. RCJ4, and Enterobacter sp. 198-previously demonstrated their particular strength as plant growth promoters for wheat, ryegrass, or avocado under abiotic stresses and P deficiency. Comparative genomic analysis of their draft genomes revealed several genes encoding key functionalities, including alkaline phosphatases, isonitrile secondary metabolites, enterobactin biosynthesis and genes associated to the production of indole-3-acetic acid (IAA) and gluconic acid. Moreover, overall genome relatedness indexes (OGRIs) revealed substantial divergence between Serratia sp. RJAL6 and its closest phylogenetic neighbours, Serratia nematodiphila and Serratia bockelmanii. This compelling evidence suggests that RJAL6 merits classification as a novel species. This in silico genomic analysis provides vital insights into the plant growth-promoting capabilities and provenance of these promising PSRB strains. Notably, it paves the way for further characterization and potential application of the newly identified Serratia species as a powerful bioinoculant in future agricultural settings.

Medium-Term Comparative Effects of Prescribed Burning and Mechanical Shredding on Soil Characteristics in Heathland and Shrubland Habitats: Insights from a Protected Natural Area

Parts of the Cantabrian Mountains (N Spain) have been colonized by woody species in the past six or seven decades as a result of a decline in livestock activity and changes in the fire regime. Various management strategies have been used to prevent the expansion of shrubs and recover grassland ecosystems for grazing activities. However, it is not clear how different vegetation treatments affect soils, which are crucial in supporting life and providing nutrients in these ecosystems. The aim of the present study was to compare the dynamics of the physicochemical and biological soil properties after two vegetation treatments: prescribed burning and shredding. Samples were obtained from plots representing alkaline and acidic soils dominated by gorse shrub (Genista hispanica subsp. occidentalis) and heath (Calluna vulgaris) plant communities, respectively. The soil samples were collected immediately before and after the treatments and one and two years later. The level of available P varied depending on the soil pH, and it only increased after the treatments in the acidic soils in the heathland community. The total N and available P concentrations were higher after the prescribed burning, and the enzymatic activity tended to be higher after the shredding treatment. Despite the significant effects on some soil variables, prescribed burning and shredding did not have important short- and medium-term effects on the chemical and soil enzymatic properties. These treatments can therefore be considered sustainable vegetation management tools, at least in the medium term.

A potential slow-release fertilizer based on biogas residue biochar: Nutrient release patterns and synergistic mechanism for improving soil fertility

The large yield of anaerobic digestates and the suboptimal efficacy of nutrient slow-release severely limit its practical application. To address these issues, a new biochar based fertilizer (MAP@BRC) was developed using biogas residue biochar (BRC) to recover nitrogen and phosphorus from biogas slurry. The nutrient release patterns of MAP@BRC and mechanisms for enhancing soil fertility were studied, and it demonstrated excellent performance, with 59% total nitrogen and 50% total phosphorus nutrient release rates within 28 days. This was attributed to the coupling of the mechanism involving the dissolution of struvite skeletons and the release of biochar pores. Pot experiments showed that crop yield and water productivity were doubled in the MAP@BRC group compared with unfertilized planting. The application of MAP@BRC also improved soil nutrient levels, reduced soil acidification, increased microbial populations, and decreased soil heavy metal pollution risk. The key factors that contributed to the improvement in soil fertility by MAP@BRC were an increase in available nitrogen and the optimization of pH levels in the soil. Overall, MAP@BRC is a safe, slow-release fertilizer that exhibits biochar-fertilizer interactions and synergistic effects. This slow-release fertilizer was prepared by treating a phosphorus-rich biogas slurry with a nitrogen-rich biogas slurry, and it simultaneously addresses problems associated with livestock waste treatment and provides a promising strategy to promote zero-waste agriculture.

Evaluation of aluminum tolerance diversity in Avena sativa L. from the VIR collection

Background. Oat is an important food and feed cereal crop in Russia. The area under oats is 10 million ha worldwide, and 3 million ha in Russia. Acid soils with excessive content of exchangeable aluminum occupy almost every third hectare in the exUSSR territory. Oats are relatively resistant to unfavorable soil factors. Among cereal crops, oat is second only to rye and triticale in terms of resistance to exchangeable Al forms. Despite the crop’s high environmental plasticity, an important condition for obtaining sustainable oat yields is the development of new cultivars with resistance to adverse environmental factors, including metal toxicity and high soil acidity.The objective of this work was to search for oat cultivars resistant to soil stressors (excess of Н+ and Al3+) for use in breeding for edaphic resistance.Materials and methods. The research material included 687 oat accessions from the VIR global plant genetic resources collection. The accessions underwent laboratory evaluation of their aluminum tolerance at the initial growth and development stages using the method of measuring radicle growth after the exposure to aluminum stress. Reproducibility of the used modification of the method was mathematically proved.Results and discussion. Significant variation in the resistance to the studied stressor was observed among the accessions. The regions acting as sources of valuable aluminum resistance genes were identified for the crop. The accessions selected for their high resistance to exchangeable aluminum can be used in breeding programs to develop high-yielding oat cultivars with edaphic resistance.

The contribution of natural and anthropogenic causes to soil acidification rates under different fertilization practices and site conditions in southern China.

Excessive application of mineral fertilizers has accelerated soil acidification in China, affecting crop production when the pH drops below a critical value. However, the contributions of natural soil acidification, induced by leaching of bicarbonate, and anthropogenic causes of soil acidification, induced by nitrogen (N) transformations and removal of base cations over acid anions, are not well quantified. In this study, we quantified soil acidification rates, in equivalents (eq) of acidity, by assessing the inputs and outputs of all major cations and anions, including calcium, magnesium, potassium, sodium, ammonium, nitrate, bicarbonate, sulphate, phosphate and chloride, for 13 long-term experimental sites in southern China. The acidification rates strongly varied among fertilizer treatments and with the addition of animal manure. Bicarbonate leaching was the dominant acid production process in calcareous soils (23 keq ha-1 yr-1) and in non-calcareous paddy soils (9.6 keq ha-1 yr-1), accounting for 80 % and 68 % of the total acid production rate, respectively. The calcareous soils were strongly buffered, and acidification led no or a limited decline in pH. In contrast, N transformations were the most important driver for soil acidification at one site with upland crops on a non-calcareous soil, accounting for 72 % of total acid production rate of 8.4 keq ha-1 yr-1. In this soil, the soil pH considerably decreased being accompanied by a substantial decline in exchangeable base cation. Reducing the N surplus decreased the acidification rate with 10 to 54 eq per kg N surplus with the lowest value occurring in paddy soils and the highest in the upland soil. The use of manure, containing base cations, partly mitigated the acidifying impact of N fertilizer inputs and crop removal, but enhanced phosphorus (P) accumulation. Combining mineral fertilizer, manure and lime in integrative management strategies can mitigate soil acidification and minimize N and P losses.

Mechanisms and implications of bacterial-fungal competition for soil resources.

Elucidating complex interactions between bacteria and fungi that determine microbial community structure, composition, and functions in soil, as well as regulate carbon (C) and nutrient fluxes, is crucial to understand biogeochemical cycles. Among the various interactions, competition for resources is the main factor determining the adaptation and niche differentiation between these two big microbial groups in soil. This is because C and energy limitations for microbial growth are a rule rather than an exception. Here, we review the C and energy demands of bacteria and fungi - the two major kingdoms in soil - the mechanisms of their competition for these and other resources, leading to niche differentiation, and the global change impacts on this competition. The normalized microbial utilization preference showed that bacteria are 1.4-5 times more efficient in the uptake of simple organic compounds as substrates, whereas fungi are 1.1-4.1 times more effective in utilizing complex compounds. Accordingly, bacteria strongly outcompete fungi for simple substrates, while fungi take advantage of complex compounds. Bacteria also compete with fungi for the products released during the degradation of complex substrates. Based on these specifics, we differentiated spatial, temporal, and chemical niches for these two groups in soil. The competition will increase under the main five global changes including elevated CO2, N deposition, soil acidification, global warming, and drought. Elevated CO2, N deposition, and warming increase bacterial dominance, whereas soil acidification and drought increase fungal competitiveness.

Entirely Biodegradable Wireless pH Sensor with Split‐Ring Resonators for Soil pH Monitoring

AbstractThis paper describes a wireless and battery‐free soil pH sensor made entirely of degradable materials. Soil pH monitoring is significant for precision agriculture and environmental conservation because soil health can be estimated by measuring soil pH. Soil pH can be measured by collecting soil samples and analyzing them in a laboratory environment or by inserting an electrode‐type sensor into the soil and measuring soil pH on site. However, neither method is suitable for wide‐area soil pH sensing for precision agriculture or environmental conservation. Herein, a fully biodegradable wireless pH sensor is presented that can be dispersed to outdoor environment to detect soil acidity. The sensor is operated wirelessly through split‐ring resonators (SRRs) that consist of patterned octacalcium phosphate (OCP)‐coated magnesium (Mg) on a poly‐lactic acid (PLA) sheet. At acidic soil pH, the degradation of each SRR results in a change in the electromagnetic response of the sensor. The operation of the sensor in six different types of acidic soils is demonstrated to distinguish the acidic soil wirelessly. It is expected that the biodegradable sensor can be applied to low‐cost, easy‐to‐use, and environmentally friendly monitoring of soil pH.

Судогда – новый сорт озимой тритикале для кормопроизводства

Abstract. The purpose of the study is to evaluate a new variety of winter triticale Sudogda according to economic and biological characteristics and properties. The variety was created by the method of mass selection of highly productive plants resistant to lodging, brown and stem rusts from the breeding line L6, obtained from the Voronezh Federal Agrarian Scientific Center named after V. V. Dokuchaev. The selection of material and its study were carried out in the soil and climatic conditions of the Central Non-Chernozem zone according to the generally accepted scheme of the breeding process for winter crops. Results. A detailed morphological description is given and the results of the study of the new variety Sudogda in competitive variety testing on light soddy-podzolic, slightly acidic soils with a low content of organic matter (1.3 %) are presented. The average yield of the Sudogda variety was 4.68 t/ha (+0.54 t/ha to the Doktrina 110 standard), the maximum yield in the favorable year of 2017 on soddy-podzolic soils reached 5.5 t/ha, on gray forest soils 6.5 t/ha, the minimum – in the dry year of 2016 3.5 t/ha (+0.47 t/ha to the standard). The variety is characterized by high winter hardiness (95 %), resistance to lodging (5.0 points), drought resistance (4.5 points). During the years of variety testing, the variety showed tolerance to brown and stem rusts, and was moderately affected by leaf septoria at the standard level. It is distinguished by high indicators of the physical qualities of grain: the weight of 1000 grains is on average 40.4 g, the nature of the grain is 704 g/l, the vitreousness is 79 %. The protein content in the grain is 15 %, which is 0.5 % higher than the standard. The variety is intended for use in grain fodder. It is recommended for cultivation on all types of soils, but tolerates light slightly acidic soddy-podzolic sandy loamy soils better than other varieties. The new variety Sudogda has been included in the State Register of Breeding Achievements of the Russian Federation since 2021 and approved for use in the North-West region, where it showed a maximum yield of 6.96 t/ha. Scientific novelty. A new plastic, mid-season, stress-resistant variety of winter triticale has been created, which is distinguished by the ability to form a high grain yield on light soddy-podzolic, slightly acidic soils of the North-West region of the Russian Federation.