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Abstract Background Fungi and bacteria coexist in a wide variety of environments, and their interactions are now recognized as the norm in most agroecosystems. These microbial communities harbor keystone taxa, which facilitate connectivity between fungal and bacterial communities, influencing their composition and functions. The roots of most plants are associated with arbuscular mycorrhizal (AM) fungi, which develop dense networks of hyphae in the soil. The surface of these hyphae (called the hyphosphere) is the region where multiple interactions with microbial communities can occur, e.g., exchanging or responding to each other’s metabolites. However, the presence and importance of keystone taxa in the AM fungal hyphosphere remain largely unknown. Results Here, we used in vitro and pot cultivation systems of AM fungi to investigate whether certain keystone bacteria were able to shape the microbial communities growing in the hyphosphere and potentially improved the fitness of the AM fungal host. Based on various AM fungi, soil leachates, and synthetic microbial communities, we found that under organic phosphorus (P) conditions, AM fungi could selectively recruit bacteria that enhanced their P nutrition and competed with less P-mobilizing bacteria. Specifically, we observed a privileged interaction between the isolate Streptomyces sp. D1 and AM fungi of the genus Rhizophagus, where (1) the carbon compounds exuded by the fungus were acquired by the bacterium which could mineralize organic P and (2) the in vitro culturable bacterial community residing on the surface of hyphae was in part regulated by Streptomyces sp. D1, primarily by inhibiting the bacteria with weak P-mineralizing ability, thereby enhancing AM fungi to acquire P. Conclusions This work highlights the multi-functionality of the keystone bacteria Streptomyces sp. D1 in fungal-bacteria and bacterial-bacterial interactions at the hyphal surface of AM fungi. Video Abstract

Background: Fungi and bacteria coexist in a wide variety of environments, and their interactions are now recognized as the norm in most agroecosystems. These microbial communities harbor keystone taxa, which facilitate connectivity between fungal and bacterial communities, influencing their composition and functions. The roots of most plants are associated with arbuscular mycorrhizal (AM) fungi, which develop dense networks of hyphae in the soil. The surface of these hyphae (called the hyphosphere) is the region where multiple interactions with microbial communities can occur, e.g., exchanging or responding to each other's metabolites. However, the presence and importance of keystone taxa in the AM fungal hyphosphere remain largely unknown. Results: Here, we used in vitro and pot cultivation systems of AM fungi to investigate whether certain keystone bacteria were able to shape the microbial communities growing in the hyphosphere and potentially improved the fitness of the AM fungal host. Based on various AM fungi, soil leachates, and synthetic microbial communities, we found that under organic phosphorus (P) conditions, AM fungi could selectively recruit bacteria that enhanced their P nutrition and competed with less P-mobilizing bacteria. Specifically, we observed a privileged interaction between the isolate Streptomyces sp. D1 and AM fungi of the genus Rhizophagus, where (1) the carbon compounds exuded by the fungus were acquired by the bacterium which could mineralize organic P and (2) the in vitro culturable bacterial community residing on the surface of hyphae was in part regulated by Streptomyces sp. D1, primarily by inhibiting the bacteria with weak P-mineralizing ability, thereby enhancing AM fungi to acquire P. Conclusions: This work highlights the multi-functionality of the keystone bacteria Streptomyces sp. D1 in fungal-bacteria and bacterial-bacterial interactions at the hyphal surface of AM fungi. 3XiVYVBxkNucerLC-WX6of Video Abstract [ABSTRACT FROM AUTHOR]

Tree species establish mycorrhizal associations with both ectomycorrhizal (EM) and arbuscular mycorrhizal fungi (AM), which play crucial roles in facilitating plant phosphorus (P) acquisition. However, little attention has been given to the effects of EM and AM species on soil P dynamics and the underlying mechanisms in subtropical forests, where P availability is typically low. To address this knowledge gap, we selected two EM species (Pinus massoniana - PM and Castanopsis carlesii - CC) and two AM species (Cunninghamia lanceolata - Chinese fir, CF and Michelia macclurei - MM) in a common garden established in 2012 in subtropical China. We investigated soil properties (e.g., pH, soil organic carbon, total nitrogen, and dissolved organic nitrogen), soil P fractions, phospholipid fatty acids (PLFAs), enzyme activities, foliar manganese (Mn) concentration, and foliar nutrients and stoichiometry. Our findings revealed that soils hosting EM species had higher levels of resin P, NaHCO3-Pi, extractable Po, total P, and a greater percentage of extractable Po to total P compared to soils with AM species. These results indicate that EM species enhance soil P availability and organic P accumulation in contrast to AM species. Moreover, EM species exhibited higher P return to soil (indicated by higher foliar P concentrations) when compared to AM species, which partly explains higher P accumulation in soils with EM species. Additionally, resin P showed a positive correlation with acid phosphatase (ACP) activity, whereas no correlation was found with foliar Mn concentration, which serves as a proxy for the mobilization of sorbed soil P. Such findings indicate that organic P mineralization has a more substantial impact than inorganic P desorption in influencing P availability in soils hosting both EM and AM species. In summary, our study contributes to a more comprehensive understanding of the effects of mycorrhizal associations on soil P accumulation in subtropical forests and provide valuable insights into plant-soil interactions and their role in P cycling in regions with limited P availability. [ABSTRACT FROM AUTHOR]

Long-term application of dairy liquid manure (DLM) can modify soil phosphorus (P) dynamics. P fractionation allows the identification of organic and inorganic P and its lability via procedures of lesser and greater power extraction. The aim was to evaluate the effect of successive DLM applications (10 years) in no-tillage on soil P fractions. The experiment was carried out in an Oxisol with a sandy clay loam texture. Treatments consisted of three DLM doses (60, 120, and 180 m3 ha−1 year−1) and the control (unmanured) (0 m3 ha−1 year−1) randomized in a complete block design with four replicates. The soil was sampled at three depths (0–0.05; 0.05–0.10, and 0.10–0.15 m), and sequential extractions were performed for each depth. DLM increased soil P concentrations in all fractions, mainly in the 0–0.05 m depth resulting in the following proportions of P (average of all DLM doses in 0–0.05 m depth): labile (29%), moderately labile (38%), low lability (17%), and residual (16%). In the unmanured treatment, the proportion was labile (18%), moderately labile (39%), low lability (22%), and residual (21%). DLM application resulted in a higher proportion of organic and inorganic labile P (water, resin, and NaHCO3) indicating a greater plant availability but also a P water pollution risk by surface runoff. [ABSTRACT FROM AUTHOR]

Phosphorus (P) unavailability in agricultural soils is a primary cause of the poor development and yield of field crops in arid and semiarid regions. The primary goal of this research project was to investigate the influence of integrated management of beneficial microbes or biofertilizers (BF), organic P-fertilizers, and inorganic P-fertilizers on wheat productivity in a wheat–maize cropping system. Field experiments were carried out during the two consecutive seasons of 2020/2021 (Y1) and 2021/2022 (Y2) according to the two-factorial randomized complete block design with three replications. Factor one consisted of twenty-one treatments of organic and inorganic P-fertilizer combinations, while factor two consisted of two different BF (PSB and Bioaab). One overall control where no P or BF was applied was also included in each replication for comparison. The experiment consisted of six treatments of sole P sources (sheep manure (SM), cattle manure (CM), legume residues (LR), non-legume residues (NLR), single super phosphate (SSP) and rock phosphate (RP)), each applied at a rate of 90 kg P ha−1. Different combinations of organic and inorganic P sources (giving 15 treatments) were applied at a rate of 50% P from each source (i.e., 45 kg P ha−1 applied from different sources in combination). The results revealed that the combined application of SSP+SM produced a significantly higher number of grains spike−1 (23.9%), spikes m−2 (4.5%), and grain yield (40.9%) over the control. Application of PSB produced the maximum number of grains spike−1 (23.9%), spikes m−2 (4.5%), thousand-grain weight (8.3%), grain yield (40.9%), and biological yield (17%) in the wheat crop as compared to Bioaab. It was concluded from the two-year study that integrated use of organic P-fertilizers (animal manures) plus inorganic P-fertilizer (SSP) along with PSB ranked first in terms of higher wheat productivity in a wheat–maize cropping system. [ABSTRACT FROM AUTHOR]

Phosphate (Pi) deficiency leads to the induction of purple acid phosphatases (PAPs) in plants, which dephosphorylate organic phosphorus (P) complexes in the rhizosphere and intracellular compartments to release Pi. In this study, we demonstrate that OsPAP3b belongs to group III low-molecular weight PAP and is low Pi-responsive, preferentially in roots. The expression of OsPAP3b is negatively regulated with Pi resupply. Interestingly, OsPAP3b was found to be dual localized to the nucleus and secretome. Furthermore, OsPAP3b is transcriptionally regulated by OsPHR2 as substantiated by DNA–protein binding assay. Through in vitro biochemical assays, we further demonstrate that OsPAP3b is a functional acid phosphatase (APase) with broad substrate specificity. The overexpression (OE) of OsPAP3b in rice led to increased secreted APase activity and improved mineralization of organic P sources, which resulted in better growth of transgenics compared to the wild type when grown on organic P as an exogenous P substrate. Under Pi deprivation, OsPAP3b knock-down and knock-out lines showed no significant changes in total P content and dry biomass. However, the expression of other phosphate starvation–induced genes and the levels of metabolites were found to be altered in the OE and knock-down lines. In addition, in vitro pull-down assay revealed multiple putative interacting proteins of OsPAP3b. Our data collectively suggest that OsPAP3b can aid in organic P utilization in rice. The APase isoform behavior and nuclear localization indicate its additional role, possibly in stress signaling. Considering its important roles, OsPAP3b could be a potential target for improving low Pi adaptation in rice. [ABSTRACT FROM AUTHOR]

Soil aggregation in forest ecosystem is considered as a significant physical process mainly influenced by manure, fertilizers or combination. This aggregation may directly alter the soil nutrient and their fractions in soil. So, soil samples were collected from two types of forests i.e. Natural Korean pine forests (NKPF) and Korean pine plantation (KPP) in order to know the quantities of organic and inorganic Phosphorus (P) amounts in different aggregate sizes viz. >5 mm, 2–5 mm, 0.25–2 mm, 5 mm) and decreased with the decreasing aggregate size, while other variables, i.e., NaOH-Pi, NaHCO3-Po, pH and T-N were not affected in aggregate size. H2O-Pi (48 ppm), NaHCO3-Pi (68 ppm), NaHCO3-Po (80 ppm), NaOH-Po (623 ppm), HCL-Po (67 ppm), SOC (20.36 ± 1.6) was estimated in medium fertilizer treatment. PCA analysis showed that spread/variance of data points on F1 (62.90%) is more than spread/variance of data points on F2 (57.74%) in NKPF and KPP, respectively, while correlation matrix showed high correlation between H2O-Pi and NaOH-Pi (0.63) and H2O-Pi and NaHCO3-Pi (0.63) while a strong negative correlation was present between Res-Pi and Po (−0.61). Moreover, litter inputs increased the organic-P fractions in soil particularly at medium treatment.

Chara is usually found in hard and alkaline waters with low level of phosphorus (P) concentration. Calcite encrustation with P co-precipitation is very important for the growth of Chara and the maintenance of a low nutrient state in aquatic ecosystems. However, the effects and mechanisms of elevated P content in water on the growth, uptake and allocation of P in Chara are not well understood. This study performed an experiment to clarify how Chara vulgaris Linn, a common and widely distributed macroalga, allocated the P it uptake at different P availability. The results indicated that the growth rate of C. vulgaris in low P treatments (LP, less than 6 μg P /L) was 0.8 times higher than that in high P treatments (HP, more than 100 μg P /L), and the growth rate was significantly increased when C. vulgaris were transferred from the water with high P content to water with low P content, indicating that high P contents in water inhibited the growth of C. vulgaris. The increase of P content in water resulted in a fourfold increase in inorganic P (IP) content, while only 0.2-fold increase in organic P (OP) content, making the stoichiometric homeostasis index (1/H) of IP 7.9 times that of OP. More than 70% of the total P (TP) accumulated in Chara in LP was used for biomass growth, while more than 60% of the TP in C. vulgaris in HP was precipitated into calcite encrustation. This study highlighted that C. vulgaris had high growth rate under low P environment, and the inhibiting effect of high P to C. vulgaris was reversible, which may be a special P competition mechanism for this species in low P water. However, in high P condition, the Ca-P co-precipitation may limit the apparent P availability and be expressed as an inhibition of growth. [ABSTRACT FROM AUTHOR]

The sources of P and N in water-carrying lakes include exogenous input and endogenous release. However, the influence of pollution from different sources on the dynamic distribution of N and P at the sediment-water interface in water-carrying lakes remains unclear. The objectives of this study were to investigate the differences in dynamic distribution characteristics of P compounds and N elements in Lake Jiaogang, a major water-carrying lake in eastern China. Four functional regions with different types of pollutant sources and different kinds of aquatic plants were selected to study the distribution of total P (TP), inorganic P, organic P, ammonium (NH4+–N), and nitrate (NO3−–N). The results revealed that regions with internal-source pollutants contained the highest concentration of TP, Ca–P, and Fe–P with high concentrations. L–P, Al–P, mostly organic P, and soluble reactive phosphorous (SRP), the region with internal-source pollutants were lower than that with the imported-source pollutant. The concentration of dissolved NH4+–N showed high in regions with imported-source pollutants, however, in regions with internal-source pollutants, the dissolved NO3−–N was with the highest concentration. Overall, P from upstream was still dominant in the sediments despite uptake by the aquatic plants. SRP showed high concentration in regions with imported-source pollutants due to the imported pollution and the improved bioavailability by plant root exudates. Feces and feed residues from aquatic livestock breeding resulted in the highest concentration of TN, NH4+–N, and dissolved NO3−–N in the sediments of the region with internal-source pollutants. High concentrations of dissolved NH4+–N were due to the input of N from imported source pollutants. This study provides insights into the contributions of P and N to the eutrophication of the water-carrying lake. [ABSTRACT FROM AUTHOR]

Phosphate solubilizing microbes (PSM) can improve soil P availability by P dissolution. These microbes can make substances that regulate plant growth, which promotes plant growth. The present study aimed to characterize PSM and determine how PSM application affected P solubilization, soil phosphatase activity, and upland rice yield. The greenhouse experiment used a factorial randomized block design (RBD) with two factors and three replications. The first factor was PSM isolates, which came in four different forms: without microbes, with microbes (Burkholderia sp.), with fungus (Penicillium sp.), and with a combination of microbes (Burkholderia sp. and Penicillium sp.). The PSM isolates were characterized to analyze the production of organic acids, phosphatase enzymes, and phytohormones. The second factor was the superphosphate fertilizer dose, which has four levels: 0, 50, 75, and 100 kg P ha−1. According to the PSM characterization, it produced organic acids such as lactate acid, oxalate acid, citric acid, and acetate acid, as well as phytohormones (IAA) and the enzyme phosphatase. The pot experiment results show that the PSM inoculation raised the available P and soil phosphatase, P content of the plant, decreased soil organic P, and increased upland rice production. For improving available P, phosphatase activity, P content of the plant, and upland rice yields, mixed inoculants of phosphate-solubilizing bacteria and fungi performed better. The availability of soil P, the activity of the enzyme phosphatase, and the upland rice yields were all improved by applying P fertilizer at 75 kg P ha−1. This study showed that PSM as a biofertilizer reduced the dosage of inorganic fertilizers by up to 25%.

Processes governing soil organic matter (SOM) decomposition and mineralization are important for soil fertility and ecosystem sustainability. However, in the sub-Saharan region, limited work has been conducted on SOM dynamics; therefore, there was an imperative need for this study. The objective of this study was to determine the phosphorus (P) and nitrogen (N) dynamics in soil under different tillage and fertilizer management practices. The field trial was arranged as a randomized split plot design, with tillage forming the whole plot and the fertilizer application rate being the sub-plot. The tillage techniques were no-till (NT), annual tillage (CT-ANNUAL) and conventional tillage every fifth season (CT-Y5), whereby NT was practiced for four consecutive seasons, and in the fifth season, conventional tillage was employed. For all these tillage techniques, urea fertilizer was applied in amounts of 60, 120 and 240 kg N ha−1 with a control for each tillage treatment. Ammonium and nitrate levels were determined calorimetrically. Sulfuric acid, at 1 M, along with 0.057 M ascorbic acid and molybdate reagent were used to extract the organic P from the soil and extractable P. The total N, ammonium, total P, organic P and extractable P in the surface soil under NT were higher (p < 0.05) compared to the values of both CT-Y5 and CT-ANNUAL. The high levels of total N, N mineralization, total P, organic P and extractable P under NT, compared to CT-Y5 and CT-ANNUAL, at the depth of 0–10 cm may be attributed to the accumulation of crop residues on the surface and less soil disturbance. Furthermore, nitrate was found in higher (p < 0.05) concentrations under CT-ANNUAL compared to CT-Y5 at all the application rates and depths. The ploughing of soil under CT-ANNUAL improves the aeration, which accelerates the decomposition of organic material and mineralization of organic N and P into soluble forms. No-till, at 60 kg N ha−1 and a 0–10 cm soil depth, had optimum total N, nitrate, ammonium, total P and organic P values, thus showing its salient impact on the maintenance of soil fertility. However, the conclusion drawn from this study is that CT-Y5, due to its average N and P pools, can be recommended to under-resourced farmers in sub-Saharan preferentially over both NT and CT-ANNUAL, because it does not require advanced technology and equipment and it sustains an average soil fertility. [ABSTRACT FROM AUTHOR]

Over the past decade, scientific studies have increasingly concentrated on the effects of global phosphorus (P) scarcity on food security. A comprehensive strategy that considers demand reduction and recycling possibilities is needed to address the global P scarcity. Reduced tillage along with crop residue retention could decrease fixation of P in soil, improve labile P content and enhance organic-P (Po) buildup and its mineralization by phosphatases; this could be an extra benefit of conservation agriculture (CA) in soils. To study the impact of long-term CA on soil organic and inorganic P fractions and their distribution, a long-term field trial was conducted under a maize-based cropping system with different tillage (zero tillage (ZT), permanent bed (PB) and conventional till (CT) and cropping system (maize–wheat–mungbean (MWMb), maize–chickpea–sesbania (MCS), maize–mustard–mungbean (MMuMb) and maize–maize–sesbania (MMS)). Phosphorus dynamics were studied through sequential fractionation (organic and inorganic P) at 0–5 and 5–15 cm soil depth. The findings showed that a higher amount of soluble and loosely bound P (SL-P) was detected in ZT among the inorganic P fractions, whereas iron-bound P (Fe-P), aluminum-bound P (Al-P), reductant soluble P (RES-P) and calcium-bound P (Ca-P) were found higher in CT in both soil depths. Among Organic-P fractions, moderately labile and non-labile Po was found higher in PB and ZT but, in the case of labile Po, it was found insignificant with respect to tillage operations. Significant synergistic effects of winter legume (chickpea) with summer legumes (sesbania and mungbean) in crop rotation were observed on SL-P, Labile Po, Humic acid-Po, Alkaline phosphatase and MBP at 0–5 and 5–15 cm soil depths. Given the potential relevance of understanding P dynamics for efficient P management in long-term conservation agriculture practices, our findings offers critical new insight for the P management for sustainable development. [ABSTRACT FROM AUTHOR]

Understanding sediment phosphorus (P) compounds is essential to managing P in lake sediments because P speciation will determine bioavailability and reactivity. Little is known about organic P (Po) in hardwater eutrophic lakes in the North American Great Plains, or the role of metals in Po cycling. Sediment cores (0–12 cm deep) collected from four lakes from the Qu’Appelle chain in Saskatchewan, Canada, were sectioned by depth and analyzed by solution P nuclear magnetic resonance spectroscopy to characterize P forms. Concentrations and pools of calcium (Ca), magnesium (Mg), iron (Fe), manganese (Mn), and aluminum (Al) were also determined. A range of P compounds was detected with significant interactions between lakes and depth for orthophosphate, phytate and DNA, and significant differences among lakes or with depth for polyphosphates and phosphonates. The main class of Po compounds identified in all lakes was orthophosphate diesters, including phospholipids and DNA, typical of living biota, suggesting that P immobilized by microbes and algae is an important pool in the sediments of these lakes. There were significant differences in metal concentrations among the lakes. In three lakes, Ca concentrations were high, and P was tightly bound with Ca compounds of low solubility. In the fourth lake with lower Ca concentrations, P appeared to be loosely bound to Al and Fe compounds. Our study indicates that there were significant differences in P compounds and the factors controlling their cycling among these four lakes in the same chain, which has implications for P management and water quality control.

Organic phosphorus (P o) is a large component of soil P, but it is often unavailable for plant uptake. Purple acid phosphatases (PAP) can hydrolyze a wide range of P o , playing an important role in P o utilization by plants. In this study, we investigated a novel secretary PvPAP1 from the As-hyperaccumulator Pteris vittata , which can effectively utilize exogenous P o , including adenosine triphosphate (ATP) and phytate. Unlike other PAP, PvPAP1 was abundantly-expressed in P. vittata roots, which was upregulated 3.5-folds under P-deprivation than P-sufficient conditions. When expressed in tobacco, its activity in the roots of PvPAP1-Ex lines was ∼8 folds greater than that in wild-type (WT) plants. Besides, PvPAP1 exhibited its secretory ability as evidenced by the sapphire-blue color on the root surface after treating with 5-bromo-4-chloro-3-indolyl phosphate. In a long-term experiment using sand media, PvPAP1 -expressing tobacco plants showed 25–30 % greater root biomass than WT plants when using ATP as the sole P source. This is because PvPAP1- expression enhanced its phosphatase activity by 6.5–9.2 folds in transgenic tobacco, thereby increasing the P contents by 39–41 % in its roots under ATP treatment and 9.4–30 % under phytate treatment. The results highlight PvPAP1 as a novel secreted phosphatase crucial for external P o utilization in P. vittata , suggesting that PvPAP1 has the potential to serve as a valuable gene resource for enhancing P o utilization by crop plants. [Display omitted] • A novel purple acid phosphatase gene PvPAP1 was isolated from P. vittata; • PvPAP1 was upregulated under P-deprivation compared to P-sufficient conditions; • Expressing PvPAP1 enhanced phosphatase activity in plants; • Expressing PvPAP1 promoted plant growth using ATP as the sole P source; • Expressing PvPAP1 increased P uptake in plant roots under ATP and phytate treatment. [ABSTRACT FROM AUTHOR]

Background: Manures and synthetic fertilisers can affect soil pH and plant-microbe processes and thus influence P forms and composition. Aims: The objective of this study was to examine the effects of the 40-year application of synthetic fertilisers or pig manure combined with synthetic fertilisers on the P forms and composition and the response of corn growth and yield to changes in P availability. Methods: A long-term field experiment with unfertilised, urea, urea+superphosphate, pig manure+urea and pig manure+urea+superphosphate fertilised soils was studied. 31P nuclear magnetic resonance spectroscopy was used to quantify P compounds. Results: The maximum corn yield was found when adding pig manure+urea, despite Olsen-P was lower than on adding manure+superphosphate. Other monoester P compounds, typically related to microbial biomass and processes were highest on adding pig manure+urea. When adding superphosphate+urea+pig manure a reduction of these P compounds was observed as well as the highest accumulation of inositol hexakisphosphate (IHP). Synthetic fertilisers increased Olsen-P, orthophosphate and other monoester and total IHP and largely decreased soil pH. The addition of pig manure greatly increased the stereoisomers of IHP (myo-IHP, scyllo-IHP, neo-IHP, and D-chiro-IHP) and the concentration of orthophosphate diesters. D-chiro-IHP was not found in unfertilised soils while neo-IHP was not detected in synthetically fertilised soils. Conclusions: P compounds related to microbial processes, such as other monoester, increased when adding pig manure. Additions of superphosphate on top of manures reduced other monoester, while they increased on adding synthetic fertilisers alone. Unfertilised soils were virtually free of P compounds related to microbial processes. [ABSTRACT FROM AUTHOR]

Drylands are arid and semi-arid areas whose main feature is their low level of precipitation. They cover nearly half of Earth's land surface and are distributed worldwide, constituting the planet's largest biome. Dryland soils have low fertility, are greatly affected by climate variability, and are vulnerable to wind and water erosion. The phosphorus-rich soil dust traveling by aeolian processes from drylands is the main source of P for the global primary productivity in P-limited areas, a fact that highlights the importance of arid and semiarid areas in the global nutrient budget. This review discusses the development of dryland soils, the sources of P in drylands, the C, N, P, relation in dryland soils, the fractionation and bioavailability of P, and biotic and abiotic factors affecting the P in drylands. Finally, the dynamic of P in biological soil crusts and resource islands is discussed. Combined, they contribute to the surface organic matter pools, alter the soil fertility, and are determinant factors in P's availability in dryland soils. We conclude the review by highlighting the gaps in knowledge that should be addressed in future research regarding biological and abiotic processes that determine the dynamics of P in drylands. [ABSTRACT FROM AUTHOR]

Processes governing soil organic matter (SOM) decomposition and mineralization are important for soil fertility and ecosystem sustainability. However, in the sub-Saharan region, limited work has been conducted on SOM dynamics; therefore, there was an imperative need for this study. The objective of this study was to determine the phosphorus (P) and nitrogen (N) dynamics in soil under different tillage and fertilizer management practices. The field trial was arranged as a randomized split plot design, with tillage forming the whole plot and the fertilizer application rate being the sub-plot. The tillage techniques were no-till (NT), annual tillage (CT-ANNUAL) and conventional tillage every fifth season (CT-Y5), whereby NT was practiced for four consecutive seasons, and in the fifth season, conventional tillage was employed. For all these tillage techniques, urea fertilizer was applied in amounts of 60, 120 and 240 kg N ha−1 with a control for each tillage treatment. Ammonium and nitrate levels were determined calorimetrically. Sulfuric acid, at 1 M, along with 0.057 M ascorbic acid and molybdate reagent were used to extract the organic P from the soil and extractable P. The total N, ammonium, total P, organic P and extractable P in the surface soil under NT were higher (p < 0.05) compared to the values of both CT-Y5 and CT-ANNUAL. The high levels of total N, N mineralization, total P, organic P and extractable P under NT, compared to CT-Y5 and CT-ANNUAL, at the depth of 0–10 cm may be attributed to the accumulation of crop residues on the surface and less soil disturbance. Furthermore, nitrate was found in higher (p < 0.05) concentrations under CT-ANNUAL compared to CT-Y5 at all the application rates and depths. The ploughing of soil under CT-ANNUAL improves the aeration, which accelerates the decomposition of organic material and mineralization of organic N and P into soluble forms. No-till, at 60 kg N ha−1 and a 0–10 cm soil depth, had optimum total N, nitrate, ammonium, total P and organic P values, thus showing its salient impact on the maintenance of soil fertility. However, the conclusion drawn from this study is that CT-Y5, due to its average N and P pools, can be recommended to under-resourced farmers in sub-Saharan preferentially over both NT and CT-ANNUAL, because it does not require advanced technology and equipment and it sustains an average soil fertility.

Over the past decade, scientific studies have increasingly concentrated on the effects of global phosphorus (P) scarcity on food security. A comprehensive strategy that considers demand reduction and recycling possibilities is needed to address the global P scarcity. Reduced tillage along with crop residue retention could decrease fixation of P in soil, improve labile P content and enhance organic-P (Po) buildup and its mineralization by phosphatases; this could be an extra benefit of conservation agriculture (CA) in soils. To study the impact of long-term CA on soil organic and inorganic P fractions and their distribution, a long-term field trial was conducted under a maize-based cropping system with different tillage (zero tillage (ZT), permanent bed (PB) and conventional till (CT) and cropping system (maize–wheat–mungbean (MWMb), maize–chickpea–sesbania (MCS), maize–mustard–mungbean (MMuMb) and maize–maize–sesbania (MMS)). Phosphorus dynamics were studied through sequential fractionation (organic and inorganic P) at 0–5 and 5–15 cm soil depth. The findings showed that a higher amount of soluble and loosely bound P (SL-P) was detected in ZT among the inorganic P fractions, whereas iron-bound P (Fe-P), aluminum-bound P (Al-P), reductant soluble P (RES-P) and calcium-bound P (Ca-P) were found higher in CT in both soil depths. Among Organic-P fractions, moderately labile and non-labile Po was found higher in PB and ZT but, in the case of labile Po, it was found insignificant with respect to tillage operations. Significant synergistic effects of winter legume (chickpea) with summer legumes (sesbania and mungbean) in crop rotation were observed on SL-P, Labile Po, Humic acid-Po, Alkaline phosphatase and MBP at 0–5 and 5–15 cm soil depths. Given the potential relevance of understanding P dynamics for efficient P management in long-term conservation agriculture practices, our findings offers critical new insight for the P management for sustainable development.

Tree species establish mycorrhizal associations with both ectomycorrhizal (EM) and arbuscular mycorrhizal fungi (AM), which play crucial roles in facilitating plant phosphorus (P) acquisition. However, little attention has been given to the effects of EM and AM species on soil P dynamics and the underlying mechanisms in subtropical forests, where P availability is typically low. To address this knowledge gap, we selected two EM species ( Pinus massoniana - PM and Castanopsis carlesii - CC) and two AM species ( Cunninghamia lanceolata - Chinese fir, CF and Michelia macclurei - MM) in a common garden established in 2012 in subtropical China. We investigated soil properties (e.g., pH, soil organic carbon, total nitrogen, and dissolved organic nitrogen), soil P fractions, phospholipid fatty acids (PLFAs), enzyme activities, foliar manganese (Mn) concentration, and foliar nutrients and stoichiometry. Our findings revealed that soils hosting EM species had higher levels of resin P, NaHCO 3 -Pi, extractable Po, total P, and a greater percentage of extractable Po to total P compared to soils with AM species. These results indicate that EM species enhance soil P availability and organic P accumulation in contrast to AM species. Moreover, EM species exhibited higher P return to soil (indicated by higher foliar P concentrations) when compared to AM species, which partly explains higher P accumulation in soils with EM species. Additionally, resin P showed a positive correlation with acid phosphatase (ACP) activity, whereas no correlation was found with foliar Mn concentration, which serves as a proxy for the mobilization of sorbed soil P. Such findings indicate that organic P mineralization has a more substantial impact than inorganic P desorption in influencing P availability in soils hosting both EM and AM species. In summary, our study contributes to a more comprehensive understanding of the effects of mycorrhizal associations on soil P accumulation in subtropical forests and provide valuable insights into plant-soil interactions and their role in P cycling in regions with limited P availability., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Lian, Xu, Yang, Yue and Peñuelas.)

Soil aggregation in forest ecosystem is considered as a significant physical process mainly influenced by manure, fertilizers or combination. This aggregation may directly alter the soil nutrient and their fractions in soil. So, soil samples were collected from two types of forests i.e. Natural Korean pine forests (NKPF) and Korean pine plantation (KPP) in order to know the quantities of organic and inorganic Phosphorus (P) amounts in different aggregate sizes viz. >5 mm, 2-5 mm, 0.25-2 mm, <0.25 mm under forest litter and synthetic fertilizer application below the treatments as undisturbed soil (CK), removed litter (RL), altered litter (AL) while the fertilizer treatments were as control; C: (No added N and P,), L: low (5 g N m -2 a -1  + 5 g P m -2 a -1 ), M: medium (15 g N m -2 a -1  + 10 g P m -2 a -1 ) and H: high concentration (30 g N m -2 a -1  + 20 g P m -2 a -1 ), respectively. The results showed that H 2 O-Pi, NaHCO 3 -Pi, Residual Pi, SOC were highest retained in larger soil aggregates (>5 mm) and decreased with the decreasing aggregate size, while other variables, i.e., NaOH-Pi, NaHCO 3 -Po, pH and T-N were not affected in aggregate size. H 2 O-Pi (48 ppm), NaHCO 3 -Pi (68 ppm), NaHCO 3 -Po (80 ppm), NaOH-Po (623 ppm), HCL-Po (67 ppm), SOC (20.36 ± 1.6) was estimated in medium fertilizer treatment. PCA analysis showed that spread/variance of data points on F1 (62.90%) is more than spread/variance of data points on F2 (57.74%) in NKPF and KPP, respectively, while correlation matrix showed high correlation between H 2 O-Pi and NaOH-Pi (0.63) and H 2 O-Pi and NaHCO 3 -Pi (0.63) while a strong negative correlation was present between Res-Pi and Po (-0.61). Moreover, litter inputs increased the organic-P fractions in soil particularly at medium treatment., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

Phytate ( myo -inositol hexakisphosphate salts) can constitute a large fraction of the organic P in soils. As a more recalcitrant form of soil organic P, up to 51 million metric tons of phytate accumulate in soils annually, corresponding to ∼65% of the P fertilizer application. However, the availability of phytate is limited due to its strong binding to soils via its highly-phosphorylated inositol structure, with sorption capacity being ∼4 times that of orthophosphate in soils. Phosphorus (P) is one of the most limiting macronutrients for agricultural productivity. Given that phosphate rock is a finite resource, coupled with the increasing difficulty in its extraction and geopolitical fragility in supply, it is anticipated that both economic and environmental costs of P fertilizer will greatly increase. Therefore, optimizing the use of soil phytate-P can potentially enhance the economic and environmental sustainability of agriculture production. To increase phytate-P availability in the rhizosphere, plants and microbes have developed strategies to improve phytate solubility and mineralization by secreting mobilizing agents including organic acids and hydrolyzing enzymes including various phytases. Though we have some understanding of phytate availability and phytase activity in soils, the limiting steps for phytate-P acquisition by plants proposed two decades ago remain elusive. Besides, the relative contribution of plant- and microbe-derived phytases, including those from mycorrhizas, in improving phytate-P utilization is poorly understood. Hence, it is important to understand the processes that influence phytate-P acquisition by plants, thereby developing effective molecular biotechnologies to enhance the dynamics of phytate in soil. However, from a practical view, phytate-P acquisition by plants competes with soil P fixation, so the ability of plants to access stable phytate must be evaluated from both a plant and soil perspective. Here, we summarize information on phytate availability in soils and phytate-P acquisition by plants. In addition, agronomic approaches and biotechnological strategies to improve soil phytate-P utilization by plants are discussed, and questions that need further investigation are raised. The information helps to better improve phytate-P utilization by plants, thereby reducing P resource inputs and pollution risks to the wider environment.