Soil Phosphatase Activity Research Articles

Changes in soil phosphorus availability and associated microbial properties after chicken farming in Lei bamboo (Phyllostachys praecox) forest ecosystems

AbstractBamboo‐chicken farming (BCF) is a popular bamboo complex management model in Southeast Asia. However, the effects of BCF on phosphorus (P) availability and associated soil microbial communities remain poorly understood. In this study, we compared the soil properties, P fractions, phosphatase activities, and bacterial community compositions in the surface soil (0–20 cm) of a typical BCF system under different grazing densities [represented as distances of 5, 15, 25, 35, and > 60 m (control site) from the henhouse, respectively]. We observed that total P (Pt) accumulation was more rapid than that of SOC and TN with increasing grazing density. Labile and moderately labile P dominated soil P accumulation under BCF. Resin‐Pi, NaHCO3‐Pi, and 1 M HCl‐Pi increased by 100–233%, 83–183%, and 414–1,314%, respectively, compared with the control. The ratio of labile and moderately labile organic P to the Pt content decreased significantly with increasing grazing density from 38.54% (control) to 17.65% (5 m site). Soil phosphatase activity increased with increasing grazing density, suggesting that BCF effectively promoted the mineralization of soil Po. Inorganic P (Resin‐Pi, NaHCO3‐Pi, and 1 M HCl‐Pi) was positively correlated with Flavobacterium, Pseudomonas, and Arthrobacter but negatively correlated with Burkholderia; this highlights the different functional bacteria involved in P cycling. We conclude that BCF generally increased soil P availability and supply capacity, and the changes in P forms were closely related to changes in soil bacterial community composition. The highly labile P and low C : P ratio under high grazing density conditions may cause soil nutrient imbalance and P leaching.

Effects of planting Melia azedarach L. on soil properties and microbial community in saline‐alkali soil

AbstractSaline‐alkali soils are widely distributed in China, affecting plant growth and sustainable development of ecosystems. Few studies have been done on the improvement of saline‐alkali soils by planting Melia azedarach in phytoremediation. This study characterized the effects of planting M. azedarach on chemical properties and microbial communities in saline‐alkali soils [bare (CK), bulk (BS), and rhizosphere soil (RS)]. Compared with the bare soil, planting M. azedarach lowered salt content and concentrations of extractable Na+, K+, Ca2+, Mg2+, and Cl−, but significantly increased organic matter, total nitrogen, total phosphorus, available phosphorus, soil urease activity, and alkaline phosphatase activity in the rhizosphere soil. High‐throughput sequencing results indicated that M. azedarach increased the Chao1 index and Shannon index of soil microbial communities. The three dominant bacterial phyla were Proteobacteria, Actinobacteria and Bacteroidetes, and the three dominant fungal phyla were Ascomycota, Basidiomycota, and Glomeromycota. Redundancy analysis indicated that total phosphorus concentration and alkaline phosphatase activity significantly influenced bacterial diversity, whereas soil Ca2+ and Mg2+ concentrations were closely related to the fungal community diversity. In conclusion, planting Melia azedarach improved soil properties, increased the diversity and richness of soil microbial communities, and thus ameliorated the saline‐alkali soil.

Biostimulating Effects of Disintegrated Waste Activated Sludge on Soil Enzyme Activities

Sludge disintegration methods are used in a variety of applications to enhance sludge characteristics or bring about a reduction in solid content of sludge. Hydrodynamic cavitation is one of the mechanical disintegration methods used on waste-activated sludge, and its efficiency has been investigated in recent years. In this study, the possible use of waste-activated sludge disintegrated by hydrodynamic cavitation and chemically assisted hydrodynamic cavitation as a soil amendment was evaluated by an incubation procedure. Possible biostimulating effects were assessed by monitoring the variations in soil enzyme activities. The obtained results indicated that sludge solubilization was effectively performed with respect to soluble chemical oxygen demand, soluble total Kjeldahl nitrogen and soluble total phosphorus. According to the incubation study, the biostimulating/bioremediating properties of waste-activated sludge were significantly improved by the applied methods. Especially after a 60-day incubation period, the levels of urease, alkaline phosphatase, β-glucosidase and dehydrogenase activities in soils applied with a high dose of disintegrated sludge were significantly higher than the levels in raw sludge-amended soils. Consequently, it is thought that mechanically and chemically disintegrated waste-activated sludge with reduced numbers of indicator bacteria can be considered as a way of soil amendment to rehabilitate the quality of environmentally stressed soils.

Rock-Solubilizing Microbial Inoculums Have Enormous Potential as Ecological Remediation Agents to Promote Plant Growth

Anthropogenic overexploitation poses significant threats to the ecosystems that surround mining sites, which also have tremendous negative impacts on human health and society safety. The technological capacity of the ecological restoration of mine sites is imminent, however, it remains a challenge to sustain the green restorative effects of ecological reconstruction. As a promising and environmentally friendly method, the use of microbial technologies to improve existing ecological restoration strategies have shown to be effective. Nonetheless, research into the mechanisms and influences of rock-solubilizing microbial inoculums on plant growth is negligible and the lack of this knowledge inhibits the broader application of this technology. We compared the effects of rock-solubilizing microbial inoculums on two plant species. The results revealed that rock-solubilizing microbial inoculums significantly increased the number of nodules and the total nodule volume of Robinia pseudoacacia L. but not of Lespedeza bicolor Turcz. The reason of the opposite reactions is possibly because the growth of R. pseudoacacia was significantly correlated with nodule formation, whereas L. bicolor’s growth index was more closely related to soil characteristics and if soil nitrogen content was sufficient to support its growth. Further, we found that soil sucrase activity contributed the most to the height of R. pseudoacacia, and the total volume of root nodules contributed most to its ground diameter and leaf area. Differently, we found a high contribution of total soil carbon to seedling height and ground diameter of L. bicolor, and the soil phosphatase activity contributed the most to the L. bicolor’ s leaf area. Our work suggests that the addition of rock-solubilizing microbial inoculums can enhance the supply capacity of soil nutrients and the ability of plants to take up nutrients for the promotion of plant growth. Altogether, our study provides technical support for the practical application of rock-solubilizing microbes on bare rock in the future.

Changes of acid and alkaline phosphatase activities in long-term chemical fertilization are driven by the similar soil properties and associated microbial community composition in acidic soil

Acid and alkaline phosphatase (ACP and ALP), encoded separately by the bacterial phoC and phoD genes, participate in the mineralization of organic phosphorus (P) to inorganic P. However, the influence of chemical fertilization on soil phosphatase activities and associated bacterial communities in acidic soils remains unclear. Here, we conducted a 27 year continuous chemical fertilization experiment consisting of the no-fertilizer control (CK), N and P fertilizer (NP), N and K fertilizer (NK), P and K fertilizer (PK), and N, P and K fertilizer (NPK) treatments, in order to investigate phosphatase activities and phoC- and phoD-harboring bacterial communities. Results demonstrated that ACP and ALP activities increased significantly in the NP (198.70 and 35.46 μg pNP g−1 soil h−1, respectively) and NPK treatments (199.62 and 36.51 μg pNP g−1 soil h−1, respectively) compared to CK (143.81 and 22.49 μg pNP g−1 soil h−1, respectively), while ALP activity was reduced for the NK treatment (13.86 μg pNP g−1 soil h−1). The abundance and diversity index of phoC- and phoD-harboring bacteria differed among treatments. The two bacterial community structures exhibited similar trends in terms of the significant differences between N-free (CK and PK) and N-containing (NP, NK and NPK) treatments (Adonis, p < 0.01). Random forest model analysis revealed that the variations in ACP and ALP activities can be explained by microbial biomass P (MBP, 9.71% and 13.20%, respectively), soil total carbon (TC, 10.89% and 8.77%, respectively) and available P (AP, 9.10% and 7.15%, respectively), and microbial factors including community composition (5.94% and 4.48%, respectively) and network clustering coefficients (6.05% and 5.15%, respectively). Furthermore, the dominant genera Stenotrophomonas and Variibacter were positively correlated with ACP and ALP activities, respectively, with their members observed as keystone species in the community network. Overall, chemical N and P fertilization was generally observed to improve soil phosphatase activities in acidic soil, with soil TC and AP identified as the primary soil variables affecting phosphatase activities by altering the associated bacterial community composition and increasing MBP. These findings improve the understanding of how fertilization influences the community composition and function of phosphate-solubilizing microorganisms in acidic soils.

Crop residue application at low rates could improve soil phosphorus cycling under long-term no-tillage management

A field experiment was conducted in northeastern China to study the effects of no-tillage (NT) and residue application rates (NT and residue application at 0% (NTR0%), 33% (NTR33%), 67% (NTR67%), and 100% (NTR100%)) on soil phosphatase activities and P species determined by 31P NMR, and their relationships at 0–10 and 10–20 cm depths. The NTR33% treatment showed significantly higher available P, microbial biomass P, pyrophosphate, scyllo-inositol hexakisphosphate (scyllo-IHP), and corrected diester contents than the NTR0% treatment. The myo-IHP concentration under the NTR33% treatment at the 0–10 cm depth was significantly greater than in all treatments except the NTR100% treatment at the 0–10 cm depth and the NTR67% and NTR100% treatments at the 10–20 cm depth. The corrected monoester content under the NTR33% treatment at the 0–10 cm depth was not significantly different from the NTR67% at the 0–10 cm depth and the NTR100% treatment at the 10–20 cm depth, but was significantly greater than in all other treatments. Both NTR33% and NTR100% treatments significantly increased acid phosphomonoesterase activity. Structural equation modeling suggested a relationship of organic P compounds with phosphodiesterase and acid phosphomonoesterase at 0–10 cm, and with alkaline phosphomonoesterase at 10–20 cm.

Mobilization of soil phosphorus and enhancement of canola yield and phosphorus uptake by Ceriporia lacerata HG2011

ABSTRACT The high-quality phosphorus (P) rocks on the Earth will be depleted within the next 50 years. P-mobilizing microbes can mobilize soil unavailable P and reduce P fertilizer use in agriculture. Therefore, incubation and field experiments were conducted to study the effects of a new white-rot fungus Ceriporia lacerata HG2011 on soil P mobilization and canola yield and P uptake to understand the potential of this fungus as a biofertilizer. In the soil incubation experiment, available P and phosphatase activity increased, whereas soil pH decreased as the fungal hyphae grew on the soil surfaces and in the soil. Accordingly, Olsen P was positively correlated with the phosphatase activity (r = 0.565, p ≤ 0.01) but negatively with the pH (r = −0.506, p ≤ 0.01 or 0.05). The mechanisms of P mobilization by this fungus could thus be soil acidification to solubilize inorganic P and phosphatase efflux to mineralize organic P. Compared with chemical fertilizers alone, the application of this fungus in combination with chemical fertilizers increased canola yield by 3.94–9.49% in the field. Our findings firstly demonstrated the new use of C. lacerata HG2011 as a biofertilizer in canola cultivation.

Effect of Seed Bio-priming with Trichoderma viride Strain BHU-2953 for Enhancing Soil Phosphorus Solubilization and Uptake in Soybean (Glycine max)

The main objective of our study was to evaluate the effectiveness of Trichoderma viride BHU-2953 as a single inoculant during seed-priming to enhance phosphorus (P) uptake in soybean. A pot experiment was conducted, taking six treatments, in a completely randomized block design to assess the P uptake, root length, apparent phosphorus recovery (APR), rhizospheric phosphatase activity, pH, soil-P status, dehydrogenase activity, and fungal colony-forming unit (CFU g−1) in three different soybean growth stages through seed-priming with T. viride along with graded fertilizer P-doses. Significantly (P < 0.05) higher soil phosphatase activity, dehydrogenase activity, CFU of T. viride, and P-content in soybean vegetative parts were observed in bio-primed treatments as compared to control and RDF (full recommended dose of P-fertilizer without seed-priming), while seed-P (%), APR (%), and root lengths of RDF were found significantly (P < 0.05) lower than bio-primed soybeans with 90% RDF but were at par with 80% RDF. Higher positive correlations between CFU and acid phosphatase (R2 = 0.89, 0.9, and 0.89; P < 0.05) and between CFU and alkaline phosphatase activities (R2 = 0.98, 0.96, and 0.97; P < 0.05) at 30, 50, and 75 DAS indicate that T. viride mediated higher soil phosphatase activities. Higher P-recoveries of bio-primed soybeans, received 90% and 80% RDF, were achieved mainly due to soil applied-P solubilization through enhanced acid phosphatase activities along with better soil exploration by plant roots. Thus, seed-priming with T. viride BHU-2953 can reduce up to 20% of the recommended P-dose in soybeans.

Shifts in composition and function of soil fungal communities and edaphic properties during the reclamation chronosequence of an open-cast coal mining dump

The diversity, composition and ecological guilds of soil fungal communities in relation to revegetation were assessed during an open-cast mining dump reclamation chronosequence of the soil <1, 5, 10, 15 and 20 years after the start of reclamation. Soil pH and electrical conductivity, total nitrogen (TN), soil organic carbon (SOC), available potassium (AK), and available phosphorus (AP) contents, and soil phosphatase (Pha), urease (U) and invertase (INV) activities were measured. Using high-throughput sequence analysis on internal transcribed spacer (ITS) sequences, 1059 soil fungal operational taxonomic units (OTUs) were identified belonging to 64 orders and these were further categorized by ecological guild. Soil fungal diversity indices were significantly different between the early (<1 year) and later reclamation communities. Nonmetric multidimensional scaling (NMDS) analysis indicates that the composition and ecological guilds of soil fungal communities were significantly different early in the process and at the end of reclamation (P < 0.05). Co-occurrence network and structural equation model analyses show that soil fungal community structure and ecological guilds were correlated with edaphic properties and had an indirect effect on soil available nutrients through direct action on soil enzymes. Overall, the data suggest that soil fungal community composition and function within an open-cast coal mining dump reclamation chronosequence changed during the period following artificial re-vegetation, with interactions between edaphic properties and soil fungal communities associated with these changes.

Effect of Phosphate Solubilizing Bacteria on Phosphatase Activities, Yield and Phosphorus Nutrition of Wheat in an Acidic Entisol

This research aims to determine the short-term prospects of phosphate solubilizing bacteria (PSB) application on growth and yield of wheat and fertility status of soil with special reference to phosphorus (P). Spectrophotometric analyses were carried out to determine acid phosphatase (APase) and alkaline phosphatase (ALPase) activities in plant roots and rhizosphere soil, P bioavailability at the salient growth stages and harvest of the wheat crop, and P nutrition at maturity. Results of the wheat field experiment conducted during winter 2014–15 showed that application of PSB significantly increased the root APase but a quite opposite trend of the APase activity between plant roots and rhizosphere soil was found. In the case of ALPase activity, the effect of PSB was more prominent in root than soil. Among the two enzymes (APase and ALPase), APase activity was constantly higher in root and soil, indicating its importance in P hydrolysis and plant nutrition under acidic and P deficient soil conditions. The combined application of Pfertilizer and PSB had a profound influence on soil available P. Considerable effect of PSB on yield could be noted, but no significant effect was observed for P nutrition. The research work clearly indicated the importance of integration of P-fertilizer and PSB for maintaining higher crop productivity and better soil fertility. The study also emphasizes the need to consider the determinants which modulate the effectiveness of PSB in P solubilization and plant growth promotion.

Improved salinity tolerance of Medicago sativa and soil enzyme activities by PGPR

Abstract Abiotic stresses such as salinity are common adverse conditions that significantly affect agricultural productivity worldwide. This study aimed to select halotolerant plant-growth-promoting rhizobacteria (PGPR) capable to promote plant growth and to improve soil functioning under salinity stress conditions. Thirty-two bacterial isolates were studied for their PGP traits and NaCl resistance. Four selected potential PGPR were identified by using 16S rDNA sequencing and tested for their PGP traits in the presence of 2–6% NaCl. Their effect on growth, chlorophyll content, oxidative stress and root arbuscular mycorrhizal (AM) colonization of Medicago sativa, was studied under salt stress in pots experiment. The bacteria were also tested for their effect on soil enzyme activities. Overall results showed that the isolates displayed various PGP properties and variable levels of NaCl resistance. The four selected potential PGPR strains were identified as Pseudomonas putida, Alcaligenes sp., Klebsiella sp., and Pseudomonas cedrina. The bacteria retained most of the PGP traits in the presence of the tested concentrations of NaCl. The inoculation of M. sativa plants by the four strains allowed overcoming the negative effects of stress due to NaCl and increased plant growth, roots AM colonization and the leaves chlorophyll content, compared to the non-inoculated control. It also lowered the levels of the indicators of oxidative damage, malondialdehyde, hydrogen peroxide, and proline. Besides, the strains had a positive effect on soil phosphatase, β-galactosidase, and arylamidase activities. This study showed that the selected isolates have an interesting potential to be used as bio-inoculants for plants growing under salt stress.

Chemical Properties, Microbial Biomass and Enzyme Dynamics of Post-Harvest Soil on Transplanted Rice with Effect of Organic Amendments

A field experiment was conducted at the farm of Tamil Nadu Agricultural University, Coimbatore during kharif season to study the effect of soil chemical properties, microbial biomass and soil enzyme dynamics on transplanted rice with organic amendments. Rice CO(R) 48 was used as a test variety. The experiment was laid out in randomized block design (RBD) with three replications and nine treatments. The treatment consists Recommended Dose of Fertilizers 100% NPK (150 : 50 : 50 kg ha-1) through inorganic fertilizers, Based on N equivalent basis, required quantities of organic manures (Dhaincha, vermicompost and Farmyard Manure @ 50% and 100%) were incorporated into the soil one week before transplanting of rice. The P and K requirement was supplied separately through inorganic sources as per treatment schedule. In the present investigation, an attempt was made to examine the influence of different levels and sources of fertilization on dynamics of soil chemical properties, microbial biomass and enzyme activities under anaerobic rice cultivation. Soil samples were taken before the start of experiment and harvest of rice for analysis of soil chemical characteristics, microbial biomass and enzyme activity. The results revealed that maximum microbial population (bacteria, fungal &amp; actinomycetes), soil enzyme dynamics (urease, dehydrogenase &amp; soil phosphatase activity), soil available macro nutrients (N, P, K) &amp; micro nutrients (Fe, Zn, Mn, Cu) were significantly influenced with application of 100% N through dhaincha + balance P &amp; K through inorganic fertilizers followed by application of 100% NPK through inorganic fertilizers + 6.25 t dhaincha. Least enzyme activity, microbial population &amp; soil available nutrients of rice were registered in absolute control.

Limited effects of the soluble organic phosphorus fraction on the root phosphorus uptake efficiency of upland rice genotypes grown in acid soil

ABSTRACT The root phosphorus (P) uptake efficiency (RE), defined as plant P uptake per unit root mass or root area, may contribute to the P efficiency of upland rice grown in acid, P-deficient soils. The identification of root traits conferring RE of rice has been compromised by the lack of attention given to P speciation when evaluating P-mining mechanisms. Here we disentangled the effect of soluble organic P (PO) from that of total soluble P (PT) on the RE in rice seedlings in acid soil. Six rice genotypes were grown for 21 days in P-deficient substrates, i.e. a sample of an acid mineral soil, an acid peat and a mixture thereof. Each of the three substrates were amended with different P doses, partially limed and incubated, yielding substrates with significant differences in total soluble P (0.005–0.41 mg P/L) and in the percentage of organic P in that pool (PO/PT, 0–55%). Plants showed a large growth response to the P addition. There was a significant genotypic variation in P uptake (0.9–1.5mg P/plant) and RE (4.4–8.3 mg P/g root mass) under moderate P deficiency but these traits were unaffected by the PO/PT in the soluble fraction of the substrates. Along the same lines, phosphatase activity in the rhizosphere soil was unaffected by genotypes and did not explain the RE among all data (R2 = 0.17, ns). A multiple regression model showed that the RE of rice seedlings was mainly affected by the inherent genotypic effects, the PO/PT and the total soluble P concentration in soil (R2 = 0.73), while the genotype-PO/PT interaction only marginally improved the RE model (R2 = 0.78). This suggests limited genotypic effects due to the better use of organic P. A root elongation test in the acid mineral soil that was either or not limed suggests that the differences in acid soil tolerance may play a larger role in the genotypic performance of RE than organic P utilization potential.

Targeting Low-Phytate Soybean Genotypes Without Compromising Desirable Phosphorus-Acquisition Traits.

Phytate-phosphorus (P) in food and feed is not efficiently utilized by humans and non-ruminant livestock, potentially contributing to high losses of P to the environment. Crops with high P-acquisition efficiency can access soil P effectively. It remains elusive whether crop genotypes with high P-acquisition efficiency can also have low seed phytate concentrations. A core collection of 256 soybean [Glycine max (L.) Merr.] genotypes from China with diverse genetic background were grown in the same environment and seeds were sampled to screen for seed phytate-P concentration. Some of these genotypes were also grown in a low-P soil in the glasshouse to measure root morphological and physiological traits related to P acquisition. Large genotypic variation was found in seed phytate-P concentration (0.69–5.49 mg P g–1 dry weight), total root length, root surface area, rhizosheath carboxylates, and acid phosphatase activity in rhizosheath soil. Geographically, seed phytate-P concentration was the highest for the genotypes from Hainan Province, whereas it was the lowest for the genotypes from Inner Mongolia. Seed phytate-P concentration showed no correlation with any desirable root traits associated with enhanced P acquisition. Two genotypes (Siliyuan and Diliuhuangdou-2) with both low phytate concentrations and highly desirable P-acquisition traits were identified. This is the first study to show that some soybean genotypes have extremely low seed phytate concentrations, combined with important root traits for efficient P acquisition, offering material for breeding genotypes with low seed phytate-P concentrations.

Effects of Fertilization Methods on Chemical Properties, Enzyme Activity, and Fungal Community Structure of Black Soil in Northeast China

Understanding the influence of fertilizer on soil quality is vital to agricultural management, yet there are few studies, particularly in black soil. In this study, soils under various treatments, namely no fertilizer, bio-organic + humic acid, bio-organic + chemical, and chemical fertilizer, were sampled to identify their major physiochemical properties, and to investigate the fungal community structure using environmental sequencing techniques. Physiochemical properties and fungal community structure were examined at four important stages of the maize life cycle: seedling, jointing, heading period, and maturity. We found that chemical fertilizer in the mature stage increased the soil available phosphorous (AP) content. Organic matter content was greatly affected by bio-organic + chemical fertilizer during the mature stage. Bio-organic + humic acid significantly increased soil phosphatase activity in maturing maize, whilst chemical fertilizers reduced invertase activity. Taken together, our results clearly illustrated that bio-organic + humic and chemical fertilization indirectly alter fungal community structure via changing soil properties (especially AP). Chemical fertilizer markedly heightened the AP content, thereby decreasing specific fungal taxa, particularly Guehomyces. OM was of positive connection with bio-organic + humic acid and Mortierella abundance, respectively, through RDA analysis, which are in agreement with our result that bio-organic + humic acid fertilization to some extent increased Mortierella abundance. Additionally, bio-organic + humic acid decreased the abundance of Fusarium and Humicola, suggesting that bio-organic + humic acid possibly could help control crop disease. These results help to inform our fundamental understanding of the interactions between fertilizers, soil properties, and fungal communities.

Mycorrhizas promote P acquisition of tea plants through changes in root morphology and P transporter gene expression

Tea (Camellia sinensis (L.) O. Kuntze) is predominantly grown in acidic soils with severe limitations of P-nutrition. The present study evaluated the effects of an arbuscular mycorrhizal (AM) fungus, Claroideoglomus etunicatum, on root morphology, leaf and root P concentration, phosphatase activity in soils and roots, and the relative expression of root P transporter genes (PT1 and PT4) in Camellia sinensis ‘Fuding Dabaicha’ seedlings in sands under two levels of P viz., 0.5 μM (P0.5) and 50 μM (P50) through Hoagland solutions (pH 4.2) for 24 weeks. Under both P0.5 and P50 conditions, AM seedlings displayed a higher growth performance (shoot biomass, root biomass, and plant height), root morphology (total length, taproot length, 2nd- and 3rd-lateral root number, and volume), and root-hair length, but lower root-hair density than non-AM seedlings. Mycorrhizal inoculation significantly increased root P concentrations in P0.5 and P50 and leaf P concentrations in P0.5 over non-mycorrhizal treatment. The AM seedlings recorded considerably higher soil acid, neutral, and total phosphatase activity under P0.5 treatment, and soil neutral and total phosphatase activity under P50 treatment, compared with the non-AM seedlings. Root acid phosphatase activity was reduced due to mycorrhization at both of P0.5 and P50. AM fungal inoculation up-regulated the relative expression of root CsPT1, while down-regulated the CsPT4 expression in P0.5 and P50 treatments. It was concluded that AM fungal inoculation significantly promoted P acquisition capacity of tea plants, especially in roots through improving root growth and enhancing soil acid phosphatase activity and root CsPT1 expression.

Effects of beneficial endophytic fungal inoculants on plant growth and nutrient absorption of trifoliate orange seedlings

Citrus plants heavily depend on soil arbuscular mycorrhizal fungi (AMF), while the application of AMF in citrus is limited because of no propagation in vitro. The present work tried to apply a culturable (in vitro) endophytic fungus Piriformospora indica into trifoliate orange (Poncirus trifoliata) and to compare the role of P. indica in plant growth and nutrient acquisition especially phosphorus (P), relative to an arbuscular mycorrhizal fungus Funneliformis mosseae. After 20 weeks, roots of trifoliate orange could be colonized by P. indica, and both P. indica and F. mosseae existed in roots together. Root fungal colonization and soil easily extractable, difficultly extractable, and total glomalin-related protein concentrations were higher under single F. mosseae inoculation than under single P. indica and dual inoculation of F. mosseae and P. indica. Single or dual microbial inoculant collectively improved plant growth including plant height, leaf number, and leaf, stem, and root biomass, compared with non-inoculation. In addition, single fungal treatment raised the content of root N, P, and Mg, and dual inoculation increased only Mg and B contents. The improvement of P by single microbial inoculant was associated with the fungi-accelerated soil phosphatase activity and the fungi-induced root phosphate transporter genes (PT3, PT5, and PT6) expression levels. The positive effects on growth and nutrients were more significant under single F. mosseae than under single P. indica and dual inoculations. It concluded that P. indica has the stimulated roles in plant growth and P acquisition of trifoliate orange, and thus has more applied potentiality in citriculture than AMF as a biofertilizer.

Effects of polycyclic aromatic hydrocarbons (PAHs) from different sources on soil enzymes and microorganisms of Malus prunifolia var. Ringo

ABSTRACT The main components of polycyclic aromatic hydrocarbons (PAHs) and the degree of contamination of soil with different oils (gasoline, diesel oil, and lubricating oil) were examined. Malus prunifolia var. Ringo was planted in soil contaminated by gasoline, diesel oil, or lubricating oil with three different concentrations which were low concentration (0.1 g kg−1), medium concentration (0.2 g kg−1), and high concentration (0.5 g kg−1) in April 2016. The changes in PAH contents and soil index in the soil were measured from July to September 2016. It showed that more naphthalene, anthracene, phenanthrene, fluorene, and flexion were detected in the three oil treatments. From July to September, three high-concentration oil treatments had inhibited soil urease activity in soil significantly except the diesel oil treatment with high concentration in August. The diesel and lubricating oil treatments had inhibited phosphatase and invertase activities in soil significantly. Three oil treatments inhibited the number of bacteria significantly in July. The total number of bacteria and fungi was highest in gasoline, and the total number of actinomycetes was highest in lubricating oil. The three oils affected the soil enzyme activity and the number of soil microorganisms and caused some damage to the soil ecological environment.

Influences of a vermicompost application on the phosphorus transformation and microbial activity in a paddy soil

A pot experiment was conducted to investigate the effects of a vermicompost (VC) application on the phosphorus (P) transformation and microbial activity in a paddy soil. Changes in the following P forms were investigated: resin-P, concentrated HCl extracted inorganic (C.HCl-P&lt;sub&gt;i&lt;/sub&gt;) and organic P (C.HCl-P&lt;sub&gt;o&lt;/sub&gt;), diluted HCl extracted inorganic P (D.HCl-P&lt;sub&gt;i&lt;/sub&gt;), NaHCO&lt;sub&gt;3&lt;/sub&gt; extracted inorganic (NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;i&lt;/sub&gt;) and organic P (NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;o&lt;/sub&gt;), NaOH extracted inorganic (NaOH-P&lt;sub&gt;i&lt;/sub&gt;) and organic P (NaOH-P&lt;sub&gt;o&lt;/sub&gt;), and residual P. The results showed that the vermicompost application significantly (P &amp;lt; 0.05) affected the pH, redox potential (Eh), water soluble Fe(II), HCl-extractable Fe(II), microbial biomass carbon (MBC), microbial biomass P (MBP), MBC/MBP ratio, and acid phosphatase activity (APA) of the paddy soil. In particular, the HCl-extractable Fe(II) increased by 25–56% with the vermicompost application when compared to the control (CK). With the exception of C.HCl-P&lt;sub&gt;i&lt;/sub&gt;, the vermicompost application greatly increased the contents of the various P forms in the soil. In particular, the labile P (resin-P, NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;i&lt;/sub&gt;, and NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;o&lt;/sub&gt;) and moderately stable P (NaOH-P&lt;sub&gt;i&lt;/sub&gt; and NaOH-P&lt;sub&gt;o&lt;/sub&gt;) were significantly (P &amp;lt; 0.01) increased. The correlation analyses showed that NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;i&lt;/sub&gt; was significantly and positively related to the MBC, MBP, and APA, while NaHCO&lt;sub&gt;3&lt;/sub&gt;-P&lt;sub&gt;o&lt;/sub&gt; was significantly and negatively related to the MBC, MBP, and APA. Both NaOH-P&lt;sub&gt;i&lt;/sub&gt; and C.HCl-P&lt;sub&gt;i&lt;/sub&gt; were significantly and negatively related to the APA. Both NaOH-P&lt;sub&gt;o&lt;/sub&gt; and C.HCl-P&lt;sub&gt;o&lt;/sub&gt; were significantly and positively related to the MBP, while NaOH-P&lt;sub&gt;i&lt;/sub&gt; was significantly and negatively related to the MBP. These results indicated that a vermicompost application could effectively enhance the dissolution and reduction of Fe and the consequent mobilisation of NaOH-P&lt;sub&gt;i&lt;/sub&gt;. In addition, the vermicompost application significantly (P &amp;lt; 0.01) increased the APA and effectively mobilised the NaOH-P&lt;sub&gt;o&lt;/sub&gt;.

Effect of nitrogen additions on soil pH, phosphorus contents and phosphatase activities in grassland

Phosphorus is a key nutrient for all plant species and a limiting factor for grassland ecosystem function. In recent years, in response to the rapid increase of global nitrogen deposition, soil phosphorus contents and phosphatase activities changed to varying degrees in grassland ecosystems. We conducted a meta-analysis to examine the responses of soil pH, total phosphorus (TP), available phosphorus (AP), as well as activities of alkaline phosphatase (AlP) and acid phosphatase (AcP) in soils to nitrogen addition amount, nitrogen type, experimental duration, and sampling depth. The correlation between soil pH and phosphatase response ratio was investigated. The results showed that nitrogen addition significantly reduced soil pH, TP and AlP activity, while significantly increased AcP activity, but had no significant effect on AP. Soil pH and AlP activity significantly decreased under nitrogen addition >5 g·m-2·a-1, and AcP activity significantly increased under high nitrogen addition (>10 g·m-2·a-1). The contents of TP and AP significantly decreased when nitrogen addition was 5-10 g·m-2·a-1. NH4NO3 treatment significantly reduced soil TP and increased AcP activity, while urea treatment significantly reduced soil pH and AlP activity. Across all nitrogen addition amounts, when the experiment duration was 3 to 10 years, soil TP content and AlP activity were significantly reduced. Soil pH was significantly reduced after three years nitrogen addition, and AcP activitiy was significantly increased after 10 years nitrogen addition. In the 0-10 cm soil layer, the TP content and AlP activity significantly decreased, while the AP content significantly increased. In >10 cm soil layer, the AP content was significantly decreased. The significant negative correlation between soil pH and AcP activity indicated that change in soil pH caused by nitrogen addition may be an important factor for the variation of soil phosphatase activity.