Surface runoff phosphorus (P) loss in relation to phosphatase activity and soil P fractions in Florida sandy soils under citrus production

Phosphorus losses by surface runoff from agricultural lands have been of public concern due to increasing P contamination to surface waters. Five representative commercial citrus groves (C1-C5) located in South Florida were studied to evaluate the relationships between P fractions in soils, surface runoff P, and soil phosphatase activity. A modified Hedley P sequential fractionation procedure was employed to fractionate soil P. Soil P consisted of mainly organically- and Ca/Mg-bound P fractions. The organically-bound P (biological P, sum of organic P in the water, NaHCO₃ and NaOH extracts) was dominant in the acidic sandy soils from the C2 and C3 sites (18% and 24% of total soil P), whereas the Ca/Mg-bound P (HCl-extractable P) accounted for 45-60% of soil total P in the neutral and alkaline soils (C1, C4 and C5 soils). Plant-available P (sum of water and NaHCO₃ extractable P fractions) ranged from 27 to 61 mg P kg⁻¹ and decreased in the order of C3>C4>C1>C2>C5. The mean total P concentrations (TP) in surface runoff water samples ranged from 0.51 to 2.64 mg L⁻¹. Total P, total dissolved P (TDP), and PO₄³⁻-P in surface runoff were significantly correlated with soil biological P and plant-available P forms (p<0.01), suggesting that surface runoff P was directly derived from soil available P pools, including H₂O- and NaHCO₃- extractable inorganic P, water-soluble organic P, and NaHCO₃- and NaOH-extractable organic P fractions, which are readily mineralized by soil microorganisms and/or enzyme mediated processes. Soil neutral (55-190 mg phenol kg⁻¹ 3 h⁻¹) and natural (measured at soil pH) phosphatase activities (77-295 mg phenol kg⁻¹ 3 h⁻¹) were related to TP, TDP, and PO₄³⁻-P in surface runoff, and plant-available P and biological P forms in soils. These results indicate that there is a potential relationship between soil P availability and phosphatase activities, relating to P loss by surface runoff. Therefore, the neutral and natural phosphatase activities, especially the natural phosphatase activity, may serve as an index of surface runoff P loss potential and soil P availability.     

Phosphorus losses from arable land in England

Abstract. Concentrations and annual loadings of molyhdate reactive P (MRP) and total (including particulate) P (TP) are reported from field drainage, catchment and erosion experiments in England. Annual losses through field drains and in catchment runoff were 0.037-0.74 kg MRP/ha and 0.37-2.64 kg TP/ha, but those in surface runoff from experimental plots measuring erosion were generally much greater (often > 3 kg MRP/ha and up to 32 kg TP/ha in a wet year). Amounts of TP in drainflow and catchment runoff depended upon factors influencing soil dispersibility, such as particle size distribution and calcium carbonate content. The results to date suggest that P losses in surface runoff and erosion from arable fields to water are best limited by: (a) maximizing crop cover, using minimal cultivation practices and where possible planting crop rows across rather than up and down the slope, (b) avoiding cultivation practices that result in dispersion of soil particles, and (c) avoiding application of P fertilizer to wet soils when rainfall is likely soon after application. Consideration should he given to maintaining field drains below peak efficiency to reduce subsurface P losses.     

Structural disruption of arable soils under laboratory conditions causes minor respiration increases

Previous field studies in N Europe have shown that the impact of soil tillage on soil respiration is mostly indirect, caused by altered distribution of plant residues in soil affecting decomposition of residues. Tillage operations alter soil moisture and temperature conditions in soil, which control decomposition dynamics. Experiments under laboratory conditions allow indirect effects of altered residue decomposition to be distinguished from direct effects of mechanical disruption, i.e., the increased exposure of substrates within aggregates and micropores upon tillage. This study examined the effects of physical disruption of soils with different soil texture, land‐use history, and soil organic C content on soil respiration under controlled abiotic conditions. Undisturbed soil samples from 7 sites (arable land and grassland) were incubated at 20°C and three different water potentials (–1, –10, and –30 kPa). Soil respiration was measured before and after physical disruption with laboratory homogenizer, using an automated respiration apparatus. Soil organic C, water content, and bulk density explained 67% of the variation in base respiration. In half of the disrupted samples, bulk density was re‐adjusted by re‐compaction to conditions prevailing before disruption. Disruption and re‐compaction generally resulted in higher respiration flushes than disruption alone. Respiration peaks increased with water content. However, total C losses were small and corresponded to < 0.1 Mg C ha^?1. Overall, physical soil disruption increased decomposition of soil organic matter only marginally and temporarily. It would be difficult to detect an effect of tillage on soil organic matter decomposition under field conditions.     

Evaluation of leaching and runoff losses of selenium from seleniferous soils through simulated rainfall

Experiments were conducted to study drainage and runoff losses of selenium (Se) from two seleniferous soils (from Simbly containing total Se 850 μg [kg soil]^–1 and from Barwa containing 1310 μg [kg soil]^–1) under simulated rainfall (250–260 mm in three rainstorms) conditions. Rainfall intensities ranged from 56 to 120 mm h^–1 with uniformity coefficients ranging from 70.6% to 84.2%. Selenium lost through drainage (sum of drainage from initially saturated soil for 24 h and through dry and wet runs) was 0.15% and 0.11% of total Se content in the two soils. In soils having similar pH and organic‐C content, losses of Se through drainage as well as runoff were defined by total Se, water‐soluble Se, CaCO₃ content, and texture of the soils. The amount of runoff water was almost two times in the soil with fine texture and less infiltration rate than in the other and that same trend was observed with respect to loss of sediment. The soil with higher CaCO₃ content and water‐soluble Se lost more Se with moving water both through leaching and runoff, whereas the other soil with fine texture lost greater amount of Se with the sediment. Total Se lost through drainage as well as runoff was 0.29% of the native Se present in both the soils suggesting that significant amount of Se could be lost from seleniferous soils during irrigation and rainfall events.     

The Phosphorus Indicators Tool: a simple model of diffuse P loss from agricultural land to water

Abstract. The Phosphorus Indicators Tool provides a catchment-scale estimation of diffuse phosphorus (P) loss from agricultural land to surface waters using the most appropriate indicators of P loss. The Tool provides a framework that may be applied across the UK to estimate P loss, which is sensitive not only to land use and management but also to environmental factors such as climate, soil type and topography. The model complexity incorporated in the P Indicators Tool has been adapted to the level of detail in the available data and the need to reflect the impact of changes in agriculture. Currently, the Tool runs on an annual timestep and at a 1 km² grid scale.
We demonstrate that the P Indicators Tool works in principle and that its modular structure provides a means of accounting for P loss from one layer to the next, and ultimately to receiving waters. Trial runs of the Tool suggest that modelled P delivery to water approximates measured water quality records. The transparency of the structure of the P Indicators Tool means that identification of poorly performing coefficients is possible, and further refinements of the Tool can be made to ensure it is better calibrated and subsequently validated against empirical data, as it becomes available.     

Increased predicted losses of phosphorus to surface waters from soils with high Olsen-P concentrations

Abstract. Diffuse soluble reactive P (SRP) & total P (TP) loads from over 50 major river catchments in Northern Ireland were predicted using an export coefficient modelling approach. Phosphorus export coefficients for each CORINE land cover class, derived from satellite imagery, allowed the prediction of P loads from a breakdown of the CORINE land cover classes by catchment using a GIS. This approach was validated using observed P loads calculated from flow and concentration data. Mean measured Olsen-P concentrations in the soil A-horizon were also determined on a catchment basis. Plots of P loads to the watercourse versus Olsen-P concentrations in the soil showed a breakpoint around 22 mg Olsen- P l⁻¹ for both SRP & TP data. Below Olsen-P concentrations of 22 mg l⁻¹, SRP & TP losses were essentially independent of Olsen-P at 0.28 and 0.63 kg P ha⁻¹ yr⁻¹, respectively. Above Olsen-P concentrations of 22 mg l⁻¹, there was considerable spread in the P loss data. Nevertheless, significant upward trends in SRP and TP losses to watercourses were detected with increasing Olsen-P at a rate of approximately 0.5 and 1.0 kg P ha⁻¹ yr⁻¹, for SRP and TP respectively, for each 10 mg l⁻¹ increase in Olsen-P.     

Phosphorus cycling in UK agriculture and implications for phosphorus loss from soil

Abstract. Phosphorus (P) use in UK agriculture is reviewed and a P balance sheet presented. The productive grassland and arable area has accumulated an average P surplus of c. 1000 kg ha^–1 over the last 65 years. Over the period 1935–1970, the annual P surplus more than doubled due to an increase in animal numbers and associated requirements for inorganic fertilizers and livestock feeds. Since 1970, surplus P has declined by c . 40% as crop yields and P offtake have continued to increase while fertilizer and manure P inputs have remained relatively constant. In 1993, P use efficiency (P imports/P exports) in UK agriculture was estimated at 25% leading to an average annual surplus of 15 kg P ha^–1 yr^–1, although the latter has since decreased slightly due to reduced fertilizer use. Intensification and specialization of agriculture has also increased the range in P surpluses that are likely between livestock and arable dominated systems. The largest P surpluses occur in the relatively limited areas of arable soils which receive manure from intensive pig and poultry units, whilst farms without manure inputs generate only small surpluses, or are in balance. The cumulative P surplus has led to a build-up of soil total and easily-exchangeable P, especially in areas receiving both fertilizers and manures. Fundamental differences in P use efficiency, surplus P accumulation and the potential for P loss to water, exist between arable and grassland farms and it is important to separate these, due to the marked regionalization of UK agriculture. More judicial use of feeds and fertilizers is required to further reduce the P surplus and minimize the long-term risk of water eutrophication.     

The estimation of losses of potassium and magnesium from chalky soils in southern England: laboratory studies

Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.
The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.
When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.
Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.     

施用粪肥对农田土壤磷素累积和饱和度增加速率的影响

针对施用粪肥导致的我国集约化种养区域农田土壤磷素高量累积和高环境风险问题,利用长期定位试验定量分析了施用粪肥对农田土壤磷素累积和磷饱和度（DPS, degree of P saturation）增加速率（每年1 kg P·hm-2磷素盈余所导致的土壤磷素含量或DPS变化量）的影响。结果表明：连续22年过量磷素投入明显提高了土壤磷素含量和DPS,0~20 cm土层土壤磷素累积、DPS增加与磷素盈余均存在明显的线性相关性。与单施化肥相比,施用粪肥对土壤全磷的累积速率影响不大,但是明显提高了土壤Olsen-P累积和DPS增加速率。施用粪肥下,每年1 kg P·hm-2的磷盈余所导致的0~20 cm土层土壤Olsen-P、CaCl2-P累积和DPS增加量分别为0.071 mg P·kg-1（r=0.608, P=0.029）、0.003 mg P·kg-1（r=0.528, P=0.066）和0.036%（r=0.863,P=0.002）,分别为不施粪肥的3.3、6.0倍和1.2倍。土壤DPS变化与磷含量变化之间也存在明显的线性关系,0~20 cm土层土壤每年全磷、Olsen-P和CaCl2-P含量增加1 mg P·kg-1所导致的土壤DPS增加值分别为0.13%、0.42%和7.78%。20~40 cm土层土壤磷素累积、DPS增加与磷素盈余之间的线性相关性均较差,但与0~20 cm土层相比,施用粪肥和不施粪肥之间累积速率的差异性有增大的趋势,说明施用粪肥促进了磷素向下层土壤的移动。施用粪肥加速了土壤有效磷累积和DPS增加,进而提高了土壤中磷素损失风险,合理施用粪肥是控制集约化种养区域农田磷面源污染的关键。     

Organic C levels in intensively managed arable soils – long-term regional trends and characterization of fractions

Substantial losses of soil organic carbon (SOC) from the plough layer of intensively managed arable soils in western Europe have recently been reported, but these estimates are associated with very large uncertainties. Following soil surveys in 1952 and 1990 of arable soils in West Flanders (Belgium), we resampled 116 sites in 2003 and thus obtained three paired measurements of the OC stocks in these soils. Ten soils were selected for detailed physical fractionation to obtain possible further explanations for changes in SOC stocks. Between 1990 and 2003, the SOC stocks decreased at an average rate of ?0.19 t OC ha^?1 year^?1. This loss is significant but is still less than half the rate of SOC decrease that was estimated previously for the whole region of Flanders, which includes the study area. Variation in SOC stocks or in the magnitude of SOC stock losses could not be related to soil texture, to changes in ploughing depth, or to recent land‐use changes. A good relationship, however, was found between the SOC losses and organic matter (OM) inputs. The results of the physical fractionation also suggested management to be the predominant factor determining variation in SOC stocks because no correlation was found between soil texture and the absolute amounts of OC present in the largest OM fractions, that is, the OC in free particulate organic matter (POM), and OC associated with the silt + clay size fraction. The proportion of OC in free POM was up to 40% of the total OC, which indicates the important impact of management on SOC and also indicates that a substantial part of the SOC still present, may in the future be lost at a time scale of years to decades assuming that the intensive management continues.     

Phosphorus sorption capacities and saturation of soils in two regions with different livestock densities in northwest Germany

Abstract. Soils in areas with high livestock density contribute to the eutrophication of aquatic ecosystems through loss of nutrients, especially phosphorus (P). In order to identify the potential for P loss from such soils we determined phosphorus extracted by water (H₂O-P), by double lactate (DL-P), and P sorption capacity (PSC) and degree of P saturation (DPS) in soil samples from two counties, one with low (Harle-catchment) and the other with very high livestock density (Vechta). Both catchments are hydrologically connected with the tidal areas of the North Sea.
The mean concentrations of H₂O-P (0.4mmol/kg) and DL-P (3.9 mmol/kg) were lower in the Harle-catchment than in the Vechta area (1.2 mmol/kg, 6.8mmol/kg). Although oxalate-extractable Al (Al_ox) and Fe (Fe_ox) and the derived PSCs varied according to soil type and to land use, the livestock density and the resulting high concentrations of oxalate-extractable P (P_ox) were shown to be the main reason for the very high DPS of up to 179% in the county of Vechta. These values exceeded DPS reported from other intensive pig feeding areas in western Europe and indicate the potential for significant P loss. Less than 40% of the variation in P_ox could be explained by the routinely determined H₂O-Por DL-P. Geostatistical analyses indicated that the spatial variability of P_ox depended on manurial history of fields and Al_ox, showed still smaller-scale variability. These were the major constraints for regional assessments of P losses and eutrophication risk from agricultural soils using available soil P-test values, digital maps and geostatistical methods.     

Estimation of nitrogen and phosphorus losses to surface water and groundwater through the implementation of the SWAT model for Norwegian soils

Scope and Background

It is acknowledged that diffuse sources cause the most important nitrogen (N) and phosphorus (P) losses to the river system and substantially enrich the groundwater in nitrates. These losses arise primary from agricultural activities mainly fertilizer applications, and they are determined by soil attributes. In cold climates, winter conditions and freezing of soils may influence the infiltration capacity of the soil and thereby can have a serious effect on the partitioning of excess precipitation and subsequently on the soil and nutrient transportation. The purpose of this article is to investigate the behaviour of six widespread and different textured soil types, on nutrient (N, P) losses under cold climate conditions. The investigation was conducted in the Norwegian Vansjø-Hobølv catchment through the application of a physical model named Soil and Water Assessment Tool (SWAT), taking into consideration the additional aspect of freezing soils during winter, which distinguishes Scandinavian from other European soils.

Methods

SWAT is a physical river basin model that was developed for the U.S.D.A. Agricultural Research Service, by the Blackland Research Center in Texas. In the current modeling approach the catchment was divided into 43 Hydrologic Response Units (HRUs) which consist of different combinations of the existed landcover and soil types. Nitrogen and phosphorus losses arising from these HRUs were estimated for the period 1990–2001 through the simultaneous simulation of water and sediment processes that are closely linked to the nutrient processes. The model took into account soil temperature in order to quantify water and nutrient transport to deeper layers, considering negligible downward movement when the soil temperature was under 0°C. It also simulated the aboveground development of the snowpack and the snowmelt processes on a daily basis. The six different soil types were distinguished in two groups according to their similarity in texture and other physical properties, one group of fine-textured soils and a group of coarse soils. The results were evaluated for different crop cultivations (barley, oats and wheat) of the aforementioned soils. Finally, the model was calibrated and validated by comparing predicted results with measured data.

Results and Discussion

Fine-textured soils caused significant runoff, sediment, total nitrogen (TN) and total phosphorus (TP) yields to the river system while coarser soils were characterized by high water drainage and nitrates leaching. The first soil group caused a mean of 517 mm of runoff in annual basis, 200 mm higher than this arising from coarse soils. Moreover, 3 tonnes of sediments per hectare, 24.6 kgN/ha and 0.54 kgP/ha were lost annually to surface water from fine soils while the average respective losses originating from coarse soils were only 1.3 tn of sediments/ha, 13.6kgN/ha and 0.17kgP/ha. The sensitivity ranking of the soil types to TN and TP losses was silty-clay-loam>silty-loam>clay>loamy>sandy-loam>sandy. An average of 277 mm of water was percolated annually under the bottom of the soil profile in coarse soils causing the additional leaching of 5.6 kgN-NO₃/ha whereas the losses originating from fine-textured soils were 153 mm and 2.5 kg/ha respectively. According to their sensitivity in nitrates leaching, the six soil types were ranked in the following order: sandy>loamy>sandy-loam>silty-loam>silty-clay-loam>clay.

Conclusions and Perspectives

The results showed that even though under cold climate conditions, with monthly periods of average air-temperatures below zero, the overall amounts of annual TN and TP losses to surface waters as well as nitrates leaching to groundwater were considerable. This demonstrates that the cold climate conditions did not affect the long-term behavior of the six widespread Norwegian soils, which on an annual basis responded similarly to the respective European soils. According to the model’s estimations, infiltration with N and P transport still occur in wintertime, and comparing to other studies that reported similar results, different possible explanations were considered. The results demonstrate the need of considering the soil differentiation in Scandinavian countries similarly to the rest of Europe in order to apply mitigation measures against nitrogen and phosphorus losses to surface and groundwater.

     

评价城市土壤磷素淋溶风险的化学指标

Soils from urban and suburban areas are normally enriched with phosphorus (P). Sixteen urban soils with a wide range of total P concentrations under typical urban land uses were sampled and analyzed for extractable P concentrations using water, sodium bicarbonate and citric acid. Meanwhile the soils were artificially leached in columns and P concentrations in the leachates were determined. With linear regression a two-stage linear relationship was found to exis tbetween concentrations of P in the leachates and soil P contents obtained by various chemical measurements, i.e., there was a “change-point” denoting the critical threshold value for extractable P between the regression lines, above which concentrations of P in leachates increased substantially. These threshold “change-point” values were 1.5 mg kg^-1 for water-soluble P and CaCl2-P, 25 mg kg^-1 for Olsen-P, and 250-350 mg kg^-1 for citric acid-P with the sharpest change and the best predictor [τ2 (upper) = 0.928, τ2 (lower) = 0.807] appearing for Olsen-P. These “change-points” were considered important criteria in assessing the risk of P leaching from urban soils and could be used as standards to delineate and target hazardous areas in urban and suburban areas.     

Phosphorus export from a paddy rice field during flood events

Abstract. A field plot experiment was conducted to investigate P mobilization from fertilized rice fields during rainfall-flooding events. The experiment tested the effects of inorganic fertilizer P, at two rates, and P fertilizer plus manure, at one rate, on the amounts of P lost in drainage water when the plots were subjected to four artificially simulated storm-flooding/drainage events over an eight day period. During the first drainage event, two days after P application, the concentrations and loads of soluble reactive P (SRP) and particulate P (PP) in the drainage water were some three to five times lower than they had been just 24 hours earlier due to rapid sorption and sedimentation. At subsequent events, the concentrations and loads of SRP in drainage water were almost two orders of magnitude lower than at the first event, i.e. the equilibrium between P release from fertilizer and manure and P sorption/fixation by the soil mineral fraction had shifted strongly in favour of the latter processes. During the first drainage event, the concentrations and loads of SRP in drainage water from the low P fertilizer treatment were similar to those on the low P fertilizer plus manure treatment, whereas, 24 hours earlier they had been significantly greater. At subsequent events, though, the highest concentrations and loads of SRP occurred in drainage water from plots treated with equal amounts of P fertilizer and manure. It is suggested that extending the time period between P application and flooding events by applying fertilizer and manure outside the main rainy season should significantly reduce the risk of P loss from paddy rice fields.     

Sorption of phosphorus by some surface soils from Quebec in relation to their properties

Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH₂PO₄ in 0.01 M CaCl₂ for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.     

Pedotransfer functions for the pool size of slowly mineralizable organic N in sandy arable soils

The major aim of this study was to evaluate how the pool size of slowly mineralizable, ‘old’ soil organic N can be derived from more easily accessible soil and site information via pedotransfer functions (PTF). Besides modeling, this pool size might be of great importance for the identification of soils with high mineralization potential in drinking‐water catchments. From long‐term laboratory incubations (ca. 200 days) at 35 °C, the pool sizes of easily mineralizable organic N (N_fast), mainly in fresh residues, and slowly mineralizable, ‘old’ soil organic N (N_slow) as well as their first‐order rate coefficients were obtained. 90 sandy arable soils from NW Germany served to derive PTFs for N_slow that were evaluated using another 20 soils from the same region. Information on former land‐use and soil type was obtained from topographical, historical, and soil maps (partly from 1780). Pool size N_slow very strongly depends on soil type and former land‐use. Mean pool sizes of N_slow were much lower in old arable lowland (105 mg N kg^–1) than upland soils (175 mg N kg^–1) possibly due to lower clay contents. Within lowlands, mean pool sizes in former grassland soils (245 mg N kg^–1) were 2 to 3 times larger than in old arable soils due to accumulation of mineralizable N. In contrast, mean pool sizes of N_slow were lowest in recently cleared, former heath‐ and woodland (31 mg N kg^–1) as a result of the input of hardly decomposable organic matter. Neither N nor C in the light fraction (density < 1.8 g cm^–3) was adequate to derive pool size N_slow in the studied soils (r² < 0.03). Instead, N_slow can be accurately (r² = 0.55 – 0.83) derived from one or two basic soil characteristics (e.g. organic C, total N, C : N, mineral fraction < 20 μm), provided that sites were grouped by former land‐use. Field mineralization from N_slow during winter (independent data set) can be predicted as well on the basis of N_slow‐values calculated from PTFs that were derived after grouping the soils by former land‐use (r² = 0.51***). In contrast, using the PTF without soil grouping strongly reduced the reliability (r² = 0.16).     

潮土磷素累积流失风险及环境阈值

潮土是中国分布比较广、施肥强度大的典型耕作土壤,潮土中磷素累积与流失对区域水环境的污染风险不容忽视。该研究在潮土面积最大的河南省采集磷素水平不同的典型潮土作为供试土壤,采用人工模拟降雨及土柱模拟试验方法,通过测定土壤中Olsen-P和溶解态活性磷CaCl2-P含量以及径流或淋滤液中各形态磷浓度,研究了潮土中磷素随地表径流和下渗流失特征,并通过分段线性模型对潮土的磷素环境阈值进行拟合。结果表明：1）不同形态磷在潮土土壤剖面中均有一定程度的累积,土壤Olsen-P和CaCl2-P含量表现为高磷最大,中磷次之,低磷最小,而磷吸持指数值表现为低磷最大,中磷次之,高磷最小。从磷素的剖面分布来看,低磷和中磷水平潮土Olsen-P和CaCl2-P含量随着土壤深度的增加而降低,而高磷水平的潮土Olsen-P和CaCl2-P含量在20～40 cm土层含量最高。2）不同磷水平潮土径流中总磷（Total Phosphorus,TP）、可溶性总磷（Total Dissolved phosphorus,TDP）和颗粒磷（Particulate Phosphorus,PP）浓度和流失量大小表现为高磷最高,中磷和低磷水平土壤次之,潮土径流流失以PP为主。3）低磷和中磷水平潮土淋滤液中的各形态磷浓度和流失量随着土层深度的增加而降低,而在高磷水平的潮土淋滤液中,20～40 cm土层淋滤液中磷浓度和流失量要显著高于其他土层,在整个土壤剖面磷素浓度随着土层深度的增加呈现先上升后下降的趋势,潮土淋滤流失以TDP为主,其中,高磷和低磷水平潮土以可溶性有机磷占主导,而中磷水平潮土以钼酸盐反应磷占主导。4）通过分段回归模型将不同含磷水平潮土的水溶性磷与土壤中Olsen-P含量进行拟合,得出潮土土壤磷素环境阈值为24.65 mg/kg,研究还表明径流和渗漏液中TP浓度与土壤CaCl2-P含量呈显著正相关,因此可通过测定CaCl2-P来预测并判断土壤磷素流失风险。