Acid Soils Research Articles

Sudogda is a new variety of winter triticale for fodder production

Sudogda is a new variety of winter triticale for fodder production

Effects of Integrated Use of <em>Lantana camara, Calliandra calothyrsus</em> and Cow Manure with Diammonium Phosphate and Potassium Chloride on Haricot Bean Yield in the Northern Part of Burundi

Effects of Integrated Use of <em>Lantana camara, Calliandra calothyrsus</em> and Cow Manure with Diammonium Phosphate and Potassium Chloride on Haricot Bean Yield in the Northern Part of Burundi

A strategy to enhance soil quality and soil organic carbon stock in abandoned lands: Pasture regeneration through shrub clearing

AbstractFarmland abandonment in Mediterranean mid‐mountain areas can lead to the degradation or recovery of soil properties. Typically, after abandonment, fields are covered with shrubs, which hinders livestock grazing and constitutes high wildfire risk. To avoid these negative effects, shrubs are cleared in selected areas. The main objective of this study is to evaluate whether shrub clearing can improve soil quality and enhance carbon sequestration. A case study was conducted in the Leza Valley (La Rioja, Spain), examining five different land uses/management practices in both acid and alkaline soil environments. These included shrubland (control), three shrub clearing sites (managed <5, 15, and 25 years ago), and control pasture (reference). Soil replicates at different depths (0–40 cm) were collected, and physico‐chemical properties were analysed. A theoretical map of potential shrub clearing areas was created, and the potential to accumulate carbon was evaluated. Results showed that shrub clearing increases soil organic carbon and nitrogen, specially in 25‐year clearings. The increases were greater and significant on alkaline environments. The cartographical analysis reveals that 3388 ha can be still cleared in the Leza Valley, which could increase soil organic carbon accumulation by up to 31.6% in 25‐year period. We propose shrub‐clearing as a strategy for enhancing carbon sequestration in Mediterranean mountain areas.

Partial substitution of manure increases N2O emissions in the alkaline soil but not acidic soils

The fertilization regimes of combining manure with synthetic fertilizer are benefits for crop yields and soil fertility in cropping systems as compared to sole synthetic fertilization, but the responses of nitrous oxide (N2O) emissions to these practices are inconsistent in the literatures. We hypothesized that it is caused by different proportions of nitrogen (N) applied as manure and various soil properties. Here, we conducted a microcosm experiment, and measured the N2O emissions from control (no N) and five manure substitution treatments (supplied 100 mg N kg−1 using the combination of urea with manure) with a range of proportions of N applied as manure (0, 25%, 50%, 75%, and 100%) in three different soil types (fluvo-aquic soil, black soil, and latosol) under aerobic condition. The stimulated effect on N2O emissions was more pronounced after manure application in an alkaline soil with high nitrification rate, due to relatively rapid soil DOC depletion and N mineralization of manure. N2O emissions from partial substitution of urea with manure were significantly higher than manure-only addition under high soil pH due to abundant labile C from manure. However, there was no difference between manure substitution treatments under acid soils. Nitrification inhibitor substantially decreased N2O emissions with increasing soil pH, but it was less effective in mitigating N2O emissions with larger proportion of manure. This is likely due to the slow nitrification under low soil pH, and denitrification derived N2O increased with increasing manure application rate. Collectively, our study shows that the application of manure substitution to alkaline soils requires careful consideration, which might have rapid nitrification potential and hence trigger significant N2O emissions. The knowledge gained in this work will help the decision-makers in optimizing a sound N fertilization regime interacted with soil properties for sustainable crop production and N2O mitigation.

The transcriptome response of Enterobacter sp. S-33 is modulated by low pH-stress.

Acidic environments naturally occur worldwide and uncontrolled use of agricultural practices may also cause acidification of soils. The development of acidic conditions disturbs the establishment of efficient microbial populations in their natural niches. The survival of Enterobacter species under acidic stress remains poorly understood. This study aimed to investigate the survival of an environmental isolate Enterobacter sp. S-33 under acidic stress and to identify the various genes involved in stress protection at the global gene transcription level. The obtained results provide new targets that will allow understanding the in-depth mechanisms involved in the adaptation of bacteria to environmental pH changes. We used the next-generation sequencing (NGS) method to analyze the expression (up-regulation & down-regulation) of genes under varying pH conditions. A total of 4214 genes were differentially expressed under acidic conditions (pH 5.0), with 294 up-regulated and 167 down-regulated. At pH 6.0, 50 genes were significantly expressed, of which 34 and 16 were identified as up-regulated and down-regulated, respectively. Many of the up-regulated genes were involved in carbohydrate metabolism, amino acid transport & metabolism, and the most down-regulated genes were related to post-translational modification, lipid transport & metabolism, etc. The observed transcriptomic regulation of genes and pathways identified that Enterobacter reduced its post-translational modification, lipid transport & metabolism, and increased carbohydrate metabolism, amino acid metabolism & transport, energy production & conversion to adapt and grow in acidic stress. The present work provides in-depth information on the characterization of genes associated with tolerance or adaptation to acidic stress of Enterobacter bacterium.

Acidification induce chemical and microbial variation in tea plantation soils and bacterial degradation of the key acidifying phenolic acids.

Camellia sinensis is an important economic plant grown in southern subtropical hilly areas, especially in China, mainly for the production of tea. Soil acidification is a significant cause of the reduction of yield and quality and continuous cropping obstacles in tea plants. Therefore, chemical and microbial properties of tea growing soils were investigated and phenolic acid-degrading bacteria were isolated from a tea plantation. Chemical and ICP-AES investigations showed that the soils tested were acidic, with pH values of 4.05-5.08, and the pH negatively correlated with K (p < 0.01), Al (p < 0.05), Fe and P. Aluminum was the highest (47-584mg/kg) nonessential element. Based on high-throughput sequencing, a total of 34 phyla and 583 genera were identified in tea plantation soils. Proteobacteria and Acidobacteria were the main dominant phyla and the highest abundance of Acidobacteria was found in three soils, with nearly 22% for the genus Gp2. Based on the functional abundance values, general function predicts the highest abundance, while the abundance of amino acids and carbon transport and metabolism were higher in soils with pH less than 5. According to Biolog Eco Plate™ assay, the soil microorganisms utilized amino acids well, followed by polymers and phenolic acids. Three strains with good phenolic acid degradation rates were obtained, and they were identified as Bacillus thuringiensis B1, Bacillus amyloliquefaciens B2 and Bacillus subtilis B3, respectively. The three strains significantly relieved the inhibition of peanut germination and growth by ferulic acid, p-coumaric acid, p-hydroxybenzoic acid, cinnamic acid, and mixed acids. Combination of the three isolates showed reduced relief of the four phenolic acids due to the antagonist of B2 against B1 and B3. The three phenolic acid degradation strains isolated from acidic soils display potential in improving the acidification and imbalance in soils of C. sinensis.

Microbial communities overwhelm environmental controls in explaining nitrous oxide emission in acidic soils

Intensively fertilized acidic soils are global hotspots of nitrous oxide (N2O) emissions, contributing to net agronomic greenhouse gas outcomes. Identifying the key drivers of soil N2O emissions is hampered by the synergistic or antagonistic effects of multiple factors. Within a framework based on the predominant role of microbial communities producing N2O, the N2O emissions are affected either by proximal regulators: temporary soil property fluctuations affect N2O production transcriptionally, or by distal regulators: persistent genetic rearrangements in local microbial communities. The proximal regulators, individually or together, may spontaneously impact distal regulators. Here, we use acidic soils from tea (Camellia sinensis L.) plantations on a broader geographic scale as a model system. Based on amplicon sequencing and properties of 195 acidic (average pH = 5.0) soils, we determined the importance of proximal and distal regulation to N2O emissions. Microbial phylogenetic diversity as a distal regulator overwhelms mineral N content as a proximal regulator in explaining high N2O emissions. Low-abundance, diverse prokaryotic communities (e.g., Acidothermu) and specialized denitrifying fungal communities (e.g., Fusarium) were associated with high N2O emissions. Revisiting the impact of proximal regulators on distal regulators revealed that soil pH is the sole proximal regulator influencing the prokaryotic rare taxa that correlated with high N2O emissions. When considering proximal regulators together (here soil properties compiled as soil fertility index), the microbial diversity were independent of soil fertility. The microbial assembly was dominated by stochastic processes. Consequently, proximal regulators have a limited impact on distal regulators of N2O emissions from acidic soils. In conclusion, the framework underscored the importance of in situ microbial communities as distal regulators in explaining high N2O emissions from acidic soils.

Genome-wide characterization, transcriptome profiling, and functional analysis of the ALMT gene family in Medicago for aluminum resistance

Aluminum (Al) is the major limiting factor affecting plant productivity in acidic soils. Al3+ ions exhibit increased solubility at a pH below 5, leading to plant root tip toxicity. Alternatively, plants can perceive very low concentrations of Al3+, and Al triggers downstream signaling even at pH 5.7 without causing Al toxicity. The ALUMINUM-ACTIVATED-MALATE-TRANSPORTER (ALMT) family members act as anion channels, with some regulating the secretion of malate from root apices to chelate Al, which is a crucial mechanism for plant Al resistance. To date, the role of the ALMT gene family within the legume Medicago species has not been fully characterized. In this study, we investigated the ALMT gene family in M. sativa and M. truncatula and identified 68 MsALMTs and 18 MtALMTs, respectively. Phylogenetic analysis classified these genes into five clades, and synteny analysis uncovered genuine paralogs and orthologs. The real-time quantitative reverse transcription PCR (qRT-PCR) analysis revealed that MtALMT8, MtALMT9, and MtALMT15 in clade 2-2b are expressed in both roots and root nodules, and MtALMT8 and MtALMT9 are significantly upregulated by Al in root tips. We also observed that MtALMT8 and MtALMT9 can partially restore the Al sensitivity of Atalmt1 in Arabidopsis. Moreover, transcriptome analysis examined the expression patterns of these genes in M. sativa in response to Al at both pH 5.7 and pH 4.6, as well as to protons, and found that Al and protons can independently induce some Al-resistance genes. Overall, our findings indicate that MtALMT8 and MtALMT9 may play a role in Al resistance, and highlight the resemblance between the ALMT genes in Medicago species and those in Arabidopsis.

Boron modulates cell wall structure that alleviate aluminum toxicity-induced root growth defects in citrus

Based on the soil acidification situation in citrus plantation of southern China and even worldwide, it's essential to explore improved methods for resistant aluminum (Al) toxicity in plant. Trifoliate (Poncirus trifoliate (L) Raf.) is the most common rootstock in China. The ambition of this research was to illustrate the influence of boron (B) on Al bound in cell wall (CW) and the mechanism in trifoliate seedlings. Healthy seedlings were exposed to 0 or 300 µM AlCl3·6H2O with 10 µM B (H3BO3, control) and 50 µM B, respectively. The results displayed that Al accumulated in roots and root tips during Al exposure. However, Al content in root rips was reduced under B sufficient that reflected by lower morin fluorescence intensity compared to B10-treated roots. More specifically, B addition abates the Al content in root CW, manifested in lower Al content in pectin and hemicellulose 1 (HC1), with HC1 being more prominent. Moreover, B addition inhibited the pectin methyl-esterase (PME) activity to reduce pectin content, while increasing the xyloglucan endotransglucosylase (XET) and xyloglucan endotransglucosylase-hydrolase (XEH) activity. Thereby HC1 content was decreased, ultimately suppressing the bound site of Al in pectin and HC1, and diminished Al content in CW with B supply. Collectively, our results illustrate that B supply was attributed to the mitigation effect of B on Al toxicity by induced devaluation of Al accumulation in CW, which was associated with the reduction of binding Al with pectin and HC1 by regulating compounds of CW through adjusting CW enzymes (PME, XET, and XEH).

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

IMPACT OF SOIL STERILIZATION FROM DIFFERENT LOCATIONS, WHEAT SEEDS CLEANING AND THEIR INTERACTIONS ON WEED CONTROL, AND YIELD AND YIELD COMPONENTS

Remediation of diesel contaminated soil by using activated persulfate with Fe3O4 magnetic nanoparticles: effect and mechanisms.

In this study, Fe3O4 magnetic nanoparticles (Fe3O4 MNPs) were assessed for their ability to enhance the activity of persulfate (PS). Various controlling factors including PS dosages, initial pH, water-soil ratio, ratio of Fe2+, and Fe3O4 MNPs to PS were considered in both the Fe2+/PS system and the Fe3O4 MNPs/PS system. Results showed that the Fe3O4 MNP-activated PS system exhibited high processing efficiency owing to the gradual release of Fe2+. This process occurred in a wide pH range (5-11), attributed to the synergistic action of sulfate radicals (SO4-·) and hydroxyl radicals (OH·) under alkaline conditions, effectively mitigating soil acidification. The ratio of Fe3O4 MNPs to PS and water-soil ratio significantly influenced the degradation rate with the highest petroleum hydrocarbon degradation rate exceeding 80% (82.31%). This rate was 3.1% higher than that achieved by the Fe2+/PS system under specific conditions: PS dosage of 0.05 mol/L, Fe3O4 MNPs to PS ratio of 1:10, water-soil ratio of 2:1, and initial pH of 11. Meanwhile, oxidant consumption in the Fe3O4 MNPs/PS system was halved compared to the Fe2+/PS system due to the slow release of Fe2+ and less ineffective consumption of SO4-·. Mechanistically, the possible degradation process was divided into three parts: the initial chain reaction, the proliferating chain reaction, and the terminating chain reaction. The introduction of Fe3O4 MNPs accelerated the degradation rate of pentadecane, heneicosane, eicosane, tritetracontane, and 9-methylnonadecane.

Nitrogen-Rich Sewage Sludge Mineralized Quickly, Improving Lettuce Nutrition and Yield, with Reduced Risk of Heavy Metal Contamination of Soil and Plant Tissues

Sewage sludge should primarily find use in agriculture, reducing the quantity directed towards alternative disposal methods like incineration or deposition in municipal landfills. This study evaluated the agronomic value and the risk of soil and plant tissue contamination with heavy metals in sewage sludge obtained from two wastewater treatment plants (WWTP). The experiment was arranged as a 2 × 5 factorial (two sewage sludges, five sanitation treatments), involving lettuce cultivation in pots over two growing cycles. The two sewage sludges were sourced from the WWTPs of Gelfa and Viana do Castelo and underwent five sanitation and stabilization treatments (40% and 20% calcium oxide, 40% and 20% calcium hydroxide, and untreated sewage sludge). The Gelfa sewage sludge, characterized by a higher initial nitrogen (N) concentration, resulted in greater dry-matter yield (DMY) (12.4 and 8.6 g plant−1 for the first and second growing cycles, respectively) compared to that from Viana do Castelo (11.0 and 8.1 g plant−1), with N release likely being a major factor influencing crop productivity. The high N concentration and the low carbon (C)/N ratio of sewage sludge led to rapid mineralization of the organic substrate, which additionally led to a higher release of other important nutrients, such as phosphorus (P) and boron (B), making them available for plant uptake. Alkalizing treatments further stimulated sewage sludge mineralization, increasing soil pH and exchangeable calcium (Ca), thereby enhancing Ca availability for plants, and indicating a preference for use in acidic soils. Cationic micronutrients were minimally affected by the sewage sludge and their treatments. The concentrations of heavy metals in the sewage sludge, soils, and lettuce tissues were all below internationally established threshold limits. This study highlighted the high fertilizing value of these sewage sludges, supplying N, P, and B to plants, while demonstrating a low risk of environmental contamination with heavy metals. Nevertheless, the safe use of sewage sludge by farmers depends on monitoring other risks, such as toxic organic compounds, which were not evaluated in this study.

Microbial mechanisms for improved soil phosphorus mobilization in monoculture conifer plantations by mixing with broadleaved trees

Replanting broadleaved trees in monoculture conifer plantations has been shown to improve the ecological environment. However, not much is known about the distribution properties of soil phosphate-mobilizing bacteria (PMB) under different mixed plantings or how PMB affects biometabolism-driven phosphorus (P) bioavailability. The phoD and pqqC genes serve as molecular markers of PMB because they regulate the mobilization of organic (Po) and inorganic (Pi) P. Differences in soil bioavailable P concentration, phoD- and pqqC-harboring PMB communities, and their main regulators were analyzed using biologically-based P (BBP) and high-throughput sequencing approaches after combining coniferous trees (Pinus massoniana) and five individual broadleaved trees (Bretschneidera sinensis, Michelia maudiae, Cercidiphyllum japonicum, Manglietia conifera, and Camellia oleifera). The findings revealed that the contents of litter P, soil organic carbon (SOC), available Pi (CaCl2–P), and labile Po (Enzyme-P) were significantly higher in conifer-broadleaf mixed plantations than those in the monospecific Pinus massoniana plantations (PM), especially in the mixed stands with the introduction of Cercidiphyllum japonicum, Michelia maudiae, and Camellia oleifera. Conifer-broadleaf mixing had little effect on the abundance of phoD and pqqC genes but significantly altered species composition within the communities. Conifer-broadleaf mixing improved soil microbial habitat mainly by increasing the pH, increasing carbon source availability and nutrient content, decreasing exchangeable Fe3+ and Al3+ content, and decreasing the activation degrees of Fe and Al oxides in acidic soils. A small group of taxa (phoD: Bradyrhizobium, Tardiphaga, Nitratireductor, Mesorhizobium, Herbaspirillum, and Ralstonia; pqqC: Burkholderia, Variovorax, Bradyrhizobium, and Leptothrix) played a key role in the synthesis of P-related enzymes (e.g., alkaline phosphomonoesterase, ALP) and in lowering the levels of mineral-occluded (HCl–P) and chelated (Citrate-P) Pi. Overall, our findings highlight that mixing conifers and broadleaves could change the PMB communities that produce ALP and dissolve Pi to make P more bioavailable.

Effects of straw return on soil carbon sequestration, soil nutrients and rice yield of in acidic farmland soil of Southern China

Effects of straw return on soil carbon sequestration, soil nutrients and rice yield of in acidic farmland soil of Southern China

Redox potential model for guiding moderate oxidation of polycyclic aromatic hydrocarbons in soils

In-situ chemical oxidation is an important approach to remediate soils contaminated with persistent organic pollutants, e.g., polycyclic aromatic hydrocarbons (PAHs). However, massive oxidants are added into soils without an explicit model for predicting the redox potential (Eh) during soil remediation, and overdosed oxidants would pose secondary damage by disturbing soil organic matter and acidity. Here, a soil redox potential (Eh) model was first established to quantify the relationship among oxidation parameters, crucial soil properties, and pollutant elimination. The impacts of oxidant types and doses, soil pH, and soil organic carbon contents on soil Eh were systematically clarified in four commonly used oxidation systems (i.e., KMnO4, H2O2, fenton, and persulfate). The relative error of preliminary Eh model was increased from 48–62% to 4–16% after being modified with the soil texture and dissolved organic carbon, and this high accuracy was verified by 12 actual PAHs contaminated soils. Combining the discovered critical oxidation potential (COP) of PAHs, the moderate oxidation process could be regulated by the guidance of the soil Eh model in different soil conditions. Moreover, the product analysis revealed that the hydroxylation of PAHs occurred most frequently when the soil Eh reached their COP, providing a foundation for further microorganism remediation. These results provide a feasible strategy for selecting oxidants and controlling their doses toward moderate oxidation of contaminated soils, which will reduce the consumption of soil organic matter and protect the main structure and function of soil for future utilization. Environmental implicationsThis study provides a novel insight into the moderate chemical oxidation by the Eh model and largely reduces the secondary risks of excessive oxidation and oxidant residual in ISCO. The moderate oxidation of PAHs could be a first step to decrease their toxicity and increase their bioaccessibility, favoring the microbial degradation of PAHs. Controlling the soil Eh with the established model here could be a promising approach to couple moderate oxidation of organic contaminants with microbial degradation. Such an effective and green soil remediation will largely preserve the soil’s functional structure and favor the subsequent utilization of remediated soil.

Direct nitrous oxide emissions from a crop rotation of maize and mung bean after different long-term fertilizer applications in Thailand

Nitrous oxide (N2O) is a greenhouse gas primarily released by fertilizers used in crop cultivation. In Thailand, cropland occupies the majority of the arable land but studies on N2O emissions from cropland remain scarce. The present study aimed to evaluate the N2O emissions, soil characteristics, and crop productivity resulting from different long-term fertilizer applications in a crop rotation of maize and mung bean. A long-term experimental field managed through crop residue incorporation combined with different fertilizer applications over 45 years was utilized in this study. It consisted of four distinct treatments: no fertilizer (CON), 134 kg N ha−1 from organic fertilizer (ORG), 188 kg N ha−1 from chemical fertilizer (CHE), and 322 kg N ha−1 from a combination of organic and chemical fertilizers (OAC). Long-term application of chemical fertilizer induced soil acidification, whereas the use of organic fertilizer maintained soil pH and enhanced soil carbon accumulation. Results showed that the OAC, CHE, and ORG practices significantly (p < 0.05) increased direct N2O emissions from the soil, particularly during the maize cultivation period. Annual cumulative N2O emissions were enhanced on average by 204 % (3.22 kg N2O ha−1) in OAC, 181 % (2.98 kg N2O ha−1) in CHE, and 79.4 % (1.90 kg N2O ha−1) in ORG compared with CON (1.06 kg N2O ha−1), indicating that larger N input rates induced larger N2O emissions. Chemical fertilizer induced significantly (p < 0.05) larger and faster N2O emissions than organic fertilizer. When considering N2O emissions per N application rate in all treatments as the emission factor, the use of N fertilizers combined with crop residues in the soil over two years averaged 0.61 % (± 0.13 %). This value was approximately 39 % lower than the default value recommended by the Intergovernmental Panel on Climate Change, which is currently used in Thailand. The consecutive addition of fertilizers significantly (p < 0.05) increased maize grain yield compared with the CON. However, no significant differences were observed among the various fertilizer treatments. Despite all fertilizer applications induced larger N2O emissions, they also produced greater crop yields. Consequently, this study recommended the practice of ORG as a means to mitigate emissions without compromising crop yield and soil quality.

Rhizobium leguminosarum bv.viciae Potential Assessment using Dosha faba Bean Isolates from Central and North Gondar, Ethiopia

Purpose: The objective this study was to evaluate nitrogen fixation effectiveness, survival and compatibility of the isolates of on two different soils that came from Dabat and Shentia sites at Gondar, Ethiopia. The author recommends that the isolates test their nitrogen fixing potential under field conditions in slightly acidic and neutral soil before being used as commercial biofertilzer inoculants. The present study provides potential nitrogen fixer input for agricultural research centers. Methodology: Soil physicochemical analysis and most probable number were done according to their standard procedure. Three top strains were selected as inoculants for faba beans grown on the slightly acidic Shentia soil and the slightly neutral Dabat soil with their control. The symbiotic effectiveness of the strains was evaluated based on plant agronomy and total nitrogen of the plant. The results of the strains analyzed by SPSS version 26. Findings: The highest rhizobium population size was 5.8 x102 cells g-1 soil, while the lowest was 1.7 x102 cell g-1 soil observed at the Dabat and Shentia sites, respectively. There is limited nitrogen and phosphorus content other were enough. It was significant difference inter-strain difference in the all agronomic parameter of all treatments in soil compared to each based on agronomic parameter, but across soils there was no significant different except shoot fresh weight. The result of these studies showed that two Rhizobium leguminosarum bv.viciae isolates and other combinations of them had considerable effect on agronomic properties. Unique Contribution to Theory, Practice and Policy: The application of biological nitrogen fixation through Rhizobium inoculums is promoted as a solution to the problem of poor soil fertility in areas where legumes are cultivated. In most of the developing countries, including Ethiopia, biological nitrogen fixation technology has not fully flourished, so this study was initiated to evaluate fixation potential of isolates.

Higher resistance of larch-broadleaf mixed forests than larch forests against soil acidification under experimental nitrogen addition

Higher resistance of larch-broadleaf mixed forests than larch forests against soil acidification under experimental nitrogen addition

Substitution of Inorganic Fertilizer with Organic Fertilizer Influences Soil Carbon and Nitrogen Content and Enzyme Activity under Rubber Plantation

Conventional fertilization practices can lead to many ecological problems, such as nutrient imbalance, soil acidity, and reduced soil fertility, in natural rubber plantations. To address these challenges, a field investigation was strategically carried out to substitute inorganic fertilizer with organic fertilizer, consisting of six treatments: no fertilization (CK), inorganic fertilizer (NPK), 25% replacement of inorganic through organic (25% manure (M)), 50% replacement of inorganic through organic (50% manure (M)), 75% replacement of inorganic through organic (75% manure (M)), and 100% organic fertilizer (100% manure). The soil physicochemical properties (soil organic carbon (SOC), total nitrogen (TN), mineral nitrogen (N), ammonium nitrogen (NH4+-N), and nitrate nitrogen (NO3−-N)), C:N, pH, and the carbon- and nitrogen-converting enzymes β-1,4-glucosidase (BG), N-acetylglucosaminidase (NAG) and L-leucine aminopeptidase (LAP) were all determined. The partial substitution of inorganic fertilizer with organic fertilizer (i.e., 75% M at surface soil layer) showed higher SOC (14.52 g·kg−1), TN (1.06 g·kg−1), N (20.07 mg·kg−1), C:N (14.63), NH4+-N (10.63 mg·kg−1), and NO3−-N (11.06 mg·kg−1) than NPK and CK. This increase in physicochemical properties after partial replacement of inorganic with organic fertilizer resulted from higher carbon and nitrogen enzyme activities (BG (143.17·nmol·g−1·h−1), NAG (153.96 nmol·g−1·h−1), and LAP (153.48 nmol·g−1·h−1)) compared to NPK and CK. Further, the Pearson correlation and redundancy analysis (RDA) analyses confirmed a significant positive correlation between SOC, N, and soil enzymes. This study presents a new strategy for assessing the impact of partially replacing inorganic fertilizer with organic fertilizer in rubber plantations in tropical regions, mainly by modifying the soil nutrient composition.

Genome-wide analysis of the MATE gene family and expression analysis of subfamily III genes in response to aluminium toxicity in pineapple

ABSTRACT Pineapple has strong adaptability to acidic soil and has become a significant economic fruit crop in the tropics and subtropics. The multidrug and toxin compound extrusion (MATE) gene family plays crucial roles in plant growth, development and responses to adverse stresses, especially in acidic soils. In this study, forty-two AcMATE genes were identified and classified into six subfamilies based on phylogenetic analysis. The chromosomal distribution, physical characteristics, phylogenetic relationships, and gene and protein structures of pineapple MATE gene family members were systematically analysed. Our results showed that six AcMATE genes can be further clustered into subfamily III with similar conserved motifs and exon-intron patterns, and are unevenly distributed on four pineapple chromosomes. Citrate exuding motif (CEM) was present in all six AcMATE proteins of subfamily III. Finally, quantitative real-time PCR experiments indicated that subfamily III AcMATE genes were highly expressed in roots and distinctly upregulated under Al stresses. In conclusion, our study illustrated that the AcMATE genes of subfamily III may function as an Al-induced citrate transporter in alleviating Al toxicity to adapt acidic soil in pineapple.