# Organic phosphorus leaching risk from agricultural soils across China

Xiaolei Sun, Roland Bol, Erwin Klumpp, Meng Li

► To cite this version:

Xiaolei Sun, Roland Bol, Erwin Klumpp, Meng Li. Organic phosphorus leaching risk from agricultural soils across China. Chemical and Biological Technologies in Agriculture, 2022, 9 (1), pp.35. 10.1186/s40538-022-00302-6 . hal-05175019

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# Organic phosphorus leaching risk from agricultural soils across China

Xiaolei Sun¹, Roland Bol¹,², Erwin Klumpp¹ and Meng Li<fnref n="3" />,⁴*

**Abstract**

**Background:** Leaching from agricultural land is one of the major pathways of phosphorus (P) loss from soils to waterbody and may induce adverse effect on territorial environment. Past studies usually focused on the loss of inorganic P (Pᵢ) while ignored the role of organic P (P₀) in leaching process. A total of 63 agricultural soil samples were collected from across China with various soil types including 21 paddy soils, 13 chernozems, 11 red soils and other type soils (n = 18) to identify the potential risk of P₀ and Pᵢ leaching from agricultural lands and to explore their relationships with soil basic properties, Fe/Al oxides, and P status.

**Results:** CaCl₂-extractable organic P (CaCl₂-P₀) accounted for 8–89% (35% on average) of CaCl₂-extractable total P (CaCl₂-P₇) and available organic P (AP₀) accounted to over half of available total P (AP₇) (57 ± 25%). CaCl₂-P₇ was positively correlated with AP₇ under all soil types except paddy soils. CaCl₂-extractable inorganic P (CaCl₂-Pᵢ) and available inorganic P (APᵢ) were strongly correlated for chernozem (r = 0.968), while CaCl₂-P₀ was strongly correlated with AP₀ for red soils (r = 0.901).

**Conclusions:** P₀ greatly contributed to the potential P leaching risk and should be included in the risk assessment of total P leaching. The control of soil AP₇ excess accumulation in both P₀ and Pᵢ fractions in agricultural land is the key point to cut down P leaching. Mitigation measures to limit P₀ leaching should be established based on the soil types.

**Keywords:** Phosphorus (P) leaching, Available organic P (AP₀), CaCl₂-extractable organic P (CaCl₂-P₀), Fe/Al oxides

<figure><img src="image_3.png" /></figure>

<footnote>*Correspondence: limeng12b@mails.ucas.ac.cn</footnote>

<footnote n="3">³ Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China
Full list of author information is available at the end of the article</footnote>
## Graphical abstract

<figure><img src="image_4.png" /></figure>

## Background

Phosphorus (P) is one of the limited elements for life survival and growth on earth [1]. Excessive application of P fertilizer in arable lands to guarantee crop production may induce P loss from soil to waterbody, causing adverse effect such as eutrophication [2, 3]. Leaching is one of the major pathways of P transport from soils to groundwater. It has received much attention since a large amount of P was detected in leachate [4–6]. Evaluating the P leaching risk is the prerequisite for making pollution control management. However, traditional monitoring methods like soil column or lysimeter experiments are difficult to implement because of the time- and cost-consuming [6]. Soil P tests such as $CaCl_2$-extractable P, water extractable P, ammonium oxalate extractable P have developed as reliable means to identify the risk of P leaching in the past studies [5].

Soil $CaCl_2$-extractable P ($CaCl_2$-P) is highly correlated with both dissolved reactive P concentrations in surface runoff and the leached P concentration in column trials so that it can work as an indicator for assessing the potential P leaching risk [5, 7, 9]. Soil available P (AP) is usually used as an agricultural proxy index which is the soil P that potentially can be used by plants. It is less strongly bound than soil residual P so that can be easily transported in soils resulting in leaching [10–12]. Based on the relationship between AP with $CaCl_2$-P, the change point at which $CaCl_2$-P concentrations dramatically increased has been defined as the maximum acceptable AP concentrations in soils to avoid P leaching [13, 14]. It means that the P leaching risk can be evaluated by comparing the soil AP with the change point value. However, AP is not a constant value, it changes over time. For example,

after fertilizer application it increases suddenly and then declines over time. AP can be adsorbed, but adsorbed P can become plant-available over timescales ranging from months to years [15, 16]. On the other hand, organic P ($P_O$) is not included in AP of change point and the relationship between available organic P ($AP_O$) and $CaCl_2$ extractable organic P ($CaCl_2$-$P_O$) has not been explored in the past studies.

P is easily fixed in the soil through, e.g., adsorption, precipitation or biological immobilization, hence only 20% of P fertilizer is taken up by crops in arable lands [17]. The mobility and loss of inorganic P ($P_I$) in soils have been explored by many studies [18–20]. Sorption is considered as the key process to controlling $P_I$ mobility in arable lands, which is affected by certain soil properties including pH, cation exchange capacity (CEC), clay content, soil organic matter (SOM) and Al, Fe, Mn oxides [18, 21, 22]. However, the role of $P_O$ in soil P leaching has received poor attention and is less understood [23]. In fact, $P_O$ has been found to account for a large part of P leachates because some $P_O$ fractions reveal smaller affinity to the soil solid phase than $P_I$ [19, 24]. Soil P content account for a large part of soil P pool and usually occurs as a complex mixture of monoesters (Mono-P) and diesters (Di-P), with smaller amounts of phosphonates (Phos-P) and organic polyphosphates [25, 26]. Research made by McDowell et al. [23] found that all dissolved $P_O$ fractions, with the exception of mono-inositol hexakisphosphate leached through aquifer gravels to depth at a higher speed than orthophosphate. Thus, $P_O$ fractions are easily transported to deep layers, and this has been proved both in montane ecosystem and agricultural lands [6, 27]. Besides, many species of $P_O$ in soils can become available
as orthophosphate for plant via microbially mediated mineralization [28]. It means that the presence and quantity of soil P₀ fractions affects the overall total P leaching. Therefore, it is necessary to consider P₀ in P leaching risk assessment.

In this study, 63 samples were taken from agricultural lands with different soil types (i.e., paddy soil, red soil, chernozem, black soil and other soils) across China. The aims of the study were (1) to assess the P₀ leaching risk in agricultural soils across China and (2) to explore the relationship of soil P₀ leaching risk with soil basic properties, particularly focusing on the effect of soil available P on P leaching.

# Materials and methods

## Soil collection

A total of 63 surface soils (0–20 cm) were point sampled by spade and pickaxes from agricultural lands across China (Additional file 1: Table S1). Soils were chosen to cover a range of soil types. All samples were air-dried at room temperature and then sieved (2, 1 and 0.15 mm) after removing the organic debris and impurities.

## Soil characterization

Soil pH was measured in water at a soil/water ratio of 1:2.5 by a FE20-FiveEasy Plus pH meter (Mettler Toledo, Switzerland). Water-soluble salt (WSS) was determined by a conductivity meter (SX-650; Tester, China) at a soil/water ratio of 1:5. The cation exchange capacity (CEC) and CaCO₃ content in soils were measured by the NaOAc compulsive exchange method [29] and gasometric method [30]. Dissolved organic carbon (DOC) was extracted by 2 M KCl with the soil/water of 1:10 and the DOC in soil extracts was analyzed by a TOC/TN analyzer (Multi N/C 2100, Analytik Jena, Germany). Soil organic matter (SOM) was analyzed by wet oxidation with H₂SO₄–K₂CrO₇ [31]. For total Fe and Al, soils were digested by with HF–H₂O₂–HNO₃ at 180 °C using a MARS 5 Xpress microwave system (CEM, USA), water-soluble Fe and Al were extracted by deionized water, free Fe and Al oxides were extracted by the sodium dithionite–sodium citrate–bicarbonate (DCB), amorphous Fe and Al oxides were extracted by acid ammonium oxalate, and complexing Fe and Al oxides were extracted using sodium pyrophosphate. The Fe and Al content were measured by ICP-OES (Optima 8000, Perkin Elmer, USA).

## P status

Soil samples were digested by HClO₄ and H₂SO₄ at 420 °C to determine the TP [32]. Extractable water-soluble P was extracted by 0.01 M CaCl₂ for 30 min at a soil/water ratio of 1:5. After filtering, a part of clear

solution was taken to detect the CaCl₂-extractable inorganic P (CaCl₂-P₁) by the ammonium molybdate–ascorbic acid method immediately [33]. The other supernatant was digested with 10% K₂S₂O₈ at 120 °C and 1.5 MPa for 30 min and then the total P content in water extractable P (CaCl₂-Pₜ) by the ammonium molybdate–ascorbic acid method was determined [34]. The organic P content (CaCl₂-P₀) was determined by the difference between CaCl₂-Pₜ and CaCl₂-P₁.

Available P (AP) was extracted by 0.5 M NaHCO₃ (pH 8.5) at a soil/water ratio of 1:20 [35]. After shaking and filtering, part of clear solution was taken to measure the available inorganic P (AP₁) using the ammonium molybdate–ascorbic acid method [33]. The other solution was digested with 10% K₂S₂O₈ at 120 °C and 1.5 MPa for 30 min, and then the solution was measured by the ammonium molybdate–ascorbic acid method to determine the total content of available P (APₜ). The difference between APₜ and AP₁ was considered as available organic P (AP₀).

## Data analysis

A one-way analysis of variance (ANOVA) was used on SPSS v22.0 software (IBM, USA) to detect differences in soil properties and P status between different soil types. Pearson correlations were used to assess the relationships between CaCl₂-extractable P with climate, basic soil properties, Fe/Al status and P status. Then, a heatmap was constructed by the Origin Pro v9.1 software (OriginLab, USA).

# Results

## Basic soil physicochemical properties

The soils collected across China had a wide range of physicochemical properties due to differences in soil type, climate characteristics, and agronomical variations (Table 1). The soil pH values ranged from 4.5 to 9.2 with an average of 7.2. Generally, paddy soils and red soils were neutral and chernozem soils were alkaline (Table 1). The soil CEC ranged from 6.2 to 49.3 cmol g⁻¹, and WSS in soils were 0.01–0.95 mS cm⁻¹ (Table 1). The soils contained 0.35–14.8% soil organic matter (SOM) in weight basis and the dissolved organic carbon (DOC) varied from 0.04 to 0.36 mg kg⁻¹ (Table 1). The CaCO₃ in the study soils was in a relative wide range with 0.81 to 73.7 mg kg⁻¹. Compared with the other soil types, chernozem soils were found to be higher in CEC and in the content of SOM, DOC and CaCO₃.

## P status

In the present study, total content of P (TP) of soil showed higher variation from 378 to 3387 mg kg⁻¹. There were only three soils which contained less than 400 mg kg⁻¹
<table><caption>**Table 1** Basic properties of soil collected across China</caption><thead><tr><th>Soils</th><th>pH</th><th>CEC (cmol g<sup>-1</sup>)</th><th>WSS (mS cm<sup>-1</sup>)</th><th>CaCO<sub>3</sub> (mg kg<sup>-1</sup>)</th><th>SOM (%)</th><th>DOC (mg kg<sup>-1</sup>)</th></tr></thead><tbody><tr><td colspan="7"><strong>Total soils (n=63)</strong></td></tr><tr><td>Min</td><td>4.47</td><td>6.23</td><td>0.01</td><td>0.81</td><td>0.35</td><td>0.04</td></tr><tr><td>Max</td><td>9.18</td><td>49.6</td><td>0.95</td><td>73.7</td><td>14.8</td><td>0.36</td></tr><tr><td>Mean</td><td>7.23</td><td>26.6</td><td>0.11</td><td>14.1</td><td>4.48</td><td>0.14</td></tr><tr><td>SD</td><td>1.29</td><td>9.37</td><td>0.13</td><td>14.9</td><td>2.68</td><td>0.07</td></tr><tr><td colspan="7"><strong>Paddy soils (n=21)</strong></td></tr><tr><td>Min</td><td>4.99</td><td>14.9</td><td>0.02</td><td>1.21</td><td>0.35</td><td>0.04</td></tr><tr><td>Max</td><td>8.47</td><td>41.7</td><td>0.30</td><td>41.7</td><td>5.80</td><td>0.34</td></tr><tr><td>Mean</td><td>6.83b</td><td>25.6b</td><td>0.09b</td><td>11.6ab</td><td>3.91b</td><td>0.12b</td></tr><tr><td>SD</td><td>1.25</td><td>6.27</td><td>0.08</td><td>12.38</td><td>1.52</td><td>0.07</td></tr><tr><td colspan="7"><strong>Red soils (n=11)</strong></td></tr><tr><td>Min</td><td>4.47</td><td>13.1</td><td>0.01</td><td>1.21</td><td>0.84</td><td>0.06</td></tr><tr><td>Max</td><td>8.04</td><td>49.3</td><td>0.95</td><td>16.2</td><td>7.00</td><td>0.36</td></tr><tr><td>Mean</td><td>6.10b</td><td>28.0ab</td><td>0.21a</td><td>6.30b</td><td>4.14b</td><td>0.16ab</td></tr><tr><td>SD</td><td>1.41</td><td>9.48</td><td>0.27</td><td>5.85</td><td>1.78</td><td>0.09</td></tr><tr><td colspan="7"><strong>Chernozem (n=13)</strong></td></tr><tr><td>Min</td><td>6.67</td><td>15.9</td><td>0.04</td><td>0.81</td><td>3.54</td><td>0.09</td></tr><tr><td>Max</td><td>8.79</td><td>46.0</td><td>0.26</td><td>73.7</td><td>14.8</td><td>0.23</td></tr><tr><td>Mean</td><td>7.87a</td><td>32.6a</td><td>0.11ab</td><td>20.6a</td><td>7.34a</td><td>0.18a</td></tr><tr><td>SD</td><td>0.78</td><td>9.64</td><td>0.06</td><td>22.1</td><td>3.34</td><td>0.04</td></tr><tr><td colspan="7"><strong>Other soils (n=18)</strong></td></tr><tr><td>Min</td><td>6.20</td><td>6.23</td><td>0.01</td><td>1.62</td><td>0.87</td><td>0.06</td></tr><tr><td>Max</td><td>9.18</td><td>41.4</td><td>0.17</td><td>43.7</td><td>10.6</td><td>0.17</td></tr><tr><td>Mean</td><td>7.92a</td><td>22.7b</td><td>0.08b</td><td>17.2ab</td><td>3.27b</td><td>0.11b</td></tr><tr><td>SD</td><td>0.87</td><td>10.5</td><td>0.05</td><td>13.4</td><td>2.32</td><td>0.02</td></tr></tbody></table>

Different letters indicate significant difference (p < 0.05) between paddy soils, red soils, chernozem, and other soils

n number of soil samples, SD standard deviation, CEC cation exchangeable capacity, WSS water-soluble salt, SOM soil organic matter, DOC dissolved organic carbon

TP (Table 2). TP was higher in paddy soils than in other soil types (Table 2). However, the potentially leachable P (CaCl₂-P) and AP of paddy soils were relatively lower than that of other soil types. The AP values were higher on average in red soils than the other soils (Table 2). And the highest values of CaCl₂-P appeared in the group of “other soils” with 3.03 mg kg⁻¹. Among total soil types, the average percent of APO was 57 ± 25% of AP (Table 2).

## Fe/Al status

As shown in Table 3, the average of total Fe (TFe) in soils was 24.8 mg kg⁻¹, which was higher than that of total Al (TAl, 3.73 mg kg⁻¹). However, water-soluble Fe (WFe) with an average of 1.10 mg kg⁻¹ was lower than water-soluble Al (WAl, 1.36 mg kg⁻¹). Three types of soil Fe/Al oxides were distinguished: free Fe/Al oxides, amorphous Fe/Al oxides, and complexing Fe/Al oxides. Highest mean values of free Fe oxides (Fe<sub>fr</sub>, 72%) and free Al oxides (Al<sub>fr</sub>, 73%) was found in total Fe oxides (Fe<sub>ox</sub>) and total Al oxides (Al<sub>ox</sub>), respectively (Table 3). Compared with other soil types, the chernozem contained more TFe,

TAl, WFe, WAl, Fe<sub>ox</sub> and Al<sub>ox</sub>. The paddy soils contained highest TFe, WFe, WAl compared with other soil types while their Fe<sub>ox</sub> (14.2 mg kg⁻¹) and Al<sub>ox</sub> (3.30 mg kg⁻¹) were less than those of red soils (18.8 mg kg⁻¹ and 5.41 mg kg⁻¹, respectively).

## Relationships of CaCl₂-extractable P with climate, soil properties and Fe/Al status

There was a positive correlation in the red soils between the measured climate parameters, i.e., mean average temperature (MAT, r=0.730) and mean average precipitation (MAP, r=0.685), with potentially leachable inorganic P (CaCl₂-P<sub>1</sub>) (Fig. 1). Soil properties showed limited effects on the CaCl₂-P. WSS was positively correlated with CaCl₂-P<sub>T</sub>, CaCl₂-P<sub>1</sub> under “total soils” (r=0.258, r=0.263). SOM was positively correlated with the CaCl₂-P<sub>T</sub> under paddy soils (r=0.460), but was negatively correlated with CaCl₂-P<sub>O</sub> under chernozem (r=−0.596) (Fig. 1). DOC showed a significantly positive relationship both with CaCl₂-P<sub>T</sub> (r=0.589) and CaCl₂-P<sub>1</sub> (r=0.647) for the “other soils”. TFe was
<table><caption>**Table 2** Soil P status</caption><thead><tr><th>Soils</th><th>TP<br>(mg kg<sup>-1</sup>)</th><th>AP<sub>T</sub><br>(mg kg<sup>-1</sup>)</th><th>AP<sub>I</sub><br>(mg kg<sup>-1</sup>)</th><th>AP<sub>O</sub><br>(mg kg<sup>-1</sup>)</th><th>AP<sub>O</sub>/AP<sub>T</sub><br>(%)</th><th>CaCl<sub>2</sub>-P<sub>T</sub><br>(mg kg<sup>-1</sup>)</th><th>CaCl<sub>2</sub>-P<sub>I</sub><br>(mg kg<sup>-1</sup>)</th><th>CaCl<sub>2</sub>-P<sub>O</sub><br>(mg kg<sup>-1</sup>)</th><th>CaCl<sub>2</sub>-P<sub>O</sub>/<br>CaCl<sub>2</sub>-P<sub>T</sub><br>(%)</th></tr></thead><tbody><tr><td colspan="10"><strong>Total soils (n=63)</strong></td></tr><tr><td>Min</td><td>378</td><td>1.55</td><td>0.27</td><td>0.03</td><td>0.23</td><td>0.97</td><td>0.16</td><td>0.20</td><td>8.13</td></tr><tr><td>Max</td><td>3387</td><td>767</td><td>281</td><td>727</td><td>94.8</td><td>9.33</td><td>8.57</td><td>3.80</td><td>88.5</td></tr><tr><td>Mean</td><td>1118</td><td>147</td><td>58.2</td><td>89.2</td><td>56.8</td><td>2.43</td><td>1.60</td><td>0.83</td><td>34.7</td></tr><tr><td>SD</td><td>576</td><td>174</td><td>69.3</td><td>128</td><td>24.8</td><td>1.99</td><td>1.52</td><td>0.80</td><td>14.5</td></tr><tr><td colspan="10"><strong>Paddy soils (n=21)</strong></td></tr><tr><td>Min</td><td>535</td><td>12.3</td><td>2.38</td><td>4.8</td><td>19.9</td><td>1.03</td><td>0.16</td><td>0.20</td><td>17.5</td></tr><tr><td>Max</td><td>2690</td><td>264</td><td>107</td><td>204</td><td>92.6</td><td>1.76</td><td>1.25</td><td>1.20</td><td>88.5</td></tr><tr><td>Mean</td><td>1252a</td><td>72.8b</td><td>24.6b</td><td>48.2b</td><td>67.5a</td><td>1.38b</td><td>0.87b</td><td>0.52a</td><td>36.8a</td></tr><tr><td>SD</td><td>517.37</td><td>65.3</td><td>28.9</td><td>49.3</td><td>21.9</td><td>0.22</td><td>0.23</td><td>0.26</td><td>16.1</td></tr><tr><td colspan="10"><strong>Red soils (n=11)</strong></td></tr><tr><td>Min</td><td>556</td><td>1.55</td><td>0.27</td><td>1.28</td><td>15.3</td><td>1.03</td><td>0.75</td><td>0.20</td><td>15.2</td></tr><tr><td>Max</td><td>1797</td><td>659</td><td>271</td><td>470</td><td>84.3</td><td>7.23</td><td>5.65</td><td>3.80</td><td>77.1</td></tr><tr><td>Mean</td><td>1114a</td><td>253ab</td><td>110a</td><td>143a</td><td>53.9ab</td><td>2.93a</td><td>1.86ab</td><td>1.07a</td><td>32.5a</td></tr><tr><td>SD</td><td>373</td><td>266</td><td>104</td><td>172</td><td>21.2</td><td>2.41</td><td>1.86</td><td>1.25</td><td>20.4</td></tr><tr><td colspan="10"><strong>Chernozem (n=13)</strong></td></tr><tr><td>Min</td><td>378</td><td>13.1</td><td>10.6</td><td>0.03</td><td>0.23</td><td>1.26</td><td>0.75</td><td>0.37</td><td>26.2</td></tr><tr><td>Max</td><td>2501</td><td>506</td><td>139</td><td>367</td><td>86.2</td><td>6.40</td><td>4.72</td><td>2.41</td><td>56.8</td></tr><tr><td>Mean</td><td>1089a</td><td>134ab</td><td>54.5b</td><td>80.0ab</td><td>41.9b</td><td>2.89a</td><td>1.87ab</td><td>1.02a</td><td>36.9a</td></tr><tr><td>SD</td><td>584</td><td>148</td><td>52.5</td><td>108</td><td>27.2</td><td>2.06</td><td>1.47</td><td>0.67</td><td>8.05</td></tr><tr><td colspan="10"><strong>Other soils (n=18)</strong></td></tr><tr><td>Min</td><td>382</td><td>33.4</td><td>9.66</td><td>11.5</td><td>6.30</td><td>0.97</td><td>0.58</td><td>0.29</td><td>8.13</td></tr><tr><td>Max</td><td>3387</td><td>767</td><td>281</td><td>727</td><td>94.8</td><td>9.33</td><td>8.57</td><td>3.77</td><td>50.8</td></tr><tr><td>Mean</td><td>985a</td><td>179a</td><td>68.5ab</td><td>111ab</td><td>56.7ab</td><td>3.03a</td><td>2.11a</td><td>0.93a</td><td>32.0a</td></tr><tr><td>SD</td><td>727</td><td>182</td><td>70.7</td><td>165</td><td>24.2</td><td>2.44</td><td>1.94</td><td>0.91</td><td>12.1</td></tr></tbody></table>

Different letters indicate significant difference (p < 0.05) between paddy soils, red soils, chernozem, and other soils

n number of soil samples, SD standard deviation, TP total P, AP<sub>T</sub> total available P, AP<sub>I</sub> available inorganic P, AP<sub>O</sub> available organic P, AP<sub>O</sub>/AP<sub>T</sub>%; CaCl<sub>2</sub>-P<sub>T</sub> total CaCl<sub>2</sub>-extractable P, CaCl<sub>2</sub>-P<sub>I</sub>, CaCl<sub>2</sub>-extractable inorganic P, CaCl<sub>2</sub>-P<sub>O</sub>, CaCl<sub>2</sub>-extractable organic P, CaCl<sub>2</sub>-P<sub>O</sub>/CaCl<sub>2</sub>-P<sub>T</sub>

negatively correlated with both CaCl<sub>2</sub>-P<sub>T</sub> and CaCl<sub>2</sub>-P<sub>I</sub> under red soils (r = -0.650, r = -0.699), while TAI was negatively correlated with CaCl<sub>2</sub>-P<sub>I</sub> (r = -0.436) and positively with CaCl<sub>2</sub>-P<sub>O</sub> (r = 0.507) in the paddy soils. However, no significant correlation was found between Fe/Al oxides with CaCl<sub>2</sub>-P under all the soil types except that Al<sub>ar</sub> had a weakly positive correlation with CaCl<sub>2</sub>-P<sub>O</sub> under “total soils” and red soils (Fig. 1).

## Relationships between CaCl<sub>2</sub>-extractable P and soil P content

TP had significantly positive relationship with both CaCl<sub>2</sub>-P<sub>T</sub> and CaCl<sub>2</sub>-P<sub>I</sub> under “total soils” and type “other soils” while it showed no special effect on CaCl<sub>2</sub>-extractable P under paddy, red and chernozem soils (Fig. 1). The relationships between soil CaCl<sub>2</sub>-P and AP were adequately described by linear equations (Figs. 2–4). CaCl<sub>2</sub>-P<sub>T</sub> was significantly affected by AP<sub>T</sub>

under all investigated soil types (total soils: p < 0.001; red soils: p < 0.001; chernozem: p = 0.001; other soils: p < 0.001) excerpt paddy soils (Fig. 2). Under paddy soils, CaCl<sub>2</sub>-P<sub>I</sub> also showed no relationship with AP<sub>I</sub> while there were strong positively relationships between CaCl<sub>2</sub>-P<sub>I</sub> with AP<sub>I</sub> in “total soils”, “red soils”, “chernozem” and “other soils” (Fig. 3). No relationship of CaCl<sub>2</sub>-P<sub>O</sub> and AP<sub>O</sub> was found neither in paddy soils (Fig. 4). As shown in Fig. 4, the strongest relationship between CaCl<sub>2</sub>-P<sub>O</sub> and AP<sub>O</sub> was found in red soils with the R value being 0.901 (p < 0.001) (Fig. 4c). In chernozem, the relationship was relatively weaker (Fig. 4d).

## Discussion

### Role of soil physicochemical properties and Fe/Al oxides on P leaching

Many soil properties including soil pH, cation exchange capacity (CEC), organic matter, moisture, soil constituents and clay contents were considered as the factors
<table><caption>**Table 3** Fe and Al oxides in soils collected across China</caption><thead><tr><th>Soils</th><th>TFe<br>(mg kg<sup>-1</sup>)</th><th>Tal<br>(mg kg<sup>-1</sup>)</th><th>WFe<br>(mg kg<sup>-1</sup>)</th><th>Wal<br>(mg kg<sup>-1</sup>)</th><th>Fe<sub>fr</sub><br>(mg kg<sup>-1</sup>)</th><th>Al<sub>fr</sub><br>(mg kg<sup>-1</sup>)</th><th>Fe<sub>ar</sub><br>(mg kg<sup>-1</sup>)</th><th>Al<sub>ar</sub><br>(mg kg<sup>-1</sup>)</th><th>Fe<sub>co</sub><br>(mg kg<sup>-1</sup>)</th><th>Al<sub>co</sub><br>(mg kg<sup>-1</sup>)</th></tr></thead><tbody><tr><td colspan="12"><strong>Total soils (n=63)</strong></td></tr><tr><td>Min</td><td>0.20</td><td>0.37</td><td>0.01</td><td>0.02</td><td>2.07</td><td>0.34</td><td>0.47</td><td>0.52</td><td>0.02</td><td>0.01</td></tr><tr><td>Max</td><td>57.7</td><td>8.72</td><td>10.7</td><td>15.5</td><td>40.3</td><td>7.73</td><td>8.70</td><td>2.72</td><td>8.48</td><td>3.42</td></tr><tr><td>Mean</td><td>24.8</td><td>3.73</td><td>1.10</td><td>1.36</td><td>11.8</td><td>2.07</td><td>3.36</td><td>1.51</td><td>1.11</td><td>0.69</td></tr><tr><td>SD</td><td>10.1</td><td>2.32</td><td>2.10</td><td>2.84</td><td>8.63</td><td>1.68</td><td>1.65</td><td>0.50</td><td>1.58</td><td>0.79</td></tr><tr><td colspan="12"><strong>Paddy soils (n=21)</strong></td></tr><tr><td>Min</td><td>9.55</td><td>0.58</td><td>0.02</td><td>0.02</td><td>2.07</td><td>0.34</td><td>0.86</td><td>0.52</td><td>0.09</td><td>0.06</td></tr><tr><td>Max</td><td>56.3</td><td>7.89</td><td>7.69</td><td>15.5</td><td>26.0</td><td>4.63</td><td>6.85</td><td>1.51</td><td>2.45</td><td>1.33</td></tr><tr><td>Mean</td><td>27.1a</td><td>3.55b</td><td>1.57a</td><td>2.40a</td><td>10.4a</td><td>1.66b</td><td>3.30b</td><td>1.16b</td><td>0.97b</td><td>0.56b</td></tr><tr><td>SD</td><td>9.26</td><td>2.47</td><td>2.56</td><td>4.34</td><td>6.92</td><td>1.31</td><td>1.43</td><td>0.27</td><td>0.67</td><td>0.36</td></tr><tr><td colspan="12"><strong>Red soils (n=11)</strong></td></tr><tr><td>Min</td><td>0.20</td><td>0.37</td><td>0.01</td><td>0.02</td><td>3.27</td><td>0.71</td><td>2.67</td><td>1.12</td><td>0.50</td><td>0.38</td></tr><tr><td>Max</td><td>25.9</td><td>6.78</td><td>10.7</td><td>8.20</td><td>40.3</td><td>6.35</td><td>8.70</td><td>2.72</td><td>8.48</td><td>3.42</td></tr><tr><td>Mean</td><td>15.9b</td><td>2.82b</td><td>1.13a</td><td>0.91a</td><td>11.2a</td><td>1.78ab</td><td>4.59a</td><td>1.90a</td><td>3.06a</td><td>1.73a</td></tr><tr><td>SD</td><td>8.29</td><td>1.93</td><td>3.19</td><td>2.42</td><td>10.6</td><td>1.59</td><td>1.83</td><td>0.52</td><td>2.79</td><td>1.22</td></tr><tr><td colspan="12"><strong>Chernozem (n=13)</strong></td></tr><tr><td>Min</td><td>16.6</td><td>0.53</td><td>0.15</td><td>0.12</td><td>6.03</td><td>0.93</td><td>2.14</td><td>1.19</td><td>0.02</td><td>0.01</td></tr><tr><td>Max</td><td>36.3</td><td>7.35</td><td>2.32</td><td>3.13</td><td>35.1</td><td>7.73</td><td>6.64</td><td>2.41</td><td>2.88</td><td>1.76</td></tr><tr><td>Mean</td><td>26.9a</td><td>2.86b</td><td>0.83a</td><td>1.00a</td><td>14.5a</td><td>3.10a</td><td>4.01ab</td><td>1.85a</td><td>0.90b</td><td>0.68b</td></tr><tr><td>SD</td><td>6.69</td><td>2.23</td><td>0.71</td><td>1.15</td><td>11.0</td><td>2.41</td><td>1.67</td><td>0.38</td><td>0.97</td><td>0.61</td></tr><tr><td colspan="12"><strong>Other soils (n=18)</strong></td></tr><tr><td>Min</td><td>1.68</td><td>2.33</td><td>0.01</td><td>0.03</td><td>4.70</td><td>0.70</td><td>0.47</td><td>0.54</td><td>0.03</td><td>0.02</td></tr><tr><td>Max</td><td>57.7</td><td>8.72</td><td>5.58</td><td>3.08</td><td>32.7</td><td>5.16</td><td>3.89</td><td>2.29</td><td>0.73</td><td>0.52</td></tr><tr><td>Mean</td><td>26.2a</td><td>5.12a</td><td>0.74a</td><td>0.67a</td><td>11.6a</td><td>1.95ab</td><td>2.21c</td><td>1.42b</td><td>0.22b</td><td>0.21c</td></tr><tr><td>SD</td><td>11.7</td><td>1.91</td><td>1.27</td><td>0.87</td><td>7.36</td><td>1.24</td><td>0.94</td><td>0.47</td><td>0.17</td><td>0.17</td></tr></tbody></table>

Different letters indicate significant difference (p < 0.05) between paddy soils, red soils, chernozem, and other soils

n number of soil samples, SD standard deviation, TFe total Fe, TAI total Al, WFe water-soluble Fe, WAI water-soluble Al, Fe<sub>fr</sub> free Fe oxides, Al<sub>fr</sub> free Al oxides, Fe<sub>ar</sub> amorphous Fe oxides, Al<sub>ar</sub> amorphous Al oxides, Fe<sub>co</sub> complexing Fe oxides, Al<sub>co</sub> complexing Al oxides

for the P leaching by influencing P adsorption/desorption in soils [36, 37]. In our study, there was no clear correlation between soil physicochemical properties and CaCl<sub>2</sub>-P (Fig. 1). In paddy soils which were slightly acidic, SOM had a significantly positive correlation with CaCl<sub>2</sub>-P<sub>T</sub>. For paddy soil samples taken after drying conditions like our samples, some studies pointed out that organic onions increased P sorption through the formation of organic matter-Al complexes [38, 39]. In fact, many studies in other soil types showed that there was a competition of sorption sides on minerals between organic matters and phosphate [40]. A study about the colloidal phosphorus mitigation from paddy soils to waterbody also verified that the addition of organic matter increased both dissolved P and colloidal P in leachate because negatively charged organic acid bonded to particles and generated negatively hydroxyl groups, which result in both site competition and electrostatic force [41]. Other studies in acidic soils also showed that low

molecular weight organic acids increased the mobility of inorganic phosphorus (P) through the chelation of Al and high-molecular-weight organic acids showed potential to inhibit phosphate adsorption [42–44]. However, there was a negative relationship between SOM and CaCl<sub>2</sub>-P<sub>O</sub> in group of “Chernozem” with alkaline conditions in the study. Yang et al. [45] reported on the influence of SOM on P adsorption/desorption under black chernozem and concluded that OM could enhance P availability by reducing the P bonding energy and increasing the P desorption to some degree. In fact, their results also showed the adsorption capacity of soil for P increased with SOM content increased and the change of P bonding energy along with SOM content first went down and then up. It means that beyond a certain SOM value, both P bond capacity and intensity were increased so that can be a reason for negative relation between SOM and CaCl<sub>2</sub>-P<sub>O</sub> in the alkaline chernozem soils studied. Besides, some studies made in alkaline
<figure><img src="image_5.png" /></figure>

soils suggested that SOM was beneficial to P adsorption because of anionic character of SOM which can bind electrostatically cations such as Ca²⁺, Fe³⁺, and Al³⁺ and these cations promote P retention [46, 47]. Overall, the influence of SOM on P adsorption depends on the type and concentration of organic material and the soil types, respectively, which is in accordance with the idea made by Debicka et al. [48].

Limited effect of Fe/Al oxides on CaCl₂-P was detected under all soil types in our study maybe due to the relatively limited number of soil samples. In fact, the process of phosphate sorption was affected by multiple soil constituents such as, carbonate content, organo-mineral complexes, metal oxides and clay minerals, because they all worked as adsorbents [18, 49, 50]. Abundance of metal oxides and their crystallinity were considered as the key factor for P adsorption [51, 52]. Higher free Al/Fe oxides usually means higher P retention and amorphous Al oxides with higher specific area is better to adsorb phosphate [51–54].

## Effects of soil P status on P leaching

More P stored in soils resulted in the higher concentration of CaCl₂-P and thus higher risk of P loss (Fig. 1). Such a significant relationship of TP with CaCl₂-P could have been expected, when all studied soil samples (n=63) were taken in consideration. P is easily accumulated in soils when P inputs exceed crop requirement because of the discrepancy between high P fixation capacity and low P use efficiency by plants. The unbalance between application of fertilizer and crop P removal also decreases the availability of P sorption sites in soils [55]. Therefore, the P concentration in surface soils was demonstrated as a key factor for P leaching in some studies [56, 57]. It works as one of the major continuous sources for P pollution in waterbodies [17, 58]. In the study, we tested arable soils from all over the China and found the CaCl₂-P₁ were 0.16–8.57 mg kg⁻¹, which was higher than that reported in the study by Zhao et al. [59]. They investigated 23 agricultural soil samples across China and found 0–2.5 mg kg⁻¹ CaCl₂-P₁. The mean available inorganic
<figure><img src="image_6.png" /><figcaption>**Fig. 2** Correlation between (a) CaCl₂-extractable total P with available total P under total soils, (b) CaCl₂-extractable total P with available total P under paddy soils, (c) CaCl₂-extractable total P with available total P under red soils, (d) CaCl₂-extractable inorganic P with available inorganic P under chernozem, (e) CaCl₂-extractable total P with available total P other soils</figcaption></figure>

P (AP₁) value that we analyzed (58.2 mg kg⁻¹) was also higher than that reported (20.7 mg kg⁻¹) in a study in 2006 [60]. Only 9.3% of the arable land in 2006 was over 40 mg AP₁ kg⁻¹, while that proportion is currently 38%. The increased application of P fertilizer resulted in the accumulation of P in arable land [11]. In comparison, 549 mg AP₁ kg⁻¹ was found in Danchi catchment [6] and 106 mg AP₁ kg⁻¹ was detected in Beijing suburbs [61], higher than that detected in an earlier study referred previously by Li et al. [60].

AP₁ was identified as important parameter for the P transport [12]. Our results also confirmed the significant correlation between AP₁ and CaCl₂-P₁ under “total soils” (r=0.752, Fig. 3). In the past research, a split-line model was usually used to describe the relationship between AP₁ and CaCl₂-P₁. There was a specific point (change point) that can be used to determine the optimal AP₁ concentrations in soils without causing P₁ leaching [13, 14]. However, less study focused on the organic forms both in AP and CaCl₂-P. In fact, organic P transport with subsurface flow plays a vital role in P transport and organic P was identified as the main form in leachate [19, 24, 62, 63]. In our study, the

CaCl₂-P included both inorganic P and organic P, with the average 34% of organic P under all soils (Table 2). However, the AP in all soils consisted of more organic P (57 ± 25%). A relatively high correlation between AP and CaCl₂-P under “total soils” was found when considered both the organic and inorganic forms (R = 0.822, Fig. 2). Furthermore, a significant positive relationship of APO with CaCl₂-PO was found among all soil types except paddy soils (Fig. 4). The *r* value was up to 0.901 in red soils, which revealed that APO was one of the key factors for P leaching in that soil type. A study conducted in red soils under arable crops found that AP₁ was positively correlated with deposition capacity and negatively with the maximum P adsorption capacity, which may result in more P leaching [64]. Fewer studies did research about the role of organic part in AP on P leaching and our results showed the mean APO was more than mean AP₁ in red soils (Table 2). Change point is a useful tool when assessing the need for implementing P leaching control management. Different with the change point can be found from the relationship between AP₁ and CaCl₂-P₁. No critical level of APO was identified where CaCl₂-PO increased dramatically. It
<figure><img src="image_7.png" /><figcaption>**Fig. 3** Correlation between (a) CaCl₂-extractable inorganic P with available inorganic P under total soils, (b) CaCl₂-extractable inorganic P with available inorganic P under paddy soils, (c) CaCl₂-extractable inorganic P with available inorganic P under red soils, (d) CaCl₂-extractable inorganic P with available inorganic P under chernozem, (e) CaCl₂-extractable inorganic P with available inorganic P under other soils</figcaption></figure>

means that the leaching risk of organic P is harder to predict and thus control than that of inorganic P.

Paddy soils showed different results from other soil types (Figs. 2–4). AP had no correlation with CaCl₂-P neither with organic or inorganic form. In fact, some studies believed that soil P test measured in the topsoil should not be used alone for P leaching risk assessment [56]. But fewer studies suggested that AP should not be used in P leaching prediction. Paddy soil is a special type of agricultural land which experiences waterlogging during rice growing period for over 6 months in the double-cropping rice system, resulting in the alternating redox cycles [65]. The shift of redox condition may alter the P adsorption and desorption by changing organic fractions and anions related to P bonded [66]. The alteration may affect AP behavior without affecting P leaching.

## Conclusions

CaCl₂ extractable total P (CaCl₂-P~T~) in arable soils sampled from all over the China was in a large range of 0.97–9.33 mg kg⁻¹ with 35% of them in organic forms on average. The mean percentage of organic P was

over half of available total P (AP~T~) (57 ± 25%) and the maximum even reached 88.5%. Therefore, the potential risk of organic P (P~O~) leaching from arable land is higher and P~O~ should be included in P leaching proxy measurements. Positive correlation was found between CaCl₂-P (organic forms, inorganic forms and total forms) with AP (organic forms, inorganic forms and total forms) under all investigated soil types except paddy soils. CaCl₂ extractable inorganic P (CaCl₂-P~I~) and available inorganic P (AP~I~) was highly correlated in the type of chernozem (r = 0.968). And the relationship of CaCl₂ extractable organic P (CaCl₂-P~O~) with available organic P (AP~O~) was strong in the type of red soils (r = 0.901) which both CaCl₂-P~O~ and AP~O~ of it were significantly higher than those of other soil types. It means that the control of AP~O~ accumulation in arable land may be the key point to limit P~O~ leaching and the mitigation measures should be constructed based on the soil type. However, rare effects of soil basic properties and Fe/Al oxides on P~O~ leaching was found in our study because of the limited number of samples, thus increasing the sample size is necessary for further study.
<figure><img src="image_8.png" /><figcaption>**Fig. 4** Correlation between (a) CaCl₂-extractable organic P with available organic P under total soils, (b) CaCl₂-extractable organic P with available organic P under paddy soils, (c) CaCl₂-extractable organic P with available organic P under red soils, (d) CaCl₂-extractable organic P with available organic P under chernozem, (e) CaCl₂-extractable organic P with available organic P other soils</figcaption></figure>

**Supplementary Information**

The online version contains supplementary material available at https://doi.org/10.1186/s40538-022-00302-6.

Additional file 1: Table S1. Soil sampling information.

**Acknowledgements**

The authors are grateful to the China Scholarship Council (CSC: 201904910544). We thank Dr. Xiangru Zhang, Mr. Chao Yang, Mr. Zhurui Tang, Mr. Songyan Li, Mr. Duo Wang, and Dr. Shengqun Liu for their assistance in soil sampling across China.

**Author contributions**

XS analyzed the data and drafted the manuscript. ML designed the experiment and contributed to the chemical analysis of soil sample. RB and EK improved the manuscript. All authors read and approved the final manuscript.

**Funding**

No funding is available.

**Availability of data and materials**

All data are presented in the manuscript.

**Declarations**

**Ethics approval and consent to participate**

The manuscript is an original work that has not been published in other journals. The authors declare no experiments involving humans and animals.

**Consent for publication**

All authors agreed to the publication.

**Competing interests**

The authors declare that they have no competing interests.

**Author details**

¹Institute of Bio- and Geosciences, Agrosphere (IBG-3), Forschungszentrum Jülich, 52425 Jülich, Germany. ²School of Natural Sciences, Environment Centre Wales, Bangor University, Bangor, UK. ³Institute of Ecological Conservation and Restoration, Chinese Academy of Forestry, Beijing 100091, China. ⁴Institute of Wetland Research, Chinese Academy of Forestry, Beijing 100091, China.

Received: 22 December 2021 Accepted: 5 May 2022

Published online: 25 May 2022

**References**

1. Condron LM, Newman S. Revisiting the fundamentals of phosphorus fractionation of sediments and soils. J Soil Sediment. 2011;11:830–40.

2. Bünemann EK. Assessment of gross and net mineralization rates of soil organic phosphorus—a review. Soil Biol Biochem. 2015;89:82–98.

3. Ceulemans T, Merckx R, Hens M, Honnay O. A trait-based analysis of the role of phosphorus vs. nitrogen enrichment in plant species loss across North-west European grasslands. J Appl Ecol. 2011;48:1155–63.

4. Fortune S, Lu J, Addiscott TM, Brookes PC. Assessment of phosphorus leaching losses from arable land. Plant Soil. 2005;269:99–108.

5. Jalali M, Jalali M. Assessment risk of phosphorus leaching from calcareous soils using soil test phosphorus. Chemosphere. 2017;171:106–17.
6. Li M, Hu Z, Zhu X, Zhou G. Risk of phosphorus leaching from phosphorus enriched soils in the Dianchi catchment. Southwestern China Environ Sci Pollut R. 2015;22:8460-70.

7. Penn CJ, Mullins GL, Zelazny LW, Sharpley AN. Estimating dissolved phosphorus concentrations in runoff from three physiographic regions of Virginia. Soil Sci Soc Am J. 2006;70:1967-74.

8. Wang Y, Zhang T, Hu Q, Tan C, O'Halloran IP, Drury CF, Reid K, Ma BL, Ball-Coelho B, Lauzon J, Reynolds WD, Welacky T. Estimating dissolved reactive phosphorus concentration in surface runoff water from major Ontario soils. J Environ Qual. 2010;39:1771-81.

9. Wang Y, Zhang T, O'Halloran IP, Hu Q, Tan C, Speranzini D, Macdonald I, Patterson G. Agronomic and environmental soil phosphorus tests for predicting potential phosphorus loss from Ontario soils. Geoderma. 2015;241-242:51-8.

10. Fischer P, Pöthig R, Venohr M. The degree of phosphorus saturation of agricultural soils in Germany: current and future risk of diffuse P loss and implications for soil P management in Europe. Sci Total Environ. 2017;599:600-1130-9.

11. Roberts TL, Johnston AE. Phosphorus use efficiency and management in agriculture. Resour Conserv Recycl. 2015;105(Part B):275-81.

12. Wang R, Yao Z, Lei Y. Modeling of soil available phosphorus surplus in an intensive wheat-maize rotation production area of the North China Plain. Agr Eco Environ. 2019;269:22-9.

13. Heckrath G, Brookes PC, Poulton PR, Goulding KWT. Phosphorus leaching from soils containing different P concentrations in the Broadbalk experiment. J Environ Qual. 1995;24:904-10.

14. Maguire R, Sims JT. Soil testing to predict phosphorus leaching. J Environ Qual. 2002;31:1601-9.

15. Johnston AE, Poulton PR, Fixen PE, Curtin D. Phosphorus: its efficient use in agriculture. Adv Agron. 2014;123:177-228.

16. Zhu J, Li M, Whelan M. Phosphorus activators contribute to legacy phosphorus availability in agricultural soils: a review. Sci Total Environ. 2018;612:522-37.

17. Sharpley A, Jarvie HP, Buda A, May L, Spears B, Kleinman P. Phosphorus legacy: overcoming the effects of past management practices to mitigate future water quality impairment. J Environ Qual. 2013;42:1308.

18. Gérard F. Clay minerals, iron/aluminum oxides, and their contribution to phosphate sorption in soils-a myth revisited. Geoderma. 2016;262:213-26.

19. Sharma R, Bell RW, Wong MTF. Dissolved reactive phosphorus played a limited role in phosphorus transport via runoff, throughflow and leaching on contrasting cropping soils from southwest Australia. Sci Total Environ. 2017;577:33-44.

20. Wang Y, Zhang T, O'Halloran IP, Tan C, Hu Q. A phosphorus sorption index and its use to estimate leaching of dissolved phosphorus from agricultural soils in Ontario. Geoderma. 2016;274:79-87.

21. Gou X, Cai Y, Wang C, Li B, Zhang Y, Tang X, Shen J, Cai Z. Effects of different long-term cropping systems on phosphorus adsorption and desorption characteristics in red soils. J Soil Sediment. 2019;20:1371-82.

22. Warrinnier R, Goossens T, Amery F, Vanden Nest T, Verbeeck M, Smolders E. Investigation on the control of phosphate leaching by sorption and colloidal transport: column studies and multi-surface complexation modelling. Appl Geochem. 2019;100:371-9.

23. McDowell RW, Worth W, Carrick S. Evidence for the leaching of dissolved organic phosphorus to depth. Sci Total Environ. 2021;755: 142392.

24. George TS, Giles CD, Menezes-Blackburn D, Condon LM, Gama-Rodrigues AC, Jaisi D, Lang F, Neal AL, Stutter MI, Almeida DS, Bol R, Cabugao KG, Celi L, Cotner JB, Feng G, Goll D, Hallama M, Krueger J, Plassard C, Rosling A, Darch T, Fraser T, Giesler R, Richardson AE, Tamburini F, Shand CA, Lumsdon DG, Zhang H, Blackwell MSA, Wearing C, Mezeli MM, Almás ÁR, Audette Y, Bertrand I, Beyhaut E, Boitt G, Bradshaw N, Brearley CA, Bruulsema TW, Ciais P, Cozzolino V, Duran PC, Mora ML, de Menezes AB, Dodd RJ, Dunfield K, Engl C, Frazão JJ, Garland G, González Jiménez JL, Graca J, Granger SJ, Harrison AF, Heuck C, Hou EQ, Johnes PJ, Kaiser K, Kjaer HA, Klumpp E, Lamb AL, Macintosh KA, Mackay EB, McGrath J, McIntyre C, McLaren T, Mészáros E, Missong A, Mooshammer M, Negrón CP, Nelson LA, Pfahler V, Poblete-Grant P, Randall M, Seguel A, Seth K, Smith AC, Smits MM, Sobarzo JA, Spohn M, Tawaraya K, Tibbett M, Voroney P, Wallander H, Wang L, Wasaki J, Haygarth PM. Organic phosphorus in the terrestrial environment: a perspective on the state of the art and future priorities. Plant Soil. 2017;427:191-208.

25. Cade-Menun BJ, Liu CW. Solution phosphorus-31 nuclear magnetic resonance spectroscopy of soils from 2005 to 2013: a review of sample preparation and experimental parameters. Soil Sci Society Am J. 2013;78:19-37.

26. Li M, Cozzolino V, Mazzei P, Drosos M, Monda H, Hu Z, Piccolo A. Effects of microbial bioeffectors and P amendments on P forms in a maize cropped soil as evaluated by 31P-NMR spectroscopy. Plant Soil. 2018;427:87-104.

27. Werner F, Haye TRDI, Spielvogel S, Prietzel J. Small-scale spatial distribution of phosphorus fractions in soils from silicate parent material with different degree of podzolization. Geoderma. 2017;302:52-65.

28. Li B, Brett MT. The influence of dissolved phosphorus molecular form on recalcitrance and bioavailability. Environ Pollut. 2013;182:37-44.

29. Chapman HD. Cation exchange capacity. In: Black CA, editor. Methods of soil analysis. American Society of Agronomy: Madison; 1965. p. 891-901.

30. Huang JS, Fisher PR, Argo WR. A protocol to quantify the reactivity of carbonate limestone for horticultural substrates. Comm Soil Sci Plant Anal. 2007;38:719-37.

31. Perrier ER, Kellogg M. Colorimetric determination of soil organic matter. Soil Sci. 1960;90:104-6.

32. Liu J, Wang H, Yang H, Ma Y, Cai O. Detection of phosphorus species in sediments of artificial landscape lakes in China by fractionation and phosphorus-31 nuclear magnetic resonance spectroscopy. Environ Pollut. 2009;157:49-56.

33. Murphy J, Riley JP. A modified single solution method for the determination of phosphate in natural waters. Anal Chim Acta. 1962;27:31-6.

34. Ebina J, Tsutsui T, Shirai T. Simultaneous determination of total nitrogen and total phosphorus in water using peroxodisulfate oxidation. Water Res. 1983;17:1721-6.

35. Olsen SR, Cole CV, Watanabe FS, Dean LA. Estimation of available phosphorus in soils by extraction with sodium bicarbonate USDA Circular 939. Washington DC: United States Department of Agriculture; 1954.

36. Guedes RS, Rodríguez-Vila A, Forján R, Covelo EF, Fernandes AR. Adsorption and risk of phosphorus loss in soils in Amazonia. J Soil Sediment. 2017;18(3):917-28.

37. Vanden Nest T, Ruysschaert G, Vandecasteele B, Houot S, Baken S, Smolders E, Cougnon M, Reheul D, Merckx R. The long term use of farmyard manure and compost: effects on P availability, orthophosphate sorption strength and P leaching. Agr Eco Environ. 2016;216:23-33.

38. Yan X, Wang D, Zhang H, Zhang G, Wei Z. Organic amendments affect phosphorus sorption characteristics in a paddy soil. Agr Eco Environ. 2013;175:47-53.

39. Yan X, Wei Z, Hong Q, Lu Z, Wu J. Phosphorus fraction and sorption characteristics in a subtropical paddy soil as influenced by fertilizer sources. Geoderma. 2017;295:80-5.

40. Fink JR, Inda AV, Bavaresco J, Barrón V, Torrent J, Bayer C. Adsorption and desorption of phosphorus in subtropical soils as affected by management system and mineralogy. Soil Till Res. 2016;155:62-8.

41. Niyungeko C, Liang X, Liu C, Liu Z, Sheteiwy M, Zhang H, Zhou J, Tian G. Effect of biogas slurry application rate on colloidal phosphorus leaching in paddy soil: a column study. Geoderma. 2018;325:117-24.

42. Clarhlm M, Skyllberg U, Rosling A. Organic acid induced release of nutrients from metal-stabilized soil organic matter—the unbutton model. Soil Biol Biochem. 2015;84:168-76.

43. Menezes-Blackburn D, Paredes C, Zhang H, Giles CD, Darch T. Organic acids regulation of chemical-microbial phosphorus transformations in soils. Environ Sci Technol. 2016;50:11521-31.

44. Lindegren M, Persson P. Competitive adsorption between phosphate and carboxylic acids: quantitative effects and molecular mechanisms. Eur J Soil Sci. 2009;60:982-93.

45. Yang X, Chen X, Yang X. Effect of organic matter on phosphorus adsorption and desorption in a black soil from Northeast China. Soil Till Res. 2019;187:85-91.

46. Borggaard OK, Raben-Lange B, Gimsing AL, Strobel BW. Influence of humic substances on phosphate adsorption by aluminium and iron oxides. Geoderma. 2005;127(3-4):270-9.

47. Zhang Y, Huang S, Guo D, Zhang S, Song X, Yue K, Zhang K, Bao D. Phosphorus adsorption and desorption characteristics of different textural fluvo-aquic soils under long-term fertilization. J Soil Sediment. 2019;19:1306-18.

48. Debicka M, Kocowicz A, Weber J, Jamroz E. Organic matter effects on phosphorus sorption in sandy soils. Arch Agron Soil Sci. 2016;62(6):840-55.
49. Cui Y, Weng L. Arsenate and phosphate adsorption in relation to oxides composition in soils: LCD modeling. Environ Sci Technol. 2013;47(13):7269-76.

50. Li M, Kang E, Wang J, Yan Z, Zhang K, Hu Z, Kang X. Phosphorus accumulation poses less influence than soil physiochemical properties on organic phosphorus adsorption on ferrasol. Geoderma. 2021;402:115324.

51. de Campos M, Antonangelo JA, van der Zee SEATM, Alleoni LRF. Degree of phosphate saturation in highly weathered tropical soils. Agr Water Manage. 2018;206:135-46.

52. Gypser S, Hirsch F, Schleicher AM, Freese D. Impact of crystalline and amorphous iron—and aluminum hydroxides on mechanisms of phosphate adsorption and desorption. J Environ Sci. 2018;70:175-89.

53. Antoniadis V, Koliniati R, Efstratiou E, Golia E, Petropoulos S. Effect of soils with varying degree of weathering and pH values on phosphorus sorption. Catena. 2016;139:214-9.

54. Camargo LA, Júnior JM, Pereira GT, Alleoni LRF. Spatial correlation between the composition of the clay fraction and contents of available phosphorus of an Oxisol at hillslope scale. Catena. 2012;100:100-6.

55. Qin Z, Shober A. The challenges of managing legacy phosphorus losses from manure-impacted agricultural soils. Curr Pollut Rep. 2018;4:265-76.

56. Djodjic F, Börling K, Bergström L. Phosphorus leaching in relation to soil type and soil phosphorus content. J Environ Qual. 2004;33(2):678-84.

57. Zhang T, Tan C, Zheng Z, Drury C. Tile drainage phosphorus loss with long-Term consistent cropping systems and fertilization. J Environ Qual. 2015;44(2):503-11.

58. Toor GS, Sims JT. Managing phosphorus leaching in mid-Atlantic soils: importance of legacy sources. Vadose Zone J. 2015;14(12):1-12.

59. Zhao X, Zhong X, Bao H, Li H, Li G, Tuo D, Lin Q, Brookes PC. Relating soil P concentrations at which P movement occurs to soil properties in Chinese agricultural soils. Geoderma. 2007;142:237-44.

60. Li H, Huang G, Meng Q, Ma L, Yuan L, Wang F, Zhang W, Cui Z, Shen J, Chen X, Jiang R, Zhang F. Integrated soil and plant phosphorus management for crop and environment in China. A review. Plant Soil. 2011;349:157-67.

61. Xie Z, Li S, Tang S, Huang L, Wang G, Sun X, Hu Z. Phosphorus leaching from soil profiles in agricultural and forest lands measured by a cascade extraction method. J Environ Qual. 2019;48:568-78.

62. Sharma R, Bell RW, Wong MTF. Phosphorus forms in soil solution and leachate of contrasting soil profiles and their implications for P mobility. J Soil Sediment. 2015;15:854-62.

63. Toor GS, Condron LM, Di HJ, Cameron KC, Cade-Menun BJ. Characterization of organic phosphorus in leachate from a grassland soil. Soil Bio Biochem. 2003;35(10):1317-23.

64. Gou X, Cai Y, Wang C, Li B, Zhang Y, Tang X, Shen J, Cai Z. Effects of different long-term cropping systems on phosphorus adsorption and desorption characteristics in red soils. J Soil Sediment. 2020;20:1371-82.

65. Long X, Yao H, Huang Y, Wei W, Zhu Y. Phosphate levels influence the utilisation of rice rhizodeposition carbon and the phosphate-solubilising microbial community in a paddy soil. Soil Bio Biochem. 2018;118:103-14.

66. Liu X, Bi Q, Qiu L, Li K, Yang X, Lin X. Increased risk of phosphorus and metal leaching from paddy soils after excessive manure application: Insights from a mesocosm study. Sci Total Environ. 2019;666:778-85.

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