Phosphorus runoff from incorporated and surface-applied liquid swine manure and phosphorus fertilizer

Excessive fertilization with organic and/or inorganic P amendments to cropland increases the potential risk of P loss to surface waters. The objective of this study was to evaluate the effects of soil test P level, source, and application method of P amendments on P in runoff following soybean [Glycine max (L.) Merr.]. The treatments consisted of two rates of swine (Sus scrofa domestica) liquid manure surface-applied and injected, 54 kg P ha(-1) triple superphosphate (TSP) surface-applied and incorporated, and a control with and without chisel-plowing. Rainfall simulations were conducted one month (1MO) and six months (6MO) after P amendment application for 2 yr. Soil injection of swine manure compared with surface application resulted in runoff P concentration decreases of 93, 82, and 94%, and P load decreases of 99, 94, and 99% for dissolved reactive phosphorus (DRP), total phosphorus (TP), and algal-available phosphorus (AAP), respectively. Incorporation of TSP also reduced P concentration in runoff significantly. Runoff P concentration and load from incorporated amendments did not differ from the control. Factors most strongly related to P in runoff from the incorporated treatments included Bray P1 soil extraction value for DRP concentration, and Bray P1 and sediment content in runoff for AAP and TP concentration and load. Injecting manure and chisel-plowing inorganic fertilizer reduced runoff P losses, decreased runoff volumes, and increased the time to runoff, thus minimizing the potential risk of surface water contamination. After incorporating the P amendments, controlling erosion is the main target to minimize TP losses from agricultural soils.     

Long-term effects of poultry litter, alum-treated litter, and ammonium nitrate on phosphorus availability in soils

Alum (Al2(SO4)(3).14H2O) additions to poultry litter result in lower ammonia (NH3) volatilization and phosphorus (P) runoff; however, the long-term effects of alum on soil P behavior have been unknown. The objectives of this study were to evaluate the long-term effects of poultry litter, alum-treated litter, and ammonium nitrate (NH4NO3) on P availability in soils and P runoff. Two studies were initiated in 1995: a small plot (1.5x3.0 m) study and a paired watershed (0.405 ha) study. In the small plot study 13 treatments (control, four rates of normal litter, four rates of alum-treated litter, and four rates of NH4NO3) were applied to tall fescue (Festuca arundinacea Schreb.) plots. Results show that after 7 yr water-extractable P (WEP) in surface soil samples was greater with normal litter, but Mehlich III P was greater in surface soils fertilized with alum-treated litter. When soil samples were taken at depth intervals to 50 cm in Year 7, Mehlich III P was only greater in the surface 5 cm for soils fertilized with alum-treated litter. At lower depths Mehlich III P was greater with normal litter, and WEP was up to 288% greater when normal litter was used, indicating that alum significantly reduced P leaching. Uptake of P by fescue was not affected by alum. Results from the paired watershed study showed P loss in runoff was 340% greater for normal litter than for alum-treated litter. This research, combined with earlier work that shows alum use improves air and soil quality, supports the use of alum as a long-term solution to reducing P runoff and leaching.     

Relationships between phosphorus levels in soil and in runoff from corn production systems

Phosphorus-enriched runoff from cropland can hasten eutrophication of surface waters. A soil P level exceeding crop needs due to long-term fertilizer and/or manure applications is one of several potential sources of increased P losses in runoff from agricultural systems. Field experiments were conducted at locations representative of three major soil regions in Wisconsin in corn (Zea mays L.) production systems to determine the effect of tillage, recent manure additions, soil P extraction method, and soil sampling depth (0-2, 0-5, and 0-15 cm) on the relationship between soil test P level and P concentrations in runoff. Runoff from simulated rainfall (75 mm h(-1)) was collected from 0.83-m2 areas for 1 h after rainfall initiation and analyzed for dissolved phosphorus (DP), total phosphorus (TP), and sediment. The DP fraction of the TP concentration in runoff ranged from 5 to 17% among sites with most of the variation in TP due to varying sediment concentration on the well-drained silt loam soils and to soil test P level on the poorly drained silty clay loam soil. In 213 observations across a range of soils and managements, good relationships occurred between soil test P level and DP concentration in runoff for most of the tests and sampling depths used. Recent manure additions and high levels of surface cover from corn residue sometimes masked this relationship. The slope of DP relative to soil test P level was markedly higher on the silty clay loam soil than on the silt loam soils possibly due to soil permeability-infiltration rate differences. Agronomic soil P tests were as effective as environmentally oriented soil P tests for predicting DP concentrations in runoff.     

Runoff phosphorus losses as related to phosphorus source, application method, and application rate on a Piedmont soil

Land application of animal manures and fertilizers has resulted in an increased potential for excessive P losses in runoff to nutrient-sensitive surface waters. The purpose of this research was to measure P losses in runoff from a bare Piedmont soil in the southeastern United States receiving broiler litter or inorganic P fertilizer either incorporated or surface-applied at varying P application rates (inorganic P, 0-110 kg P ha(-1); broiler litter, 0-82 kg P ha(-1)). Rainfall simulation was applied at a rate of 76 mm h(-1). Runoff samples were collected at 5-min intervals for 30 min and analyzed for reactive phosphorus (RP), algal-available phosphorus (AAP), and total phosphorus (TP). Incorporation of both P sources resulted in P losses not significantly different than the unfertilized control at all application rates. Incorporation of broiler litter decreased flow-weighted concentration of RP in runoff by 97% and mass loss of TP in runoff by 88% compared with surface application. Surface application of broiler litter resulted in runoff containing between 2.3 and 21.8 mg RP L(-1) for application rates of 8 to 82 kg P ha(-1), respectively. Mass loss of TP in runoff from surface-applied broiler litter ranged from 1.3 to 8.5 kg P ha(-1) over the same application rates. Flow-weighted concentrations of RP and mass losses of TP in runoff were not related to application rate when inorganic P fertilizer was applied to the soil surface. Results for this study can be used by P loss assessment tools to fine-tune P source, application rate, and application method site factors, and to estimate extreme-case P loss from cropland receiving broiler litter and inorganic P fertilizers.     

Effect of poultry diet on phosphorus in runoff from soils amended with poultry manure and compost

Phosphorus in runoff from fields where poultry litter is surface-applied is an environmental concern. We investigated the effect of adding phytase and reducing supplemental P in poultry diets and composting poultry manures, with and without Fe and Al amendments, on P in manures, composts, and runoff. We used four diets: normal (no phytase) with 0.4% supplemental P, normal + phytase, phytase + 0.3% P, and phytase + 0.2% P. Adding phytase and decreasing supplemental P in diets reduced total P but increased water-extractable P in manure. Compared with manures, composting reduced both total P, due to dilution of manure with woodchips and straw, and water-extractable P, but beyond a dilution effect so that the ratio of water-extractable P to total P was less in compost than manure. Adding Fe and Al during composting did not consistently change total P or water-extractable P. Manures and composts were surface-applied to soil boxes at a rate of 50 kg total P ha(-1) and subjected to simulated rainfall, with runoff collected for 30 min. For manures, phytase and decreased P in diets had no significant effect on total P or molybdate-reactive P loads (kg ha(-1)) in runoff. Composting reduced total P and molybdate-reactive P loads in runoff, and adding Fe and Al to compost reduced total P but not molybdate-reactive P loads in runoff. Molybdate-reactive P in runoff (mg box(-1)) was well correlated to water-extractable P applied to boxes (mg box(-1)) in manures and composts. Therefore, the final environmental impact of dietary phytase will depend on the management of poultry diets, manure, and farm-scale P balances.     

Environmental and production consequences of using alum-amended poultry litter as a nutrient source for corn

Field trials were established to compare alum-treated poultry litter (ATPL), normal poultry litter (NPL), and triple superphosphate (TSP) as fertilizer sources for corn (Zea mays L.) when applied at rates based on current litter management strategies in Virginia. Trials were established in the Costal Plain and Piedmont physiographic regions near Painter and Orange, VA, respectively. Nitrogen-based applications of ATPL or NPL applied at rates estimated to supply 173 kg of plant-available nitrogen (PAN) ha(-1) resulted in significantly lower grain yields than treatments receiving commercial fertilizer at the same rate in 2000 and 2001 at Painter. These decreases in grain yield at the N-based application rates were attributed to inadequate N availability, resulting from overestimates of PAN as demonstrated by tissue N concentrations. However, at Orange no treatment effects on grain yield were observed. Applications of ATPL did not affect Al concentrations in corn ear-leaves at either location. Exchangeable soil Al concentrations were most elevated in treatments receiving only NH4NO3 as an N source. At N-based application rates, the ATPL resulted in lower Mehlich 1-extractable P (M1-P) and water-extractable soil phosphorus (H2O-P) concentrations compared to the application of NPL. A portion of this reduction could be attributed to lower rates of P applied in the N-based ATPL treatments. Runoff collected from treatments which received ATPL 2 d before conducting rainfall simulations contained 61 to 71% less dissolved reactive phosphorus (DRP) than treatments receiving NPL. These results show that ATPL may be used as a nutrient source for corn production without significant management alterations. Alum-treated poultry litter can also reduce the environmental impact of litter applications, primarily through minimizing the P status of soils receiving long-term applications of litter and reductions in runoff DRP losses shortly after application.     

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.     

Phosphorus and nitrogen in rainfall simulation runoff after fresh and composted beef cattle manure application

Fresh beef cattle (Bos taurus) manure has traditionally been applied to cropland in southern Alberta, but there has been an increase in application of composted manure to cropland in this region. However, the quality of runoff under fresh manure (FM) versus composted manure (CM) has not been investigated. Our objective was to compare runoff quality under increasing rates (0, 13, 42, 83 Mg ha(-1) dry wt.) of FM and CM applied for two consecutive years to a clay loam soil cropped to irrigated barley (Hordeum vulgare L.). We determined total phosphorus (TP), particulate phosphorus (PP), dissolved reactive phosphorus (DRP), total nitrogen (TN), NH4-N, and NO3-N concentrations and loads in runoff after one (1999) and two (2000) applications of FM and CM. We found significantly (P < or = 0.05) higher TP, DRP, and NH4-N concentrations, and higher DRP and TN loads under FM than CM after 2 yr of manure application. The TP loads were also higher under FM than CM at the 83 Mg ha(-1) rate in 2000, and DRP loads were higher for FM than CM at this high rate when averaged over both years. Application rate had a significant effect on TP and DRP concentrations in runoff. In addition, the slope values of the regressions between TP and DRP in runoff versus application rate were considerably higher for FM in 2000 than for FM in 1999, and CM in both 1999 and 2000. Significant positive relationships were found for TP and DRP in runoff versus soil Kelowna-extractable P and soil water-extractable P for FM and CM in 2000, indicating that interaction of runoff with the soil controlled the release of P. Total P and DRP were the variables most affected by the treatments. Overall, our study found that application of CM rather than FM to cropland may lower certain forms of P and N in surface runoff, but this is dependent on the interaction with year, application rate, or both.     

Managing broiler litter application rate and grazing to decrease watershed runoff losses

Pasture management and broiler litter application rate are critical factors influencing the magnitude of nutrients being transported by runoff from fields. We investigated the impact of pasture management and broiler litter application rate on nutrient runoff from bermudagrass (Cynodon dactylon) pastures. The experiment was conducted on a Ruston fine sandy loam with a factorial arrangement on 21 large paddocks. Runoff water was collected from natural rainfall events from 2001 to 2003. Runoff water and soil samples were analyzed for nutrients and sediments. Runoff was generally greater (29%) from grazed than hayed pastures regardless of the litter application rate. There was greater inorganic N in the runoff from grazed paddocks when litter rate was based on N rather than P. The mean total P loss per runoff event for all treatments ranged from 7 to 45 g ha(-1) and the grazed treatment with litter applied on N basis had the greatest total P loss. Total dissolved P was the dominant P fraction in the runoff, ranging from 85% to 93% of the total P. The soluble reactive P was greater for treatments with litter applied on N basis regardless of pasture management. Runoff total sediments were greater for N-based litter application compared to those which received litter on P basis. Our results indicate that litter may be applied on N basis if the pasture is hayed and the soil P is low. In contrast, litter rates should be based on a P-basis if pasture is grazed.     

Relationships between soil and runoff phosphorus in small Alberta watersheds

Field-scale relationships between soil test phosphorus (STP) and flow-weighted mean concentrations (FWMCs) of dissolved reactive phosphorus (DRP) and total phosphorus (TP) in runoff are essential for modeling phosphorus losses, but are lacking. The objectives of this study were (i) to determine the relationships between soil phosphorus (STP and degree of phosphorus saturation (DPS)) and runoff phosphorus (TP and DRP) from field-sized catchments under spring snowmelt and summer rainfall conditions, and (ii) to determine whether a variety of depths and spatial representations of STP improved the prediction of phosphorus losses. Runoff was monitored from eight field-scale microwatersheds (2 to 248 ha) for 3 yr. Soil test phosphorus was determined for three layers (0 to 2.5 cm, 0 to 5 cm, and 0 to 15 cm) in spring and fall and the DPS was determined for the surface layer. Average STP (0 to 15 cm) ranged from 3 to 512 mg kg(-1), and DPS (0 to 2.5 cm) ranged from 5 to 91%. Seasonal FWMCs ranged from 0.01 to 7.4 mg L(-1) DRP and from 0.1 to 8.0 mg L(-1) TP. Strong linear relationships (r2=0.87 to 0.89) were found between the site mean STP and the FWMCs of DRP and TP. The relationships had similar extraction coefficients, intercepts, and predictive power among all three soil layers. Extraction coefficients (0.013 to 0.014) were similar to those reported for other Alberta studies, but were greater than those reported for rainfall simulation studies. The curvilinear DPS relationship showed similar predictive ability to STP. The field-scale STP relationships derived from natural conditions in this study should provide the basis for modeling phosphorus in Alberta.     

Phosphorus runoff during four years following composted manure application

Repeated manure application can lead to excessive soil test P (STP) levels and increased P concentration in runoff, but also to improved water infiltration and reduced runoff. Research was conducted to evaluate soil P tests in prediction of P concentration in runoff and to determine the residual effects of composted manure on runoff P loss and leaching of P. The research was conducted from 2001 to 2004 under natural runoff events with plots of 11-m length. Low-P and high-P compost had been applied during the previous 3 yr, resulting in total applications of 750 and 1150 kg P ha(-1). Bray-P1 in the surface 5 cm of soil was increased from 16 to 780 mg kg(-1) with application of high-P compost. Runoff and sediment losses were 69 and 120% greater with no compost than with residual compost treatments. Runoff P concentration increased as STP increased, but much P loss occurred with the no-compost treatment as well. Agronomic soil tests were predictive of mean runoff P concentration, but increases in STP resulted in relatively small increases in runoff P concentration. Downward movement of P was not detected below 0.3 m. In conclusion, agronomic soil tests are useful in predicting long-term runoff P concentration, and risk of P loss may be of concern even at moderate soil P levels. The residual effect of compost application in reducing sediment and runoff loss was evident more than 3 yr after application and should be considered in P indices.     

NUTRIENT AND β17‐ESTRADIOL LOSS IN RUNOFF WATER FROM POULTRY LITTERS1

ABSTRACT: A main water quality concern is accelerated eutrophication of fresh waters from nonpoint source pollution, particularly nutrient transport in surface runoff from agricultural areas and confined animal feeding operations. This study examined nutrient and β₁₇‐estradiol concentrations in runoff from small plots where six poultry litters were applied at a rate of about 67 kg/ha of total phosphorus (TP). The six poultry litter treatments included pelleted compost, pelleted litter, raw litter, alum (treated) litter, pelleted alum litter, and normal litter (no alum). Four replicates of the six poultry litter treatments and a control (plots without poultry litter application) were used in this study. Rainfall simulations at intensity of 50 mm/hr were conducted immediately following poultry litter application to the plots and again 30 days later. Composite runoff samples were analyzed for soluble reactive phosphorus (SRP), ammonia (NH₄), nitrate (NO₃), TP, total nitrogen (TN) and β₁₇‐estradiol concentrations. In general, poultry litter applications increased nutrient and β₁₇‐estradiol concentrations in runoff water. Ammonia and P concentrations in runoff water from the first simulation were correlated to application rates of water extractable NH₄ (R²= 0.70) and P (R²= 0.68) in the manure. Results suggest that alum applications to poultry litter in houses in between flocks is an effective best management practice for reducing phosphorus (P) and β₁₇‐estradiol concentrations in runoff and that pelleted poultry litters may increase the potential for P and β₁₇‐estradiol loss in runoff water. Inferences regarding pelleted poultry litters should be viewed cautiously, because the environmental consequence of pelleting poultry litters needs additional investigation.     

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.     

Estimating runoff phosphorus losses from calcareous soils in the Minnesota River basin

Bioavailable phosphorus (BAP) in stormwater runoff is a key issue for control of eutrophication in agriculturally impacted watersheds. Laboratory experiments were conducted in soil runoff boxes to determine BAP content in simulated storm runoff in 10 (mostly) calcareous soils from the Minnesota River basin in southern Minnesota. The soluble reactive phosphorus (SRP) portion of the runoff BAP was significantly correlated with soil Mehlich-III P, Olsen P, and water-extractable P (all r2 > 0.90 and p < 0.001). A linear relationship (r2 = 0.88, p < 0.001) also was obtained between SRP in runoff and the phosphorus saturation index based on sorptivity (PSIs) calculated with sorptivity as a measure of the inherent soil P sorption capacity. Runoff levels of BAP estimated with iron oxide-impregnated paper were predicted well by various soil test P methods and the PSI, of the soils, but correlation coefficients between these variables and runoff BAP were generally lower than those for runoff SRP. Using these relationships and critical BAP levels for stream eutrophication, we found corresponding critical levels of soil Mehlich-III P and Olsen P (which should not be exceeded) to be 65 to 85 and 40 to 55 mg kg(-1), respectively.     

Management practice effects on phosphorus losses in runoff in corn production systems

Phosphorus losses in runoff from cropland can contribute to nonpoint-source pollution of surface waters. Management practices in corn (Zea mays L.) production systems may influence P losses. Field experiments with treatments including differing soil test P levels, tillage and manure application combinations, and manure and biosolids application histories were used to assess these management practice effects on P losses. Runoff from simulated rainfall (76 mm h(-1)) was collected from 0.83-m2 areas for 1 h after rainfall initiation and analyzed for dissolved reactive P (DRP), bioavailable P, total P (TP), and sediment. In no-till corn, both DRP concentration and load increased as Bray P1 soil test (STP) increased from 8 to 62 mg kg(-1). A 5-yr history of manure or biosolids application greatly increased STP and DRP concentrations in runoff. The 5-yr manure treatment had higher DRP concentration but lower DRP load than the 5-yr biosolids treatment, probably due to residue accumulation and lower runoff in the manure treatment. Studies of tillage and manure application effects on P losses showed that tillage to incorporate manure generally lowered runoff DRP concentration but increased TP concentration and loads due to increased sediment loss. Management practices have a major influence on P losses in runoff in corn production systems that may overshadow the effects of STP alone. Results from this work, showing that some practices may have opposite effects on DRP vs. TP losses, emphasize the need to design management recommendations to minimize losses of those P forms with the greatest pollution potential.     

Evaluation of phosphorus transport in surface runoff from packed soil boxes

Evaluation of phosphorus (P) management strategies to protect water quality has largely relied on research using simulated rainfall to generate runoff from either field plots or shallow boxes packed with soil. Runoff from unmanured, grassed field plots (1 m wide x 2 m long, 3-8% slope) and bare soil boxes (0.2 m wide and 1 m long, 3% slope) was compared using rainfall simulation (75 mm h(-1)) standardized by 30-min runoff duration (rainfall averaged 55 mm for field plots and 41 mm for packed boxes). Packed boxes had lower infiltration (1.2 cm) and greater runoff (2.9 cm) and erosion (542 kg ha(-1)) than field plots (3.7 cm infiltration; 1.8 cm runoff; 149 kg ha(-1) erosion), yielding greater total phosphorus (TP) losses in runoff. Despite these differences, regressions of dissolved reactive phosphorus (DRP) in runoff and Mehlich-3 soil P were consistent between field plots and packed boxes reflecting similar buffering by soils and sediments. A second experiment compared manured boxes of 5- and 25-cm depths to determine if variable hydrology based on box depth influenced P transport. Runoff properties did not differ significantly between box depths before or after broadcasting dairy, poultry, or swine manure (100 kg TP ha(-1)). Water-extractable phosphorus (WEP) from manures dominated runoff P, and translocation of manure P into soil was consistent between box types. This study reveals the practical, but limited, comparability of field plot and soil box data, highlighting soil and sediment buffering in unamended soils and manure WEP in amended soils as dominant controls of DRP transport.     

Repeated compost application effects on phosphorus runoff in the Virginia Piedmont

Increasing amounts of animal and municipal wastes are being composted before land application to improve handling and spreading characteristics, and to reduce odor and disease incidence. Repeated applications of composted biosolids and manure to cropland may increase the risk for P enrichment of agricultural runoff. We conducted field research in 2003 and 2004 on a Fauquier silty clay loam (Ultic Hapludalfs) to compare the effects of annual (since 1999) applications of composted and uncomposted organic residuals on P runoff characteristics. Biosolids compost (BSC), poultry litter-yard waste compost (PLC), and uncomposted poultry litter (PL) were applied based on estimated plant-available N. A commercial fertilizer treatment (CF) and an unamended control treatment (CTL) were also included. Corn (Zea mays L.) and a cereal rye (Secale cereal L.) cover crop were planted each year. We applied simulated rainfall in fall 2004 and analyzed runoff for dissolved reactive P (DRP), total dissolved P (TDP), total P (TP), total organic C (TOC), and total suspended solids (TSS). End of season soil samples were analyzed for Mehlich-3 P (M3P), EPA 3050 P (3050P), water soluble P (WSP), degree of P saturation (DPS), soil C, and bulk density. Compost treatments significantly increased soil C, decreased bulk density, and increased M3P, 3050P, WSP, and DPS. The concentration of DRP, TDP, and TP in runoff was highest in compost treatments, but the mass of DRP and TDP was not different among treatments because infiltration was higher and runoff lower in compost-amended soil. Improved soil physical properties associated with poultry litter-yard waste compost application decreased loss of TP and TSS.     

Evaluation of the phosphorus source component in the phosphorus index for pastures

A phosphorus (P) index for pastures was developed to write nutrient management plans that determine how much P can be applied to a given field. The objectives of this study were to (i) evaluate and compare the P index for pastures, particularly the P source component, and an environmental threshold soil test P level by conducting rainfall simulations on contrasting soils under various management scenarios; and (ii) evaluate the P index for pastures on field-scale watersheds. Poultry litter was applied to 12 small plots on each of six farms based on either an environmental threshold soil test P level or on the P index for pastures, and P runoff was evaluated using rainfall simulators. The P index was also evaluated from two small (0.405 ha) watersheds that had been fertilized annually with poultry litter since 1995. Results from the small plot study showed that soil test P alone was a poor predictor of P concentrations in runoff water following poultry litter applications. The relationship between P in runoff and the amount of soluble P applied was highly significant. Furthermore, P concentrations in runoff from plots with and without litter applications were significantly correlated to P index values. Studies on pastures receiving natural rainfall and annual poultry litter applications indicated that the P index for pastures predicted P loss accurately without calibration (y = 1.16x - 0.23, r(2) = 0.83). These data indicate that the P index for pastures can accurately assess the risk of P loss from fields receiving poultry litter applications in Arkansas and provide a more realistic risk assessment than threshold soil test P levels.     

Phosphorus runoff losses from subsurface-applied poultry litter on coastal plain soils

The application of poultry litter to soils is a water quality concern on the Delmarva Peninsula, as runoff contributes P to the eutrophic Chesapeake Bay. This study compared a new subsurface applicator for poultry litter with conventional surface application and tillage incorporation of litter on a Coastal Plain soil under no-till management. Monolith lysimeters (61 cm by 61 cm by 61 cm) were collected immediately after litter application and subjected to rainfall simulation (61 mm h(-1) 1 h) 15 and 42 d later. In the first rainfall event, subsurface application of litter significantly lowered total P losses in runoff (1.90 kg ha(-1)) compared with surface application (4.78 kg ha(-1)). Losses of P with subsurface application were not significantly different from disked litter or an unamended control. By the second event, total P losses did not differ significantly between surface and subsurface litter treatments but were at least twofold greater than losses from the disked and control treatments. A rising water table in the second event likely mobilized dissolved forms of P in subsurface-applied litter to the soil surface, enriching runoff water with P. Across both events, subsurface application of litter did not significantly decrease cumulative losses of P relative to surface-applied litter, whereas disking the litter into the soil did. Results confirm the short-term reduction of runoff P losses with subsurface litter application observed elsewhere but highlight the modifying effect of soil hydrology on this technology's ability to minimize P loss in runoff.     

A COMPARISON OF RUNOFF QUALITY EFFECTS OF ORGANIC AND INORGANIC FERTILIZERS APPLIED TO FESCUEGRASS PLOTS1

ABSTRACT: Application of fertilizer can degrade quality of runoff, particularly during the first post-application, runoff-producing storm. This experiment assessed and compared runoff quality impacts of organic and inorganic fertilizer application for a single simulated storm occurring seven days following application. The organic fertilizers used were poultry (Gallus gallus domesticus) litter, poultry manure, and swine (Sus scrofa domesticus) manure. All fertilizers were applied at an application rate of 217.6 kg N/ha. Simulated rainfall was applied at 50 mm/h for an average duration of 0.8 h. Runoff samples were collected, composited, and analyzed for nitrate N (NO₃-N), ammonia N (NH₃-N), total Kjeldahl N (TKN), ortho-P (PO₄-P), total P (TP), chemical oxygen demand (COD), total suspended solids (TSS), fecal coliforms (FC), and fecal streptococci (FS). Application of the fertilizers did not alter the hydrologic characteristics of the receiving plots relative to the control plots. Concentrations of fertilizer constituents were almost always greater from treated than from control plots and were usually much greater. Flow-weighted mean concentrations of NH₃-N, PO₄-P, and TP were highest for the inorganic fertilizer treatment (42.0, 26.6, and 27.9 mg/L, respectively). Runoff COD and TSS concentrations were greatest for the poultry litter treatment. Concentrations of FC and FS were greater for fertilized than for control plots with no differences among fertilized plots, but FC concentrations for all treatments were in excess of Arkansas' primary and secondary contact standards. Mass losses of fertilizer constituents were low (≤ 3 kg/ha) and were small proportions (≤ 3 percent) of amounts applied.