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Article

Long-Term Nitrogen Addition Promotes Microbial Mineralization of Organic Phosphorus Supporting Phosphorus Uptake in Spring Wheat

by
Huaqiang Li
1,
Peng Qi
1,2,3,*,
Xiaodong Yin
4,
Xiaojiao Wang
5,
Run Gan
6,
Jianglong Xue
1,
Yangzi Han
1,
Meixia Lu
1,
Guopeng Liang
7,8 and
Hailiang Li
1
1
College of Resources and Environmental Sciences, Gansu Agricultural University, Lanzhou 730070, China
2
Gansu Provincial Key Laboratory of Arid Land Crop Science, Gansu Agricultural University, Lanzhou 730070, China
3
Engineering Research Center for the Resource Utilization of Livestock and Poultry Wastes in Gansu Province, Lanzhou 730070, China
4
Minle County Agricultural and Rural Bureau, Zhangye 734500, China
5
College of Management, Gansu Agricultural University, Lanzhou 730070, China
6
Jinchang Institute of Agronomy, Jinchang 737100, China
7
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
8
Institute for Global Change Biology, University of Michigan, Ann Arbor, MI 48109, USA
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(11), 2632; https://doi.org/10.3390/agronomy15112632
Submission received: 19 October 2025 / Revised: 10 November 2025 / Accepted: 11 November 2025 / Published: 17 November 2025
(This article belongs to the Section Soil and Plant Nutrition)
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Abstract

The mechanism of microbial-mediated mineralization of organic phosphorus (P) under nitrogen (N) addition in farmland soil is still unclear. To determine the effects of N addition on the composition, structure, and P transformation function of microbial community and soil P fractions in croplands, we conducted a field experiment on the Central Gansu Loess Plateau in 2017. The current study analyzed a subset of 12 plots from the 48-plot factorial experiment, comprising four levels of N addition in the absence of P fertilization. The treatment included control (0 kg N ha−1 year−1, N0), low N (75 kg N ha−1 year−1, N75), medium N (115 kg N ha−1 year−1, N115), and high N (190 kg N ha−1 year−1, N190). We determined soil P fractions and microbial properties in the 0–20 cm depth from 2019 to 2023. We found that N fertilization significantly enhanced the mineralization of soil organic P, primarily by altering microbial community structure and increasing the abundance of key taxa (e.g., RB41 and Filobasidium), which in turn boosted the activities of alkaline phosphatase (ALP) and phytase (PHY). The most pronounced stimulations in microbial biomass carbon (MBC) and ALP activity were observed under the N115 treatment. Concurrently, N addition led to substantial reductions in labile inorganic and organic P pools; for instance, the content of Ca2-P decreased most markedly under N190, by 42.82% in 2023, while labile organic P forms (LOP, MLOP, MROP) also declined significantly. Structural Equation Modeling (SEM) confirmed that N addition influenced P availability through direct pathways and indirect pathways mediated by shifts in microbial community structure, ALP, and PHY. In conclusion, our study has identified the N115 treatment (115 kg N ha−1 year−1) as the optimal level for promoting microbial-mediated organic P mineralization. To maintain soil productivity in the rain-fed agricultural systems of the Loess Plateau, we recommend applying a moderate amount of N fertilizer at this optimal rate, along with strategic P supplementation. This approach can effectively mitigate soil P deficiency and enhance the availability of P.

1. Introduction

Nitrogen (N) and phosphorus (P) are globally recognized as essential limiting nutrients for plant growth and crop productivity [1]. Recent anthropogenic activities have driven a significant increase in atmospheric N deposition rates [2]. This phenomenon has shifted ecosystem nutrient limitation patterns from N limitation to P limitation, exacerbating soil N:P stoichiometric imbalances and intensifying systemic P constraints [3]. In agricultural soils characterized by low P availability, N deposition/addition has been demonstrated to amplify P limitation in both plant and microbial communities, ultimately leading to a decrease in crop yield [4].
P predominantly exists in inorganic forms within soils, constituting 70–80% of total P content [5]. Many studies have demonstrated that P was adsorbed by iron/aluminum (hydr)oxides in acidic soils and formed precipitates with calcium ions in alkaline soils or immobilized by microorganisms [6]. This process significantly restricts the availability of soil P, resulting in a pronounced reliance on alternative pathways for P mobilization. Additionally, a significant portion of organic P persists as a latent reservoir, inaccessible for direct plant uptake until mineralized into bioavailable inorganic forms—a process critical to global P cycling [7]. Moreover, P fractions exhibit marked heterogeneity in mobility and bioavailability [8], with different responses to N addition observed across ecosystems [9]. When N deposition elevates plant–microbial P demand [10], soil P availability under inorganic P scarcity becomes governed by organic P mineralization. This process prioritizes the mobilization of labile organic fractions to meet biological requirements [11]. Consequently, N addition typically reduces labile P pool proportions [12]. Furthermore, globally, N deposition alters the soil P cycle by regulating microbial biomass, extracellular enzyme activity, soil organic matter dynamics, and soil pH [13]. Field experiments have shown that N input can increase carbon, N, and P in microbial biomass by 18.11–41.73% and increase the activity of phosphatase, thus promoting the hydrolysis of organic P [14]. Therefore, it is necessary to advance the current understanding of soil organic P mineralization and its main driving factors and clarify how N deposition affects the mineralization and supply of soil organic P in croplands.
Despite evidence that the addition of N increases microbial and enzymatic (phosphatase) activity, the exact mechanism by which N modulates the structure of the microbial community to boost long-term organic P mineralization in calcareous agricultural areas remains poorly explored. Many studies have concluded that soil microorganisms play a significant role in P transformation and maintenance of soil P effectiveness. Microorganisms can influence the soil P cycle by secreting phosphatase and phytase, and these enzymes can promote the mineralization of organic P by breaking ester bonds or preventing the formation of ester bonds, transforming the P in the mesophilic or refractory decomposition state to the readily decomposable state, and ultimately releasing effective P that can be absorbed and utilized by plants [15]. In P-limited ecosystems, N addition increases microbial activity and thus alters microbial community structure, which in turn affects microbial uptake of effective P and soil P activity and facilitates P transformation between different forms [16].
The Loess Plateau has a history of more than 5000 years of farming. It is one of the most serious areas of soil erosion in the world and the largest area of loess accumulation on the Earth, which has an important impact on climate change. For a long time, the soil in this area has been “N-poor and P-poor” due to climatic reasons and the special properties of the soil, coupled with excessive human development and utilization [17]. To address this knowledge gap, we conducted a field experiment and hypothesized the following: (1) Long-term N fertilization elicits alterations in the structure and function of microbial communities, subsequently promoting enzymatic mineralization of organic P. The microbially driven mechanism constitutes a pivotal link in sustaining P uptake by spring wheat under N-enriched conditions. (2) Under the scenario of continuous N input, the accelerated mineralization of labile organophosphorus compounds may pose a threat to the long-term sustainability of soil P reservoirs.

2. Materials and Methods

2.1. Site Description

This study was conducted from 2019 to 2023 at the Comprehensive Experimental Station of Dry Farming Agriculture of Gansu Agricultural University (35°28′ N, 104°44′ E) located in Lijiaobao Town, Dingxi District, Dingxi City, Gansu Province, China, where the field experiment started in 2017 (Figure S1). The experimental area is at an altitude of 1971 m, with an annual frost-free period of 140 days. It is a typical rain-fed agricultural area, with an annual mean temperature of 6.4 °C and an annual mean precipitation of 390 mm (Figure S2). The field site has a soil developed from loess parent material, classified as Haptic Calcisol (Siltic, Aric) according to the IUSS Working Group WRB (2022) classification [18]. The soil has a loose texture (54% sand, 33% silt, and 13% clay). Initial 0–20 cm soil properties (samples collected in March 2017): bulk density 1.17 g cm−3, soil organic carbon (SOC) 8.87 g kg−1, pH 8.4, total N (TN) 0.86 g kg−1, total potassium (TK) 28.0 g kg−1, total P (TP) 0.82 g kg−1, available P (AP) 21.2 mg kg−1, and available potassium (AK) 139 mg kg−1.

2.2. Experimental Design

The analysis in this study is grounded in a long-term field experiment. The entire experiment adopted a completely randomized block design and was structured as a two-factor experiment. It encompassed 4 N levels (0, 75, 115, and 190 kg N ha−1 year−1) crossed with 4 P levels (0, 75, 115, and 190 kg P2O5 ha−1 year−1), resulting in 16 treatment combinations. Each treatment was replicated three times, bringing the total number of experimental plots to 48. To specifically assess the long-term impacts of N fertilizer, this study focused on the analysis of 12 sub-plots selected from the 48 factorial plots. These sub-plots featured four different N fertilizer application rates under P-free conditions: control (0 kg N ha−1 year−1, N0), low N (75 kg N ha−1 year−1, N75), medium N (115 kg N ha−1 year−1, N115), and high N (190 kg N ha−1 year−1, N190) (Figure S3). The N fertilizer used was urea (containing 46% pure N). It was applied as an N fertilizer in a single basal application each year in March before spring wheat sowing from 2019 to 2023. Each treatment plot covered an area of 22.5 m2 (4.5 m × 5 m). The test crop was spring wheat (Dingxi 40), which was sown in late March and harvested in late July each year. The seeding rate was set at 187.5 kg ha−1, with a row spacing of 20 cm and a seeding depth of 7 cm. After harvest, crop straw was removed from the field and not returned. This management practice, while common in the region, results in the continual export of P and other nutrients from the soil system, thereby creating a trajectory of gradual P depletion over time, particularly in the absence of P fertilizer inputs.

2.3. Soil Sampling and Analyses

In 2019, 2020, and 2023, soil samples were collected from the 0–20 cm tillage layer after spring wheat harvesting using the “S” type 5-point sampling method. Samples were mixed well, passed through a 2 mm sieve, and divided into two parts: one of which was naturally air-dried for measurements of soil chemical properties, and the other was stored in a refrigerator at −20 °C for determining soil enzyme activity. In addition, soil samples were also collected by using the same aforementioned method during the flowering stage in 2023, which were stored in dry ice boxes and transferred to a −80 °C refrigerator as soon as possible for subsequent analysis of microbial community structure. The purified samples were sent to a sequencing company for high-throughput sequencing analysis on the Illumina MiSeq platform.
Before wheat harvest on 25 July 2019, 2020, and 2023, 20 wheat plants were randomly selected from each plot, washed with deionized water, divided into seeds and straw, baked at 105 °C for 30 min, dried at 80 °C until constant weight, and weighed to calculate the mass of the dry matter. The P content of each organ of the plant was determined by using the H2SO4-H2O2 cooking–vanadium–molybdenum yellow colorimetric method [19].
Soil total P (TP) was determined by using H2SO4-HClO4 acid solubilization and the molybdenum–antimony colorimetric method, while soil total N (TN) was determined by using H2SO4 digestion and the Kjeldahl method [19]. The NaHCO3 leaching and molybdenum–antimony colorimetric method was used to determine soil active P (AP) [19]. Soil inorganic P fractions were classified into six classes: Ca2-P, Ca8-P, Al-P, Fe-P, O-P, and Ca10-P according to the previous method [20]. Specifically, accurately weigh 1.00 g of an air-dried soil sample that has been passed through a 0.149 mm mesh sieve, and then sequentially classify it according to the following extraction methods: extract soluble P (Ca2-P) using 0.25 mol L−1 NaHCO3; extract P (Ca8-P) with 0.5 mol L−1 NH4OAc; extract P (Al-P) employing 0.5 mol L−1 NH4F; extract P (Fe-P) using 0.1 mol L−1 NaOH-0.1 mol L−1 Na2CO3; extract P (O-P) with 0.3 mol L−1 sodium citrate; and extract P (Ca10-P) using 0.5 mol L−1 H2SO4. The content of each inorganic P form was then determined spectrophotometrically. Soil organic P was classified into four groups according to the solubility in acid and alkali solutions with different concentrations: reactive organic P (LOP), moderately reactive P (MLOP), moderately stable organic P (MROP), and highly stable organic P (HROP) [21]. The specific process is as follows: Place 1 g of air-dried soil that has passed through a 2 mm sieve into a centrifuge tube. Add the following solutions sequentially: 0.5 mol L−1 NaHCO3 (pH 8.5), 1 mol L−1 H2SO4, 0.5 mol L−1 NaOH, and 0.5 mol L−1 NaOH. After shaking and filtering, perform the measurement. The organic P in each extract was determined by the difference between the total P and the inorganic P in the extract, usually after oxidation digestion (Porg = Ptotal − Pinorg). Soil pH was determined by using the potentiometric method with a water–soil ratio of 2.5:1 (LY/T1239-1999), and soil organic carbon (SOC) was determined by using the external heating method with potassium dichromate–concentrated sulfuric acid [19]. Soil microbial carbon (MBC), N (MBN), and P (MBP) were determined by using the chloroform fumigation method. Soil alkaline phosphatase activity (ALP) was determined by using the colorimetric method, and soil phytase activity (PHY) was measured by using the vanadium–molybdenum method [22]. Finally, the enzyme activities were expressed as nanomoles of substrate released per hour per gram of dry soil (nmol g−1 h−1).

Sampling Strategy Rationale

Soil sampling for the determination of chemical properties and enzyme activities was carried out post-harvest in 2019, 2020, and 2023. This sampling timing was selected to assess the long-term cumulative impacts of N fertilization and the baseline soil fertility status following crop removal, a factor of significant agronomic importance for guiding fertilization practices in the subsequent growing season. Due to unavoidable constraints encountered in 2021 and 2022, the sampling plan required adjustment, and systematic sampling could not be completed. Nevertheless, data from these three representative years are sufficient to effectively capture the temporal trends in soil biogeochemistry.
In contrast, soil samples for microbial community analysis (DNA extraction) were solely collected during the flowering stage in 2023. This phenological stage marks the peak of plant growth and root exudation, a period when microbial activity and their responses to nutrient management are anticipated to be most pronounced. Although this design prevents a direct temporal comparison between the microbial community (sampled during flowering in 2023) and soil chemical/enzyme properties (sampled post-harvest across multiple years), it enables an in-depth analysis of the microbial structure during a critical and dynamic growth phase under long-term N application regimes. Consequently, the two sampling strategies were devised to address complementary objectives within the long-term experiment.

2.4. Soil DNA Extraction and High-Throughput Sequencing

Total genomic DNA was extracted from soil samples using the TGuide S96 Magnetic Soil DNA Kit (Tiangen Biotech (Beijing) Co., Ltd., Beijing, China) according to the manufacturer’s instructions. The quality and quantity of the extracted DNA were examined using electrophoresis on a 1.8% agarose gel, and DNA concentration and purity were determined with a NanoDrop 2000 UV–Vis spectrophotometer (Thermo Scientific, Wilmington, NC, USA). The hypervariable region V3-V4 of the bacterial 16S rRNA gene was amplified with primer pairs 338F: 5′-ACTCCTACGGGAGGCAGCA-3′ and 806R: 5′-GGACTACHVGGGTWTCTAAT-3′ [23]. Both the forward and reverse 16S primers were tailed with sample-specific Illumina index sequences to allow for deep sequencing. The PCR was performed in a total reaction volume of 10 μL: DNA template 5–50 ng, forward primer (10 μM) 0.3 μL, reverse primer (10 μM) 0.3 μL, KOD FX Neo Buffer 5 μL, dNTP (2 mM each) 2 μL, KOD FX Neo 0.2 μL, and finally ddH2O up to 20 μL. After initial denaturation at 95 °C for 5 min, followed by 35 cycles of denaturation at 95 °C for 30 s, annealing at 50 °C for 30 s, and extension at 72 °C for 40 s, and a final step at 72 °C for 7 min. The fungal ITS gene was amplified by PCR (95 °C for 3 min, followed by 35 cycles at 95 °C for 30 s, 55 °C for 30 s, and 72 °C for 40 s and a final extension at 72 °C for 5 min) using primers ITS1F 5′-CTTGGTCATTTAGAGGAAGTAA-3′ and ITS2R 5′-GCTGCGTTCTTCATCGATGC-3′. The amplified products were purified with Omega DNA purification kit (Omega Inc., Norcross, GA, USA) and quantified using Qsep-400 (BiOptic, Inc., New Taipei City, Taiwan, ROC). The amplicon library was paired-end sequenced (2 × 250) on an Illumina novaseq6000 (Beijing Biomarker Technologies Co., Ltd., Beijing, China).

2.5. Statistical Analyses

Experimental data were statistically analyzed by using Excel (2019) and SPSS (25.0), and all data were tested for normality and the chi-square test. Two-way ANOVA was used to determine the interaction effect of N addition rate and year. One-way ANOVA was used to test the significance of the P fractions under different N addition treatments, and Duncan’s method was used to test the significance of the difference between the means of the treatments at the p < 0.05 level. Canoco (5.0) was used for the redundancy analysis, and the “RandomForest”, “piecewiseSEM”, and “readxl” in R (4.5.1) were used to perform the random forest modeling (MSE) and structural equation modeling (SEM) analysis. Soil microbial community diversity was analyzed by using BMKCloud (https://international.biocloud.net/), and soil microbial taxa that were enriched under each treatment were identified by using the LEfSe (Linear Discriminant Analysis Effect Size) method, with the LDA value set at >2.5 and the relative abundance of taxa at >1%. The differences in the composition of bacterial and fungal communities were assessed by using principal coordinate analysis (PCoA) based on the Bray-Curtis distance, and the predictions of gene functions were made by using PICRUSt and FUNGuild and analyzed by using BMKCloud ((https://international.biocloud.net/ (accessed on 9 November 2025))), and Origin (2021).

3. Results

3.1. Effects of Different N Addition Rates on Different Forms of P in Soil

The effects of N addition rate and continuous N addition time on the contents of inorganic P (Ca8-P, Al-P, Fe-P, Ca10-P, and O-P) and organic P (LOP, MLOP, and HROP) in the topsoil showed a significant interaction (Table 1). The contents of TP, AP, total inorganic P, and total organic P in soil exhibited significant negative correlations with N addition rates (p < 0.05). The content of total inorganic P/total organic P demonstrated a consistent upward trend and reached its highest in 2023. Although the plant’s total P accumulation increased significantly with the increase in N addition rate (p < 0.05), it decreased over time, reaching its lowest level during the study period in 2023. The contents of different forms of inorganic and organic P were significantly different between N addition treatments (p < 0.05; Figure 1). Compared with N0, inorganic P contents (e.g., Ca2-P, Ca8-P, Al-P, Fe-P, and Ca10-P) under other treatments were lower (p < 0.05). For example, Ca2-P decreased the most under N190 treatment (−42.82% in 2023), and Ca10-P decreased the least under N190 treatment (−2.44% in 2019). By contrast, O-P content increased the most under N190 treatment (+42.39% in 2020). In addition, when compared to N0, the organic P (e.g., LOP, MLOP, and MROP) under the other treatments was significantly lower (p < 0.05), with a decrease ranging from 2.74% to 39.03%. Among them, LOP decreased the most under N190 treatment (−39.03% in 2020). When compared to N0, however, HROP content was significantly higher (p < 0.05) under other N treatments.
Between years, the contents of several inorganic (e.g., O-P) and organic P fractions (e.g., MLOP, MROP, and HROP) showed a general decreasing trend (p < 0.05), with the extent of reduction varying both by P fraction and sampling year (Figure 1). Meanwhile, the contents of Ca2-P and Ca8-P exhibited an initial increase followed by a decrease, whereas an opposite trend was observed for Ca10-P and Fe-P.

3.2. Effects of Different N Addition Rates on Soil Enzyme Activity, Microbial Biomass, and Physicochemical Properties

N addition had significant (p < 0.05) effects on ALP and PHY, regardless of the year (Table 2). Both ALP and PHY activities showed a trend of increasing and then decreasing with the increase in N addition, and the highest and lowest values were found for N115 and N0 treatments, respectively. When compared to N0, MBC, MBN, and MBP were significantly higher under other N treatments (p < 0.05), and their highest and lowest values were found under N115 and N0 treatments, respectively. TN and N:P showed an increasing trend with the increase in N addition, which had the highest values under N190 treatment. SOC content showed an increasing and then decreasing trend and was highest under N115 treatment. Moreover, soil pH decreased with the increase in N addition, and the highest and lowest values were found for N0 and N190 treatments, respectively. Compared to N0, N115 and N190 decreased by 1.4–1.8% and 1.9–2.2%, respectively (Table S1).

3.3. Effects of Different N Addition Rates on Microbial Community Structure

Bacterial community genus-level analysis showed that higher relative abundance values of Sphingomonas (2.21–3.07%), RB41 (2.39–2.87%), and MND1 (1.00–1.65%) were found under N75, N115, and N190 than under N0 (Figure 2a). It should be emphasized that both Sphingomonas and RB41 are extensively acknowledged for their involvement in the decomposition of soil organic matter, a process that can directly facilitate the mineralization of organic P. The results of the LEfSe analysis of bacteria at the genus level showed significant differences between N0, N115, and N190. More specifically, when compared to N0, Amycolatopsis and Bdellovibrio were significantly higher under N115 treatment, and Lamia, OLB13, Sporosarcina, and Nitrosospira were significantly higher in N190 treatment (Figure 2b).
For the fungal communities, Mortierella (15.39–32.06%) showed a trend of decreasing first and then increasing, with the increase in N addition rate. The relative abundance values under N75, N115, and N190 treatments were lower than N0. By contrast, with the increase in N addition rate, the relative abundance of Fusarium (9.52–24.84%), Chaetomium (5.58–12.88%), Acremonium (1.61–3.84%), and Filobasidium (0.76–2.82%) showed an increasing and then decreasing trend. Notably, Filobasidium has been reported as a potential producer of phosphatases, which are key enzymes in organic P mineralization. The relative abundance of Botryotrichum (1.96–12.56%) was significantly increased by N addition, with the highest value (12.56%) under N190 treatment (Figure 2c). Fungal LEfSe analysis showed significant differences between N0 and N75 and N115 treatments. When compared to N0, higher values were found for Pseudaleuria and Spiromyces under N75 treatment and for Typhula and Filobasidium under N115 treatment (Figure 2d). The enrichment of Filobasidium, a genus known to be associated with P solubilization, under the N115 treatment further highlights its potentially pivotal role in the microbial-driven P cycle.
Chao1 index of bacteria was higher under N75, N115, and N190 than N0 (Figure 3a). The highest value was found under N115 treatment, indicating that N addition increased the richness of soil bacterial microorganisms. The Shannon index increased first and then decreased with the increase in the N addition rate. The results of soil fungi showed that, compared with N0, Chao1 was lower under N75, N115, and N190 treatments (Figure 3b), indicating that N addition decreased the richness of soil fungi. According to the PCoA analysis, PC1 and PC2 explained 81.41% and 4.45% of soil bacterial community structure (Figure 3c), respectively. Furthermore, the taxa of N75, N115, and N190 treatments were closely connected or clustered, which were separated from N0, indicating that N addition significantly altered the soil bacterial community. For fungi, samples under N0 and N190 were clearly distinguished in the main coordinate space (Figure 3d), and samples under N75 and N115 were more dispersed in the main coordinate space. These results indicate that these samples had some differences in characteristics and that N addition significantly changed fungal community structure.

3.4. Correlations Between P Components and Soil Microbial Variables

Random forest analysis revealed that the RB41 (bacteria), the Filobasidium, and the Botryotrichum (fungi) were identified as key microorganisms affecting the organic P fractions (Figure 4a,b). Key environmental factors affecting organic P were ALP, MBC, AP, TP, stem P, and leaf P. For inorganic P, the primary influencing factors were ALP, TP, AP, pH, N:P ratio, stem P, and leaf P. Calcium-bound (Ca2-P, Ca8-P), aluminum-bound (Al-P), and organic P fractions (LOP, MLOP, and MROP) were identified as primary determinants of AP dynamics (Figure 4e,f). Correlation analysis revealed that ALP and PHY activities exhibited negative associations with inorganic P components and active organic P pools, while showing positive correlations with microbial taxa RB41 (bacteria) and Filobasidium (fungi) (Figure 5a). The SEM demonstrated that N fertilization primarily enhances soil P availability through indirect pathways mediated by the microbial community (Figure 5b). Specifically, N application induced alterations in the microbial community structure, leading to the enrichment of key taxa, including RB41 and Filobasidium. Subsequently, these taxa modulated the activities of ALP and PHY, which ultimately facilitated the mineralization of organic P. This model effectively accounted for 75%, 69%, and 99% of the variance in ALP/PHY activities and organic P content, respectively. The path coefficients provided further elaboration on these relationships, confirming the substantial direct impacts of Filobasidium (path coefficient = 0.75) and RB41 (path coefficient = 0.47) on enzyme activities. In terms of the influence on organic P pools, N fertilization rates, enzyme activities (ALP, PHY), MBC, and microbial taxa (Filobasidium, RB41) exerted negative regulatory effects, while MBP demonstrated a positive regulatory influence (Figure 5c).

4. Discussion

4.1. Effect of N Addition on Soil P Fractions

We found that N addition changed soil P fractions and reduced soil TP, total inorganic P, and total organic P content. N addition reduced inorganic P (Ca2-P, Ca8-P, Ca10-P, Al-P, and Fe-P) and reactive organic P (LOP, MLOP, and MROP) contents, and O-P and HROP contents increased with increasing N addition (Figure 1). This may be due to the fact that, with the increase in N addition, the growth rate of the plant was improved. Therefore, in order to maintain its own N:P nutrient balance (Table S1), the plant demanded more P [24,25], which in turn led to a decrease in the content of soil inorganic P components with the increase in N addition. These findings confirm the first hypothesis that long-term N addition reduced available soil inorganic P concentrations. Plants and microorganisms sustained their P requirements through mobilization of labile organic P fractions, a response to N-induced P limitations [25]. The increased HROP and O-P content may be because these two forms of P are difficult for crops to absorb and utilize [14]. N addition could stimulate crop P uptake (Table S2), leading to greater use of labile P. As a result, the accumulation of these two less-soluble forms of P increased in the soil, while the overall soil P pool declined. When soil inorganic P is deficient, the effective source of soil P depends largely on organic P mineralization, and unstable organic P is particularly important, as it tends to be the first to undergo mineralization to meet plant and microbial needs [12,26], and thus unstable P is likely to be reduced with N addition [27]. Soil-soluble inorganic P, the most dynamically active P pool, is significantly influenced by short-term fluctuations in soil solution chemistry, plant–microbial interactions, and leaching processes [28,29]. Adsorbed inorganic P on mineral surfaces exhibits higher conversion potential to soluble forms in response to soil solution dynamics compared to more stabilized fractions [30]. LOP and MLOP undergo mineralization-driven transformation into bioavailable inorganic P, a process mediated by soil mineral adsorption during weathering [31]. These transformations occur predominantly at the solution/mineral interface, where mineralization-released phosphate either becomes adsorbed (forming unstable inorganic P) or enters the soil solution (contributing to soluble inorganic P) [32,33]. Collectively, these processes underscore the critical role of organic P mineralization in reducing soil total P reserves while simultaneously generating bioavailable inorganic P to sustain plant growth.
As depicted in Figure 1, the interannual variations in specific P fractions unveil intricate dynamic processes. Over the course of the study period, organic P, including MLOP and MROP, demonstrates an overall declining trend, which aligns precisely with our proposed hypothesis. The gradual depletion of the more stable P pool, namely HROP, may imply that microorganisms are engaged in a slow yet continuous activation of recalcitrant organic P under conditions of persistent P deficiency. The contrasting trend observed in inorganic P components, such as Ca2-P and Ca8-P, which initially increased and subsequently decreased, can be ascribed to the complex interplay between N fertilizer application and plant uptake [34]. For example, the early-stage stimulation of mineralization may transiently elevate the levels of readily available inorganic P. Accelerated microbial mineralization is swiftly transforming stable organic P and insoluble inorganic P into soluble P reservoirs. This process partially compensates for the reduction in TP reserves while giving priority to meeting the immediate P demands of crops. Nevertheless, over the long term, the high plant uptake rates under N fertilization conditions are likely to result in the depletion of these P reservoirs. N addition significantly reduced the content of reactive organic P (p < 0.05; Figure 1), and this dynamic change may be closely related to the biochemical effects triggered by N inputs. First, the increase in SOC content stimulates microbial activity and then promotes the mineralization of organic P through the biomineralization process [35]. Second, competitive adsorption of NH4+ significantly reduces the fixation capacity of Fe-Al oxides to LOP, leading to the release of active components to the solution phase. In addition, C:N:P stoichiometric imbalance induced by N input may indirectly affect organic P stability by altering substrate availability [36]. While interconversions among stabilized, moderately stabilized, and occluded P pools can temporarily replenish bioavailable inorganic P under N addition regimes, thereby alleviating short-term P limitations, these transformation processes risk depleting soil P reserves over extended periods [37].

4.2. Effects of N Addition on Soil Microbial Variables

N addition can stimulate the production of phosphatase, which can decompose organic P compounds and make them available for plant absorption [38]. Our study found that N addition significantly increased ALP and PHY activities (Table 2) and also increased the dominant genera with higher relative abundance: Sphingomonas (2.21–3.07%), RB41 (2.39–2.87%), and MND1 (1.00–1.65%) (Figure 2a). This result may be related to P limitation (C:N:P stoichiometric imbalance) exacerbated by N inputs, forcing microorganisms to acquire P resources through enhanced phosphatase secretion [39]. Meanwhile, N addition significantly enhanced the relative abundance of Ascomycetes, Actinobacteria, and Acidobacteria, which is consistent with the findings of on P-cycle microorganisms in antimony mine soils [40]. These phyla play an important role in P transformation, promoting the dissolution and mineralization of organic P, thereby providing plants with available active P and alleviating soil P limitation. In contrast, Aspergillus is an important taxon in calcareous soils that promotes organic acid synthesis and antibiotic production and facilitates P solubilization [41]. In this study, we showed that the addition of an appropriate amount of N could promote the growth of the strain of RB41 (Figure 2a), and the strain was positively correlated with organic P (Figure 4a). RB41 can decompose organic substances and convert them into inorganic substances, thus releasing nutrients for plants and other organisms to utilize and playing an important role in regulating nutrient balance [42]. This suggests that appropriate N addition facilitates the survival and reproduction of these genera and also promotes the growth of crops [43].
Genus-level analysis of the fungal community showed that the relative abundance of Mortierella was relatively high (15.39–32.06%), which was the dominant genus (Figure 2b). Mortierella promotes plant growth and is a beneficial microorganism in the soil that can supplement N, solubilize P, and enhance plant disease resistance. It has the potential to solubilize soil P through the secretion of diverse organic acids [44,45,46]. In this study, the relative abundance of Mortierella exhibited a decreasing trend with increasing N addition, consistent with its known preference for neutral to alkaline environments. This shift in community structure can be regarded as one of the biological consequences of the material–energy balance within the soil ecosystem under N-enriched conditions. Even without significant overall soil acidification, altered competitive pressures and resource availability (such as intensified competition for available carbon and P) likely conferred a competitive advantage to other more adaptable species (e.g., Filobasidium, RB41) relative to Mortierella. As a result, its growth and reproduction could be inhibited, ultimately leading to a decrease in its relative abundance. Random forest analysis revealed that fungal genera Filobasidium and Botryotrichum were significantly associated with organic P dynamics, demonstrating the capacity to decompose soil organic P compounds and enhance nutrient cycling efficiency (Figure 4b). These taxa mediated organic P decomposition through three core pathways: acidification-driven dissolution, enzymatic hydrolysis, and cometabolic conversion. Functional predictions indicated that soil bacterial communities primarily engaged in metabolic processes (79.7–80.1%), with secondary functional categories including global and overview maps (42.5–42.7%), carbohydrate metabolism (9.0–9.1%), and amino acid metabolism (7.5–7.7%) (Table S3 and Figure S4a). Through metabolic activities, soil microorganisms actively participate in material transformation and regulate biogeochemical processes [47], while N addition-induced P-cycle intensification promoted plant metabolic efficiency. Fungal functional analysis demonstrated that N addition significantly enhanced arbuscular mycorrhizal fungi (AMF) abundance (Figure S4b), suggesting that mycorrhizal symbiosis improves plant acquisition of soil-insoluble P. AMF are particularly effective in enhancing plant access to recalcitrant P in nutrient-depleted soils [48].

4.3. Mechanism of Microbial-Mediated Organic P Mineralization Under N Addition

In this study, soil microbial biomass and phosphatase activity played a dominant role in controlling the response of organic P transformation to N addition. We found that N addition significantly increased MBC (197.20–255.82 mg kg−1), MBN (31.61–59.67 mg kg−1), and MBP (7.55–24.21 mg kg−1) contents (p < 0.05; Table 2), which was similar to the results of previous studies [49,50]. This response likely stems from N supplementation providing essential nutrients for microbial proliferation. Exogenous N inputs may indirectly enhance MBC and MBP acquisition efficiency [51], thereby stimulating MBC and MBP accumulation. MBP is a readily degradable form of P that indirectly affects ALP activity by influencing the abundance of the phoD gene [52]. Elevated N inputs upregulated microbial enzymatic metabolism, increased phoD gene abundance, and enhanced microbial productivity, ultimately driving significant changes in phosphatase activity that accelerated organic P mineralization [16]. In addition, N addition significantly increased SOC and MBC contents (p < 0.05; Table 2 and Table S1), aligning with Heuck et al.’s (2015) [53] observation that microbial P acquisition depends on carbon availability, while MBP accumulation correlates with MBC pool size. Abundant carbon sources enhance microbial diversity, thereby altering bacterial community composition [54]. P-solubilizing microorganisms (PSMs) play pivotal roles in activating recalcitrant P through enzymatic conversion to bioavailable forms, enhancing plant P uptake efficiency [55]. We found that MBP directly influenced Filobasidium abundance, which in turn significantly modulated ALP and phytase (PHY) activities (Figure 5b). This is likely due to phospholipids and nucleic acids constituting the majority of soil MBP, which belongs to the easily degradable P form and can be directly used as metabolic substrates of the P phase. The increase in the relative abundance of the P-solubilizing fungi Filobasidium was significantly and positively correlated with the elevated ALP and PHY activity (Figure 5a), indicating that microorganisms convert desorbed organic P into inorganic P through enhanced enzymatic degradation. Additionally, PSMs fix some of the P during growth [56], which returns to the soil after death and becomes a source of P uptake by plants (Table S2). These findings underscore the capacity of bacterial and fungal communities to accelerate P mineralization [57]. They improve the bioavailability of plants to use insoluble P in soil, dissolve insoluble inorganic P, mineralize insoluble organic P, and act as biofertilizers by enabling growing plants to obtain otherwise unavailable P [58]. ALP and PHY emerged as critical enzymes mediating microbial-driven P transformations, with microbial P demand directly regulating extracellular phosphatase secretion and soil P availability [59]. Our results showed that N addition increased the demand for P by microorganisms, resulting in increased ALP and PHY activity (Table 2), and the phosphate-solubilizing process was closely related to fungi (Filobasidium) (Figure 5b). This interdependency extends to coupled N-P biogeochemical cycles, where N inputs accelerate P cycling, stimulate phosphatase activity, and enhance P mineralization rates [60]. In summary, soil P transformation dynamics can be complicated by the indirect effects of N input on environmental factors. Although long-term N addition reduces soil P availability, the resultant depletion of soluble inorganic P is rapidly replenished by labile inorganic P fractions. These labile inorganic pools may be further replenished through organic P mineralization; however, this process exhibits slower kinetics, requiring extended timeframes.

5. Limitations and Implications

This study offers a systems-level perspective on microbial-mediated P cycling by integrating community structure with enzyme activity. However, the mechanistic interpretations are confined to the framework of this particular approach.
Firstly, in this study, we relied on structural shifts in the microbial community (e.g., the enrichment of Filobasidium) and enzyme assays to infer functional attributes, without conducting direct profiling of P-cycling functional genes (e.g., phoD, phoC, pstS). Secondly, the lack of isotopic tracers hindered in situ tracking of P fluxes.
Therefore, future research should build on the relationships identified in this study. Specifically, it should employ metagenomic and metatranscriptomic analyses to directly link taxonomic shifts to the abundance and expression of key functional genes. Coupling these analyses with stable isotope probing (SIP) techniques will establish a causal, multi-dimensional framework that connects gene expression, enzyme activity, and P transformation in situ.

6. Conclusions

To investigate the microbial-mediated mineralization process of organic P under N addition, we utilized high-throughput sequencing to evaluate the responses of soil P fractions, enzyme activities, and microbial community structure. Our long-term field experiment revealed that N fertilization significantly modified soil P composition by promoting the microbial mineralization of organic P, mainly through increases in MBC and ALP activity. This promotion was most evident under a moderate N input of 115 kg N ha−1 year−1 (N115), which we identified as the optimal level for stimulating this biological process. A key novel discovery of our research was the identification of the fungal genus Filobasidium as a keystone taxon. Its strong positive correlation with ALP and PHY activities highlighted its crucial role in regulating the enzymatic turnover of organic P, thereby driving the enhanced P availability to support spring wheat uptake.
Consequently, to maintain soil productivity in the rain-fed agroecosystems of the Loess Plateau, we recommend a balanced nutrient management strategy: combining moderate N fertilization at the identified optimal rate (N115) with strategic P supplementation. This approach capitalizes on the N-induced microbial mechanism to maximize P availability while preventing the depletion of the soil’s labile P reservoir. Our study elucidates the pivotal role of microbial community restructuring, especially through key taxa like Filobasidium, in sustaining soil P cycling under long-term N enrichment. This provides a mechanistic foundation for sustainable nutrient management.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/agronomy15112632/s1, Figure S1: Location of the experimental site. Revision No. GS (2023)2767; Figure S2: Average monthly rainfall during the experiment; Figure S3: N and P ecological stoichiometry test plot map; Figure S4: Relative abundance of soil microbial gene functions. Table S1: Effects of N addition on soil physical and chemical properties; Table S2: Effects of N addition on P content in organs, above-ground biomass and yield of spring wheat; Table S3: Abundance of primary functional genes of soil bacteria in different treatments.

Author Contributions

Conceptualization, P.Q. and H.L. (Huaqiang Li); methodology, P.Q. and H.L. (Huaqiang Li); software, H.L. (Huaqiang Li); validation, P.Q. and H.L. (Huaqiang Li); formal analysis, H.L. (Huaqiang Li); investigation, P.Q., H.L. (Huaqiang Li), X.Y., R.G., M.L., X.W. and Y.H.; resources, P.Q.; data curation, H.L. (Huaqiang Li), X.Y. and J.X.; writing—draft preparation, H.L. (Huaqiang Li); writing—review and editing, H.L. (Huaqiang Li) and P.Q.; visualization, H.L. (Huaqiang Li); supervision, P.Q., G.L. and H.L. (Hailiang Li).; project administration, P.Q.; funding acquisition, P.Q.; resources, P.Q. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the National Natural Science Foundation of China (Nos. 42567006, 32560318, 32260549), the State Key Laboratory of Aridland Crop Science, Gansu Agricultural University (No. GSCS-2022-Z02), the National Key R&D Program of China (No. 2022YFD1900300), and the Science and Technology Project of Gansu Province (No. 25JRRA807).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data presented in this study are available upon request from the corresponding author. The data are not publicly available due to privacy requirements.

Acknowledgments

The authors sincerely thank the anonymous reviewers for their valuable comments and suggestions that improved the quality of this paper. The authors also gratefully acknowledge the help of Peng Qi for his comments on the first draft of this manuscript.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. Mason, R.E.; Craine, J.M.; Lany, N.K.; Jonard, M.; Ollinger, S.V.; Groffman, P.M.; Fulweiler, R.W.; Angerer, J.; Read, Q.D.; Reich, P.B.; et al. Evidence, causes, and consequences of declining nitrogen availability in terrestrial ecosystems. Science 2022, 376, eabh3767. [Google Scholar] [CrossRef]
  2. Yu, G.; Jia, Y.; He, N.; Zhu, J.; Chen, Z.; Wang, Q.; Piao, S.; Liu, X.; He, H.; Guo, X.; et al. Stabilization of atmospheric nitrogen deposition in China over the past decade. Nat. Geosci. 2019, 12, 424–429. [Google Scholar] [CrossRef]
  3. Cui, Y.; Zhang, Y.; Duan, C.; Wang, X.; Zhang, X.; Ju, W.; Chen, H.; Yue, S.; Wang, Y.; Li, S.; et al. Ecoenzymatic stoichiometry reveals microbial phosphorus limitation decreases the nitrogen cycling potential of soils in semi-arid agricultural ecosystems. Soil Tillage Res. 2020, 197, 104463. [Google Scholar] [CrossRef]
  4. Regus, J.U.; Wendlandt, C.E.; Bantay, R.M.; Gano-Cohen, K.A.; Gleason, N.J.; Hollowell, A.C.; O’Neill, M.R.; Shahin, K.K.; Sachs, J.L. Nitrogen deposition decreases the benefits of symbiosis in a native legume. Plant Soil 2017, 414, 159–170. [Google Scholar] [CrossRef]
  5. Shen, J.; Yuan, L.; Zhang, J.; Li, H.; Bai, Z.; Chen, X.; Zhang, W.; Zhang, F. Phosphorus dynamics: From soil to plant. Plant Physiol. 2011, 156, 997–1005. [Google Scholar] [CrossRef] [PubMed]
  6. Chen, S.; Yan, Z.; Zhang, S.; Fan, B.; Cade-Menun, B.J.; Chen, Q. Nitrogen application favors soil organic phosphorus accumulation in calcareous vegetable fields. Biol. Fertil. Soils 2019, 55, 481–496. [Google Scholar] [CrossRef]
  7. Menezes-Blackburn, D.; Giles, C.; Darch, T.; George, T.S.; Blackwell, M.; Stutter, M.; Shand, C.; Lumsdon, D.; Cooper, P.; Wendler, R.; et al. Opportunities for mobilizing recalcitrant phosphorus from agricultural soils: A review. Plant Soil 2018, 427, 5–16. [Google Scholar] [CrossRef]
  8. Richards, S.; Marshall, R.; Lag-Brotons, A.J.; Semple, K.T.; Stutter, M. Phosphorus solubility changes following additions of bioenergy wastes to an agricultural soil: Implications for crop availability and environmental mobility. Geoderma 2021, 401, 115150. [Google Scholar] [CrossRef]
  9. Tian, J.; Dungait, J.A.J.; Lu, X.; Yang, Y.; Hartley, I.P.; Zhang, W.; Mo, J.; Yu, G.; Zhou, J.; Kuzyakov, Y. Long-term nitrogen addition modifies microbial composition and functions for slow carbon cycling and increased sequestration in tropical forest Soil. Glob. Change Biol. 2019, 25, 3267–3281. [Google Scholar] [CrossRef]
  10. Li, Y.; Niu, S.; Yu, G. Aggravated phosphorus limitation on biomass production under increasing nitrogen loading: A meta-analysis. Glob. Change Biol. 2016, 22, 934–943. [Google Scholar] [CrossRef] [PubMed]
  11. Zeng, Q.X.; Zeng, X.M.; Lin, K.M.; Zhang, Q.F.; Cheng, L.; Zhou, J.C.; Lin, Q.Y.; Chen, Y.M.; Xu, J.G. Responses of soil phosphorus fractions and microorganisms to nitrogen application in a subtropical Phyllostachys pubescen forest. Ying Yong Sheng Tai Xue Bao 2020, 31, 753–760. [Google Scholar]
  12. Deng, Q.; Hui, D.; Dennis, S.; Reddy, K.C. Responses of terrestrial ecosystem phosphorus cycling to nitrogen addition: A meta-analysis. Glob. Ecol. Biogeogr. 2017, 26, 713–728. [Google Scholar] [CrossRef]
  13. Widdig, M.; Heintz-Buschart, A.; Schleuss, P.-M.; Guhr, A.; Borer, E.T.; Seabloom, E.W.; Spohn, M. Effects of nitrogen and phosphorus addition on microbial community composition and element cycling in a grassland Soil. Soil Biol. Biochem. 2020, 151, 108041. [Google Scholar]
  14. Jiao, Y.P.; Qi, P.; Wang, X.J.; Yao, Y.M.; Wu, J.; Cai, L.Q.; Zhang, R.Z. Effects of nitrogen and phosphorus fertilization on inorganic phosphorus forms of typical farmland soil in the dry farming area of the Loess Plateau. J. Plant Nutr. Fertil. 2020, 26, 1459–1472. [Google Scholar]
  15. Mirabello, M.J.; Yavitt, J.B.; Garcia, M.; Harms, K.E.; Turner, B.L.; Wright, S.J. Soil phosphorus responses to chronic nutrient fertilisation and seasonal drought in a humid lowland forest, Panama. Soil Res. 2013, 51, 215–221. [Google Scholar] [CrossRef]
  16. Cui, H.Y.; Sun, W.; Delgado-Baquerizo, M.; Song, W.Z.; Ma, J.Y.; Wang, K.Y.; Ling, X.L. Cascading effects of N fertilization activate biologically driven mechanisms promoting P availability in a semi-arid grassland ecosystem. Funct. Ecol. 2021, 35, 1001–1011. [Google Scholar] [CrossRef]
  17. Chen, Y.F.; Wang, H.; Niu, B.; Yin, L.N.; Wang, S.W.; Deng, X.P. Response of nitrogen fertilizer productivity of spring maize on the Loess Plateau to different tillage measures: A meta-analysis. Chin. J. Eco-Agric. 2024, 32, 755–765. [Google Scholar]
  18. Yamamoto, S.; Endo, T. Soils on the Loess Plateau. In Restoration and Development of the Degraded Loess Plateau, China; Tsunekawa, A., Liu, G., Yamanaka, N., Du, S., Eds.; Springer: Japan, Tokyo, 2014; pp. 35–47. [Google Scholar]
  19. Bao, S.D. Soil and Agricultural Chemistry Analysis; China Agriculture Press: Beijing, China, 2000. [Google Scholar]
  20. Yang, J.C.; Wang, Z.G.; Zhou, J.; Jiang, H.M.; Zhang, J.F.; Pan, P.; Han, Z.; Lu, C.; Li, L.L.; Ge, C.L. Inorganic phosphorus fractionation and its translocation dynamics in a low-P Soil. J. Environ. Radioact. 2012, 112, 64–69. [Google Scholar] [CrossRef]
  21. Bowman, R.A.; Cole, C.V. Transformations of Organic Phosphorus Substrates in Soils as Evaluated by NaHCO3 Extraction. Soil Sci. 1978, 125, 49–54. [Google Scholar] [CrossRef]
  22. Burns, R.G.; DeForest, J.L.; Marxsen, J.; Sinsabaugh, R.L.; Stromberger, M.E.; Wallenstein, M.D.; Weintraub, M.N.; Zoppini, A. Soil enzymes in a changing environment: Current knowledge and future directions. Soil Biol. Biochem. 2013, 58, 216–234. [Google Scholar] [CrossRef]
  23. Bolyen, E.; Rideout, J.R.; Dillon, M.R.; Bokulich, N.A.; Abnet, C.C.; Al-Ghalith, G.A.; Alexander, H.; Alm, E.J.; Arumugam, M.; Asnicar, F.; et al. Reproducible, interactive, scalable and extensible microbiome data science using QIIME 2. Nat. Biotechnol. 2019, 37, 852–857. [Google Scholar] [CrossRef] [PubMed]
  24. Crowley, K.F.; McNeil, B.E.; Lovett, G.M.; Canham, C.D.; Driscoll, C.T.; Rustad, L.E.; Denny, E.; Hallett, R.A.; Arthur, M.A.; Boggs, J.L.; et al. Do Nutrient Limitation Patterns Shift from Nitrogen Toward Phosphorus with Increasing Nitrogen Deposition Across the Northeastern United States? Ecosystems 2012, 15, 940–957. [Google Scholar] [CrossRef]
  25. Fan, Y.; Lin, F.; Yang, L.; Zhong, X.; Wang, M.; Zhou, J.; Chen, Y.; Yang, Y. Decreased soil organic P fraction associated with ectomycorrhizal fungal activity to meet increased P demand under N application in a subtropical forest ecosystem. Biol. Fertil. Soils 2018, 54, 149–161. [Google Scholar] [CrossRef]
  26. Nasto, M.K.; Alvarez-Clare, S.; Lekberg, Y.; Sullivan, B.W.; Townsend, A.R.; Cleveland, C.C. Interactions among nitrogen fixation and soil phosphorus acquisition strategies in lowland tropical rain forests. Ecol. Lett. 2014, 17, 1282–1289. [Google Scholar] [CrossRef] [PubMed]
  27. Blake, L.; Johnston, A.E.; Poulton, P.R.; Goulding, K.W.T. Changes in soil phosphorus fractions following positive and negative phosphorus balances for long periods. Plant Soil 2003, 254, 245–261. [Google Scholar] [CrossRef]
  28. Frossard, E.; Condron, L.M.; Oberson, A.; Sinaj, S.; Fardeau, J.C. Processes Governing Phosphorus Availability in Temperate Soils. J. Environ. Qual. 2000, 29, 15–23. [Google Scholar] [CrossRef]
  29. Turner, B.L.; Haygarth, P.M. Phosphorus Forms and Concentrations in Leachate under Four Grassland Soil Types. Soil Sci. Soc. Am. J. 2000, 64, 1090–1099. [Google Scholar] [CrossRef]
  30. Hou, E.Q.; Tang, S.B.; Chen, C.R.; Kuang, Y.W.; Lu, X.K.; Heenan, M.; Wen, D.Z. Solubility of phosphorus in subtropical forest soils as influenced by low-molecular organic acids and key soil properties. Geoderma 2018, 313, 172–180. [Google Scholar] [CrossRef]
  31. Barrow, N.J. A mechanistic model for describing the sorption and desorption of phosphate by Soil. Eur. J. Soil Sci. 2015, 66, 9–18. [Google Scholar] [CrossRef]
  32. Guppy, C.N.; Menzies, N.W.; Moody, P.W.; Blamey, F.P.C. Competitive sorption reactions between phosphorus and organic matter in soil: A review. Soil Res. 2005, 43, 189–202. [Google Scholar] [CrossRef]
  33. Uroz, S.; Calvaruso, C.; Turpault, M.-P.; Frey-Klett, P. Mineral weathering by bacteria: Ecology, actors and mechanisms. Trends Microbiol. 2009, 17, 378–387. [Google Scholar] [CrossRef]
  34. Petrović, D.; Szeler, K.; Kamerlin, S.C.L. Challenges and advances in the computational modeling of biological phosphate hydrolysis. Chem. Commun. 2018, 54, 3077–3089. [Google Scholar] [CrossRef]
  35. Zhang, W.N.; Yang, Z.; Yan, Y.P.; Wang, X.M.; Yin, H.; Xu, R.K.; Tan, W.F.; Feng, X.H. Research Progress on Soil Organic Phosphorus Mineralization and Its Regulation. Acta Pedol. Sin. 2025, 62, 334–347. [Google Scholar]
  36. Peñuelas, J.; Poulter, B.; Sardans, J.; Ciais, P.; van der Velde, M.; Bopp, L.; Boucher, O.; Godderis, Y.; Hinsinger, P.; Llusia, J.; et al. Human-induced nitrogen-phosphorus imbalances alter natural and managed ecosystems across the globe. Nat. Commun. 2013, 4, 2934. [Google Scholar] [CrossRef] [PubMed]
  37. Yu, Q.S.; Hagedorn, F.; Penuelas, J.; Sardans, J.; Tan, X.P.; Yan, Z.B.; He, C.Q.; Ni, X.F.; Feng, Y.H.; Zhu, J.L.; et al. Differential Responses of Soil Phosphorus Fractions to Nitrogen and Phosphorus Fertilization: A Global Meta-Analysis. Glob. Biogeochem. Cycles 2024, 38, e2023GB008064. [Google Scholar] [CrossRef]
  38. Yu, Q.S.; Ma, S.H.; Ni, X.F.; Ni, X.L.; Guo, Z.M.; Tan, X.P.; Zhong, M.Y.; Abu Hanif, M.; Zhu, J.L.; Ji, C.J.; et al. Long-term phosphorus addition inhibits phosphorus transformations involved in soil arbuscular mycorrhizal fungi and acid phosphatase in two tropical rainforests. Geoderma 2022, 425, 116076. [Google Scholar] [CrossRef]
  39. Belinque, H.; Pucheu, N.; Kerber, N.; Rubio, G. Utilization of organic phosphorus sources by oilseed rape, sunflower, and soybean. J. Plant Nutr. Soil Sci. 2015, 178, 339–344. [Google Scholar] [CrossRef]
  40. Liu, S.; Zeng, J.; Yu, H.; Wang, C.; Yang, Y.; Wang, J.; He, Z.; Yan, Q. Antimony efflux underpins phosphorus cycling and resistance of phosphate-solubilizing bacteria in mining soils. ISME J. 2023, 17, 1278–1289. [Google Scholar] [CrossRef] [PubMed]
  41. Zhang, M.Y.; Liang, W.; Tu, Z.N.; Li, R.H.; Zhang, Z.Q.; Ali, A.; Xiao, R. Succession of bacterial community during composting: Dissimilarity between compost mixture and biochar additive. Biochar 2021, 3, 229–237. [Google Scholar] [CrossRef]
  42. Amini, S.; Ghadiri, H.; Chen, C.R.; Marschner, P. Salt-affected soils, reclamation, carbon dynamics, and biochar: A review. J. Soils Sediments 2016, 16, 939–953. [Google Scholar] [CrossRef]
  43. Lu, C.; Hong, Y.; Liu, J.; Gao, Y.; Ma, Z.; Yang, B.; Ling, W.; Waigi, M.G. A PAH-degrading bacterial community enriched with contaminated agricultural soil and its utility for microbial bioremediation. Environ. Pollut. 2019, 251, 773–782. [Google Scholar] [CrossRef]
  44. Liao, X.; Fang, W.; Lin, L.; Lu, H.L.; St Leger, R.J. Metarhizium robertsii produces an extracellular invertase (MrINV) that plays a pivotal role in rhizospheric interactions and root colonization. PLoS ONE 2013, 8, e78118. [Google Scholar] [CrossRef]
  45. Osorio, N.W.; Habte, M. Soil Phosphate Desorption Induced by a Phosphate-Solubilizing Fungus. Commun. Soil Sci. Plant Anal. 2014, 45, 451–460. [Google Scholar] [CrossRef]
  46. Zhang, H.S.; Wu, X.H.; Li, G.; Qin, P. Interactions between arbuscular mycorrhizal fungi and phosphate-solubilizing fungus (Mortierella sp.) and their effects on Kostelelzkya virginica growth and enzyme activities of rhizosphere and bulk soils at different salinities. Biol. Fertil. Soils 2011, 47, 543–554. [Google Scholar] [CrossRef]
  47. Wu, Z.X.; Hao, Z.P.; Sun, Y.Q.; Guo, L.P.; Huang, L.Q.; Zeng, Y.; Wang, Y.; Yang, L.; Chen, B.D. Comparison on the structure and function of the rhizosphere microbial community between healthy and root-rot Panax notoginseng. Appl. Soil Ecol. 2016, 107, 99–107. [Google Scholar] [CrossRef]
  48. Lambers, H.; Albornoz, F.; Kotula, L.; Laliberté, E.; Ranathunge, K.; Teste, F.P.; Zemunik, G. How belowground interactions contribute to the coexistence of mycorrhizal and non-mycorrhizal species in severely phosphorus-impoverished hyperdiverse ecosystems. Plant Soil 2018, 424, 11–33. [Google Scholar] [CrossRef]
  49. Samuelson, L.; Mathew, R.; Stokes, T.; Feng, Y.; Aubrey, D.; Coleman, M. Soil and microbial respiration in a loblolly pine plantation in response to seven years of irrigation and fertilization. For. Ecol. Manag. 2009, 258, 2431–2438. [Google Scholar] [CrossRef]
  50. Tu, L.H.; Chen, G.; Peng, Y.; Hu, H.L.; Hu, T.X.; Zhang, J.; Li, X.W.; Liu, L.; Tang, Y. Soil Biochemical Responses to Nitrogen Addition in a Bamboo Forest. PLoS ONE 2014, 9, e102315. [Google Scholar] [CrossRef]
  51. Shen, R.-C.; Xu, M.; Chi, Y.-G.; Yu, S.; Wan, S.-Q. Soil Microbial Responses to Experimental Warming and Nitrogen Addition in a Temperate Steppe of Northern China. Pedosphere 2014, 24, 427–436. [Google Scholar] [CrossRef]
  52. He, R.Y.; Luo, Z.Z.; Li, L.L.; Niu, Y.N.; Zhang, Y.Q.; Li, L.L.; Liu, J.H.; Chen, Z.M. Long-Term Phosphate Addition Changes Soil P Accumulation via phoD-Harbouring Bacterial Community in Loess Plateau. Eur. J. Soil Sci. 2025, 76, e70067. [Google Scholar] [CrossRef]
  53. Heuck, C.; Weig, A.; Spohn, M. Soil microbial biomass C:N:P stoichiometry and microbial use of organic phosphorus. Soil Biol. Biochem. 2015, 85, 119–129. [Google Scholar] [CrossRef]
  54. Luo, G.; Sun, B.; Li, L.; Li, M.; Liu, M.; Zhu, Y.; Guo, S.; Ling, N.; Shen, Q. Understanding how long-term organic amendments increase soil phosphatase activities: Insight into phoD- and phoC-harboring functional microbial populations. Soil Biol. Biochem. 2019, 139, 107632. [Google Scholar] [CrossRef]
  55. Marra, L.M.; de Oliveira-Longatti, S.M.; Soares, C.R.; de Lima, J.M.; Olivares, F.L.; Moreira, F.M. Initial pH of medium affects organic acids production but do not affect phosphate solubilization. Braz. J. Microbiol. 2015, 46, 367–375. [Google Scholar] [CrossRef]
  56. Turner, B.L.; Driessen, J.P.; Haygarth, P.M.; McKelvie, I.D. Potential contribution of lysed bacterial cells to phosphorus solubilisation in two rewetted Australian pasture soils. Soil Biol. Biochem. 2003, 35, 187–189. [Google Scholar] [CrossRef]
  57. Alori, E.T.; Glick, B.R.; Babalola, O.O. Microbial Phosphorus Solubilization and Its Potential for Use in Sustainable Agriculture. Front. Microbiol. 2017, 8, 971. [Google Scholar] [CrossRef] [PubMed]
  58. Sharma, S.B.; Sayyed, R.Z.; Trivedi, M.H.; Gobi, T.A. Phosphate solubilizing microbes: Sustainable approach for managing phosphorus deficiency in agricultural soils. SpringerPlus 2013, 2, 587. [Google Scholar] [CrossRef] [PubMed]
  59. Cui, H.; Zhou, Y.; Gu, Z.H.; Zhu, H.H.; Fu, S.L.; Yao, Q. The combined effects of cover crops and symbiotic microbes on phosphatase gene and organic phosphorus hydrolysis in subtropical orchard soils. Soil Biol. Biochem. 2015, 82, 119–126. [Google Scholar] [CrossRef]
  60. Marklein, A.R.; Houlton, B.Z. Nitrogen inputs accelerate phosphorus cycling rates across a wide variety of terrestrial ecosystems. New Phytol. 2012, 193, 696–704. [Google Scholar] [CrossRef]
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Figure 1. Changes in the contents of different soil P fractions under N addition. Ca2-P, dicalcium phosphate (a), Ca8-P, octacalcium phosphate (b), Ca10-P, apatite (c), Al-P, aluminum phosphate (d), Fe-P, ferric phosphate (e), O-P, closed storage phosphorus (f), AP, available phosphorus (g), Total inorganic phosphorus (h), LOP, labile organic phosphorus (i), MLOP, moderately labile organic phosphorus (j), MROP, moderately resistant organic phosphorus (k), HROP, highly resistant organic phosphorus (l), total organic phosphorus (m), TP, total phosphorus (n), total inorganic phosphorus/total organic phosphorus (o), and TP of plant (p). Each value represents the average ± standard deviation (n = 3); N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively. Differences (p < 0.05) between years are indicated by upper-case letters, and differences (p < 0.05) between N addition rates are indicated by lower-case letters.
Figure 1. Changes in the contents of different soil P fractions under N addition. Ca2-P, dicalcium phosphate (a), Ca8-P, octacalcium phosphate (b), Ca10-P, apatite (c), Al-P, aluminum phosphate (d), Fe-P, ferric phosphate (e), O-P, closed storage phosphorus (f), AP, available phosphorus (g), Total inorganic phosphorus (h), LOP, labile organic phosphorus (i), MLOP, moderately labile organic phosphorus (j), MROP, moderately resistant organic phosphorus (k), HROP, highly resistant organic phosphorus (l), total organic phosphorus (m), TP, total phosphorus (n), total inorganic phosphorus/total organic phosphorus (o), and TP of plant (p). Each value represents the average ± standard deviation (n = 3); N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively. Differences (p < 0.05) between years are indicated by upper-case letters, and differences (p < 0.05) between N addition rates are indicated by lower-case letters.
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Figure 2. Relative abundance (>1%) and LEfSe analysis of dominant genera of soil microorganisms under different N addition rates. (a,b) represent bacterial genus-level relative abundance and LEfSe analysis, respectively; (c,d) represent fungal genus-level relative abundance and LEfSe analysis, respectively; The figures show the genera with LDA Score greater than 2.5; Nodes with different colors represent the bacterial taxa that were significantly enriched in the corresponding treatments and had significant influences on the discrepancies among treatments; the light yellow nodes indicate the bacterial taxa that showed no significant difference among different treatments or had no significant effect on the discrepancies among treatments. N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively.
Figure 2. Relative abundance (>1%) and LEfSe analysis of dominant genera of soil microorganisms under different N addition rates. (a,b) represent bacterial genus-level relative abundance and LEfSe analysis, respectively; (c,d) represent fungal genus-level relative abundance and LEfSe analysis, respectively; The figures show the genera with LDA Score greater than 2.5; Nodes with different colors represent the bacterial taxa that were significantly enriched in the corresponding treatments and had significant influences on the discrepancies among treatments; the light yellow nodes indicate the bacterial taxa that showed no significant difference among different treatments or had no significant effect on the discrepancies among treatments. N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively.
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Figure 3. α-diversity and β-diversity of soil microbial community under N addition. (a): α-diversity of bacteria; (b): α-diversity of fungi; (c): β-diversity of bacteria; (d): β-diversity of fungi. Chao1 represents community richness, and Shannon represents community diversity. Each point in panels (c,d) represents a sample; different colors represent different samples/groups. N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively. In the figure, letters a, b, and c indicate significant differences between groups, with different letters denoting statistically significant differences (p < 0.05).
Figure 3. α-diversity and β-diversity of soil microbial community under N addition. (a): α-diversity of bacteria; (b): α-diversity of fungi; (c): β-diversity of bacteria; (d): β-diversity of fungi. Chao1 represents community richness, and Shannon represents community diversity. Each point in panels (c,d) represents a sample; different colors represent different samples/groups. N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively. In the figure, letters a, b, and c indicate significant differences between groups, with different letters denoting statistically significant differences (p < 0.05).
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Figure 4. Random forest model analysis. The analysis identified key predictors of organic P for bacteria (a) and fungi (b). Environmental factors were key predictors of organic P (c) and inorganic P (d), while inorganic P components (e) and organic P components (f) were key predictors of AP. * and ** indicate significant differences at p < 0.05 and p < 0.01 levels, respectively. The blue represents a significant positive correlation, the Orange represents a correlation, but not significant.
Figure 4. Random forest model analysis. The analysis identified key predictors of organic P for bacteria (a) and fungi (b). Environmental factors were key predictors of organic P (c) and inorganic P (d), while inorganic P components (e) and organic P components (f) were key predictors of AP. * and ** indicate significant differences at p < 0.05 and p < 0.01 levels, respectively. The blue represents a significant positive correlation, the Orange represents a correlation, but not significant.
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Figure 5. Factors affecting the responses of P fractions to N addition. Ca2-P (dicalcium phosphate), Ca8-P (octacalcium phosphate), Ca10-P (apatite), Al-P (aluminum phosphate), Fe-P (ferric phosphate), O-P (closed storage phosphorus), LOP (labile organic phosphorus), MLOP (moderately labile organic phosphorus), MROP (moderately resistant organic phosphorus), HROP (highly organic phosphorus), AP (available phosphorus), PHY (phytase), ALP (alkaline phosphatase), MBC (microbial biomass carbon), MBP (microbial biomass phosphorus). For panel (a), *, **, and *** indicate significant differences at p < 0.05, p < 0.01, and p < 0.001 levels, respectively; for panel (b), the organic P composition is represented by the PC1 axis of PCA. Organic P components include LOP, MLOP, MROP, and HROP. The number on the arrow is the standardized path coefficient. The blue solid arrow represents a significant positive correlation, the red solid arrow represents a significant negative correlation, and the dotted arrow represents a correlation, but not significant. The thickness of the arrow represents the magnitude of the correlation. Panel (c) indicates the excitation effect of each index on organic P.
Figure 5. Factors affecting the responses of P fractions to N addition. Ca2-P (dicalcium phosphate), Ca8-P (octacalcium phosphate), Ca10-P (apatite), Al-P (aluminum phosphate), Fe-P (ferric phosphate), O-P (closed storage phosphorus), LOP (labile organic phosphorus), MLOP (moderately labile organic phosphorus), MROP (moderately resistant organic phosphorus), HROP (highly organic phosphorus), AP (available phosphorus), PHY (phytase), ALP (alkaline phosphatase), MBC (microbial biomass carbon), MBP (microbial biomass phosphorus). For panel (a), *, **, and *** indicate significant differences at p < 0.05, p < 0.01, and p < 0.001 levels, respectively; for panel (b), the organic P composition is represented by the PC1 axis of PCA. Organic P components include LOP, MLOP, MROP, and HROP. The number on the arrow is the standardized path coefficient. The blue solid arrow represents a significant positive correlation, the red solid arrow represents a significant negative correlation, and the dotted arrow represents a correlation, but not significant. The thickness of the arrow represents the magnitude of the correlation. Panel (c) indicates the excitation effect of each index on organic P.
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Table 1. Interactive effects of N addition and time on the contents of soil P fractions.
Table 1. Interactive effects of N addition and time on the contents of soil P fractions.
TargetsN AdditionTimeN Addition × Time
SigFpSigFpSigFp
Ca2-P***64.437<0.001***38.244<0.001ns2.341>0.05
Ca8-P*6.708<0.05**30.425<0.01**5.375<0.01
Al-P*4.991<0.05**18.916<0.01***6.292<0.001
Fe-P*8.854<0.05*9.154<0.05**5.341<0.01
Ca10-P*6.659<0.05***122.559<0.001***15.416<0.001
O-P*5.756<0.05ns4.473>0.05***14.603<0.001
LOP**26.736<0.01***39.910<0.001**5.532<0.01
MLOP**12.163<0.01**11.878<0.01***10.764<0.001
MROP***76.868<0.001***221.853<0.001ns1.331>0.05
HROP***49.179<0.001***37.794<0.001*2.632<0.05
TP**14.838<0.01***91.185<0.001***62.549<0.001
AP*5.318<0.05ns0.840>0.05***30.586<0.001
Total inorganic P***150.182<0.001***232.688<0.001***12.238<0.001
Total organic P***112.130<0.001***214.667<0.001***10.219<0.001
Total inorganic P/Total organic P***36.637<0.001***68.854<0.001***19.654<0.001
Note: Ca2-P: dicalcium phosphate, Ca8-P: octacalcium phosphate, Ca10-P: apatite, Al-P: aluminum phosphate, Fe-P: ferric phosphate, O-P: closed storage phosphorus, LOP: labile organic phosphorus, MLOP: moderately labile organic phosphorus, MROP: moderately resistant organic phosphorus, HROP: highly organic phosphorus, Olsen-P: rapidly available phosphorus, TP: total phosphorus. “*”, “**”, and “***” indicate significant differences at p < 0.05, p < 0.01, and p < 0.001 levels, respectively; ns: p > 0.05.
Table 2. Effects of N addition on soil enzyme activity and microbial biomass carbon, nitrogen, and phosphorus.
Table 2. Effects of N addition on soil enzyme activity and microbial biomass carbon, nitrogen, and phosphorus.
YearTreatmentAlkaline Phosphatase
/(mg g−1 24 h−1)		Phytase
/(U g−1)		Microbial Biomass Carbon
/(mg kg−1)		Microbial Biomass Nitrogen
/(mg kg−1)		Microbial Biomass Phosphorus
/(mg kg−1)
2019N01.08 ± 0.01 c1.01 ± 0.38 c231.10 ± 5.88 c31.61 ± 1.19 c7.55 ± 0.56 c
N751.11 ± 0.04 c1.18 ± 0.03 b242.36 ± 6.75 b35.61 ± 0.93 ab12.12 ± 0.90 a
N1151.42 ± 0.02 a1.39 ± 0.07 a255.82 ± 3.88 a37.45 ± 1.12 a13.43 ± 0.49 a
N1901.33 ± 0.03 b1.06 ± 0.03 c246.33 ± 3.57 ab33.87 ± 0.22 bc10.78 ± 0.78 b
2020N01.57 ± 0.038 c1.08 ± 0.03 c208.67 ± 10.50 c45.15 ± 3.61 c15.03 ± 1.02 c
N751.63 ± 0.03 c1.15 ± 0.02 b227.04 ± 2.01 b53.25 ± 2.65 b23.17 ± 1.27 a
N1152.12 ± 0.02 a1.42 ± 0.06 a243.67 ± 2.52 a59.67 ± 3.06 a24.21 ± 1.87 a
N1901.70 ± 0.23 b1.12 ± 0.01 bc235.08 ± 5.57 ab54.65 ± 2.01 ab19.58 ± 0.27 b
2023N00.95 ± 0.44 c1.09 ± 0.02 c197.20 ± 7.80 c48.82 ± 0.36 c11.63 ± 0.38 c
N751.07 ± 0.64 c1.27 ± 0.05 b227.97 ± 6.57 b51.83 ± 0.34 b14.75 ± 0.33 a
N1151.51 ± 0.10 a1.36 ± 0.03 a247.43 ± 2.64 a53.26 ± 0.37 a15.26 ± 0.29 a
N1901.30 ± 0.60 b1.15 ± 0.03 c238.60 ± 2.66 a51.35 ± 0.27 b12.86 ± 0.17 b
Note: Each value represents the average ± standard deviation (n = 3); N0, N75, N115, and N190 represent 0, 75, 115, and 190 kg N ha−1 year−1, respectively; and different letters for each variable in each year represent significant difference between N treatments (p < 0.05).
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Li, H.; Qi, P.; Yin, X.; Wang, X.; Gan, R.; Xue, J.; Han, Y.; Lu, M.; Liang, G.; Li, H. Long-Term Nitrogen Addition Promotes Microbial Mineralization of Organic Phosphorus Supporting Phosphorus Uptake in Spring Wheat. Agronomy 2025, 15, 2632. https://doi.org/10.3390/agronomy15112632

AMA Style

Li H, Qi P, Yin X, Wang X, Gan R, Xue J, Han Y, Lu M, Liang G, Li H. Long-Term Nitrogen Addition Promotes Microbial Mineralization of Organic Phosphorus Supporting Phosphorus Uptake in Spring Wheat. Agronomy. 2025; 15(11):2632. https://doi.org/10.3390/agronomy15112632

Chicago/Turabian Style

Li, Huaqiang, Peng Qi, Xiaodong Yin, Xiaojiao Wang, Run Gan, Jianglong Xue, Yangzi Han, Meixia Lu, Guopeng Liang, and Hailiang Li. 2025. "Long-Term Nitrogen Addition Promotes Microbial Mineralization of Organic Phosphorus Supporting Phosphorus Uptake in Spring Wheat" Agronomy 15, no. 11: 2632. https://doi.org/10.3390/agronomy15112632

APA Style

Li, H., Qi, P., Yin, X., Wang, X., Gan, R., Xue, J., Han, Y., Lu, M., Liang, G., & Li, H. (2025). Long-Term Nitrogen Addition Promotes Microbial Mineralization of Organic Phosphorus Supporting Phosphorus Uptake in Spring Wheat. Agronomy, 15(11), 2632. https://doi.org/10.3390/agronomy15112632

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