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Liming and manuring to ameliorate soil acidity and enhance mineralization in acid tropical soils could promote their agronomic productivity. Synthetic lime and poultry-droppings manure’s effects in sandy-loam Ultisols were evaluated on soybean growth, exploring its relationships with soil pH, soil available P and plant P content. Lime was applied at 0, 2.5 and 5 t ha–1 equivalents and manure at 0, 25 and 50 t ha–1 equivalents to 2.5-kg potted soils. Crop growth was monitored, and soil-plant analysis done during and after six weeks of growth, respectively. Treatment had more pronounced effects on plant height than leafiness of the soybean plants, being generally highest in lime2.5+manure50 where the plants were about three times taller compared to unamended control. Soybean plants grew better due to 2.5 than 0 and 5 t ha–1 lime and to 50 than 0 and 25 t ha–1 manure. Plant height and leaf area depended on soil pH’s influence on soil available P (R2 = 0.69**) and plant P content (R2 = 0.85**), respectively; above-soil biomass depended on soil pH or plant height (R2 = 0.74**). Moderate liming (2.5 t ha–1) with ample manuring (50 t ha–1) could enhance crop early-stage vegetative growth in low-fertility tropical soils, due largely to amelioration of soil acidity to enhance plant uptake of bioavailable P.

Phosphorus (P) fertilizer is a significant cost in crop production. Understanding the mechanisms behind P fertilizer–soil–crop interactions can enhance phosphorus use efficiency (PUE) and increasing yield. We conducted a rice cultivation bucket experiment in red soil (pH = 5.9) and lime concretion black soil (pH = 7.8) and applied single superphosphate (SSP), calcium magnesium phosphate (CMP), diammonium phosphate (DAP), triple superphosphate (TSP), ammonium polyphosphate (APP), and a control group (CK, no P fertilizer). We analyzed rice P uptake and utilization patterns, evaluated the impact of varying P fertilizer formulations on rice root morphology, yield, and PUE, and investigated changes in soil P pools. In red soil, the APP treatment produced the greatest total root length, rice yield, PUE and increased soil Olsen-P, NaHCO3-Pi at anthesis. In lime concretion black soil, the TSP and APP treatments had the highest rice yields and increased Olsen-P, H2O-P, NaHCO3-Pi at anthesis. Moreover, the TSP treatment had the greatest total root length and root surface area at anthesis and the APP treatment had the largest PUE. Random forest regression analysis revealed that residual-P and Olsen-P significantly impacted rice yield in red soil and lime concretion black soil, respectively. We recommend using APP in red soil and TSP and APP in lime concretion black soil for rice cultivation to optimize soil P pool characteristics and root morphology for nutrient uptake, ultimately leading to the highest yields and PUE.

Phosphorus (P) fertilizer is a significant cost in crop production. Understanding the mechanisms behind P fertilizer–soil–crop interactions can enhance phosphorus use efficiency (PUE) and increasing yield. We conducted a rice cultivation bucket experiment in red soil (pH = 5.9) and lime concretion black soil (pH = 7.8) and applied single superphosphate (SSP), calcium magnesium phosphate (CMP), diammonium phosphate (DAP), triple superphosphate (TSP), ammonium polyphosphate (APP), and a control group (CK, no P fertilizer). We analyzed rice P uptake and utilization patterns, evaluated the impact of varying P fertilizer formulations on rice root morphology, yield, and PUE, and investigated changes in soil P pools. In red soil, the APP treatment produced the greatest total root length, rice yield, PUE and increased soil Olsen-P, NaHCO 3 -Pi at anthesis. In lime concretion black soil, the TSP and APP treatments had the highest rice yields and increased Olsen-P, H 2 O-P, NaHCO 3 -Pi at anthesis. Moreover, the TSP treatment had the greatest total root length and root surface area at anthesis and the APP treatment had the largest PUE. Random forest regression analysis revealed that residual-P and Olsen-P significantly impacted rice yield in red soil and lime concretion black soil, respectively. We recommend using APP in red soil and TSP and APP in lime concretion black soil for rice cultivation to optimize soil P pool characteristics and root morphology for nutrient uptake, ultimately leading to the highest yields and PUE. [ABSTRACT FROM AUTHOR]

This study focused on alfalfa (Medicago sativa) to investigate the effect of partial root-zone drying irrigation (PRDI) on N-fixing crops available soil P. A three-year field experiment was designed with two irrigation methods and four irrigation volumes. Two irrigation methods consisted of PRDI and conventional furrow irrigation (CFI), and four irrigation volumes were set as 70% ETc (alfalfa water requirement), 85% ETc, 100% ETc and 115% ETc. This study showed that the PRDI had no effect on alfalfa seasonal forage yield but increased alfalfa P uptake. The PRDI decreased the soil available P content and stock but had no effect on the total P content and stock, which demonstrates that effect of PRDI on crop available soil P was different when different P forms were used to estimate crop available soil P. This study also showed that the variation in the coefficient was below 3% between soil P (available or total P) contents and soil P stocks, indicating that soil P contents and stocks were similar when estimating alfalfa available soil P under PRDI conditions. The findings of this study present a pattern of estimating the N-fixing crops available soil P in relation to PRDI. [ABSTRACT FROM AUTHOR]

Irrational phosphorus (P) nutrient management practices often fail to match of P fertilizer type, soil P transformation and crop P demand, lead to increased accumulation of legacy P, reduced PUE, and pollution, affecting crop production. A pot experiment incorporating soil types and P fertilizer types (SSP, simple superphosphate; CMP, calcium magnesium phosphate; DAP, diammonium phosphate; TSP, triple superphosphate; APP, ammonium polyphosphate; CK, no P application) to establish coupling of the soil and P fertilizer types, soil P pool characteristics, crop P uptake. In calcareous soil, the available P concentrations in rhizosphere soil were higher under TSP and DAP, with the increase in NaHCO3-Pi concentration the most. In non-calcareous soil, the NaHCO3-Pi and NaOH-Pi increased the most under SSP, DAP, and TSP at anthesis. Shoot P accumulation at maturity was highest under TSP and APP, TSP and DAP, respectively, in the two soil. TSP and APP significantly increased yield and PUE in the calcareous soil, while TSP and DAP performed better in the non-calcareous soil. NaHCO3-Pi and NaOH-Po are potentially available P sources in calcareous and non-calcareous soil, which remarkably affect shoot P uptake through H2O-P. Comprehensive assessment of the relationship between soil P pool characteristics, yield and PUE, TSP and APP are recommended for application in calcareous soils and TSP and DAP for application in non-calcareous soils in wheat cropping systems. [ABSTRACT FROM AUTHOR]

The responses of soil P availability and cotton growth to biochar addition under different P supply levels are not well documented. Thus, a pot experiment was conducted to investigate the effects of biochar addition on soil nutrient status, microbial characteristics related to P cycling and cotton growth with or without adequate P supply. Biochar was added to soil grown cotton at three rates of 0, 3 and 30 t ha−1 under two P fertilizer levels of 0 and 150 kg P2O5 ha−1, respectively. Results showed that biochar addition had significantly positive effects on soil P availability, phosphate solubilizing bacteria number, phosphatase activities (except acid phosphatase activity), cotton nutrients uptake and seedcotton yield, regardless of P fertilization level. The magnitude of soil available P content increase after biochar addition with P fertilizer was greater than without P fertilizer. And 3 t ha−1 biochar was better than 30 t ha−1 biochar for converting soil P into available P. Under a given P fertilizer level, biochar addition had fertilizer-like diminishing effect on seedcotton yield. Conclusively, the co-application of P fertilizer and the appropriate amount of biochar could be beneficial for soil P availability in cotton production. [ABSTRACT FROM AUTHOR]

Managing soil phosphorus (P) in agroecosystems with high P levels is crucial to mitigate P loss in water sources without compromising yields. The objective of this study was to assess maize silage (Zea mays L.) + interseeding cover crop of annual ryegrass (Lolium multiforum) or using a relay cover crop and starter P (P0, P10, and P20) on (i) P leaching, (ii) changes in soil P status, and (iii) maize yield, cover crop biomass and P uptake. A six-year study was conducted between 2018 and 2023 in two sites. Leachate samples were collected every two weeks between 2021and 2023. The concentration of P in leachate exceeded 0.5 mg L–1 indicating a high risk of P leaching at the current levels of soil P. High concentration of P in leachate with a peak at 0.9 mg L–1 in August and 1.45 mg L–1 in October during 2021 and 2022 was pronounced under interseeded compared to relay cover crop system due to improve water infiltration contributing to the downward movement of P. In contrast, the concentration of P in leachate was high under relay cover crops in February and March particularly in 2023, which could be attributed to the delay in cover crops establishment and growth in early spring. The concentration of P extracted using anion exchange membranes (PO 4AEMs) increased with increasing starter P rate during the first weeks after planting maize silage. There were spikes of PO 4AEMs , reaching 1.18 and 1.73 µg cm–2 d–1 during the 4th, 7th, and 8th weeks after planting maize which coincided with high soil moisture content occurring after irrigation or rainfall events. The lack of dry matter yield response to starter P at harvest was due to high initial soil P. The soil P status remained significantly high averaging 196.6 mg kg–1 as Mehlich-3 P, despite negative cumulative P budgets. A close observation of the relationships among soil P indicators shows a trend of rapidly decreasing water extractable P under interseeding compared with relay cover crops. It is possible that the production of high biomass under interseeding cover crops increased the amount of P taken up from the soil. We conclude that interseeding cover crops within cash crops in high P soils could be effective at decreasing soil P, but could enhance P leached in the first years of cropping due to high water infiltration along the soil profile. • P leached was assessed in high-P soils in maize-interseeding cover crop systems. • P in leachate > 0.5 mg L–1 across cropping systems and sampling periods. • Maize dry matter yield was not affected by P fertilizer due to high initial soil P. • Soil P remained high at 196.6 mg kg–1 after six years despite negative P budgets. • High risk of P leached at the levels of soil P in the study sites. [ABSTRACT FROM AUTHOR]

Irrational phosphorus (P) nutrient management practices often fail to match of P fertilizer type, soil P transformation and crop P demand, lead to increased accumulation of legacy P, reduced PUE, and pollution, affecting crop production. A pot experiment incorporating soil types and P fertilizer types (SSP, simple superphosphate; CMP, calcium magnesium phosphate; DAP, diammonium phosphate; TSP, triple superphosphate; APP, ammonium polyphosphate; CK, no P application) to establish coupling of the soil and P fertilizer types, soil P pool characteristics, crop P uptake. In calcareous soil, the available P concentrations in rhizosphere soil were higher under TSP and DAP, with the increase in NaHCO3-Pi concentration the most. In non-calcareous soil, the NaHCO3-Pi and NaOH-Pi increased the most under SSP, DAP, and TSP at anthesis. Shoot P accumulation at maturity was highest under TSP and APP, TSP and DAP, respectively, in the two soil. TSP and APP significantly increased yield and PUE in the calcareous soil, while TSP and DAP performed better in the non-calcareous soil. NaHCO3-Pi and NaOH-Po are potentially available P sources in calcareous and non-calcareous soil, which remarkably affect shoot P uptake through H2O-P. Comprehensive assessment of the relationship between soil P pool characteristics, yield and PUE, TSP and APP are recommended for application in calcareous soils and TSP and DAP for application in non-calcareous soils in wheat cropping systems.

Soil microbiomes play important roles in both transformation and utilization of phosphorus (P) in agroecosystems. By targeting at 18S rRNA, pqqC, and phoD genes, respectively, the community compositions of soil arbuscular mycorrhizal (AM) fungi and inorganic P‐solubilizing and organic P‐mineralizing prokaryotes were investigated across fields with annual crops or vegetables and orchards with peach trees or tea bushes in a common Agri‐technology Park, representing four typical agricultural land‐use types in Eastern China. Both annual crop and vegetable fields exhibited higher soil fertility and phosphatase activity, while both peach tree and tea bush orchards contained greater abundances of AM fungal and pqqC genes. Land‐use type also significantly affected the community compositions of soil AM fungi, and pqqC‐ and phoD‐harboring prokaryotes, with soil available P as the common driver for all functional groups above. Three main ecological clusters (modules) with distinctive interactive features, that is, synergistic, competitive, and inactive were observed in the co‐occurrence network comprised of the three groups involved in P‐cycling. The modules exhibited various distributions among the four land‐use types, and the correlations with soil pH, available P and K, and N:P were shown. Altogether, the results demonstrated the changes in gene abundances, diversity indices, community compositions, and interrelationships of functional groups involved in P‐cycling in response to distinct land‐use types, and highlighting the synergistic potential among groups to alleviate P deficiency. [ABSTRACT FROM AUTHOR]

Abstract Soil microbiomes play important roles in both transformation and utilization of phosphorus (P) in agroecosystems. By targeting at 18S rRNA, pqqC, and phoD genes, respectively, the community compositions of soil arbuscular mycorrhizal (AM) fungi and inorganic P‐solubilizing and organic P‐mineralizing prokaryotes were investigated across fields with annual crops or vegetables and orchards with peach trees or tea bushes in a common Agri‐technology Park, representing four typical agricultural land‐use types in Eastern China. Both annual crop and vegetable fields exhibited higher soil fertility and phosphatase activity, while both peach tree and tea bush orchards contained greater abundances of AM fungal and pqqC genes. Land‐use type also significantly affected the community compositions of soil AM fungi, and pqqC‐ and phoD‐harboring prokaryotes, with soil available P as the common driver for all functional groups above. Three main ecological clusters (modules) with distinctive interactive features, that is, synergistic, competitive, and inactive were observed in the co‐occurrence network comprised of the three groups involved in P‐cycling. The modules exhibited various distributions among the four land‐use types, and the correlations with soil pH, available P and K, and N:P were shown. Altogether, the results demonstrated the changes in gene abundances, diversity indices, community compositions, and interrelationships of functional groups involved in P‐cycling in response to distinct land‐use types, and highlighting the synergistic potential among groups to alleviate P deficiency.

Nanoscale zero-valent iron (nZVI) shows an excellent degradation effect on chlorinated contaminants in soil, but poses a threat to plants in combination with phytoremediation. Arbuscular mycorrhizal (AM) fungus can reduce the phyototoxicity of nZVI, but their combined impacts on polychlorinated biphenyls (PCBs) degradation and plant growth remain unclear. Here, a greenhouse pot experiment was conducted to investigate the influences of nZVI and/or Funneliformis caledonium on soil PCB degradation and ryegrass (Lolium perenne L.) antioxidative responses. The amendment of nZVI significantly reduced not only the total and homolog concentrations of PCBs in the soil, but also the ryegrass biomass as well as soil available P and root P concentrations. Moreover, nZVI significantly decreased leaf superoxide disutase (SOD) activity, while tended to decrease the protein content. In contrast, the additional inoculation of F. caledonium significantly increased leaf SOD activity and protein content, while tended to increase the catalase activity and tended to decrease the malondialdehyde content. The additional inoculation of F. caledonium also significantly increased soil alkaline phosphatase activity, and tended to increase root P concentration, but had no significantly effects on soil available P concentration, the biomass and P acquisition of ryegrass, which could be attributed to the fixation of soil available nutrients by nZVI. Additionally, F. caledonium facilitated PCB degradation in the nZVI-applied soil. Thus, AM fungus can alleviate the nZVI-induced phytotoxicity, showing great application potentials in accompany with nZVI for soil remediation.

Purpose: Both earthworm (Eisenia fetida L.) and phosphorus (P)-releasing (PR) bacteria, including organic P-mineralizing (OPM) and inorganic P-solubilizing (IPS), are able to convert difficult-to-use P into phytoavailable P. However, there is a undesirable gap between soil P mobilization and root P acquisition when mycorrhization is enhanced. The aim of this study was to investigate the combined effects of earthworm and PR bacteria on soil P mobilization, mycorrhizal colonization, and P acquisition of maize (Zea mays L.). Materials and methods: This study consisted of three parallel experiments. Firstly, a 90-day microcosm experiment was carried out to test the diversified effects of earthworm, OPM bacterium Bacillus megaterium, and IPS bacterium Kluyvera intermedia, on available P concentration in an autoclaved soil with or without P amendment. Secondly, a 16-week greenhouse pot experiment was conducted to compare the differential effects of earthworm, B. megaterium, and K. intermedia on P mobilization, mycorrhizal colonization, and P acquisition of maize in the same autoclaved soil receiving chemical fertilizers and Funneliformis caledonium. Thirdly, a microplot experiment was established to verify the combined effects of earthworm and PR bacteria on P mobilization and mycorrhizal P acquisition of maize in a field where the soil used in the former two experiments were collected. Results and discussion: In the microcosm experiment, earthworm significantly increased soil available P concentration coupled of declined soil pH regardless of P amendment, while B. megaterium and K. intermedia further enhanced P mobilization in P-fertilized soils. In the greenhouse experiment, PR bacteria and earthworm co-increased mycorrhizal colonization and plant biomass, as well as soil alkaline phosphatase (ALP) activity and available P concentration compared to the control, and individual P acquisition compared to the single inoculation treatments. In the field experiment, both PR bacteria and earthworm significantly increased mycorrhizal colonization and tended to increase soil ALP activity, available P concentration, root biomass, and individual P acquisition, while the combined inoculation significantly increased ALP activity and available P concentration, and thereby individual P acquisition by 29% relative to the control. Conclusions: Combined inoculation of PR bacteria and earthworm greatly increased soil available P concentration and maize P acquisition and grain yield. Although the combined inoculation had a lower root mycorrhizal colonization than the single inoculation treatments due to the greatly increased amounts of readily soluble P, it had a higher mycorrhization level than the control. These observations suggest that the combined application could enhance soil P mobilization and be expropriated to elaborate indigenous mycorrhizal fungal function. [ABSTRACT FROM AUTHOR]

Purpose: Phytophthora blight caused by Phytophthora capsici (Pc) is one of the most economically destructive soilborne diseases of pepper (Capsicum annum L.) on a global scale. Biocontrol using antagonistic microbes, such as Purpureocillium lilacinum (Pl) and arbuscular mycorrhizal (AM) fungus Funneliformis caledonium (Fc), is one of the significant strategies for ecologically sound plant disease management. The purpose of this work was to investigate the sole and combined suppression of pepper Phytophthora blight by Fc and Pl. Materials and methods: The 14-week pot experiment with three pepper plants per pot included five treatments: control (non-inoculation), inoculation with Pc, inoculation with Pc and Pl (Pc + Pl), inoculation with Pc and Fc (Pc + Fc), and inoculation with Pc, Pl, and Fc (Pc + Pl + Fc). Pots were randomly arranged with eight replicates per treatment. The incidence and severity of Phytophthora blight at plant full productive stage were recorded. The biomasses and N, P, and K concentrations of pepper shoots, roots, and fruits were all measured. In addition, root mycorrhizal colonization rate and soil pH, phosphatase activity, and available P concentration were also tested. Results and discussion: The inoculation of Pc induced both high incidence (92%) and severity (33%) of pepper Phytophthora blight, and the alleviating effects of Pl, Fc, and Pl + Fc were 46%, 79%, and 59%, respectively. The Fc significantly increased (P < 0.05) root mycorrhizal colonization, nutrient (N, P, and K) acquisition, plant biomass, and fruit yield of pepper, while Pl only significantly increased (P < 0.05) plant nutrient (N and P) acquisition and tended to increase the fruit yield. The Pc, Pl, and Fc all had additive effects on decreasing soil pH, but only Fc significantly increased (P < 0.05) soil phosphatase activity and available P concentration, contributing partly to the elevated P acquisition as well as the increased P concentrations in both shoot and root. Conclusions: Compared with the sole inoculation of Fc, the extra inoculation of Pl had negative effects on mycorrhizal colonization, soil P mobilization, and plant growth and nutrient acquisition. It suggests that AM fungus (Fc) has the superiority of formatting symbioses with plant roots and enhancing soil P mobilization for the suppression of pepper Phytophthora blight compared with Pl, and the joint application of different fungal agents to improve plant health needs careful consideration. [ABSTRACT FROM AUTHOR]

Phosphorus (P) availability generally limits crop productivity in agroecosystems and is closely linked to soil organic P mineralization by phosphatases secreted by plant roots and soil microbes. Intercropping is a sustainable alternative for efficiently improving crop productivity. However, the response of soil phosphatase activity to intercropping and the variations in this response with agronomic and climate/soil conditions remain unclear. This meta-analysis of 120 studies across agroecosystems shows that intercropping significantly improves soil phosphatase activity, plant total P uptake and yield by 18 %, 8 % and 8 %, respectively, implying that intercropping can alleviate P limits on crop productivity. The positive effect of intercropping with legumes and woody plants on soil phosphatase activity is greater than that of intercropping with gramineous plants and forbs. However, both inorganic and organic P fertilizer application reduces the positive effect of intercropping on soil phosphatase activity, particularly under intercropping with legumes. The promotion of soil phosphatase activity by intercropping is weaker in arid areas where mean annual precipitation is lower than 600 mm. The positive correlations of soil phosphatase activity with both plant total P uptake and yield further emphasize the importance of high organic P mineralization for plant growth in intercropping systems. Overall, our results indicate that the effect of intercropping on soil phosphatase activity is influenced by intercropping type, application of P fertilizers, microbial biomass and climatic factors, and this meta-analysis provides a theoretical reference for choosing suitable intercropping systems to achieve yield increase and sustainable development. • Intercropping with legumes and woody plants had higher increase on phosphatase. • P fertilizer reduces the positive effect of intercropping on soil phosphatase. • The promotion of soil phosphatase by intercropping is weaker in arid areas. • Plant total P uptake and yield increased with the increase of phosphatase. • Intercropping type, fertilization and MB were the main factors affecting phosphatase. [ABSTRACT FROM AUTHOR]

Purpose: Intercropping of chili pepper (Capsicum annuum L.) with corn (Zea mays L.) is one of the main valuable intercropping patterns. However, the potential contribution of arbuscular mycorrhizal (AM) fungal hyphal networks is still poorly understood. The purpose of this work was to resolve the changes of AM fungal propagation and colonization in the pepper/corn intercropping systems due to the constitution of hyphal networks and the networks' effects on plant nutrient uptake and interspecific competitive relations. Materials and methods: An 18-week pot experiment on an unsterilized soil was carried out to test mycorrhizal performance and P acquisition of chili pepper and sweet corn (Zea mays L. var. rugosa Bonaf.) in two compartments, which were absolutely separated (Sep) by polyvinyl chloride (PVC) layer or semi-separated (Semi-Sep) by nylon mesh (30 μm) screen that only allows the passage of AM fungal hyphae but not plant roots. Root mycorrhizal colonization rates and the biomasses and P concentrations of shoots, roots, and fruits of pepper and corn were all measured. The total P acquisition of each crop per pot and the acquisition ratio of one to two crops were assessed. Soil pH, organic C, total P, available P, AM fungal abundance, and acid phosphatase activity were also tested. Results and discussion: In the Sep system, root mycorrhizal colonization, P acquisition amount, shoot biomass, and rhizosphere AM fungal abundance of corn were all higher (P < 0.05) than those of pepper, but soil available P concentration was lower (P < 0.05) in corn compartment than in pepper one. Compared with Sep, Semi-Sep had higher (P < 0.05) mycorrhizal colonization rates with both intercrops and higher (P < 0.05) soil acid phosphatase activity and AM fungal abundance in corn and pepper compartments, respectively. Semi-Sep decreased (P < 0.05) soil available P concentrations with both compartments, but did not narrow the difference of soil available P concentration between compartments, suggesting there was no gradient diffusion of soil available P between compartments. Semi-Sep increased (P < 0.05) the P acquisition ratio and fruit yield of pepper, but not corn. Conclusions: Constitution of hyphal networks increased mycorrhizal colonization with both intercrops, and corn supplied part of photosynthetic C for increasing AM fungal propagules in pepper compartment by gradient expansion since AM fungi formed better symbioses with corn. Hyphal networks increased pepper fruit yield via improving P distribution to pepper, but acquired relatively higher P from corn compartment via elevating the soil acid phosphatase activity, suggesting enhanced P competitive ability of pepper against corn upon hyphal networks. [ABSTRACT FROM AUTHOR]

Crop rotation and soil management can promote expressive changes in accumulated (legacy) soil phosphorus (P) lability since cover crops can cycle more P into plant tissue, and have a beneficial effect on the subsequent cash crop. This study aimed to understand the P dynamics in soil under different P sources and cover crops over six consecutive cropped years, and also to track how changes over time can achieve more efficient use of soil P in a high P-fixing soil from south Brazil. It was used five cover crops (common vetch, white lupin, fodder radish, ryegrass, and black oat) plus fallow in winter, meanwhile the summer crops were treated with soluble P fertilizer (SSP- single superphosphate) or rock phosphate (RP) every year from 2009 to 2014, under a no-tillage system. Soil samples were taken after six years of cultivation (2014) and analyzed for P fractionation by the Hedley procedure. Next the results were compared to the results previously obtained at the beginning of this period (2009), and after the third summer cycle (2011). Cover crops affected P cycling under phosphate fertilizer when SSP was used and all cover crops were able to utilize more moderately labile (mod-labile) P and enhance the proportion of labile P fractions in the soil. In general, white lupin was the cover crop most effective in retaining the most P available for the subsequent crop in the soil and may be considered a P-mobilizing species, regardless of the source of the applied P. Rock phosphate promoted the highest proportion of inorganic P accumulated in the soil while the lowest one was recorded under SSP. Organic P fractions were depleted over the period, either with or without fertilizer, being the main source of plant extractable P in non-fertilized conditions over the period. [ABSTRACT FROM AUTHOR]

Soil Phosphorous (P) availability is a limiting factor for plant growth and regulates biological metabolism in plantation ecosystems. The effect of variations in soil microbial P cycling potential on the availability of soil P during succession in plantation ecosystems is unclear. In this study, a metagenomics approach was used to explore variations in the composition and diversity of microbial P genes along a 45-year recovery sequence of Robinia pseudoacacia on the Loess Plateau, as well soil properties were measured. Our results showed that the diversity of P cycling genes (inorganic P solubilization and organic P mineralization genes) increased significantly after afforestation, and the community composition showed clear differences. The gcd and ppx genes were dominant in inorganic P transformation, whereas phnM gene dominated the transformation of organic P. The abundance of genes involved in inorganic P solubilization and organic P mineralization was significantly positively correlated with P availability, particularly for phnM , gcd , ppx , and phnI genes, corresponding to the phyla Gemmatimonadetes, Acidobacteria, Bacteroidetes , and Planctomycetes. The critical drivers of the microbial main genes of soil P cycling were available P (AP) and total N (TN) in soil. Overall, these findings highlight afforestation-induced increases in microbial P cycling genes enhanced soil P availability. and help to better understand how microbial growth metabolism caused by vegetation restoration in ecologically fragile areas affects the soil P cycling. • The diversity of microbes with P cycling genes increased by afforestation. • PhnM , gcd , ppx , and phnl genes dominated the increase of soil P availability. • The key drivers of the microbial main genes of soil P cycling were AP and TN. [ABSTRACT FROM AUTHOR]

Winter wheat (Triticum aestivum L.) production in northwestern China as a monoculture is hampered by unfertile soil and drought. With the fast-developing Chinese chemical fertilizer industry, many farmers now use more nitrogen (N) fertilizer as topdressing for winter wheat in early spring, in addition to a basal dose of N fertilizer applied in the previous autumn at seeding time. The objective of this study was to evaluate the increase in grain yield of dryland winter wheat by early spring N fertilizer topdressing, and its relationship to soil moisture, available N, phosphorus (P) and potassium (K). Field experiments with no N fertilizer topdressing (Fb) and N fertilizer topdressing (Fb+t) treatments were carried out over two growing seasons at 54 site-years to assess the relationship between increase in winter wheat grain yield by early spring N fertilizer topdressing and soil moisture, available N, P and K in Changwu county, Shaanxi province, China. Compared to Fbtreatment, the Fb+ttreatment produced grain yields lower at 10 site-years, and increased by <10% at 21 site-years and by >10% at 23 site-years. The results indicated that topdressing N fertilizer could increase wheat grain yield when soil nitrate-N accumulation in the 0–20, 20–40 and 40–60 cm depths was less than 121.7, 36.4 and 24.1 kg N ha−1, and soil moisture content in the 40–60, 60–80 and 80–100 cm depths was more than 15.7%, 16.7% and 16.9%, respectively. The findings also suggested that it is not necessary to analyze soil for ammonium-N, available P and K before topdressing N fertilizer. It is necessary to analyze 0–60 cm soil profile for nitrate-N and 40–100 cm depth for soil moisture before topdressing N fertilizer for winter wheat in dryland areas of northwestern China. [ABSTRACT FROM AUTHOR]

Zeolite can increase fertilizer use efficiency in rice production. Zeolite's positive effect on nitrogen (N) and phosphorus (P) utilization has been validated in lowland paddy fields, but little information is available on its effect on P accumulation, translocation, and partitioning in lowland rice, especially under water stress. We conducted a two-year field experiment to evaluate the effect of zeolite and irrigations on soil P availability, dry matter accumulation, and P accumulation, partitioning, and translocation. Regardless of irrigation, zeolite application accumulated greater dry matter (DM) across growth stages than the non-zeolite control (Z 0). A zeolite application rate of 10 t ha−1 (Z 10) increased soil available P, plant P accumulation, stem and leaf P translocation, and panicle P partitioning across growth stages compared to Z 0. Z 10 increased grain yield, water use efficiency (WUE), and economic benefit by 21.4%, 35.5%, and 20.9%, respectively, compared to Z 0. For the irrigation treatments, alternate wetting and drying irrigation (AWD) increased DM and shoot P accumulation at all stages (except DM at tillering and shoot P accumulation at tillering and yellow ripening) relative to continuous flooding (CF). AWD produced similar grain yields but higher WUE than CF. Significant correlations between grain yield, shoot P accumulation, and soil available P indicated that zeolite enhanced grain yield by improving soil P availability and plant P uptake. These results showed that 10 t ha−1 zeolite combined with AWD irrigation achieved the highest soil available P, plant P accumulation, grain yield, WUE, and economic benefit, and could be an alternative management option for improving fertilizer P utilization, increasing rice production, and enhancing farmer profits in water-deficient regions. • Zeolite application increased soil P availability and plant P accumulation. • Zeolite application (10 t ha−1) increased P translocation in stems and leaves and P partitioning in panicles. • Grain yield positively correlated with shoot P accumulation and soil P availability. • Zeolite application (10 t ha−1) combined with AWD achieved the highest grain yield, WUE, and economic benefit. [ABSTRACT FROM AUTHOR]

The return of crop residues to the soil is a common agricultural management practice for nutrient recycling and carbon sequestration. It is known that nitrogen (N) fertilization can influence crop residue decomposition and nutrient release. However, it is unclear whether the effect of N fertilization interact with plastic film mulching (PFM) or residue type. We conducted a two-year field study to quantify the main and interactive effects among N fertilization (including no input (N 0), 135 kg N ha−1 yr−1 (N 135), and 270 kg N ha−1 yr−1 (N 270)), PFM (with and without mulching) and residue type (roots, stems, and leaves) on the decomposition and nutrient releases of crop residues in a long-term field experiment with combined mulching and fertilization treatments. We did not observe any interactive effects among N fertilization, plastic film mulching and residue type on crop residue decomposition and nutrient releases. Crop residue decomposition was delayed at N 135 but remained unchanged at N 270 when compared to N 0. The positive correlation between decomposition and soil available phosphorus (P) suggest that soil P status played an important role for crop residue decomposition. The two levels of N fertilization both slowed down N release from crop residues, but did not change P release. PFM accelerated crop residue decomposition by 10% in the first growing season but did not affect the release of N and P. Decomposition and N release rates were higher for leaves than for roots and stems. Overall, this study highlights the independent effects of cropland management on the fate of crop residue returned to soil. • Decomposition was retarded by low N addition but unchanged under high N input. • Lower P status explained the retarded decomposition at low N level. • N fertilization decreased N release but did not change P release. • Plastic film mulching (PFM) enhanced residue decomposition by 10%. • No interactive effects on residue decomposition between N fertilization and PFM. [ABSTRACT FROM AUTHOR]

Field-scale variation of soil phosphorus (P) information is very important for P fertilizer application and its soil sampling design in grassland. A total of 108 soil samples were collected from a long-term (41 years) grazed grassland P experiment field at Teagasc, Johnstown Castle, Wexford, Ireland, in March 2009. There were six P treatments (P0-0, P0-30, P15-15, P15-5, P30-30, and P30-0) since 1968, with changes since 1999. Each treatment had 6 replicate plots (a total of 36 plots, 3 soil samples per plot). The samples were analyzed for available (Morgan’s) P, potassium (K), magnesium (Mg), lime requirement (LR), and pH. The highest mean available P concentration was found in the P30-30 (30 kg P ha−1pre- and post-1998) plots, and the lowest mean available P concentration was found in the P0-0 (no P fertilizer since 1968) plots. Significant differences of mean P, Mg, LR, and pH values in different treatments were observed. There was a positive proportional effect for both the 36 plots and the 6 treatments for the P data: the local standard deviation increased with the increase of local mean. The proportional effect should be considered in order to optimize sampling design. Fewer samples can reflect soil P status in fields with low soil P levels, while more attention should be paid to the fields with high P levels in order to reduce environmental consequences of uniform applications. [ABSTRACT FROM PUBLISHER]

Abstract: Soil samples collected from a long-term (19-year) experimental field with seven treatments were analyzed for fatty acids methyl esters (FAMEs) to determine fertilization regime effects on microbial community structure in sandy loam soils. The amounts of FAMEs in bacteria, actinomycetes, and fungi were highest with the two organic manure (OM)-fertilized treatments (OM and 1/2 OMN – half OM plus half mineral fertilizer), lowest with the NK treatment, and fell in the middle levels with three mineral P-fertilized treatments (NPK, NP and PK) and the control with no fertilizer (CK), with the exception of fungi which showed no significant difference among the five treatments without OM fertilization. Principal component analysis of FAME patterns indicated that NPK was not significantly different from CK, but the two manure-containing treatments and the P-deficiency treatment (NK) were significantly different from CK and NPK. Redundancy analysis plot showed that FAME amounts significantly correlated to soil organic C and total N contents, while soil available P and total P contents, which were greatly decreased by the NK treatment, also had positive and substantial effects on soil microbial FAMEs. The results demonstrated the importance of P fertilization as well as organic manure in maintaining soil microbial biomass and impacting community structure. [Copyright &y& Elsevier]

High rates of soil depletion, food insecurity, and poverty are widespread in western Kenya, which calls for urgent and affordable solutions. A field experiment was carried out during 2003 short rains and 2004 long rains in western Kenya to study the effectiveness of “PREP-PAC” on soil properties, maize (Zea mays L.), and legume yields of six maize–legume intercrops. The experiment was conducted in a randomized complete block design, with four replications and two levels of fertility (no fertilizer and PREP-PAC). The maize variety, cv ‘KSTP’ (94), was intercropped with six legume types, namely: Bambaranuts (Vigna subterranean L., Var. Dark brown), Soybean (Glycine max L., Var. TGX 14482E), Yellow grams (Vigna radiate L., local type), Groundnuts (Arachis hypogaea L., Var. Uganda red stripped), Beans (Phaseolus vulgaris L., Var. KK15), and Cowpeas (Vigna unguiculata L., Var. white type). The farm was characterized by low pH of 5.35, low soil available phosphorus (P) below the critical value of 10 mg P/kg, and generally low exchangeable cations. Results indicated a significant (P < 0.05) increase in soil pH, soil available P (P < 0.0001), maize and legume yields (P < 0.0001) throughout the cropping seasons. Intercrops with bambaranuts, beans, and groundnuts produced better legume yields compared to the rest of the legumes. Therefore, the authors of this study concluded that, PREP-PAC is effective with elevated N input (60 kg N ha−1) on restoring soil fertility and improving farm productivity in western Kenya. However, availability and accessibility of PREP-PAC in local markets needs to be improved. [ABSTRACT FROM PUBLISHER]

The heavy use of organophosphorus pesticides in northeastern China strongly affects the ecological functions and the quality of the soil environment. In this work, a 30-day soil incubation experiment was conducted to evaluate the potential of using soil available P and the activities of soil dehydrogenase and acid phosphatase as indicators of the application of methamidophos and glyphosate. Two kinds of unpolluted soils, phaiozem and burozem, were selected as the test soils. The higher application rate of organophosphorus pesticide to the two soils caused more release of PO4 3− which finally entered the soil available P pool, suggesting that soil available P is one of the effective chemical markers for biodegradation of organophosphorus pesticides. Methamidophos exhibited a significant inhibitory effect on the activity of soil dehydrogenase. The extent of enzyme inhibition was almost positively correlated with the insecticide concentration, and the enzyme activity was gradually restored after day 15. However, its effect on soil acid phosphatase activity (stimulation or inhibition) seemed to be indefinite, and varied with the application rate, soil type, and incubation time. In the case of glyphosate, soil acid phosphatase activity was depressed significantly and the depressing extent could be a function of herbicide concentration and incubation time, but soil dehydrogenase activity showed an irregular variation with the herbicide application rate and soil type. In general, dehydrogenase activity was a good biochemical indicator for the biodegradation of methamidophos, but for glyphosate biodegradation the indicator was acid phosphatase activity. [ABSTRACT FROM AUTHOR]

The P efficiency, crop yield, and response of wheat to arbuscular mycorrhizal fungus (AMF) Glomus caledonium were tested in an experimental field with long-term (19 years) fertilizer management. The experiment included five fertilizer treatments: organic amendment (OA), half organic amendment plus half mineral fertilizer (1/2 OM), mineral fertilizer NPK, mineral fertilizer NK, and the control (without fertilization). AMF inoculation responsiveness (MIR) of wheat plants at acquiring P were estimated by comparing plants grown in unsterilized soil inoculated with G. caledonium and in untreated soil containing indigenous AMF. Without AMF inoculation, higher crop yields but lower colonization rates were observed in the NPK and two OA-inputted treatments, and NPK had significantly ( P < 0.05) lower impacts on organic C and available P in soils and thereby P acquisition of wheat plants compared with OA and 1/2 OM. G. caledonium inoculation significantly ( P < 0.05) increased colonization rates with the NPK and two P-deficient treatments but significantly ( P < 0.05) increased vegetative biomass, crop yield, and P acquisition of wheat as well as soil alkaline phosphatase (ALP) activity, only with the NPK treatment. This gave an MIR of ca. 45% on total P acquisition of wheat plants. There were no other remarkable MIRs. It suggested that the MIR is determined by soil available P status, and rational combination of AMF with chemical NPK fertilizer can compensate for organic amendments by improving P-acquisition efficiency in arable soils. [ABSTRACT FROM AUTHOR]

A study was carried out to investigate changes in the soil plant-available P, the P nutrition and the growth of Pinus radiata seedlings grown in association with understory, broom ( Cytisus scoparius L.) or ryegrass ( Lolium multiflorum) on Orthic Allophanic Soil, following the application of three rates of triple superphosphate (TSP) (0, 50, and 100 mg·kg−1P) under a glasshouse condition. The application of P fertilizer enhanced P availability in the rhizospheric of radiata seedlings and the bulk soils in a P-deficient site. P availability in the rhizospheric soils of ryegrass and broom, grown in association with radiata, were also increased by the presence of radiata roots. P concentrations in new shoot needles, old shoot needles, stem and roots of radiata pine increased with increase rates of TSP application, but the effects of ryegrass and broom on P nutrition of radiata seedlings depended on the soil P status. In the absence of P fertilizer addition (control treatment), P concentrations in new shoot needles, old shoot needles, stem, and roots of radiata grown in association with broom were higher than those with ryegrass, whereas, when P fertilizer was added (50 and 100 mg·kg−1) the P concentration was lower. This is probably related to the growth of broom that may have removed much of the plant-available P in the soil as indicated by the consistently lower Bray-2 P concentration in the rhizosphere soil of radiata in association with broom than that in the rhizosphere soil of radiata in association with grass at the two high P rates. Furthermore, in the high P fertile soil (application rate of 100 mg·kg−1), the dry matter yield of radiata was lower when it was grown with broom than with ryegrass. This result suggests that in moderate to high P fertile soils, P. radiata seedlings grow better with ryegrass than with broom, because broom grows vigorously in high P fertile soil and competes with P. radiata for P and perhaps for other nutrients as well. [ABSTRACT FROM AUTHOR]

Nitrogen (N) fertilization increases zinc (Zn) acquisition in cereal crops. However, little is known about the effects of N fertilization on grain Zn concentration in relation to availability of soil N and phosphorous (P) and root mycorrhizal colonization. The present study used a 12-year location-fixed field experiment with winter wheat grown at five N fertilization rates (0, 80, 160, 240 and 320 kg N ha−1). The objective was to assess effects of phytoavailability of soil N and P and root mycorrhizal colonization on wheat Zn nutrition during three-year field measurements. Zinc concentration in wheat grains was increased with N fertilization in a linear-plateau fashion, and it reached the plateau of 30.3 ± 0.4 mg kg−1 when soil mineral N (nitrate-N) levels were 8.5 ± 1.0 mg kg−1 and above at maturity. Similarly, total shoot Zn uptake and Zn remobilization from vegetative tissues to grains were also increased significantly and then attained a plateau as the N rates increased. The enhancements in grain Zn concentration by N fertilization mainly occurred in the crease tissue, embryo and aleurone fractions of the grain. Long-term N fertilization was also associated with increases in root mycorrhizal colonization up to 8.8 ± 2.9 mg kg−1 soil available mineral N at maturity. Shoot Zn uptake at maturity increased quadratically with the increase in shoot N uptake and root mycorrhizal colonization rate, whereas there was an inverse relationship between shoot Zn uptake and soil P availability. The results suggest that grain Zn concentration of wheat plants grown under long-term N fertilization was closely related to the soil mineral N status and showed clear increases with decreased soil available P concentration and improved root mycorrhizal colonization rates. • Soil mineral N affected uptake, remobilization and concentration of Zn in wheat. • N fertilization increased grain Zn concentration only in soil with low mineral N. • Reduced soil available P was positively associated with grain Zn concentrations. [ABSTRACT FROM AUTHOR]

The alkaline phosphatase-harboring community (the phoD community hereafter) plays an important role in organic P mineralization. Here, we comparatively studied the biogeographical patterns of abundant and rare phoD subcommunities and their roles in mediating soil phosphatase (ALP) activity and available P content in three representative steppe regions in China, namely the Inner Mongolian Plateau, the Loess Plateau, and the Qinghai-Tibetan Plateau. The results indicated that soil ALP activity, available P content, soil and microbial biomass C:P, N:P ratios varied significantly among steppe regions. Significant differences in diversity, metabolic energy and assembly processes were observed between abundant and rare phoD subcommunities. First, richness of the rare taxa was significantly higher than that of the abundant subcommunities. Second, testing of metabolic theory of ecology showed that rare subcommunities had a higher metabolic activation energy than the abundant taxa. Thirdly, deterministic other than stochastic processes dominated in the community assembly of both subcommunities. Soil pH was the key environmental determinant in community assembly processes for both subcommunities. The relationships among P-cycling parameters and between these parameters and phoD diversity were scale-dependent. The phylogenetic beta diversity of the rare phoD taxa had higher correlations with P-cycling parameters than that with the abundant taxa. More rare than abundant genera were significantly correlated with P limitation and ALP activity at different spatial scales. The rare Frankia was the key genus detecting P limitation, producing ALP and enhancing soil available P in Qinghai-Tibet. • Biogeographic patterns of rare and abundant phoD subcommunities are studied. • The subcommunities are different in metabolic energy and assembly processes. • Rare phoD subcommunities are the major drivers of soil ALP activity and available P. [ABSTRACT FROM AUTHOR]

Influence of application of phosphorus solubilizing bacteria (PSB), Bacillus megatherium var. Phosphaticum, at 10 kg ha−1 of lignite based culture with and without varying amounts of P fertilizer was studied on soil available P changes and sugarcane growth and yield. The PSB application increased the PSB population in the rhizosphere and the plant available P status in the soil. It also enhanced tillering, stalk population and stalk weight, and led to a cane yield increase of 12.6% over no application. When used in conjunction with P fertilizers, PSB reduced the required P dosage by 25%. In addition, it was found that 50% of the costly super phosphate could be replaced by rock phosphate (RP), a cheap source of P, when applied in conjunction with PSB. The PSB improved juice quality and sugar yields. The influence of PSB was greatest when RP constituted a part of the P fertilizers applied. [Copyright &y& Elsevier]

Nanoscale zero-valent iron (nZVI) shows an excellent degradation effect on chlorinated contaminants in soil, but poses a threat to plants in combination with phytoremediation. Arbuscular mycorrhizal (AM) fungus can reduce the phyototoxicity of nZVI, but their combined impacts on polychlorinated biphenyls (PCBs) degradation and plant growth remain unclear. Here, a greenhouse pot experiment was conducted to investigate the influences of nZVI and/or Funneliformis caledonium on soil PCB degradation and ryegrass (Lolium peren ne L.) antioxidative responses. The amendment of nZVI significantly reduced not only the total and homolog concentrations of PCBs in the soil, but also the ryegrass biomass as well as soil available P and root P concentrations. Moreover, nZVI significantly decreased leaf superoxide disutase (SOD) activity, while tended to decrease the protein content. In contrast, the additional inoculation of F. caledonium significantly increased leaf SOD activity and protein content, while tended to increase the catalase activity and tended to decrease the malondialdehyde content. The additional inoculation of F. caledonium also significantly increased soil alkaline phosphatase activity, and tended to increase root P concentration, but had no significantly effects on soil available P concentration, the biomass and P acquisition of ryegrass, which could be attributed to the fixation of soil available nutrients by nZVI. Additionally, F. caledonium facilitated PCB degradation in the nZVI-applied soil. Thus, AM fungus can alleviate the nZVI-induced phytotoxicity, showing great application potentials in accompany with nZVI for soil remediation. [Display omitted] • Nanoscale zero-valent iron (nZVI) accelerated the degradation of soil PCBs. • nZVI aggravated oxidative stress and inhibited ryegrass growth. • AM fungus alleviated the phytotoxicity rather than P-limitation induced by nZVI. • AM fungus further enhanced PCB degradation in the nZVI-applied soil. • nZVI and AM fungus jointly facilitated phytoremediation of PCB-contaminated soils. [ABSTRACT FROM AUTHOR]

Due to limits in global phosphate rock reserves for fertilizer use, it is vital to increase phosphorus fertilizer use efficiency (PFUE) to maintain agricultural productivity and food security. With 865 observations from 82 papers we investigated how PFUE in cereal crops was affected by climate (mean annual temperature), soil (pH, texture, available P), and management factors (crop type, fertilizer type and amount). We found that P content in aboveground biomass increased by 12.4% (95% confidence intervals 11.5–13.4%) of the P fertilizer applied across all observations. This PFUE was lower in maize than in rice and wheat, and was lowest in soil with near neutral pH. Our results indicate that there is much opportunity for improving PFUE in cereal crops. • Grain and aboveground P fertilizer use efficiency were on average 9.1% and 12.4%. • P fertilizer use efficiency varied among crops and fertilizer type. • P fertilizer use efficiency was lowest in soil with near neutral pH. • There is much opportunity for improving P fertilizer use efficiency in cereal crops. [ABSTRACT FROM AUTHOR]

• Alternating drought and flooding influenced soil P fractions. • P fertilization altered proportions of inorganic P fractions. • Short-term drought-rewetting in rice induced soil P release and transformation. Successive application of phosphorus (P) fertilizer under different cropping systems could result in remarkable changes in soil P fractions, accompanied by inducing soil P accumulation and increasing eutrophication risks. However, relatively little attention has been paid to annual changes in soil P fractions and P losses via runoff in drought-rewetting paddy fields. In the present study, we explored inter-annual variations in soil P speciation, availability and runoff P in a five-year field trial in a winter wheat and summer rice rotations system, and in different rice-growth stages. Four P fertilization treatments were applied, including P fertilization in both farming seasons (wheat and rice) (PR + W), application of P fertilizer only in rice-growing seasons (PR), application of P fertilizer only in wheat-growing seasons (PW), and no P fertilization (Pzero). Our results showed that P fertilization treatments (PW, PR, and PR + W) significantly altered the proportions of inorganic P (Pi) fractions, while no P fertilization in the wheat-growing seasons (Pzero, PR) significantly decreased NaHCO 3 -Pi contents in the wheat-growing seasons and decreased NaHCO 3 -Pi and NaOH-Pi concentrations in the rice-growing seasons (p < 0.05). Application of P fertilizer in the wheat-growing seasons treatments (PW, PR+W) maintained the stability of soil P fractions both in the wheat- and rice-growing seasons. Moreover, compared to the PR+W treatment, the PW treatment reduced total P (TP) losses from runoff. For inter-annual drought-rewetting variation in P speciation and availability, there was a significant correlation between Olsen-P and NaHCO 3 -Pi and NaOH-Pi contents in the wheat-growing seasons, and Olsen-P was significantly correlated with NaHCO 3 -Pi, NaOH-Pi, and HCl-P in the rice-growing seasons. Furthermore, we focused on the change in detailed rice-growth stages, and found aeration significantly increased NaHCO 3 -Pi, NaOH-Pi, NaOH-Po and HCl-P contents, and there was a significant correlation between soil Olsen-P and the P fractions in the A-aeration growth stage in rice, which could be attributed to the short-term drought-rewetting cycle facilitating the release of soil P. The present study revealed changes in soil P speciation and availability in a drought-rewetting cycle in paddy soils, and indicated the optimized agricultural P management strategies had the potential to reduce environmental risks. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) fungi can ameliorate not only plant phosphorus (P) nutrition but also soil P mobilization, while P mobilization occurs secondarily and may in turn limit P acquisition at certain crop growth stages. It can be termed as the "mycorrhiza-inducible P limitation", which has so far largely escaped study. A pot experiment was conducted to test the dynamic P acquisition of maize (Zea mays L.) at the vegetative growth stage and P mobilization in the soil in response to AM fungal inoculation in an unsterilized arable alkaline soil. The experiment included two fertilization levels and two AM inoculation levels, i.e., nitrogen (N), P, and potassium (K) fertilization (NPK) and non-fertilization (control), as well as Funneliformis mosseae inoculation (+M) and non-inoculation (–M). Regardless of fertilization, +M increased mycorrhizal colonization and plant biomass at weeks 4 and 8 but increased tissue P concentration only at week 4 compared with those of –M. In addition, the plant P acquisition and shoot biomass in the control+M treatment at weeks 4 and 8 were close to and much lower than those of NPK–M, respectively. Furthermore, the increase in soil P mobilization potential, which was achieved by the accelerated soil alkaline phosphatase activity and the decreased soil pH, was lower than the increase in root P-acquiring efficiency, which was achieved by the enhanced mycorrhization and ZEAma;Pht1;6 (a mycorrhiza- inducible Pi transporter in maize root) expression. Regardless of fertilization, +M thus significantly decreased soil available P concentrations compared with those in the –M treatments. Therefore, there was a large, real gap between soil P mobilization and root P acquisition in response to enhanced root mycorrhizal colonization, substantially limiting plant P acquisition and growth. [ABSTRACT FROM AUTHOR]