Dissolved Reactive Phosphorus Concentrations Research Articles

Phosphorus runoff: effect of tillage and soil phosphorus levels.

Continued inputs of fertilizer and manure in excess of crop requirements have led to a build-up of soil phosphorus (P) levels and increased P runoff from agricultural soils. The objectives of this study were to determine the effects of two tillage practices (no-till and chisel plow) and a range of soil P levels on the concentration and loads of dissolved reactive phosphorus (DRP), algal-available phosphorus (AAP), and total phosphorus (TP) losses in runoff, and to evaluate the P loss immediately following tillage in the fall, and after six months, in the spring. Rain simulations were conducted on a Typic Argiudoll under a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. Elapsed time after tillage (fall vs. spring) was not related to any form of P in runoff. No-till runoff averaged 0.40 mg L(-1) and 0.05 kg ha(-1) DRP and chisel-plow plots averaged 0.24 mg L(-1) and 0.02 kg ha(-1) DRP concentration and loads, respectively. The relationship between DRP and Bray P1 extraction values was approximated by a logistic function (S-shaped curve) for no-till plots and by a linear function for tilled plots. No significant differences were observed between tillage systems for TP and AAP in runoff. Bray P1 soil extraction values and sediment concentration in runoff were significantly related to the concentrations and amounts of AAP and TP in runoff. These results suggest that soil Bray P1 extraction values and runoff sediment concentration are two easily measured variables for adequate prediction of P runoff from agricultural fields.

Effect of broadcast manure on runoff phosphorus concentrations over successive rainfall events.

Concern over eutrophication has directed attention to manure management effects on phosphorus (P) loss in runoff. This study evaluates the effects of manure application rate and type on runoff P concentrations from two, acidic agricultural soils over successive runoff events. Soils were packed into 100- x 20- x 5-cm runoff boxes and broadcast with three manures (dairy, Bos taurus, layer poultry, Gallus gallus; swine, Sus scrofa) at six rates, from 0 to 150 kg total phosphorus (TP) ha(-1). Simulated rainfall (70 mm h(-1)) was applied until 30 min of runoff was collected 3, 10, and 24 d after manure application. Application rate was related to runoff P (r2 = 0.50-0.98), due to increased concentrations of dissolved reactive phosphorus (DRP) in runoff; as application rate increased, so did the contribution of DRP to runoff TP. Varied concentrations of water-extractable phosphorus (WEP) in manures (2-8 g WEP kg(-1)) resulted in significantly lower DRP concentrations in runoff from dairy manure treatments (0.4-2.2 mg DRP L(-1)) than from poultry (0.3-32.5 mg DRP L(-1)) and swine manure treatments (0.3-22.7 mg DRP L(-1)). Differences in runoff DRP concentrations related to manure type and application rate were diminished by repeated rainfall events, probably as a result of manure P translocation into the soil and removal of applied P by runoff. Differential erosion of broadcast manure caused significant differences in runoff TP concentrations between soils. Results highlight the important, but transient, role of soluble P in manure on runoff P, and point to the interactive effects of management and soils on runoff P losses.

Distribution of inorganic nitrogen and phosphorus concentrations in stream flow of two Southern Piedmont watersheds.

Innate distributions or variability of nutrient concentrations within the fluvial system must be better understood to establish nutrient guidelines that are applicable and to discern which areas or landscape positions within the watershed are more vulnerable to nutrient losses. This work was conducted to (1) determine the system-wide spatial distribution of N and P concentrations in biweekly stream samples from two Southern Piedmont watersheds, and (2) determine the relationship between N and P concentrations in biweekly samples and watershed morphological features. From December 1998 through December 2000 samples were collected biweekly from 17 sampling sites located on Rose Creek and from 18 sampling sites located on Greenbrier Creek. The samples were analyzed for ammonium (NH4), nitrate (NO3), and dissolved reactive phosphorus (DRP) concentrations. We found that spatial autocorrelation of nitrate concentrations was evident and that some spatial autocorrelation of DRP concentrations was also present. We further found that the fluvial network morphological feature, drainage density, explained part of the spatial autocorrelation found for nitrate but did not for DRP. These results indicate that innate variability of nutrient concentrations within streams exists and suggest that decision makers should begin to consider location within the watershed when making nutrient management guidelines and decisions.

Phosphorus budget as a water quality management tool for closed aquatic mesocosms

Since the start-up of the St. Lawrence Mesocosm (SLM) at the Montreal Biodome in 1992, phosphorus has accumulated slowly, reaching about 18 mg P l −1 in 2000. It was decided that this concentration should be lowered to about 2 mg P l −1 to maintain a safe nitrogen : phosporus (N : P) ratio of about 10. Before deciding what type of treatment to use for the removal of phosphorus, a P budget was estimated for 1998 in order to evaluate the different pathways of phosphorus in the mesocosm. The resulting budget had only a 1% difference between the inputs ( CV=12.9%) and the sum of the outputs and changes in P pools ( CV=12.5%). P inputs amounted to 40.5 kg for 1998: food for fish and invertebrates contributed 76% of the inputs while seabird guano contributed 20%. Filtration and general cleaning removed 51% of the inputs while water losses removed 22%. The slight but constant difference between total phosphorus and dissolved reactive phosphorus (DRP) in 1998 and previous years led us to believe that only DRP (mostly orthophosphate) accumulated in the system. The accumulation of DRP was 10% of the inputs in 1998. The budget showed that the importance of water losses is relative and depends on the DRP concentration in the SLM. Furthermore, it was possible to compare this P budget with an N budget of the SLM prepared in 1995. The comparison helped us understand why nitrate in closed-circuit mesocosms are characterized by a high, never-ending accumulation while DRP is characterized by a net increase in the first few years after start-up followed by a very small increase in the following years. Considering its low CV, this P budget was considered a useful water quality management tool in designing a P removal unit for the SLM. This budget may also serve as a guideline for managers of closed-circuit systems such as marine aquariums and aquacultures as well as for designers of P removal units.

Using phosphorus concentration in the soil solution to predict phosphorus desorption to water.

The growing concerns about water eutrophication have made it urgent to restrict losses of phosphorus (P) from agricultural soils and to develop methods for predicting such losses. In this work, we used the paradigm of P sorption-desorption curves to confirm the hypothesis that the amount of dissolved reactive phosphorus (DRP) released to a dilute electrolyte tends to be proportional to the concentration of DRP in the soil solution raised to a power that decreases with increasing solution to soil ratio (W). The hypothesis was tested for a group of 12 widely ranging European agricultural soils fertilized with P in excess of crop needs. Phosphorus desorption was studied under near-static and turbulent conditions in laboratory experiments. The concentration of DRP in the 1:1 soil to water extract (P1:1) was used as a proxy for the DRP concentration in the soil solution. The amount of desorbed P was found to be correlated with P1:1 raised to a power that decreased from 0.7 to 0.9 at W=100 to 0.2 to 0.4 at W=10 000. Correlation was not improved by introducing additional variables related to P sorption-desorption properties. Olsen P was found to be of lower predictive value than P1:1. Also, the index of degree of soil saturation with phosphorus (DSSP) based on oxalate extraction failed to predict P desorption. The fact that P1:1 seemingly predicts P desorption accurately for a wide range of soils makes it potentially useful in areas of high soil diversity.

Phosphorus export from an agricultural watershed: linking source and transport mechanisms.

Many source and transport factors control P loss from agricultural landscapes; however, little information is available on how these factors are linked at a watershed scale. Thus, we investigated mechanisms controlling P release from soil and stream sediments in relation to storm and baseflow P concentrations at four flumes and in the channel of an agricultural watershed. Baseflow dissolved reactive phosphorus (DRP) concentrations were greater at the watershed outflow (Flume 1; 0.042 mg L(-1)) than uppermost flume (Flume 4; 0.028 mg L(-1)). Conversely, DRP concentrations were greater at Flume 4 (0.304 mg L(-1)) than Flume 1 (0.128 mg L(-1)) during stormflow. Similar trends in total phosphorus (TP) concentration were also observed. During stormflow, stream P concentrations are controlled by overland flow-generated erosion from areas of the watershed coincident with high soil P. In-channel decreases in P concentration during stormflow were attributed to sediment deposition, resorption of P, and dilution. The increase in baseflow P concentrations downstream was controlled by channel sediments. Phosphorus sorption maximum of Flume 4 sediment (532 mg kg(-1)) was greater than at the outlet Flume 1 (227 mg kg(-1)). Indeed, the decrease in P desorption between Flumes 1 and 4 sediment (0.046 to 0.025 mg L(-1)) was similar to the difference in baseflow DRP between Flumes 1 and 4 (0.042 to 0.028 mg L(-1)). This study shows that erosion, soil P concentration, and channel sediment P sorption properties influence streamflow DRP and TP. A better understanding of the spatial and temporal distribution of these processes and their connectivity over the landscape will aid targeting remedial practices.

Phosphorus and ammonium concentrations in surface runoff from grasslands fertilized with broiler litter.

Application of broiler (Gallus gallus domesticus) litter to grasslands can increase ammonium (NH4-N) and dissolved reactive phosphorus (DRP) concentrations in surface runoff, but it is not known for how long after a broiler litter application that these concentrations remain elevated. This long-term study was conducted to measure NH4-N and DRP in surface runoff from grasslands fertilized with broiler litter. Six 0.75-ha, fescue (Festuca arundinacea Schreb.-)bermudagrass [Cynodon dactylon (L.) Pers.] paddocks received broiler litter applications in the spring and fall of 1995-1996 and only inorganic fertilizer N in the spring of 1997-1998. Surface runoff from each paddock was measured and analyzed for NH4-N and DRP. Broiler litter increased flow-weighted NH4-N and DRP concentrations from background values of 0.5 and 0.4 mg L(-1), respectively, to values > 18 mg L(-1) in a runoff event that took place immediately after the third application. Ammonium concentrations decreased rapidly after an application and were not strongly related to time after application or runoff volume. In contrast, DRP concentrations tended to decrease more slowly, reaching values near 1 mg L(-1) by 19 mo after the last application. Dissolved reactive P concentrations decreased linearly with the natural logarithm of days after application (p<0.03), and increased linearly with the natural logarithm of runoff volume (p<0.0001).

Phosphorus losses in furrow irrigation runoff.

Phosphorus (P) often limits the eutrophication of streams, rivers, and lakes receiving surface runoff. We evaluated the relationships among selected soil P availability indices and runoff P fractions where manure, whey, or commercial fertilizer applications had previously established a range of soil P availabilities on a Portneuf silt loam (coarse-silty, mixed, superactive, mesic Durinodic Xeric Haplocalcid) surface-irrigated with Snake River water. Water-soluble P, Olsen P (inorganic and organic P), and iron-oxide impregnated paper-extractable P (FeO-Ps) were determined on a 0.03-m soil sample taken from the bottom of each furrow before each irrigation in fall 1998 and spring 1999. Dissolved reactive phosphorus (DRP) in a 0.45-microm filtered runoff sample, and iron-oxide impregnated paper-extractable P (FeO-Pw), total P, and sediment in an unfiltered runoff sample were determined at selected intervals during a 4-h irrigation on 18.3-m field plots. The 1998 and 1999 data sets were combined because there were no significant differences. Flow-weighted average runoff DRP and FeO-Pw concentrations increased linearly as all three soil P test concentrations increased. The average runoff total P concentration was not related to any soil P test but was linearly related to sediment concentration. Stepwise regression selected the independent variables of sediment, soil lime concentration, and soil organic P extracted by the Olsen method as related to average runoff total P concentration. The average runoff total P concentration was 1.08 mg L(-1) at a soil Olsen P concentration of 10 mg kg(-1). Soil erosion control will be necessary to reduce P losses in surface irrigation runoff.

Runoff Water Quality from Poultry Litter‐Treated Pasture and Forest Sites

AbstractIn the Ozark Highlands of the USA (36–38° N, 91–95° W), annual application of poultry litter to pasture land is a routine waste management practice. The objective of this study was to measure the effect of site characteristics and poultry litter application on runoff and nutrient transport from grazed pasture and forest sites at different landscape positions. Sixteen pairs of 1 × 2 m plots were established on Nixa (loamy‐skeletal, siliceous, active, mesic Glossic Fragiudults) and Clarksville (loamy‐skeletal, siliceous, semiactive, mesic Typic Paleudults) cherty silt loams. One plot of each pair received 4.5 Mg ha−1 of poultry litter. Rainfall was simulated at 75 mm h−1 for 1 h (25‐yr return period storm) one month after litter application. A composite runoff sample was analyzed for dissolved reactive phosphorus (DRP), total phosphorus (TP), ammonia N (NH3‐N), nitrate N (NO3‐N), total Kjeldahl nitrogen (TKN), and total suspended solids (TSS). Poultry litter‐treated plots had consistently higher concentrations of all water quality parameters tested compared to untreated plots. Concentration of DRP in runoff from untreated plots was linearly correlated with three soil P tests (0.35 &lt; r2 &lt; 0.85). Soil P on litter‐treated plots had little effect on runoff DRP, which averaged 2.20 mg L−1. High variation in runoff resulted in only NO3‐N showing significantly greater losses due to poultry litter treatment at two pasture sites. Results indicate that variation in runoff has a significant effect on nutrient transport from grazed pastures receiving poultry litter.

Simulation of dissolved phosphorus from cropped and grassed clayey soils in southern Finland

Agricultural phosphorus (P) loading is a major contributor to eutrophication of surface waters in Finland. Of the various forms of P in runoff from cultivated fields, dissolved reactive phosphorus (DRP) is immediately available for algal growth and can directly accelerate eutrophication. The applicability of an empirical model developed in southeastern USA was evaluated by simulating DRP in surface runoff from two cropped and grassed clayey soils (Vertic Cambisols) in southwestern Finland. The model relates DRP in a runoff event, e.g. to desorbable soil P ( P D ), runoff volume ( V) and the concentration of total suspended solids (TSS) in runoff. The model overestimated the mean concentration of DRP by a factor of 110–1645. In addition, the observed and simulated mean concentrations of DRP in plots with different winter covers, crops and P status did not correlate with each other. The predictions improved when P D was estimated by water extractions instead of Bray extractions, and the model was simplified by excluding the dependence of DRP concentration on V. The correct level of results could, however, only be achieved by calibration. In order to improve the model fit, the dependence of DRP concentration on V, runoff duration and TSS should be assessed under Finnish conditions and the model should be modified accordingly.

Effects of Poultry Litter Application Rate and Rainfall Intensity on Quality of Runoff from Fescuegrass Plots

AbstractA 4 × 2 factorial experiment with three replications was conducted to determine how quality of runoff from grassed areas treated with poultry (Gallus gallus domesticus) litter is impacted by litter application rate and rainfall intensity for storms occurring 1 d after application. Poultry litter was applied at 0, 218, 435, and 870 kg N ha−1 to plots established with fescuegrass (Festuca arundinacea Schreb.) on a Captina silt loam soil (fine‐silty, mixed, mesic Typic Fragiudult). Simulated rainfall was applied 24 h after litter application at 5 and 10 cm h−1 until runoff had occurred for a duration of 0.5 h. Flow‐weighed composite samples were collected and analyzed for total Kjeldahl nitrogen (TKN), ammonia nitrogen (NH3‐N), nitrate nitrogen (NO3‐N), total phosphorus (TP), dissolved reactive phosphorus (DP), chemical oxygen demand (COD), total suspended solids, and electrical conductivity. Increasing the litter application rate significantly increased runoff concentrations of all litter constituents investigated. Concentrations of TKN, TP, DP, and COD significantly decreased with increasing rainfall intensity because of more runoff and the associated dilution. Masses of litter constituents transported off the plots via runoff significantly increased with both litter application rate and rainfall intensity. For a given rainfall intensity, the proportions of applied litter constituents lost in runoff were generally indendent of application rate with the exception of total N at the high rainfall intensity.

Sources of Nitrogen and Phosphorus to Northern San Francisco Bay

We studied nutrient sources to the Sacramento River and Suisun Bay (northern San Francisco Bay) and the influence which these sources have on the distributions of dissolved inorganic nitrogen (DIN) and dissolved reactive phosphorus (DRP) in the river and bay. We found that agricultural return flow drains and a municipal wastewater treatment plant were the largest sources of nutrients to the river during low river flow. The Sutter and Colusa agricultural drains contributed about 70% of the transport of DIN and DRP by the river above Sacramento (about 20% of the total transport by the river) between August 8 and September 26, 1985. Further downstream, the Sacramento Regional Wastewater Treatment Plant discharged DIN and DRP at rates that were roughly 70% of total DIN and DRP transport by the river at that time. Concentrations at Rio Vista on the tidal river below the Sacramento plant and at the head of the estuary were related to the reciprocals of the river flows, indicating the importance of dilution of the Sacramento waste by river flows. During very dry years, elevated DIN and DRP concentrations were observed in Suisun Bay. We used a steady-state, one-dimensional, single-compartment box model of the bay, incorporating terms for advection, exchange, and waste input, to calculate a residual rate for all processes not included in the model. We found that the residual for DIN was related to concentrations of chlorophylla (Chla). The residual for DRP was also related to Chla at high concentrations of Chla, but showed significant losses of DRP at low Chla concentrations. These losses were typically equivalent to about 80% of the wastewater input rate.

Nitrogen and phosphorus in the Ngongotaha Stream

Abstract This paper gives the data and methods used to calculate the nitrogen and phosphorus loads of the Ngongotaha Stream, near Rotorua, New Zealand. The variations in concentration with time and with flow rate are given in some detail, as examples of what may happen in other streams of the central volcanic plateau, and a novel way to define a flow‐concentration curve is described. Nitrate, ammonia, dissolved reactive phosphorus (DRP), total phosphorus (TP), and total Kjeldahl nitrogen (TKN) concentrations were measured, and mean concentrations in 1976 base flow were found to be 527, 25, 32, 48, and 162 mg m‐3 respectively. Nitrate concentrations showed seasonal variations, and although changes occurred during floods, they were not correlated with flow rate. DRP concentrations showed little variation, except that they dropped at the peak of the largest floods. TP was strongly correlated with flow rate during floods, and TP loads could best be calculated by allowing for a curvilinear relationship between concentration and flow rate. The logarithms of the TP load carried by a flood and the peak flow rate of the flood were highly correlated (R = 0.984). The annual loads of nitrate, ammonia, DRP, TP, and TKN were estimated to be 34, 1.3, 2.9, 6.0, and 26 tonnes in 1976.

An Empirical Model to Estimate the Relative Importance of Roots in Phosphorus Uptake by Aquatic Macrophytes

A simple empirical model for predicting the relative contribution of roots in phosphorus uptake by submersed macrophytes is presented. The model requires only approximate dissolved reactive phosphorus (DRP) concentrations in the sediment pore water and overlying water as inputs and can explain 97% of the observed variance. It has the form: P = 99.8/1 + 2.66 (s/w)−0.83 where P is the relative contribution of the root in phosphorus uptake, s and w are the pore water and overlying water DRP concentrations, respectively. The nonspecificity of the model makes it readily applicable to environmental problems related to the role of macrophytes in phosphorus cycling and suggests a similar phosphorus uptake behavior for morphologically different species.Key words: macrophytes, phosphorus, empirical model

Distribution and Biological Availability of Reactive High Molecular Weight Phosphorus in Natural Waters in New Zealand

Eutrophic lakes and many streams on the central volcanic plateau of the North Island, New Zealand, contain dissolved chemically reactive phosphorus which is not orthophosphate. Sephadex gel (G25-150) chromatograms reveal that one reactive component is of high molecular weight (MW &gt; 5000) while a second component elutes in the same way as phosphate-phosphorus (PO4-P). The reactive high molecular weight phosphorus (RHMW-P) in streams generally forms only a small proportion of the dissolved reactive phosphorus (DRP). In some eutrophic lakes the proportion of RHMW-P in the DRP is high (70–80%). Each lake may have a characteristic distribution of the two forms of reactive phosphorus. In summer where DRP concentrations are low (&lt;2 mg∙m−3) in lake surface waters, PO4-P seems to dominate over RHMW-P which is consistent with long 32PO4 turnover times which are found in many of the central volcanic plateau lakes. Algal growth responses to phosphorus uptake were similar for PO4-P and RHMW-P, but not all of the RHMW-P was taken up by Chlorella in bioassays. The proportion of the RHMW-P taken up by Chlorella was different for each lake examined, posing problems in relating DRP concentrations to algal growth responses in lakes.Key words: reactive phosphorus, phosphate-phosphorus, algae, Chlorella, growth, bioassay, freshwater analysis, molybdenum blue method, Sephadex gel chromatography