Alkaline Phosphomonoesterase Activity Research Articles

Long-term organic fertilization reshapes the communities of bacteria and fungi and enhances the activities of C- and P-cycling enzymes in calcareous alluvial soil

Soil microbial communities and extracellular enzymes are pivotal in governing the dynamics of soil carbon (C) and phosphorus (P) cycling. Nevertheless, comprehending the underlying regulatory factors and intricate interactions among these vital indicators remains an inadequately explored aspect, especially within the scenario of long-term fertilization. Long-term fertilization experiments were conducted on calcareous alluvial soil. The five fertilization regimes selected were as follows: without fertilization treatment (CK); inorganic NK fertilization treatment (NK); inorganic NPK fertilization treatment (NPK); organic fertilization treatment (M); and combined inorganic NPK with organic fertilization treatment (NPKM). The soil physicochemical properties, β-glucosidase (BG), and alkaline phosphomonoesterase (ALP) activities were determined, together with microbial (bacterial and fungal) community DNA sequences and subsequent bioinformatics analysis after 38 years of different fertilization. The results showed that the content of soil organic carbon (SOC) and available P and the activities of BG and ALP were the highest after M and NPKM treatments, which were 79–104 %, 26–36 times, 161–171 %, and 75–91 % higher than CK, respectively. Hierarchical clustering analysis showed that the bacterial and fungal community structures in M and NPKM treatments were similar, but the community structures in non-organic fertilization treatments (CK, NK, and NPK) were significantly different from those in organic fertilization treatments. The indicator species and correlation analysis combined revealed that most indicator species in organic fertilizer treatments were significantly positively correlated with soil BG and ALP, while most indicator species in non-organic fertilizer (CK and NK) treatments were significantly negatively correlated with soil BG and ALP. Organic fertilization treatments favored the growth of the bacterial genus Lysobacter and the fungal genera Acremonium and Mortierella and were significantly positively correlated with BG and ALP activities. Redundancy analysis revealed that SOC is the most important factor in shaping microbial community structure. Co-occurrence network analysis showed organic fertilization had higher network complexity, more keystone taxa, and more associations among microbial taxa compared with non-organic fertilization (CK + NK). Structural equation models revealed that microbial community structure is the direct driving factor of BG and ALP activities and their interactions, and SOC modulated the relationship between microbial community structure and BG and ALP activities. This study highlights how the application of organic fertilizer enhanced the C- and P-cycling enzyme activities, reshaped the soil microbial communities, and regulated these crucial indicators and their interactions by SOC.

Long-term nitrogen fertilization and sweetpotato cultivation in the wheat-sweetpotato rotation system decrease alkaline phosphomonoesterase activity by regulating soil phoD-harboring bacteria communities

The alkaline phosphomonoesterase (ALP)-harboring community (phoD-harboring community) plays a crucial role in the conversion of organic phosphorus (P) into available P (AP). However, the response mechanisms of phoD-harboring communities to fertilization strategies, crop types, and their interactions within the wheat-sweetpotato rotation are poorly understood. A nine-year field experiment of different fertilization strategies was established under the wheat-sweetpotato rotation. After harvesting the crop, we collected soil samples without fertilization (CK), inorganic NK fertilization (NK), inorganic NPK fertilization (NPK), and a combined application of inorganic NPK and organic fertilizer (NPKM). We employed high-throughput sequencing and enzymology techniques to analyze the composition and functional activity of phoD-harboring bacterial communities as well as their correlation with soil physicochemical properties. The results showed that long-term nitrogen (N) fertilization, especially inorganic N, significantly reduced soil pH and ALP activity while increasing AP compared with CK. The AP content in sweetpotato season was significantly higher than that in wheat season. Inorganic N fertilization dramatically reshaped the communities of phoD-harboring bacteria and decreased diversity. The phoD-harboring bacterial communities in sweetpotato season were significantly different from those in wheat season. The N fertilization significantly reduced the relative abundance of Acuticoccus, Methylibium, Rhizobacter, and Roseivivax, which was positively correlated with ALP activity. These groups in sweetpotato season decreased significantly compared with wheat season. A structural equation model indicates that pH and AP play a significant role in regulating the phoD-harboring bacteria communities, ALP activity, and their interactions. We demonstrate that fertilization strategies and crop types have a substantial impact on the phoD-harboring bacteria communities and functions, which are closely linked to soil pH and AP levels. Our study highlights the detrimental effects of soil acidification resulting from inorganic N fertilization on P-cycling bacterial communities and functions. However, the combination of inorganic and organic fertilizer can mitigate these adverse effects.

Short-term legacy effects of long-term nitrogen and water addition on soil chemical properties and micro-bial characteristics in a temperate grassland.

Nitrogen deposition and summer precipitation in eastern Inner Mongolia are predicted to increase in recent decades. However, such increases in nitrogen inputs and precipitation may not be continuous under the future new patterns of global change, with the direction and magnitude of which may change or weaken. The legacy effects of nitrogen and water addition after cessation on ecosystems are still unclear. Based on a 13-year nitrogen and water addition experiment in temperate grassland of northern China, we examined the short-term (2 years) legacy effects of historical nitrogen and water addition on soil physicochemical properties and microbial properties after the cessation of nitrogen and water addition in the 14th year. The results showed that the positive effects of historical nitrogen addition on most of soil nutrient variables diminished after two years of cessation, including ammonium nitrogen, nitrate nitrogen, dissolved organic carbon and nitrogen, and Olsen-P concentrations. In contrast, there were legacy effects on soil microbial characteristics. For example, the historical nitrogen input of 15 g N·m-2·a-1 reduced microbial biomass carbon, respiration, and alkaline phosphomonoesterase activity by 73.3%, 81.9%, and 70.3% respectively. It implied that microbial parameters restored slowly in comparison with soil nutrients, showing a hysteresis effect. Results of Pearson's correlation and redundancy analysis showed that the legacy effects of historical nitrogen addition on microbial parameters could be attributed to the negative effects of nitrogen addition on soil pH. Historical water addition showed significant legacy effects on soil pH, ammonium nitrogen, dissolved organic carbon and nitrogen, respiration, and soil enzyme activities, which significantly interacted with historical nitrogen addition. These results are of great significance to predict the changes in grassland ecosystem functions and services under the local environmental improvement conditions, and to reveal the restoration mechanism of degraded grassland.

Ecological restoration of tidal flat and its effects on soil characteristic and bacterial community

AbstractVegetation restoration is a vital ecological remediation technology for greening saline‐alkaline soils. However, little attention is paid to the seasonal changes of soil remediation under different vegetation coverage. This study investigated a recently restored coastal tidal flat located on the island of Zhoushan, by examining shifts in physicochemical properties, enzyme activities, and bacterial communities over 1 year. Soils under Suaeda australis (SUA), Phragmites australis (PHR), Tamarix chinensis (TAM), and two hybrid treatments (SUA+PHR and SUA+TAM) were collected seasonally. Results showed that the seasonal climate variations and vegetation types played important roles in soil physicochemical properties and soil enzyme activities during vegetation restoration. Vegetation could stimulate the activities of soil microbial enzymes, of which PHR‐covered soils exhibited higher catalase activities, higher alkaline phosphomonoesterase activities were observed in summer except for PHR. The combined communities had the highest urease activities in spring and summer, and the highest levels of polyphenol oxidase activity were found in summer or autumn. Furthermore, the bacterial alpha diversity revealed that SUA‐ and SUA+PHR‐covered soils were not markedly affected as the season progressed, whereas PHR and SUA+TAM were characterized by an increase–decrease trend, as well as TAM exhibited highest in autumn. Proteobacteria, Bacteroidetes, Acidobacteria, Actinobacteria, and Chloroflexi were the dominant phyla in each vegetation types. This study deepens our understanding of the effects of halophyte cultivation on coastal ecosystem phytoremediation.

Incorporating biotic phosphorus-acquisition strategies into soil phosphorus transformation under long-term salinization in a tidal wetland

Tidal wetland plants can maintain high primary productivity under salinization, even with low phosphorus (P) availability. However, little is known about how they adapt to salinization-induced ecosystem P limitation over time. We established mesocosms using tidal freshwater wetland soils and the salt-tolerant plant Cyperus malaccensis and subjected them to short-term (6 months) and long-term (3.5 years) salinization. Overall, short-term salinization did not change plant or microbial biomass nitrogen/P ratios, whereas long-term salinization increased both, indicating that short-term salinization did not alter ecosystem P limitation, but long-term salinization exacerbated it. Concurrently, short-term salinization reduced the moderately labile inorganic P (Pi) pool, whereas long-term salinization also reduced the hydrolyzable organic P (Po) and primary mineral P pools. During both short- and long-term salinization, moderately labile Pi mobilization exhibited a negative correlation with Fe sulfide concentration and a positive correlation with Fe(III) concentrations. These results suggested that both short- and long-term salinization obtained P through abiotic P-acquisition strategies. Mobilization of the primary mineral P pool and hydrolyzable Po pools was negatively linked to root arbuscular mycorrhizal fungi (AMF) biomass and soil alkaline phosphomonoesterase (ALP) activity, respectively. This indicated that long-term salinization acquired P via biotic P-acquisition strategies. Specifically, soil microorganisms increased fungi predominance and thereby increased ALP activity to convert hydrolyzable Po, while tidal wetland plants enhanced root AMF associations to release carboxylate to transform primary mineral P. Overall, our results highlight that abiotic P-acquisition strategies could offset the ecosystem P limitation during short-term salinization, whereas biotic P-acquisition strategies play a more important role in soil P transformation under long-term salinization. Through biotic P-acquisition, tidal wetland ecosystems can maintain high plant primary productivity through biotic P-acquisition even under P-limited conditions, exhibiting increased resilience to sea-level rise.

Long-term implementation of a silvopastoral system enhances soil P availability and bacterial diversity

A silvopastoral system (SPS) is defined as a type of agroforestry system wherein grasses combine with legumes, shrubs, and trees for animal nutrition. Its use, as an alternative to grasslands, represents a promising strategy to increase livestock industry sustainability. In this work, we explored the long-term impact of the implementation of a SPS on soil P nutrition, soil phosphomonoesterase activity, and microbial diversity. For this, we harnessed a 9-year-old SPS consisting of a tree (Alnus acuminata), two shrubs (Sambucus nigra and Sambucus peruviana), and a grass (Cenchrus clandestinrr44us), as well as a nearby pasture consisting solely of the C. clandestinus grass, which we used for comparison. We collected samples during the rainy and dry seasons. The implementation of the SPS enhanced the availability of labile soil P, compared to the nearby pasture; this increase concomitantly occurred with a decrease of moderately-labile P. We also noted that labile Pi and Po significantly correlated with alkaline phosphomonoesterase activity, suggesting a potential role of this soil enzymatic activity on P availability within the SPS. There was an increase of diversity and a shift in the bacterial community in the SPS compared to the pasture. Within the SPS, the tree and shrub strips had the largest influence on soil P availability and phosphomonesterase activity. Altogether, this study documents the benefits of the implementation of a SPS on soil P availability and bacterial diversity.

Differences in available phosphorus in temperate and subtropical forest soils

Soil P availability is influenced by the acid phosphomonoesterase (ACP) activity, microbial biomass P (MBP), pH, and other soil properties. To date, there is no clear understanding about how the enzyme catalytic efficiency (Vmax/Km) and the abundance of the phoC and phoD genes that encode ACP and alkaline phosphomonoesterase (ALP) influence the available P contents at different depths in temperate and subtropical forest soils. We investigated how the soil enzyme kinetic parameters, phoC and phoD gene abundance, pH, total P contents, and other soil properties influenced the P availability in soils from a temperate forest (ChangBai Mountain) and a subtropical forest (QianYanZhou Plantation). The results showed that the DNA contents and the ACP and ALP activities were positively correlated with the available P contents in the temperate forest soil. The phoC and phoD gene abundance and the ALP activity were positively correlated with the available P contents in the subtropical forest soil. The ACP-Vmax/Km and DNA contents were positively correlated with the available P contents in topsoil (0–10 cm). The total P contents, pH, MBP, and ACP-Vmax/Km in subsoil (10–30 cm) were positively correlated with the available P contents. A structural equation model showed that DNA content had the greatest effect on the soil available P in temperate forest soil, and phoC and phoD gene abundance had the greatest effect on the soil available P in subtropical forest soil. The mechanism of H+ dissolution affected the P availability through low pH in the topsoil and weathering in the subsoil. Overall, these findings provided an improved understanding about how the catalytic efficiencies of ACP and ALP and the phoC and phoD gene abundance, influenced the P availability in temperate and subtropical forest soils at different depths. We also gained insights into how the P availability was affected by H+ dissolution and the parent material in topsoil and subsoil, respectively.

Livestock grazing-exclusion under global warming scenario decreases phosphorus mineralization by changing soil food web structure in a Tibetan alpine meadow

The exclusion of grazing has been used extensively in alpine meadows on the Tibetan Plateau. Studies, however, have shown reported recent trends of decreasing concentrations of soil nutrients because of grazing exclusion and climate change. The effects of excluding grazing on the soil biogeochemical process of phosphorus cycling in alpine meadows are unclear, especially under climatic warming. We conducted a 5-year grazing-exclusion and warming-manipulation experiment to examine the effects of excluding grazing on fractions of soil phosphorus, microbial and nematode communities and enzymatic activities in treatments of low grazing intensity, grazing exclusion, and combined grazing exclusion and warming. Our results indicated that excluding grazing significantly decreased bacterivore and omnivore-predator densities, phoD gene abundance and alkaline phosphomonoesterase activity (in the 0–5 cm layer by −34, −41, −38 and −42 %) at altitudes of 3850 m, 4000 m, 4150 m and 4250 m, respectively. Structural equation modeling indicated that bacterivores positively affected phoD gene abundance, alkaline phosphomonoesterase activity and inorganic‑phosphorus fractions. Combined grazing exclusion and warming significantly decreased bacterivore and omnivore-predator densities but significantly increased fungivore density (in the 0–5 cm layer by 238, 172, 119 and 65 %) at altitudes of 3850, 4000, 4150 and 4250 m, respectively. Structural equation modeling also indicated that the combined grazing-exclusion and warming treatment increased the soil fungi and fungivores, but the higher abundances of fungi and fungivores did not significantly affect acid phosphomonoesterase activity or inorganic‑phosphorus fractions. Alternatively, the combined grazing-exclusion and warming treatment significantly increased the concentrations of amorphous and free aluminum, which were positively correlated with the maximum adsorption of phosphorus. The combined grazing-exclusion and warming treatment thus significantly decreased the availability of resin phosphorus (−63, −51, −81 and −67 %) in the 0–5 cm layer at altitudes of 3850, 4000, 4150 and 4250 m, respectively. Our results suggested that light grazing (0.5 yak ha−1 year−1) could increase phosphorus mineralization and the activity of soil enzymes in alpine meadows under global warming. An adequate load of livestock pressure at each altitude can be an effective management technique, mainly under warming, to maintain an adequate, sustainable and equilibrated phosphorus cycle in the plant-soil system.

Close relationship between the gene abundance and activity of soil extracellular enzyme: Evidence from a vegetation restoration chronosequence

Extracellular enzymes (EEs) play vital roles in the transformations of soil organic matter, yet the regulators of EE activity remain unclear. Inducible EE production predicts that EE activity is determined by microbial nutrient status. Alternatively, EE production can be constitutive (continuous and baseline-level expression of EE gene regardless of the nutrient status), and in this case EE gene abundance potentially affects EE activity. Here, we examined whether EE gene abundance was a key regulator of EE activity along a vegetation restoration chronosequence. For the four hydrolytic EEs related to microbial acquisition of carbon, nitrogen and phosphorus, their gene abundance ratios (obtained from metagenomic sequencing) were positively related to corresponding activity ratios (R2 = 0.43–0.94). These relationships were maintained in the structural equation modeling when the effects of microbial nutrient status and soil property were considered. The gene-enzyme link was further confirmed by the positive relationship between the absolute abundance of phoD gene (obtained from qPCR analysis) and the alkaline phosphomonoesterase activity. Overall, our results suggest that constitutive EE production may contribute significantly to soil EE activity. The direct gene-enzyme link highlights the development of gene-informed Earth system models to better predict the soil carbon dynamics under global change.

Climate and edaphic factors drive soil enzyme activity dynamics and tolerance to Cd toxicity after rewetting of dry soil

The intense drying-rewetting cycle due to climate change can affect soil microbial community composition and function, resulting in long-term consequences for belowground carbon and nutrient dynamics. However, how climatic and edaphic factors influence the responses of enzymes to rewetting and their responses to additional perturbation (e.g., heavy metal pollution) after the drying-rewetting history are not well understood. In this study, we collected 18 surface soils from farmlands across various climate zones in China. We chose dehydrogenase (DHA) and alkaline phosphomonoesterase (ALP) as representative intracellular and extracellular enzymes, respectively, and investigated their tolerance to additional perturbation by adding metal ions (i.e., Cd2+) upon rewetting. In all soils, rewetting increased DHA activities but did not affect ALP activities compared to air-dried soils. Rewetting increased the tolerances of DHA and ALP to Cd stress, suggesting that the drying-rewetting history may reduce the susceptibility of soil enzymes to additional disturbance. The results demonstrate that differentiating enzymes based on their location in the soil will improve our ability to assess the stress response of microbial communities to drastic fluctuations in soil moisture, thereby better predicting the legacy of climate change on microbial function in soils contaminated with heavy metals.

Spatiotemporal distributions and relationships of phosphorus content, phosphomonoesterase activity, and bacterial phosphomonoesterase genes in sediments from a eutrophic brackish water lake in Chile

Phosphorus (P) cycling by microbial activity is highly relevant in the eutrophication of lakes. In this context, the contents of organic (Po) and inorganic (Pi) phosphorus, the activity of acid (ACP) and alkaline (ALP) phosphomonoesterase (Pase), and the abundances of bacterial Pase genes (phoD, phoC, and phoX) were studied in sediments from Budi Lake, a eutrophic coastal brackish water lake in Chile. Our results showed spatiotemporal variations in P fractions, Pase activities, and Pase gene abundances. In general, our results showed higher contents of Pi (110–144 mg kg−1), Po (512–576 mg kg−1), and total P (647–721 mg kg−1) in sediments from the more anthropogenized sampling sites in summer compared with those values of Pi (86–127 mg kg−1), Po (363–491 mg kg−1) and total P (449–618 mg kg−1) in less anthropogenized sampling sites in winter. In concordance, sediments showed higher Pase activities (μg nitrophenyl phosphate g−1 h−1) in sediments from the more anthropogenized sampling sites (9.7–22.7 for ACP and 5.9 to 9.6 for ALP) compared with those observed in less anthropogenized sampling sites in winter (4.2–12.9 for ACP and 0.3 to 6.7 for ALP). Higher abundances (gene copy g−1 sediment) of phoC (8.5–19 × 108), phoD (9.2–47 × 106), and phoX (8.5–26 × 106) genes were also found in sediments from the more anthropogenized sampling sites in summer compared with those values of phoC (0.1–1.1 × 108), phoD (1.4–2.4 × 106) and phoX (0.7–1.2 × 106) genes in the less anthropogenized sites in winter. Our results also showed a positive correlation between P contents, Pase activities, and abundances of bacterial Pase genes, independent of seasonality. The present study provided information on the microbial activity involved in P cycling in sediments of Budi Lake, which may be used in further research as indicators for the monitoring of eutrophication of lakes.

The relationships of bacterial-feeding nematodes, phoD-harboring bacteria and alkaline phosphomonoesterase activity under the combined application of organic and inorganic fertilizers in an alkaline soil

Bacterial-feeding nematodes have the potential to increase soil alkaline phosphomonoesterase (AlP) activity by affecting the composition of phoD-harboring bacterial community or the abundance of phoD gene. However, the relationships between bacterial-feeding nematodes, composition of phoD-harboring bacterial community, phoD gene abundance and AlP activity with inorganic plus organic fertilization in alkaline soil where AlP is dominant is yet to be properly understood. Four fertilization regimes: non-fertilized control (CK), chemical nitrogen (N), phosphorus (P) and potassium (K) fertilizers (NPK), crop straw plus chemical fertilizers (SNPK), as well as pig manure plus chemical fertilizers (MNPK), were used in determining the variation in soil bacterial-feeding nematodes, composition of phoD-harboring bacterial community, phoD gene abundance and AlP activity under different fertilization treatments as well as their relationships. Results showed that both inorganic and organic fertilizer application significantly enhanced the activity of soil AlP, which significantly decreased under NPK application compared with SNPK and MNPK treatments. Partial least squares path modeling showed that AlP activity was directly and positively affected by composition of phoD-harboring bacterial community and microbial biomass carbon (MBC), and the bacterial-feeding nematode dominant genus Eucephalobus, which was affected by MBC directly, could affect AlP activity in an indirect way by its significant direct positive effect on phoD-harboring bacterial community composition. Of those 12 top bacterial genera that harbored phoD, just the gram-positive bacteria Massilia and Saccharothrix showed significant positive correlation with AlP, while Saccharothrix showed obvious positive correlation with Eucephalobus. Overall, these results suggest that the dominant genus Eucephalobus may be the beneficial indigenous bacterial-feeding nematode that can increase the activity of soil AlP within the alkaline soil, which is affected by MBC directly and can be likely to positively affect the composition of phoD-harboring bacterial community through a passive food ingestion mechanism and then promote AlP activity indirectly, of which Saccharothrix is the intermediary bacteria for the increase in AlP activity caused by the bacterial-feeding nematode.

Impacts of biochar and phosphorus application on soil phosphorus availability and soybean phosphorus uptake

Biochar is beneficial to soil phosphorus (P) availability and crop growth, but the effects vary greatly across different soil types. We investigated the effects of rice straw biochar (4% of total mass) and P application (0, 30, and 90 kg P·hm-2) on soil P availability, phosphomonoesterase activity, and soybean P uptake by using lateritic red soil (pH 4.91) and cinnamon soil (pH 7.24) as test materials. The results showed that biochar application at different P levels significantly increased available P and total P in both soils. Biochar application with 30 kg P·hm-2 increased soil available P with maxima at 192.6% and 237.1% in lateritic red soil and cinnamon soil, respectively. Biochar application with 30 kg P·hm-2 in lateritic red soil significantly increased the activity of alkaline phosphomonoesterase by 78.9%, decreased the content of active organic P by 39.3%, and subsequently stimulated soybean P absorption and growth. Biochar amendment significantly reduced active organic P content in cinnamon soil, but did not affect soil phosphomonoesterase activity and plant growth. The content of active organic P was significantly negatively correlated with soil available P content. In summary, the effect of biochar on soil P availability varied across different soil types (lateritic red soil > cinnamon soil) and P levels (better at 30 kg P·hm-2). Our results could provide scientific basis for a promising application of biochar in reducing the amount of P fertilizer and increasing soybean P uptake, especially in lateritic red soil.

Influence of land use on the microbiological properties of urban soils

Advancing towards sustainable cities needs a better understanding of all components of urban ecosystems, including soils, but the biological component of urban soils remains poorly studied compared to natural and agricultural soils. With the objective of advancing knowledge in this aspect, we studied the microbiological properties in 61 soils of the city of Santiago de Compostela (NW Spain), under several land uses (urban grassland, urban forest, urban garden, and periurban arable land). We determined thirteen extracellular enzymatic activities as a proxy of microbial community functioning, along with measures of microbial activity (basal respiration), microbial abundance (DNA extraction and real-time PCR), and the composition of microbial communities (Illumina MiSeq sequencing on 16S rRNA and ITS marker regions). Results showed a high variability in all of the microbiological variables among soils, reflecting the typical spatial heterogeneity of urban soils. Respiration and enzymatic activities were highly correlated to soil organic matter contents but not affected by land use within the city, with the exception of alkaline phosphomonoesterase activity, which was higher in urban garden soils and correlated positively to pH and availability of phosphorus and nitrogen. Unlike fungal abundance, we recorded a higher bacterial abundance in the urban grasslands than in the other land uses. While the composition of bacterial communities was structured in a more homogeneous, land use-dependent manner (33% variance, pAdonis = 0.001), the respective fungal communities were more heterogeneous and less influenced by group-dependent characteristics (18%, pAdonis = 0.001). Soil pH had a larger influence on the bacterial community composition (28% variance) compared to the fungal composition (8.5% variance). Overall, these findings provide evidence that the typically high soil heterogeneity of urban ecosystems is the main driving force for the urban soil microbiome, with soil organic matter determining largely microbial activity.

Dynamics of phoD- and gcd-Harboring Microbial Communities Across an Age Sequence of Biological Soil Crusts Under Sand-Fixation Plantation.

Biological soil crusts (BSCs) are important for restoring vegetation and improving soil fertility in arid or semiarid desertified land. However, studies on the contribution of BSC microbes to phosphorus (P) transformation remains limited. The microbial diversity involved in P transformation and its dynamic along BSC development should be examined to further understand the microbial regulatory mechanism of the P-cycling process. This paper investigates the soil properties, P fractions, and potential of P transformation across a chronosequence (0-, 8-, 20-, and 35-year) of the BSC under Caragana microphylla plantation on the moving sand dunes in Horqin Grassland, China. An abundance of phoD and gcd genes was detected, and the diversities and structures of phoD- and gcd-haboring microbial communities were illustrated via high-throughput sequencing. Soil nutrient content, activity of alkaline phosphomonoesterase, potential of organic P (OP) mineralization, and the abundance of phoD and gcd genes all linearly increased along with BSC age. The microbial quantity and species diversity of the phoD community were greater than those of gcd. BSC development increased the availability of inorganic P (IP) fractions, and both NaHCO3-Pi and NaOH-Pi were positively correlated with the abundance of the two genes and the activity of alkaline phosphomonoesterase. The phyla of Actinobacteria, Planctomycetes, and Proteobacteria and the family of Streptomycetaceae were the most dominant taxa in the phoD community, Proteobacteria was the dominant phylum in the gcd community in BSC soils, and Rhizobium and Planctomyces were the most dominant genera. The dominant taxa quantitatively responded to soil property improvement, but the basic compositions and dominant taxa did not change along with BSC development. The structures of phoD and gcd communities were linked to soil properties, and pH available K, and total K tend to be the direct determining factors.

An invasive and native plant differ in their effects on the soil food-web and plant-soil phosphorus cycle

Although invasive species threaten the functional integrity of ecosystems significantly, their impacts on essential ecosystem processes such as soil phosphorus (P) cycling are not well understood. In a field experiment, we used a randomized complete block design to study how an invasive plant species may disrupt soil functioning, particularly P cycling compared to a native plant species. After three years of experiments, we compared soil P properties and soil micro food-webs (microorganisms and nematodes) induced by these two species. We also compared plant biomass and P allocation in the different tissues for these plants. A second microcosm experiment was performed to check whether the interactions of nematode and microorganisms affected the ecological processes of soil organic P mineralization. Compared to native species, invasive species had higher alkaline phosphomonoesterase (ALP)-producing bacteria, bacterivorous nematodes, and ALP activity and induced a stronger acceleration of soil organic P decomposition through the more interactions between ALP-producing bacteria and bacterivores. Moreover, the mycorrhizal colonization rate of the invasive species was higher than the native species, allowing it to absorb more P and allocate more to above-ground biomass, and thus maintaining its faster expansion. The invasive species had lower nucleic acid P, structural P, and residual P in foliar than the native species because invasive species allocate more P to metabolic P for photosynthesis. Our study suggests that invasive plants can enhance the organic P decomposition through microbial-microfaunal interactions. In addition, invasive plants might have higher P utilization efficiency than native ones. Although these findings need to be generalized with more native and invasive plant species, they still provide novel mechanistic explanations into how invasive species can expand quickly in P-poor lower latitudes.

Flooding and straw returning regulates the partitioning of soil phosphorus fractions and phoD-harboring bacterial community in paddy soils.

Flooding and straw returning are effective agricultural practices in promoting phosphorus (P) availability in paddy soils. However, little is known about the effects of these practices and their interaction on the soil P pools and functional microbes responsible for soil P mobilization. Our 4-year paddy field experiment aimed to analyze the responses of soil P fractions and phoD-harboring bacterial communities in a double-rice cropping system to intermittent flooding (IF) and continuous flooding (CF), in plots with (+ S) and without (-S) straw return. Compared to IF, CF significantly increased soil citrate-P and marginally decreased the HCl-P fractions, suggesting that the stable inorganic P pools are transferred to labile inorganic P at lower redox potentials. Compared to the -S treatments, + S treatments significantly increased the labile organic fractions (enzyme-P). Correspondingly, a decreased soil total organic P concentration was observed in + S treatment. Additionally, + S treatment significantly increased the activity of acid phosphomonoesterase and alkaline phosphomonoesterase and the abundance of phoD-harboring bacteria. These results indicated that straw promoted organic P minimization to release orthophosphate. The diversity of the phoD-harboring bacteria and complexity of the co-occurrence network decreased under the CF + S treatment; however, all keystone species of the phoD-harboring bacteria were retained in this oxygen-deficient environment. This study highlights that irrigation regimes mediate the processes of inorganic P mobilization, while straw returns regulate the processes of organic P mineralization. Additionally, flooding could be a more effective agricultural practice than straw returning to promote soil P availability in paddy soils. KEY POINTS: •Soil P pools and phoD-harboring bacteria communities were assessed. •Straw return mainly affects the mineralization of organic P. •Continuous flooding mainly affects the mobilization of inorganic P.

Long-term organic substitution management affects soil phosphorus speciation and reduces leaching in greenhouse vegetable production

Excessive phosphorus (P) fertilizer and manure application is widespread in greenhouse vegetable production, causing P accumulation and groundwater pollution. The partial substitution of chemical fertilizer with organic amendments may effectively address this problem; however, little is known about P speciation and transformation at the molecular scale. Here, we combined P K-edge X-ray absorption near-edge structure, 31P nuclear magnetic resonance spectroscopy, and chemical extraction to characterize P speciation and assess P leaching in a 10-year field experiment including chemical fertilizer (4CN) and replacement of half the chemical N fertilizer with manure (2CN+2 MN), straw (2CN+2SN), or combined manure and straw (2CN+1 MN+1SN) treatments. Compared to the 4CN treatment, organic substitution treatments resulted in 10.0–16.3% lower P accumulation and 57.3–102% higher organic P. Newberyite was detected in the organic substitution treatments, making up 6.9–13.0% of the total P, and the hydroxyapatite proportion was 7.3–15.6% lower than that in the 4CN treatment. Moreover, 2CN+2 MN treatment increased the orthophosphate diester content and labile P (Resin-P and NaHCO3–P) proportion, and 2CN+2SN treatment increased the orthophosphate monoester content and moderately labile P (NaOH–P) proportion. The 2CN+1 MN+1SN treatment exhibited the advantages of both manure and straw application. Partial least squares path modeling revealed that labile P was affected mainly by manure application and pH, and moderately labile P was influenced mainly by straw application and alkaline phosphomonoesterase activity. Compared with the 4CN treatment, the organic substitution treatments significantly decreased the total P leaching losses by 21.3–48.8%. Our results provide new insights into soil P transformation in response to different organic amendments. Combined manure, straw, and chemical fertilizer application (2CN+1 MN+1SN treatment) was a more effective practice for developing sustainable P management practices by comprehensively considering soil P transformation, vegetable yields, and environmental losses.

Growth Response of Ginger (Zingiber officinale), Its Physiological Properties and Soil Enzyme Activities after Biochar Application under Greenhouse Conditions

This study aimed to investigate the effects of biochar (1%, 2%, and 3%) on seed germination, plant growth, root morphological characteristics, and physiological properties of ginger (Zingiber officinale) and soil enzymatic activities. Pot experiments under greenhouse conditions at 24 °C (day) and 16 °C (night) showed after six weeks that biochar additions of 2% and 3% significantly increased seed germination, plant height, leaf length, leaf number, as well as shoot and root dry weights compared to the control. Total root length significantly increased by 30%, 47%, and 74%, with increasing biochar contents (1%, 2%, and 3%) compared to the control. Root surface area, projected area, root diameter, and root volume reached a maximum at the 3% biochar treatment. The treatment with 2% biochar significantly increased fluorescein diacetate hydrolase and phenoloxidase activities by 33% and 59% compared to the control; so did the addition of 3% biochar, which significantly increased fluorescein diacetate hydrolases, phenoloxidase, and acid and alkaline phosphomonoesterase activity in soil compared to the control. Treatment with 3% biochar increased relative water content by 8%, chlorophyll content by 35%, and carotenoid content by 43% compared to the control. These results suggest that biochar can improve the performance of the rhizome of ginger and increase the activity of soil enzymes, thereby improving soil nutrient supply.

Phosphorus fractions in biochar-amended soil — chemical sequential fractionation, 31P NMR, and phosphatase activity

ABSTRACT In this study, we assessed the effects of biochar application for five years on soil phosphorus (P) factions by chemical sequential P fractionation, phosphatase activity, and 31P NMR. Four treatments were included in this research: two biochar (0 and 2.63 t ha−1) levels blended with two P fertilizer levels (0 and 26 kg P ha−1), respectively. We found elevated levels of soil pH, total carbon (C), and total P in soil exposed to biochar. The inorganic (Ca8 – P, Al – P, Fe – P, and Ca10 – P) and organic (LOP and HROP) P fractions were all enhanced by biochar regardless of the application of P fertiliser. 31P NMR spectra further showed that ortho – P, monoester – P, and diester – P levels in the soil with added biochar combined with P fertiliser were 464.5 mg kg−1, 74.3 mg kg−1, and 13.9 mg kg−1, respectively, which were the highest among all treatments. Biochar application increased alkaline phosphomonoesterase activity by 24.4–32.7% and decreased phosphodiesterase activity by 10.2–11.0%. In conclusion, biochar application significantly improves soil P fractions and regulates phosphatase activity.