Soil Alkaline Phosphatase Activity Research Articles

Matching Phosphorus Fertilizer Types with Soil Type in Rice Cultivation Optimizes Yield, Soil Phosphorus Availability, and Phosphorus Fertilizer Use Efficiency

Inefficient phosphorus (P) fertilizer application often accumulates soil P, wasting valuable phosphate resources and contributing to environmental pollution. Given the suboptimal P fertilizer use efficiency (PUE), understanding soil P dynamics and selecting appropriate fertilizers is crucial. Fluvo-aquic soil and yellow-cinnamon soils were used in a rice pot trial to compare five P fertilizer types: single superphosphate (SSP), diammonium phosphate (DAP), calcium magnesium phosphate (CMP), triple superphosphate (TSP), and ammonium polyphosphate (APP), alongside a no P, control (CK). In fluvo-aquic soil, TSP and APP significantly increased rhizosphere P availability at anthesis, while SSP increased yield and shoot P accumulation at maturity. In yellow-cinnamon soil, DAP had the highest rhizosphere P availability at anthesis, while APP significantly increased shoot P accumulation at anthesis and shoot P accumulation and grain yield at maturity. Moreover, PUE was highest with SSP and CMP in fluvo-aquic soil and APP and TSP in yellow-cinnamon soil. Throughout the experiment, increased soil alkaline phosphatase activity promoted NaOH-Po conversion to NaHCO3-Pi, increasing rice shoot P uptake, yield, and PUE in both soils. Based on the above findings, it is recommended to apply SSP and TSP to fluvo-aquic soil and APP and TSP to yellow-cinnamon soil to achieve higher yield and PUE, which can be further confirmed by subsequent field-scale studies.

Synergistic contributions of plant growth-promoting rhizobacteria and exogenous fulvic acid to enhance phytoremediation efficiency of perfluorooctanoic acid (PFOA)-contaminated soils: Boosting PFOA bioavailability and elevating pak choi tolerance

Perfluorooctanoic acid (PFOA), a synthetic perfluoroalkyl compound, has caused extensive soil contamination over several decades, posing serious health risks to humans through bioaccumulation in plants and subsequent transfer via the food chain. Due to the durability of PFOA in soil and its propensity to migrate and accumulate in plants, phytoremediation has been recognized as an effective remediation method. However, the phytotoxicity of PFOA and the adsorption of PFOA by soil hindered the efficiency of traditional phytoremediation. Therefore, this research employed plant growth-promoting rhizobacteria (PGPR)-assisted phytoremediation, augmented with the bio-stimulant fulvic acid (FA), to devise an effective soil remediation strategy tailored for PFOA contamination removal. The results indicated that Rhizobium sp. strain ZY2, endowed with PGP traits, significantly increased the root weight and shoot weight of pak choi by 194.67 % and 37.38 %, respectively, versus the non-inoculation treatment. Furthermore, inoculation with strain ZY2 enhanced soil alkaline phosphatase, protease, and cellulase activities, bolstering soil nutrient cycling and resource availability. On the other hand, compared to treatment with strain ZY2 alone, additional exogenous FA drastically reduced the residual fraction of PFOA in soil from 34.1 % to 1.9 %, likely mediated by complex electrostatic and hydrophobic interactions between FA and soil components. Ultimately, FA addition increased PFOA concentration in pak choi by 8.1-fold. Furthermore, FA could increase the relative abundance of beneficial rhizosphere bacteria (Actinobacterota and Methylotener, etc.), thereby creating a more favorable microenvironment for plant growth. In conclusion, the combined use of strain ZY2 and FA in phytoremediation notably strengthened plant resilience to PFOA, minimized soil sorption, and achieved high remediation efficacy, offering an effective system to mitigate PFOA-soil pollution's environmental and health risks.

Effect of Humic Acids Extracted From Different Organic Sources and Inoculation of Bacillus Subtilis or Aspergillus Niger in Alkaline Phosphatase Activity in Calcareous Soil

Humic acids have received a large attention of researching and development as amendments for poor fertility conditions and deteriorating physical properties, since the process of extracting is an easy common process to implement, as well as dilution of these acids with water enables to be used at economically acceptable levels over large areas. It is necessary to notice that the properties of these acids depending on the organic source and the concentration added to the soil.A laboratory experiment was conducted at the department of soil Sciences and water resources, collage of Agriculture ,University of Basrah ,Iraq to demonstrate the effect of humic acids extracted from different sources and inoculation with Bacillus subtilis or Aspergillus niger on alkaline phosphatase activity in calcareous soil calcareous, southern Iraq. Humic acids extracted from wheat straw, alfalfa leaves, goat manure, and poultry manure which composted previously . Humic acid levels were 0, 25 and 50 L ha-1 .The soil also inoculated with Bacillus subtilis or Aspergillus niger, then samples were incubated at 28±2°C. After 7 or 30 days of incubation the activity of alkaline phosphatase was estimated . Enzyme phosphatase activity was increased in soils treated with humic acid as compared to control with highest activity at Poultry manure (391.54 µg p-nitrophenol gm-1 soil.1h-1).The results also indicated that increasing the level of humic acid significantly increased enzyme activity. For soil treated with Bacillus subtilis and Aspergillus niger , phosphatase activity increased-as compared to control with a higher activity at Bacilluas subtilis (373.1 µg p-nitrophenol gm-1 soil.1h-1).

Composted maize straw under fungi inoculation reduces soil N2O emissions and mitigates the microbial N limitation in a wheat upland

Enhancement of microbial assimilation of inorganic nitrogen (N) by straw addition is believed to be an effective pathway to improve farmland N cycling. However, the effectiveness of differently pretreated straws on soil N2O emissions and soil N-acquiring enzyme activities remains unclear. In this study, a pot experiment with four treatments (I, no addition, CK; II, respective addition of maize straw, S; III, composted maize straw under no fungi inoculation, SC; and IV, composted maize straw under fungi inoculation, SCPA) at the same quantity of carbon (C) input was conducted under the same amount of inorganic N fertilization. Results showed that the seasonal cumulative N2O emissions following the SCPA treatment were the lowest at 4.03 kg N ha−1, representing a significant reduction of 19 % compared with the CK treatment. The S and SC treatments had no significant effects on N2O emissions. The decrease of soil N2O emissions following the SCPA treatment was mainly attributed to the increase of microbial N assimilation and the increased abundance of functional genes related to N2O reductase. The SCPA treatment significantly decreased soil alkaline phosphatase (ALP) activity and increased leucine aminopeptidase (LAP) activity at the basal fertilization, while increased soil ALP and LAP activity, decreased soil N-Acetyl-β-D-Glucosidase (NAG) activity at harvest. Compared with the CK treatment, the S, SC, and SCPA treatment significantly increased soil β-glucosidase (β-GC) activity at harvest. The decrease in the (NAG+LAP)/ALP ratio following the SCPA treatment indicated that the composted maize straw under fungi inoculation alleviated microbial N limitation at harvest. Moreover, PICRUSt analysis also suggested that the SCPA treatment increased the abundance of bacterial genes associated with N assimilation and N2O reduction, whereas the S and SC treatment did not significantly affect the abundance of N2O reduction genes compared with the CK treatment. Our results suggest that the composted maize straw under fungi inoculation would reduce the risk of N2O emissions and effectively mitigate the microbial N limitation in dryland wheat system.

Efficient cadmium-resistant plant growth-promoting bacteria loaded on pig bone biochar has higher efficiency in reducing cadmium phytoavailability and improving maize performance than on rice husk biochar

Green agriculture faced challenges due to the shortage of efficient cadmium (Cd)-resistant plant growth-promoting bacteria (CdR-PGPB) and their low survival rate and activity during application. In this study, a diverse range of efficient CdR-PGPB were isolated from the rhizosphere soil of Desmodium elegans, especially those with high phosphate-solubilizing capabilities (272.87–450.45 mg L−1). Two highly efficient CdR-PGPB namely, XH1 and XH3 were loaded on to rice husk biochar (RHB) and pig bone biochar (PBB), labelled as RHBM and PBBM respectively. This study aimed to explore their effectiveness and mechanisms in promoting maize growth in a Cd-contaminated planting system. Results showed that PBBM performed best among all treatments. It significantly decreased soil phytoavailable Cd by 53.19 % and Cd content in maize shoot by 85.89 %. It also increased soil available phosphorus by 145.72 %, soil alkaline phosphatase activity by 76.34 %, maize shoot/root biomass by 47.06 %/67.98 %, Chlorophyll (a/b) content by 66.80 %/134.13 % and peroxidase activity by 171.96 %. These results were achieved through the synergistic action of efficient CdR-PGPB and PBB. Therefore, PBBM proved to be a promising and innovative application technique for sustainable agricultural development in Cd-contaminated farmland ecosystems.

Improving the enrichment of Cd and Zn in leaf mustard (Brassica juncea) by using metal-activating probiotics

Microbial-assisted phytoremediation is of great significance for the remediation of soil contaminated with heavy metals (HMs). Probiotics are beneficial microorganisms that can improve soil structure and fertility and promote plant growth. This study aimed to investigate the effect of two kinds of probiotics, including Lactobacillus casei (L) and Bacillus licheniformis (B), on activating the remediation potentiality of leaf mustard [Brassica juncea (L.) Czerniak.] for mining soil contaminated by Cd and Zn. The results showed that addition of two probiotics significantly reduced soil pH (with 0.05–0.32 units) and improved the available contents of soil HMs (16.0%–59.9% for Cd and 7.1%–23.9% for Zn) in the indoor-incubation experiment. After probiotic treatments, available Cd and Zn in potting soil treated with 1×109 cfu mL-1 of B were 1.65-fold and 1.66-fold of the control, respectively. Meanwhile, soil alkaline phosphatase, urease and sucrose activities were increased, indicating that soil microbial metabolic activities were also motivated. Addition of L and B significantly improved the biomass and chlorophyll contents of leaf mustard. The contents of Cd, Zn in shoot and root were significantly increased with 1×105 cfu mL-1 of L treatment (shoot: 75.2%, 71.9%; root: 36.8%, 61.2%). Furthermore, the activity of antioxidant enzymes such as superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and the level of malondialdehyde (MDA) were increased or inhibited, indicating that the resistance of plants to HMs was enhanced. These results indicated that two kinds of probiotics could improve the activities of Cd and Zn directly in mining soil and promote the growth of leaf mustard, thus increasing the efficiency of phytoremediation for HMs. The study provides a reference value for probiotic-assisted phytoremediation of soil contaminated with HMs.

Effects of soil conditioners on vineyard saline soil physicochemical properties and bacterial community in arid areas

AbstractSoil salinization adversely affects soil quality and ecosystem. Many researches have tried to ameliorate saline soils by soil conditioners. However, little is known about the differences in the responses of soil bacterial communities to natural and artificial conditioners applied to saline soils. Therefore, in this study, the effects of natural humic acid (IK), synthetic polymer (IP), and composite material (IF) (mixture of IK and IP (1:1)) on bacterial community structure and functional genes in saline soil were evaluated to clarify their differences. The results showed that the application of the three soil conditioners significantly reduced soil pH and Na+ content but increased soil alkaline phosphatase, urease, invertase and catalase activities, bacterial diversity, and nutrients, compared to the control (no conditioner). IK application increased bacterial relative abundance (e.g., Subgroup_6, RB41, MND1, and KD4‐96) and metabolic functions (e.g., Two‐component system and Biosynthesis of amino acids) by increasing soil nitrogen and maintaining K+ and Na+ balance. IP application increased soil alkaline phosphatase and urease activities as well as bacterial relative abundance (e.g., Subgroup_6, RB41, MND1, Gemmatimonadaceae, and KD4‐96) and metabolic functions (e.g., Quorum sensing and carbon metabolism) by increasing soil organic carbon/nitrogen content. IF application increased the bacterial relative abundance of Subgroup_6, RB41, and MND1 by increasing soil available nitrogen and regulated their metabolic pathways (e.g., ABC transporters and microbial metabolism). On the whole, IK, IP, and IF could regulate the structure and function of soil bacterial community in saline soils. This study clarifies difference in the effects of different soil conditioners on the amelioration of saline soils from the perspective of soil microbiology, and provides a reference for the amelioration of saline soils in arid areas.

Effect of Mild Organic Substitution on Soil Quality and Microbial Community

Mild organic substitution is advantageous for sustainable agricultural development. In order to determine the proper fertilization strategy, it is essential to investigate the impact of substituting chemical fertilizers with varying levels of organic manure on soil nutrients, microbial communities, and crop productivity. Four treatments were implemented: no fertilizer, sole chemical fertilizer, 20% organic manure substitution, and 40% organic manure substitution. Bacterial and fungal communities were characterized through high-throughput sequencing of the 16S rRNA gene V3–V4 region and the V4 region, respectively. The 20% and 40% organic manure substitutions increased soil organic matter (SOM) content, total nitrogen (TN) content, and reduced soil pH compared to the control (CK). The 20% organic manure substitution showed the most significant improvements in soil alkaline phosphatase, urease, and invertase activities. Soil nutrient enhancement increased bacterial alpha diversity, with a milder impact on fungal alpha diversity compared to bacteria. Different fertilization treatments elevated the relative abundance of bacterial Bacteroidetes (8.11%, 21.25%, and 1.88%), Actinomycetes (12.65%, 26.36%, and 15.33%), and fungal Ascomycota (16.19%, 10.44%, and 12.69%), known for degrading recalcitrant organic matter. The sole chemical fertilizer treatment increased the pathogenic Cheatotryiales. Shared species, primarily from bacterial Actinomycetes, Firmicutes, Proteobacteria, and fungal Ascomycota phyla, were found at 20% and 40% organic manure substitution levels. Specifically, the 20% organic manure substitution level promoted the relative abundance of beneficial plant growth-promoting taxa, Oxalobacteraceae and Massilia, and suppressed pathogens, with an increase in the relative abundance of the Purpureocillium genus and Mortierellomycota. These findings suggest that a 20% OF substitution can maintain crop yield, enhance soil nutrients and enzyme activities by fostering beneficial soil bacteria, inhibiting soil-borne pathogens, and refining microbial community structure.

Plant invasion alters soil phosphorus cycling on tropical coral islands: Insights from Wollastonia biflora and Chromolaena odorata invasions

Plants may modify soil biogeochemical properties that facilitate their invasion of new sites which may be mediated by soil microorganisms. We compared microbially-mediated soil phosphorus (P) cycling among sites with different degrees of invasion by Wollastonia biflora and Chromolaena odorata on two coral islands. Wollastonia biflora and C. odorata outcompeted all native species and invested more P in leaves (45–136% more than the native species). We found a decrease in the proportion of HCl–P and organic P, and a corresponding increase in the proportion of labile inorganic P (Pi) of the soil total P concentrations following plant invasion. Leaf P concentrations in invasive species were positively correlated with the proportion of labile Pi, suggesting that HCl–P and organic P were the major P sources for invasive plants, and that plant invasion increased soil P-cycling rates as a result of root carboxylate release (evidenced by greater leaf manganese concentrations) and enhanced soil alkaline phosphatase activity. The latter was confirmed by an increased soil phoD gene abundance after plant invasion. Soil P availability was elevated after plant invasion which was associated with increases in the release of root carboxylates and microbial activities that are involved in mobilization of HCl–P and mineralization of organic P, respectively, especially in the wet season. This, in turn, strongly increased leaf P concentrations of invasive species to sustain rapid plant growth, and presumably depriving competitors of P. These novel insights into soil P cycling through the enrichment of a specific soil microbial community and root carboxylate release in invaded ecosystems enhance our understanding of plant invasion mechanisms on coral islands.

Optimizing the manure substitution rate based on phosphorus fertilizer to enhance soil phosphorus turnover and root uptake in pepper (Capsicum).

In contemporary agriculture, the substitution of manure for chemical fertilizer based on phosphorus (P) input in vegetable production has led to a significant reduction in P fertilizer application rates, while, the effect of manure substitution rates on soil P transformation and uptake by root remain unclear. This research conducts a pot experiment with varying manure substitution rates (0%, 10%, 20%, 30%, 40%, 50%, 75% and 100%) based on P nutrient content to elucidate the mechanisms through which manure substitution affects P uptake in pepper. The result showed that shoot and root biomass of pepper gradually increased as manure substitution rate from 10% to 40%, and then gradually decreased with further increases in the substitution rate. Soil alkaline phosphatase activity and arbuscular mycorrhizal (AM) colonization gradually increased with manure substitution rates improvement. Specifically, when the substitution rate reached 30%-40%, the alkaline phosphatase activity increased by 24.5%-33.8% compared to the fertilizer treatment. In contrast, phytase activity and the relative expression of phosphate transporter protein genes in the root system was declined after peaking at 30% manure substitution. Additionally, soil available P remained moderate under 30%-40% substitution rate, which was reduced by 8.6%-10.2% compared to that in chemical fertilizer treatment, while microbial biomass P was comparable. In the current study, soil labile P similar to or even higher than that in chemical fertilizer treatment when the substitution rate was ≤40%. Correlation heatmaps demonstrated a significant and positive relationship between soil available P and factors related to labile P and moderately labile P. This finding suggested that substituting 30%-40% of chemical P with manure can effectively enhance root length, AM colonization, soil enzyme activity, soil labile P, and consequently improve P uptake in pepper. These findings provide valuable insights for future organic agricultural practices that prioritize P supply, aiming to standardize organic P management in farmland and achieve high crop yields and maintain soil health.

Arbuscular mycorrhizal fungi drive bacterial community assembly in halophyte Suaeda salsa

Halophytes inhabit saline soils, wherein most plants cannot grow, therefore, their ecological value is outstanding. Arbuscular mycorrhizal (AM) fungi can reconstruct microbial communities to assist plants with stress tolerance. However, little information is available on the microbial community assembly of AM fungi in halophytes. A pot experiment was conducted to investigate the effects of AM fungi on rhizosphere bacterial community structure and soil physiochemical characteristics in the halophyte Suaeda salsa at 0, 100, and 400 mM NaCl. The results demonstrated that AM fungi increased soil alkaline phosphatase (ALP) activity at the three NaCl concentrations, and decreased available P, available K, and the activity of soil catalase (CAT) at 100 mM NaCl. AM fungi decreased the Shannon index of the community at 0 and 100 mM NaCl and increased Sobs index at 400 mM NaCl. Regarding the bacterial community structure, AM fungi substantially decreased the abundance of Acidobacteria phylum at 0 and 100 mM NaCl. AM fungi significantly increased the abundance of genus Ramlibacter, an oxyanion-reducing bacteria that can clean out reactive oxygen species (ROS). AM fungi recruited the genera Massilia and Arthrobacter at 0 and 100 mM NaCl, respectively. Some strains in the two genera have been ascribed to plant growth promoting bacteria (PGPB). AM fungi increased the dry weight and promoted halophyte growth at all three NaCl levels. This study supplements the understanding that AM fungi assemble rhizosphere bacterial communities in halophytes.

Effects of brackish water irrigation and biochar application on fertility, enzyme activity, and winter wheat yield in coastal saline‐alkali soils

AbstractSoil salinization is a common form of land degradation in coastal regions. The Yellow River Delta is a typical coastal saline‐alkali soils distribution region, with saline‐alkali soils accounting for nearly half of the total area of the region. In view of the lack of fresh water in the region, the use of brackish water and biochar made from agricultural waste to improve coastal saline‐alkali soils has a good application prospect, but there are fewer studies on this at present. To explore water conservation, fertilization, and yield enhancement solutions appropriate for saline‐alkali soils in the Yellow River Delta region, this study focused on investigating the impact of biochar addition on the fertility, enzyme activity, and winter wheat yield in saline‐alkali soils under brackish water irrigation conditions. The research was conducted through outdoor potting experiments, utilizing a local moderately saline‐alkali soil as the subject of study. The study design established three different irrigation water mineralization levels (0, 2, and 4 g L−1) during the research. Two types of biochar, wheat straw biochar (WB) and corn straw biochar (CB) were used with four different applications (0, 5, 10, and 20 t ha−1). There were 21 treatments; each replicated three times. The research findings indicated that brackish water irrigation adversely affected soil fertility and soil alkaline phosphatase activity and soil sucrase activity but increased soil urease activity and soil peroxidase activity. In contrast, biochar application improved soil fertility and enzyme activities. The soil fertility and enzyme activities of K2Y10 treatment was higher than that of CK (fresh water, no biochar application) except for soil total nitrogen, which increased by 5.5%–71.2%. While brackish water irrigation decreased winter wheat yield. Biochar application increased winter wheat yield, with the K2Y10 treatment showing the highest yield under brackish water irrigation conditions, and increased by 17.7% compared to CK. In conclusion, the study recommends a combination of water‐saving measures, fertilizer cultivation, and yield increase strategies to improve saline‐alkali soils in the Yellow River Delta region effectively. Specifically, irrigating with 2 g L−1 brackish water and application 10 t ha−1 of CB demonstrated greater efficacy in addressing the challenges of saline‐alkali soils in the region.

The phoD-Harboring Microorganism Communities and Networks in Karst and Non-Karst Forests in Southwest China

Phosphorous (P) limitation is common not only in tropical rainforest and savanna ecosystems, but also in karst forest ecosystems. Soil phoD-harboring microorganisms are essential in soil P cycles, but very little information is available about them in karst ecosystems. A total of 36 soil samples were collected from two types of forest ecosystems (karst and non-karst) over two seasons (rainy and dry), and the diversity and community structure of soil phoD-harboring microorganisms were measured. The contents of available P (AP), soil total P (TP), microbial biomass P (MBP) and the activity of alkaline phosphatase (ALP) in karst forest soils were higher than those in non-karst forest soils, whereas the contents of CaCl2-P, citrate-P, enzyme-P and the activity of acid phosphatase (ACP) were the opposite. Soil AP content was significantly higher in the rainy season than in the dry season, whereas ALP activity was the opposite. The community structure of phoD-harboring microorganisms was more influenced by forest-type than season. The network connectivity was higher in non-karst forests than in karst forests. Two dominant orders, Burkholderiales and Rhizobiales, were the keystone taxa in these networks in two forests, and their relative abundances were higher in non-karst forests than in karst forests. The microorganic diversity indices (e.g., Shannon–Wiener, Evenness, Richness, and Chao1) were substantially higher in karst than in non-karst forests. These indices were positively correlated with the contents of SOC and TN in the two forests; meanwhile, richness and evenness indices were positively correlated with citrate-P, HCl-P, and TP in non-karst forests. Structural equation modelling results showed that the relative abundance of phoD-harboring microorganisms was mainly influenced by pH and AP, with direct affection of soil AP, pH, and ALP activity, and indirect affection of ALP activity through affecting AP. These findings highlight that the P cycle is mainly regulated by the diversity of phoD-harboring microorganisms in karst forest ecosystems, whereas it is mainly regulated by dominant taxa in non-karst forest ecosystems. In future, regulating the interaction networks and keystone taxa of phoD-harboring microorganisms may be critical to alleviating P limitations in karst forest ecosystems.

Influences of nitrogen input forms and levels on phosphorus availability in karst grassland soils

The availability of soil phosphorus (P), a crucial nutrient influencing plant productivity and ecosystem function, is impacted by continuously increasing nitrogen (N) enrichment, which changes the soil P cycle. The effect of varying forms of N input on soil P dynamics in P-limited karst grassland ecosystems remains unclear. To address this knowledge gap, we conducted a greenhouse experiment to explore the effects of various forms of N addition [Ca(NO3)2, NH4Cl, NH4NO3, Urea] on soil P fractions in these ecosystems, applying two levels (N1: 50 mg N kg−1soil, N2: 100 mg N kg−1soil) of N input in two soils (yellow soil, limestone soil). Results indicated that P fractions in both soil types were significantly affected by N additions, with yellow soil demonstrating a higher sensitivity to these additions, and this effect was strongly modulated by the form and level of N added. High N addition, rather than low N, significantly affect the P fractions in both soil types. Specially, except for Ca(NO3)2, high N addition significantly increased the available P in both soils, following the order: Urea and NH4NO3 > NH4Cl > Ca(NO3)2, and decreased NaHCO3-Pi in both soils. High N addition also significantly reduced NaOH-Po and C.HCl-Po fractions in yellow soil. Additionally, the response of root biomass and alkaline phosphatase activity in both soils to N input paralleled the trends observed in the available P fractions. Notably, changes in soil available P were strongly correlated with plant root biomass and soil alkaline phosphatase activity. Our study highlights that the N addition form significantly influences soil P availability, which is closely tied to plant root biomass and alkaline phosphatase activity. This finding underscores the importance of considering N input form to boost soil fertility and promote sustainable agriculture.

Unlocking the potential of glyphosate-resistant bacterial strains in biodegradation and maize growth.

Glyphosate [N-(phosphonomethyl)-glycine] is a non-selective herbicide with a broad spectrum activity that is commonly used to control perennial vegetation in agricultural fields. The widespread utilization of glyphosate in agriculture leads to soil, water, and food crop contamination, resulting in human and environmental health consequences. Therefore, it is imperative to devise techniques for enhancing the degradation of glyphosate in soil. Rhizobacteria play a crucial role in degrading organic contaminants. Limited work has been done on exploring the capabilities of indigenously existing glyphosate-degrading rhizobacteria in Pakistani soils. This research attempts to discover whether native bacteria have the glyphosate-degrading ability for a sustainable solution to glyphosate contamination. Therefore, this study explored the potential of 11 native strains isolated from the soil with repeated glyphosate application history and showed resistance against glyphosate at higher concentrations (200 mg kg-1). Five out of eleven strains outperformed in glyphosate degradation and plant growth promotion. High-pressure liquid chromatography showed that, on average, these five strains degraded 98% glyphosate. In addition, these strains promote maize seed germination index and shoot and root fresh biomass up to 73 and 91%, respectively. Furthermore, inoculation gave an average increase of acid phosphatase (57.97%), alkaline phosphatase (1.76-fold), and dehydrogenase activity (1.75-fold) in glyphosate-contaminated soil. The findings indicated the importance of using indigenous rhizobacteria to degrade glyphosate. Therefore, by maintaining soil health, indigenous soil biodiversity can work effectively for the bioremediation of contaminated soils and sustainable crop production in a world facing food security.

Earthworms facilitated pepper (Capsicum annuum L.) growth via enhancing the population and function of arbuscular mycorrhizal fungi in a low-density polyethylene-contaminated soil

Microplastics (MPs) produced by the decomposition of plastics exist persistently, interfering with soil fertility and plant nutrition. Both arbuscular mycorrhizal (AM) fungi and earthworms are beneficial in terrestrial ecosystems, but their interactions under MPs contamination are unclear so far. Here, the influences of inoculating earthworms (Eisenia fetida) on indigenous AM fungi and pepper (Capsicum annuum L.) growth were investigated in a vegetable soil treated with 0.1% low-density polyethylene (LDPE), while the specific interactions of earthworm and AM fungus (Funneliformis caledonium) under LDPE contamination were further resolved in another experiment using sterilized soil. Inoculation of earthworms shifted soil AM fungal community structure, replacing the predominant genus Glomus by Paraglomus, and increased the abundance, diversity (i.e., Shannon) index, and root colonization rate of AM fungi by 108, 34.6 and 45.0%, respectively. Earthworms also significantly decreased soil pH, and significantly increased soil alkaline phosphatase (ALP) activity, shoot biomass and fruit yield of pepper by 394, 82.8 and 188%, respectively. In the sterilized soil, both E. fetida and F. caledonium improved pepper growth, while the latter noticeably increased phosphorus (P) translocation efficiency from root to shoot, and the combination induced the highest soil ALP activity and pepper fruit yield. Furthermore, the significantly interactive effects between earthworm and AM fungus were observed in soil pH and available P concentration, as well as in shoot P concentration and fruit yield of pepper. This study revealed the interaction between earthworms and AM fungi under MPs contamination conditions for the first time, indicating that earthworms could facilitate vegetable growth via enhancing the propagation and P-promoting function of AM fungi in LDPE-contaminated soils.Graphical

Assessment of Phosphorus Mobilizing Capacity of Bacillus spp. Isolated from Mangrove Rhizospheric Sediment and its Potential Application in Aquaculture

Background: Phosphatase producing bacteria (PPB) plays a major role in mineralising organic P into inorganic form. Though application of bacterial biofertilizers are practiced in agriculture, their application is very limited in aquaculture. Method: The PPB isolates were screened and isolated from rhizospheric sediment of mangrove, Avicennia marina of Ennore creek, Tamil Nadu. Their P transformation potential and the possibilities of their application in aquaculture to mineralise organic P to inorganic P were studied. Result: Twenty PPB isolates were screened in the study site and their Alkaline Phosphatase (ALP) activity was in the range of 13.6-20.4 µmol.ml-1.hr-1. Out of this, five Bacillus sp isolates were selected to assess their P transformation potential at various salinity. The P mobilizing potential of these isolates were compared with the commercial PPB following a microcosm study for a period of 14 days. During the study period, there is a significant increase in phosphorus in water as well as ALP activity and available phosphorus concentrations in sediments were observed between control and treatment tanks. Among the treatment groups, B. subtilis treatment tanks showed maximum P in water ie. 1.60mg.L-1, followed by B. altitudinis –1.49mg.L-1; B. pumilus –1.47mg.L-1; the soil ALP activity was in the order of commercial P products greater than B. pumilus greater than B. subtilis greater than B. paramycoides greater than B. altitudinis greater than B. aryabhattai. In terms of available phosphorus content in sediments on 14th day, there is no significant difference observed between B. pumilus and commercial product with respect to available P content of sediment.

New insights into the role of soil properties in driving cadmium-induced hormesis in soil alkaline phosphatase under vegetation cover change

This study investigated the hormetic responses of soil alkaline phosphatase (ALP) to exogenous Cd under five different vegetation cover types in a typical coastal wetland, including mudflat (Mud), Phragmites australis (PA), Spartina alterniflora (SA), Metasequoia glyptostroboides (MG), and Cinnamomum camphora (CC). The results showed that the activity of soil ALP was significantly enhanced by exogenous 0.3–1.0, 0.2–0.8, 0.05–0.3, 0.05–0.6, and 0.05–0.60 mg Cd /kg in Mud, PA, SA, MG, and CC, respectively. Moreover, the Horzone (an integrated indicator of the stimulation phase) of Mud and PA was significantly higher than that of SA, MG, and CC. Multiple factor analysis revealed that soil chemical properties and soil bacteria community play an important role in the hormetic effect of soil ALP to Cd stress. Soil electric conductivity (EC) and the relative abundance of Gammaproteobacteria were also identified as key drivers of the hormetic effects of Cd on soil ALP under five vegetation cover types. These findings suggest that the soil ecosystem had better resistance to exogenous Cd stress under mudflat and native species (PA) than invasive species (SA), and artificial forests (MG and CC) when soil ALP activity was the test endpoint. Consequently, this study is beneficial for future ecological risk assessment of soil Cd contamination under divergent vegetation covers.

Global patterns of soil phosphatase responses to nitrogen and phosphorus fertilization

Hydrolysis of organic phosphorus (P) by soil phosphatases is an important process of P cycling in terrestrial ecosystems, significantly affected by nitrogen (N) and/or P fertilization. However, how soil acid phosphatase (ACP) and alkaline phosphatase (ALP) activities respond to N and/or P fertilization and how these responses vary with climatic regions, ecosystem types, and fertilization management remain unclear. This knowledge gap hinders our ability to assess P cycling and availability from a global perspective. We performed a meta-analysis to evaluate the global patterns of soil ACP and ALP activities in response to N and/or P addition. We also examined how climatic regions (arctic to tropical), ecosystem types (cropland, grassland, and forest), and fertilization management (experiment duration and fertilizer type and application rate) affected changes in soil phosphatases after fertilization. It was shown that N fertilizer resulted in 10.1% ± 2.9% increase in soil ACP activity but a minimal effect on soil ALP activity. In contrast, P fertilizer resulted in 7.7% ± 2.6% decrease in soil ACP activity but a small increase in soil ALP activity. The responses of soil ACP and ALP activities to N and/or P fertilization were largely consistent across climatic regions but varied with ecosystem types and fertilization management, and the effects of ecosystem types and fertilization management were enzyme-dependent. Random forest analysis identified climate (mean annual precipitation and temperature) and change in soil pH as the key factors explaining variations in soil ACP and ALP activities. Therefore, N input and ecosystem types should be explicitly disentangled when assessing terrestrial P cycling.

Coupling amendment of biochar and organic fertilizers increases maize yield and phosphorus uptake by regulating soil phosphatase activity and phosphorus-acquiring microbiota

Biochar and organic fertilizers are important alternatives to mineral fertilizers. Thus, it is important to understand how the co-application of biochar and organic fertilizers influences crop productivity and soil-plant phosphorus (P) trade-offs. Herein, we conducted a field fertilization experiment for eight years with maize-cabbage rotation. This experiment contained five treatments: no fertilization (CK), mineral fertilizers (CF), CF + biochar (BF), 20% substitution of mineral nitrogen (N) with organic fertilizers (OF), and OF + biochar (BOF). The fertilization regimes of all plots were maintained since 2013. The results showed that soil P pool composition but not P bioavailability differed significantly between the five treatments. Compared with the CF treatment, soil labile-P content in the BF, OF, and BOF treatments significantly increased by 12–23% and soil stable-P content decreased by 13–19%. Besides, the soil moderately labile-P content in the OF and BOF significantly decreased by 40% and 10% and increased by 31% in the BF as compared to the CF. The activities of soil acid (ACP) and alkaline phosphatase (ALP) in the BF, OF, and BOF significantly increased by 8–44% and 16–49% respectively compared to the CK. Furthermore, the abundance of P-acquiring genes (bpp, phoD, phoX, ppx, ppk, and phnK) in the BF, OF, and BOF increased by 22–114% compared to the CK. Plant P uptake and maize yield were significantly correlated with soil ACP and ALP activities as well as the abundance of phnK, ppx, phoD, phoX, and pqqC genes but not to the contents of soil P components. In conclusion, the co-application of biochar and organic fertilizer on maize productivity increases was mainly related to the improvement of soil phosphatase activity and P-acquiring gene abundance.