Soil Phosphorus Availability Research Articles

Partial substitution of chemical fertilizer with organic fertilizer and slow-release fertilizer benefits soil microbial diversity and pineapple fruit yield in the tropics

The partial substitution of chemical fertilizers with organic fertilizer and slow-release fertilizer is an effective approach for improving crop yield and soil quality. However, few studies have paid close attention to pineapples in the tropics. Here, a 2-year field experiment was conducted to elucidate the differences in pineapple rhizosphere soil microorganisms, bulk soil chemical characteristics, and pineapple fruit yield under different fertilization treatments (CK: no fertilizer application; FP: conventional chemical fertilizer application; OPT: reduced chemical fertilizer application; OPTO: based on OPT, with organic fertilizer replacing 20 % of nitrogen (N); OPTS: based on OPTO, with slow-release fertilizer replacing 15 % of N), and the links between soil microorganisms and soil chemical properties and pineapple fruit yield were analyzed. Compared with FP, OPT, OPTO and OPTS treatments significantly increased bulk soil pH and organic matter (OM) content while reducing the amount of available phosphorus (AP), available potassium (AK), nitrate nitrogen (NO3−) and ammonium nitrogen (NH4+); in addition, they also highly increased the bacterial diversity index and pineapple yield (P < 0.05). It was found that Proteobacteria, Actinobacteria, Chloroflexi and Acidobacteria were the four major bacterial phyla (relative abundances >10 %) in all treatments, while Ascomycota was the main phylum of fungi. Specifically, the OPTS treatment increased the abundance of Chloroflexi, Acidobacteria and Basidiomycota but decreased the abundance of Proteobacteria, Actinobacteria and Ascomycota. Correlation analysis found that bulk soil pH, OM, AP, AK, NO3− and NH4+ levels were all important factors influencing the formation of the rhizosphere soil microbial community. Overall, the OPTS treatment resulted in relatively high soil nutrient content, microbial diversity and the number of beneficial microorganisms, which increased pineapple yield. Therefore, OPTS can be used as a high-yield and sustainable fertilization method for pineapple.

Effects of Intercropping Oat and Common Vetch on Plant Biomass Yield and Soil Nitrogen and Phosphorus Availability in Different Soil Characteristics

Effects of Intercropping Oat and Common Vetch on Plant Biomass Yield and Soil Nitrogen and Phosphorus Availability in Different Soil Characteristics

Phosphate, Lime and Bentonite Affect Heavy Metals and Phosphorus Availability in Acidic and Calcareous Soils

ABSTRACT This work investigated the effect of soil amendments on the mobility of heavy metals and P in acidic and calcareous heavy metal polluted soils after incubated for one year. Compared to phosphate alone, the phosphate+bentonite amendment had lower available P concentrations (13.1 and 16.3% in the acidic and calcareous soils, respectively) and similar heavy metal immobilization capacity. The lime amendment increased soil P availability possibly by increasing the negative charges of soil particles in both soils. Lime amendment greatly reduced the DTPA-extractable concentrations of Cd, Cu, Mn, Ni, Pb and Zn in both soils; greater reductions were observed with higher rate compared to the lower rate and in the acidic soil compared to the calcareous soil, especially for Cd, Mn, Ni and Zn (23.9–95.3% lower than the control). The bentonite in the phosphate+bentonite treatment may have reduced soil P availability by adsorption of soluble P. Based on the results, phosphate+bentonite instead of phosphate alone may be used to reduce heavy metal and P availability in heavy metal contaminated soil. When only lime is used, caution should be taken with respect to potential soil P losses and subsequent off-site degradation in water and environmental quality.

Bioindication of Environmental Conditions Using Solar Park Vegetation

Solar parks are currently considered a new source of carbon-free energy. At the same time, they encroach on our landscape and create new conditions for flora and fauna. Vegetation responds to changes in living conditions. The aim of this study was to evaluate the changes in soil conditions induced by solar parks using vegetation bioindicators. A vegetation assessment was carried out in a solar park located in the cadastral territory of the municipality of Unín (Czech Republic). Among the soil conditions observed, this study focused on soil moisture, pH, nitrogen availability, phosphorus availability, and salinity. A total of 77 taxa of vascular plants were identified. Based on the bioindication of vegetation, it can be concluded that there are changes in the conditions between sites under photovoltaic panels (PV) and between rows of PV panels. Under PV panels, species with extreme values of the monitored soil criteria have a higher representation. These species can tolerate salinity, deficiency, or excess nitrogen and phosphorus. Different conditions under PV panels lead to diversity in species composition. This results in significant fragmentation of solar couplet vegetation. However, extreme conditions may create room for invasive plant species to establish themselves. Thus, it is necessary to monitor changes in vegetation, especially under PV panels, in the following years. The characterization of environmental conditions based on vegetation biomonitoring shows the diversity of solar park conditions. Diverse conditions are also important for landscape fragmentation.

Preparation of Novel Biodegradable Polymer Slow-Release Fertilizers to Improve Nutrient Release Performance and Soil Phosphorus Availability.

Inspired by the gradual collapse of carbon chain and the gradual release of organic elements into the external environment during the degradation of biodegradable polymers, a novel biodegradable polymer slow-release fertilizer containing nutrient nitrogen and phosphorus (PSNP) was prepared in this study. PSNP contains phosphate fragment and urea formaldehyde (UF) fragment, which are prepared by solution condensation reaction. Under the optimal process, the nitrogen (N) and P2O5 contents of PSNP were 22% and 20%, respectively. The expected molecular structure of PSNP was confirmed by SEM, FTIR, XRD, and TG. PSNP can release N and phosphorus (P) nutrients slowly under the action of microorganisms, and the cumulative release rates of N and P in 1 month were only 34.23% and 36.91%, respectively. More importantly, through soil incubation experiment and leaching experiment, it was found that UF fragments released in the degradation process of PSNP can strongly complex soil high-valence metal ions, thus inhibiting the phosphorus nutrient released by degradation to be fixed in the soil and ultimately effectively increasing the soil available P content. Compared with ammonium dihydrogen phosphate (ADP), a small molecule phosphate fertilizer that is easily soluble, the available P content of PSNP in the 20-30 cm soil layer is almost twice that of ADP. Our study provides a simple copolymerization method to prepare PSNP with excellent slow-release N and P nutrients, which can promote the development of sustainable agriculture.

Effects of 24 Years Different Straw Return on Soil Carbon, Nitrogen, Phosphorus, and Extracellular Enzymatic Stoichiometry in Dryland of the Loess Plateau, China

Exploring the biogeochemical cycle characteristics of soil carbon, nitrogen, and phosphorus in farmland in the dryland of the loess plateau can provide scientific basis and technical support for efficient crop production and sustainable land use. Here, based on a long-term (24 year) straw return field experiment in Shouyang, Shanxi province, the effects of different straw return regimes, i.e., straw mulching (SM), direct straw return (DS), animal-digested straw return (AS), and non-straw return (CK), on the stoichiometric ratio of soil elements and extracellular enzyme activities were studied. The vector angle and length were calculated to indicate the resource constraints faced by microorganisms. The vector angle was greater than 45° and less than 45°, indicating that microorganisms were limited by phosphorus and nitrogen, respectively. The greater the deviation from 45°, the greater the degree of limitation, and the longer the vector length, the more severely limited by carbon. The results showed that ① the soil C/N and C/P of long-term straw returning ranged from 9.81 to 14.28 and from 14.58 to 21.92, with the mean values of 12.36 and 17.51, respectively, which were 6.0% and 4.2% lower than that at the initial stage of the experiment. The soil N/P was distributed between 1.27 and 1.57, with an average of 1.42, which was 2.2% higher than that in the initial stage. The soil C/N and C/P ratios showed a trend of first decreasing and then increasing, the soil N/P ratio basically showed a flat trend, and there was no significant difference in soil element metering ratios between different straw returning treatments. ② Compared with the 24-year long-term non-straw return treatment, the activities of β-1,4-glucosidase (BG) and β-1,4-N-acetylglucosaminidase (NAG) in the soil of the long-term straw mulching treatment increased by 134.4% and 107.5% (P<0.05), the activities of BG and alkaline phosphatase (AP) in the soil of the long-term straw mulching treatment decreased by 59.3% and 59.5% (P<0.05), respectively, and the activities of NAG in the soil of the long-term straw mulching treatment increased by 102.8% (P<0.05). Under the long-term straw returning treatment, soil microorganisms were faced with carbon and phosphorus limitation as a whole. Long-term straw mulching aggravated microbial carbon limitation, and animal-digested straw return could alleviate the degree of carbon limitation. Compared with that in the 24-year long-term non-straw return treatment, soil EEAC/N could be significantly reduced by the animal-digested straw return treatment, and soil EEAC/P could be increased by the direct straw return treatment. The three straw returning methods had no significant indigenous effect on soil EEAN/P. The overall vector angle was greater than 45°, and the vector length increased by 3.8%-20.1% compared with that in the initial stage. ③ Correlation analysis showed that C and N inputs were significantly negatively correlated with BG activity; available nitrogen was significantly correlated with NAG activity, AP activity, and EEAC/N; C/P was significantly positively correlated with EEAC/N; there were significant correlations between N/P and NAG activity, AP activity, EEAC/N, and EEAC/P; and there was no significant correlation between EEAN/P and any environmental factors. In conclusion, the availability of soil nitrogen and phosphorus elements and N/P ratio had significant effects on soil extracellular enzyme activity and stoichiometric characteristics under different long-term straw returning treatments. In the future, more attention should be paid to the improvement of organic carbon and the promotion of nitrogen and phosphorus availability in farmland soil in soil-efficient cultivation and agricultural production activities.

Effects of Nitrogen and Phosphorus Addition on Soil Nutrient Content and Stoichiometry in Desert Grassland

In order to discuss the response of soil nutrient content, stoichiometric ratio, and dynamic nutrient balance to the addition of multiple restrictive nutrients, the correlation between available nutrients and total nutrients in soil, as well as the indication of soil total and available stoichiometric characteristics, were studied in a desert grassland subjected to 4 years of nutrient addition treatments. The Ningxia desert grassland was used as the research object to carry out nitrogen (N) and phosphorus (P) addition experiments. The experiment included four treatments:control (CK), N addition[10 g·(m2·a)-1], P addition[10 g·(m2·a)-1], and NP co-addition (10 g·(m2·a)-1 N+10 g·(m2·a)-1 P). The results showed that:① in the fourth year of nutrient addition, soil total nitrogen (TN) content was significantly increased. The N:P ratio was significantly increased by N addition, and soil organic carbon (SOC) content was significantly increased by P addition and NP co-addition. In the third and fourth years of nutrient addition, the soil available N:P ratio (AN:AP) was significantly increased by N addition; N addition and NP co-addition significantly increased the content of ammonium nitrogen (NH4+-N) and nitrate nitrogen (NO3--N) but significantly reduced the soil available C:N ratio. P addition and NP co-addition significantly increased total phosphorus (TP) and soil available phosphorus (AP), whereas it significantly reduced the soil total and available C:P and N:P ratios. ② The interaction between N addition and P addition had a combined effect on NH4+-N, AP, available C:N, and AN:AP ratio of desert grassland. ③ The soil C:N ratio was relatively stable in desert grassland, soil N:P ratio was mainly limited by soil TP content, and the soil available C:P and AN:AP ratios were mainly limited by soil AP content. ④ There were cumulative effects of N and P additions on soil N, SOC, and inorganic nitrogen. N limitation in desert grassland was alleviated by N addition, whereas it was aggravated by P addition and NP co-addition. The variation coefficients of soil available stoichiometric characteristics were higher than that of soil total stoichiometric characteristics. Soil available stoichiometry was more sensitive to N and P addition than soil total stoichiometry in desert grassland, which could better reflect the effects of N and P addition on soil ecological stoichiometry and as a rapid indicator of soil nutrient status in desert grassland.

Mixed-Species Acacia Plantation Decreases Soil Organic Carbon and Total Nitrogen Concentrations but Favors Species Regeneration and Tree Growth over Monoculture: A Thirty-Three-Year Field Experiment in Southern China

Mixed-species plantations of trees with N-fixing species have the potential of promoting forest productivity and soil fertility. However, few studies in the literature have addressed the advantages of mixed-species plantations of leguminous trees over monocultures of leguminous trees based on in situ inventories over a long time period. Here, we monitored the dynamics of tree community composition, vegetation biomass, soil nutrients, and soil microbial phospholipid fatty acids (PLFAs), in an Acacia mangium monoculture plantation during 33 years of development and compared it with a mixed-species plantation of A. mangium associated with 56 native species which were underplanted 14 years after the initial establishment. Leaf N and phosphorus (P) concentrations of three main species in the overstory and understory of the A. mangium monoculture were measured. Our results showed that the soil organic carbon (SOC), total nitrogen (TN), and available phosphorus (AP) concentrations significantly increased over time during the approximately thirty years of A. mangium monoculture plantation, while the disadvantages were associated with new species regeneration and the increment of vegetation biomass. In the A. mangium monoculture plantation, leaf N concentration of A. mangium,Rhodomyrtus tomentosa, and Dicranopteris dichotoma continuously increased from 21 to 31 years, while the leaf P concentration of A. mangium and R. tomentosa decreased. The mixed-species plantations of A. mangium with native tree species had lower SOC and soil TN concentrations, more new tree species recruitment in the understory, and faster vegetation biomass increment than the A. mangium monoculture. However, the PLFAs of soil microbial groups were slightly different between the two types of plantations. We conclude that improved soil N nutrient condition by A. mangium monoculture benefits N absorption by A. mangium, R. tomentosa, and D. tomentosa, while low soil AP limits P absorption by A. mangium and R. tomentosa. Meanwhile, transforming the A. mangium monoculture into a mixed-species plantation via the introduction of multiple native species into the A. mangium monoculture decreases SOC and TN concentrations but the advantages include improving forest regeneration and maintaining forest growth in a long-term sequence. These findings provide useful and practical suggestions for managing forest monocultures of A. mangium in subtropical regions.

Role of Aspergillus niger in Solubilizing P in Togo Rock Phosphate during Composting with Different Organic Wastes

The immobilization and mineralization processes carried out by soil microorganisms have a significant role in controlling the availability of phosphorus in soil. A class of helpful microorganisms known as phosphate solubilizing microbes are able to hydrolyze insoluble organic and insoluble inorganic phosphorus compounds into soluble P (phosphorus) form that is readily taken by plants. The objective of this study was to evaluate the role of different organic waste and Aspergillus niger in solubilizing P in Togo rock phosphate during composting. Composts were prepared using rice straw and citrus waste that had been inoculated with Aspergillus niger and supplemented with rock phosphate. The results showed that co-inoculation system with PSF (i.e. Aspergillus niger) provided optimum condition for P solubilization.

Effects of Watermelon Cropping Management on Soil Bacteria and Fungi Biodiversity

Watermelons grown in sandy soil are rich in trace elements, particularly selenium, and are therefore also known as selenium-rich sand watermelons. However, continuous watermelon cultivation in the same sandy field decreases soil fertility and degrades the ecosystem, ultimately resulting in low-quality watermelons. Introducing different crops into the crop pattern could alleviate the problems posed by continuous cropping. A field experiment was conducted to explore the effects of different crop patterns on soil microbial communities and soil properties via standard techniques. The results showed that 14,905 bacterial and 2150 fungal operational taxonomic units were obtained and assigned to eight bacterial and five fungal phyla, respectively. Soil bacterial communities primarily comprised Proteobacteria, Planctomycetes, Actinobacteria, and Acidobacteria, and the soil fungal community was dominated by Ascomycota, Chytridiomycota, and Basidiomycota. Different crop patterns had a significant effect on the Chao and ACE indexes of fungal communities in the soil. The rotation of six years of watermelon and one year of wheat had the highest richness indexes of all the rotations. Different crop patterns had significant effects on soil properties, such as organic matter (OM), total nitrogen (TN), total potassium (TK), available phosphorus (AP), available K, nitrate nitrogen (NN), and pH. The soil OM, TN, NN, and pH of six years of watermelon and one year of wheat cultivation were significantly higher than those of the other three crop patterns. In addition, the soil TK and AP of the continuous watermelon planting treatment were significantly higher than those of the other three crop patterns. Redundancy analysis results revealed many complex relationships between soil properties and soil bacterial or fungal communities. Employing different crop patterns plays an important role in the effective regulation of soil microbial diversity and properties.

Host filtering, not competitive exclusion, may be the main driver of arbuscular mycorrhizal fungal community assembly under high phosphorus

Abstract A major goal in ecology is understanding the factors which determine the diversity and distribution of organisms. The outcome of the symbiotic relationship between plants and arbuscular mycorrhizal (AM) fungi is strongly influenced by soil phosphorus (P) availability. Despite this knowledge, there is still much to uncover about how soil P status can shape the taxonomic and phylogenetic assembly of root‐colonising AM fungi. Additionally, there is a paucity of understanding about the implications of these changes for the outcome of the AM symbiosis in terms of plant growth, nutrient status and defence traits. We conducted a factorial pot experiment where sorghum (Sorghum bicolor) was grown under three different P treatments (low, medium and high), in the presence or absence of a natural AM fungal community. By analysing the diversity and community structure of the fungal community colonising roots, we aimed to determine if and how soil P influences the relatedness of these communities and whether competitive exclusion or environmental filtering play a more significant role in their assembly. Additionally, we evaluated the concomitant outcomes for plant growth, nutrient acquisition and defensive chemistry (phenolics). Increasing P availability reduced AM fungal richness and increased community evenness. Root‐colonising AM fungal communities under the high P treatment had significantly reduced phylogenetic diversity and comparatively lower mean pairwise distances among all treatments. This indicated that AM fungal communities became more closely related (phylogenetically clustered) with increasing soil P. The mycorrhizal growth and mycorrhizal P responses of plants were positive under low and medium P, but this was lost under high P, however, plant phenolics were increased. Our results suggest that under high P conditions, environmental filtering plays an important role in AM fungal community assembly as host plants alter their selectivity of fungal functional groups prioritising those associated with enhancing plant stress resistance and defences, rather than nutrient acquisition. Here we demonstrated how soil P status can shape taxonomic and phylogenetic assembly of AM fungi and the associated functional outcomes for the host. Read the free Plain Language Summary for this article on the Journal blog.

Dosage effects of organic manure on bacterial community assemblage and phosphorus transformation profiles in greenhouse soil.

Manure is a potential substitute for chemical phosphate fertilizer, especially in intensive agriculture, such as greenhouse farming, but the associations between soil phosphorus (P) availability and the soil microbial community under manure application instead of chemical phosphate fertilizers are still rarely addressed. In this study, a field experiment in greenhouse farming with manure application instead of chemical phosphate fertilizers was established, including five treatments: a control with conventional fertilization and chemical phosphate fertilizer substitution treatments using manure as the sole P resource at 25% (0.25 Po), 50% (0.50 Po), 75% (0.75 Po), and 100% (1.00 Po) of the control. Except for 1.00 Po, all the treatments applied with manure harbored similar levels of available P (AP) as the control. Most of the bacterial taxa involved in P transformation were enriched in manure treatments. Treatments of 0.25 Po and 0.50 Po significantly enhanced bacterial inorganic P (Pi) dissolution capacity, while 0.25 Po decreased bacterial organic P (Po) mineralization capacity. In contrast, the 0.75 Po and 1.00 Po treatments significantly decreased the bacterial Pi dissolution capacity and increased the Po mineralization capacity. Further analysis revealed that the changes in the bacterial community were significantly correlated with soil pH, total carbon (TC), total nitrogen (TN), and AP. These results revealed the dosage effect of the impact of manure on soil P availability and microbial P transformation capacity and emphasized that an appropriate dosage of organic manure is important in practical production.

Isolation of Peanut (&amp;lt;i&amp;gt;Arachis hypogaea&amp;lt;/i&amp;gt; L.) Nodulating Rhizobia and Assessment of Their Phosphate Solubilizing Activity

Phosphate-solubilizing bacteria can enhance the dissolution of insoluble phosphorus in the soil, promoting the availability of soluble phosphorus. Thus, their application can reduce the use of chemical fertilizers and ease sustainable agriculture. The study aimed at isolating and assessing the phosphate solubilizing activity of peanut rhizobia isolated from root nodules of peanut in three Cameroonian soils (Douala, Bafoussam and Ebolowa). Rhizobia were trapped by seeding peanut in plastic pots containing different soils. 45 days later, at the flowering time, root nodules were harvested. From these nodules, rhizobia were isolated, purified on Yeast Extract Mannitol Agar (YEMA) medium and authenticated by inoculating them on sterile sand containing peanut plants and watered with a nutrient solution without nitrogen. The phosphate solubilizing activity of the rhizobia isolates was then assessed in Modified Mineral Salt Medium (MMSM) containing bromocresol green and where the soluble phosphate was replaced by insoluble inorganic phosphates from Cameroon, Algeria, Senegal and tricalcium phosphate in both solid and broth media. The results were analysed statistically by one-way ANOVA using SPSS. A collection of twenty-five isolates was constituted among which 04 from Douala, 12 from Bafoussam and 09 from Ebolowa. All isolates were distinct morphologically. There was significant solubilization of inorganic phosphate in both solid and broth media (p<0.05). Isolated bacteria were characterized as being phosphate solubilizers with values ranging from 1.75 (AhBf1 on Algeria rock phosphate) to 18.9 mg/L (AhDa3 on Algeria rock phosphate). The Algeria rock phosphate was the most solubilized by peanut nodulating bacteria, followed by the tricalcium phosphate, the Senegal rock phosphate and the Cameroon rock phosphate. The solubilizing activity of inorganic phosphates in the broth medium was associated with a global decrease in the pH of the culture medium. The peanut nodulating rhizobia isolates that show the best solubilizing capacity could alleviate the problem of phosphorus availability in agricultural soils.

Low Nocturnal Temperature Alters Tomato Foliar and Root Phosphorus Fractions Allocation by Reducing Soil Phosphorus Availability

Low nocturnal temperature (LNT) is a major constraint for protected tomato production in China during winter and spring, which leads to tomato phosphorus (P) deficiency symptoms. The soil P fractions reflect soil P availability. The foliar and root P fractions reflect the adaptation strategies of tomatoes to LNT. However, the relationship between plant P fractions and soil P fractions under LNT is not well understood. Therefore, we conducted a 40-day indoor incubation experiment with four nocturnal temperatures (15, 12, 9 and 6 °C). Tomato growth status, plant P fractions and soil P fractions were determined. Then, structural equation model (SEM) was used to analyze the direct and/or indirect effects of LNT on soil P fractions, plant P fractions and tomato shoot dry weight (SDW). The results showed that LNT decreased soil P availability by decreasing soil labile P and increasing soil moderately labile P. The foliar inorganic P, metabolite P, nucleic acid P and residual P were decreased under 9 and 6 °C. The root nucleic acid P and lipid P were decreased, while metabolite P was increased under 9 and 6 °C. Tomato foliar and root P fraction allocation was directly influenced by the increase in soil moderately labile P, while the decline in SDW was directly influenced by the decrease in soil labile P. In conclusion, LNT affects tomato P fractions allocation by reducing soil P availability, which limits the shoot dry matter production in tomatoes.

Linkages between Plant Community Composition and Soil Microbial Diversity in Masson Pine Forests.

Plant species identity influences soil microbial communities directly by host specificity and root exudates, and indirectly by changing soil properties. As a native pioneer species common in early successional communities, Masson pine (Pinus massoniana) forests are widely distributed in subtropical China, and play a key role in improving ecosystem productivity. However, how pine forest composition, especially the dominance of plant functional groups, affects soil microbial diversity remains unclear. Here, we investigated linkages among woody plant composition, soil physicochemical properties, and microbial diversity in forests along a dominance gradient of Masson pine. Soil bacterial and fungal communities were mainly explained by woody plant community composition rather than by woody species alpha diversity, with the dominance of tree (without including shrub) species and ectomycorrhizal woody plant species accounting for more of the variation among microbial communities than pine dominance alone. Structural equation modeling revealed that bacterial diversity was associated with woody plant compositional variation via altered soil physicochemical properties, whereas fungal diversity was directly driven by woody plant composition. Bacterial functional groups involved in carbohydrate and amino acid metabolism were negatively correlated with the availability of soil nitrogen and phosphorus, whereas saprotrophic and pathogenic fungal groups showed negative correlations with the dominance of tree species. These findings indicate strong linkages between woody plant composition than soil microbial diversity; meanwhile, the high proportion of unexplained variability indicates great necessity of further definitive demonstration for better understanding of forest-microbe interactions and associated ecosystem processes.

Vegetation restoration of abandoned cropland improves soil phosphorus availability and microbial activities in the Danxia degraded region

Phosphorus is a limiting nutrient in subtropical region soils. The Danxia degraded region (DDR) is a typical ecologically degraded area in the south subtropical region of China, and mitigation measures for reconverting farmland to forest have been implemented to prevent further land degradation. However, whether vegetation restoration can alter soil P fractions (SPF) and P availability in the DDR remains unclear, and the mechanisms influencing P availability require further study. In this study, we collected soil samples from the main vegetation cover types, namely arbor forest, shrubland, and abandoned cropland, in the DDR to explore the characteristics of SPF, acid phosphatase (ACP), microbial community and their influencing factors. Results showed that vegetation restoration significantly affected soil P availability by modifying the SPF. Labile, moderately labile, and aggregate-occluded P content in the soil increased, whereas the proportion of stable P decreased. Vegetation restoration promoted the secretion of soil ACP and significantly increased the abundance of soil bacteria, fungi, actinomycetes, arbuscular mycorrhizal fungi, and the overall microbial abundance. Arbor forest soils presented higher SPF content and microbial activity than the soils from abandoned croplands and shrublands. This increases in soil microbial abundance was significantly correlated with soil microbial biomass and dissolved organic carbon. The results of redundancy and variance partitioning analyses indicated that soil nutrients and soil properties jointly drove SPF transformation in the DDR. Soil nutrient supply significantly affected soil microbial activity and SPF transformation. Vegetation restoration increased microbial activity by increasing the soil nutrient supply, and the resulting synergistic effect altered the SPF distribution and availability. This study provides a theoretical basis for the sustainable use of soil P resources in the DDR.

Soil phosphorus form affects the advantages that arbuscular mycorrhizal fungi confer on the invasive plant species, Solidago canadensis, over its congener.

Interactions between plants and arbuscular mycorrhizal fungi (AMF) are strongly affected by soil phosphorus (P) availability. However, how P forms impact rhizosphere AMF diversity, community composition, and the co-occurrence network associated with native and invasive plants, and whether these changes in turn influence the invasiveness of alien species remain unclear. In this work, we performed a greenhouse experiment with the invasive species Solidago canadensis and its native congener S. decurrens to investigate how different forms of P altered the AMF community and evaluate how these changes were linked with the growth advantage of S. canadensis relative to S. decurrens. Plants were subjected to five different P treatments: no P addition (control), simple inorganic P (sodium dihydrogen phosphate, NaP), complex inorganic P (hydroxyapatite, CaP), simple organic P (adenosine monophosphate, AMP) and complex organic P (myo-inositol hexakisphosphate, PA). Overall, invasive S. canadensis grew larger than native S. decurrens across all P treatments, and this growth advantage was strengthened when these species were grown in CaP and AMP treatments. The two Solidago species harbored divergent AMF communities, and soil P treatments significantly shifted AMF community composition. In particular, the differences in AMF diversity, community composition, topological features and keystone taxa of the co-occurrence networks between S. canadensis and S. decurrens were amplified when the dominant form of soil P was altered. Despite significant correlations between AMF alpha diversity, community structure, co-occurrence network composition and plant performance, we found that alpha diversity and keystone taxa of the AMF co-occurrence networks were the primary factors influencing plant growth and the growth advantage of invasive S. canadensis between soil P treatments. These results suggest that AMF could confer invasive plants with greater advantages over native congeners, depending on the forms of P in the soil, and emphasize the important roles of multiple AMF traits in plant invasion.

Effects of Five–Year Inorganic and Organic Fertilization on Soil Phosphorus Availability and Phosphorus Resupply for Plant P Uptake during Maize Growth

A better understanding of the P dynamic resupply roles of fertilization from soil solids to solution is urgently required to optimize sustainable P fertilizer management practices for efficient supply. A five–year fertilization experiment was used to investigate the effects on soil P fractions and availability, the kinetic P resupply based on a novel simulation technique (Diffusive gradients in thin films (DGT) and DGT–induced fluxes in sediments and soils (DIFS) ) and to identify dominant factors during the maize season under five treatments (no fertilizer (CK), chemical fertilizer (NPK), chemical fertilizer combined with bone meal fertilizer (NPKC), crop straw (NPKS) and bioorganic fertilizer (NPKM)). The results showed that the NPKC and NPKM treatments had higher enhancement effects on Olsen–P and organic P and inorganic Ca2–P, Ca8–P, Al–P and Fe–P at maize growth stages, and they buffered pH decrease to delay the substantial Fe–P and Al–P release until a late stage. Inorganic Ca2–P, Ca8–P, Al–P and Fe–P heavily effected the Olsen–P levels. The NPKS, NPKC and NPKM treatments yielded higher CDGT–P levels and a stronger resupply capacity, reflected by higher R and CE/Csoln and smaller Tc values. The simulation and path model results revealed that the maize plant P uptake was determined by soil P resupply and an inorganic P supply pool. They were positively dominated by soil organic matter (SOM). Our results suggested that organic fertilization, especially NPKC and NPKM treatments, provided greater enhancement effects on the P supply pool and P resupply for higher plant P uptake, identifying them as highly effective P management practices for developing sustainable agriculture.

Soil nutrients and the responses of microbial community structure to pine bark and vinegar residues in blueberry cultivation

The addition of suitable acidic organic materials to improve the soil for blueberry (Vaccinium spp.) cultivation is the foundation for ensuring the sustainable development of blueberry industry in China. However, the effects of managing orchards with different inputs of organic material to improve the soil nutrients varied substantially. To unearth the best types of organic material to improve the soil fertility for blueberry cultivation and the rates to use in their application, a cultivation experiment used rooting zone restriction container and one-year-old seedlings of highbush blueberry (Vaccinium corymbosum L. variety “Legacy”) as the test materials and pure soil as the control (CK) in this study. We compared the effects of three rates of application of pine bark and vinegar residue on the soil nutrients and microbial community structures, three concentrations of 1884, 3768, and 5652 m3 km−2 of pine bark and three of 2826, 5652, and 8478 m3 km−2 vinegar residue were designed to add to the soil, and they were designated PB1, PB2, and PB3 and VR1, VR2, and VR3, respectively. Surface soil samples were collected for analysis after the blueberry shrubs had been planted for one year. The results showed that compared with the CK, the PB1 treatment significantly increased the total potassium (TK), alkaline hydrolyzed nitrogen (AN) and available phosphorus (AP) contents in the soil. The PB2 and PB3 treatments significantly enhanced the soil organic matter (SOM), total phosphorus (TP), AN, and AP contents but significantly reduced the microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass phosphorus (MBP) contents. The VR1, VR2 and VR3 treatments significantly increased the contents of soil pH, total nitrogen (TN), available potassium (AK), SOM, AN, MBC and MBP. The PB1, PB2, VR1, VR2, and VR3 treatments markedly enhanced the bacterial Shannon index. However, the VR3 treatment markedly reduced the number of fungal species and the Chao 1, ACE, Simpson, and Shannon indices when compared with those of the CK. The soil fungal diversity was more easily regulated by soil nutrients than the bacterial diversity. A redundancy analysis showed that the dominant bacterial phyla were primarily regulated by the soil AN, while the dominant fungal phyla were primarily regulated by the SOM and MBN. In conclusion, the vinegar residue was more effective than the pine bark at improving the soil nutrients. The VR2 treatment not only significantly improved the soil nutrients but also maintained the soil microbial diversity, which rendered it the best organic material to improve the cultivation of blueberry soil.

Different Cropping Patterns to Restore Saline-Alkali Soils in Northeast China Affect the Abundance of Functional Genes in the Soil Nitrogen Cycle

Considerable attention has been paid to the establishment of an appropriate cropping patterns for the restoration of saline-alkali lands. This study’s goal was to explore changes in nitrogen-cycling (N-cycling) gene (nitrogen fixation: nifH; nitrification: AOA, AOB, and nxrB; denitrification: narG, norB, and nosZ) abundance of three cropping patterns at two soil depths in saline-alkali soils. Results showed that rotation and mixture promoted soil nutrients. N-cycling functional genes were significantly influenced by soil depths and cropping patterns. Compared with monoculture, rotation decreased the abundance of nifH, AOA, narG, and nosZ and increased the abundance of AOB; mixture decreased the abundance of AOA, narG, and nosZ and increased the abundance of AOB and nxrB in the 0–15 cm soil depth. Rotation increased all genes abundance; mixture increased nosZ abundance and decreased nxrB abundance in 15–30 cm soil depth. Soil protease, cellulase, nitrate reductase, pH, AK (available potassium), and AP (available phosphorus) were important factors influencing N-cycling gene abundance. In conclusion, rotation and mixture not only reduced soil salinity but also improved soil fertility and nitrogen cycling. These findings can provide some theories for the sustainable development of N-cycling during the restoration of saline-alkali soils.