Browsing by Author "Mullins, Gregory L."

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    Agronomy Handbook
    Brann, Daniel Edward; Abaye, Azenegashe Ozzie; Peterson, Paul R.; Chalmers, David R.; Whitt, David L.; Chappell, Glenn F.; Herbert, D. Ames Jr.; McNeill, Sam; Baker, James C.; Donohue, Stephen J.; Alley, Marcus M.; Evanylo, Gregory K.; Mullins, Gregory L.; Hagood, Edward Scott; Stallings, Charles C.; Umberger, Steven H.; Swann, Charles W.; Reed, David T.; Holshouser, David L. (Virginia Cooperative Extension, 2009-05-01)
    Provides readers with a source of agronomic information such as field crops, turfgrasses, variety selection, seed science, soil management, nutrient management and soil suitability for urban purposes that does not change frequently - pesticide and varietal information changes frequently and is therefor not included.
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    Assessment of Spectral Reflectance as Part of a Variable-Rate Nitrogen Management Strategy for Corn
    Lewis, Emily Kathryn (Virginia Tech, 2004-08-02)
    Spectral reflectance-based, remote sensing technology has been used to adjust in-season nitrogen (N) fertilizer rates for wheat to account for spatial variability in grain yield potential at a sub-meter resolution. The objective of this study was to examine the relationships among spectral reflectance indices, corn tissue N content, chlorophyll measurements, plant size and spacing measurements, and grain yield to develop a similar strategy for variable-rate N management in corn. Irrigated and non-irrigated studies were conducted during the 2002 and 2003 growing seasons in eastern Virginia. Plots were treated with various rates of preplant, starter, and sidedress N fertilizer to establish a wide range of grain yield potential. Spectral measurements, tissue N, chlorophyll measurements, and plant physical measurements were collected at growth stages V6, V8, and V10. At maturity, grain yield was determined and correlated with in-season data and optimum N rate to calibrate in-season, variable-rate N fertilization strategies. Results from these studies indicate that spectral reflectance is well correlated with plant N uptake and chlorophyll meter readings and can also be correlated with final grain yield. These relationships may be used to develop a model to predict in-season, variable N application rates for corn production at a sub-meter resolution.
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    Availability and Surface Runoff of Phosphorus from Compost Amended Mid-Atlantic Soils
    Spargo, John Thomas (Virginia Tech, 2004-12-14)
    The accumulation of P in soil from land-applied biosolids and manure increases the risk for P enrichment of agricultural runoff. Transport of these residuals to areas where P may be efficiently utilized is necessary to reduce the threat to water quality. Composting can improve biosolids and manure handling characteristics to make their transportation more feasible; however, little is known about P dynamics in compost-amended soil. We investigated the factors controlling P solubility and plant availability in two soils, a Kempsville fine sandy loam (Typic Hapludult) and a Fauquier silty clay loam (Ultic Hapludalf), amended with one of 4 composts (2 biosolids composts and 2 poultry litter - yard waste composts), poultry litter, or inorganic P (as KH2PO4) in incubation and greenhouse pot studies. We also compared the effects of compost, poultry litter and commercial fertilizer on surface P runoff from a Fauquier silty clay loam that had received compost, poultry litter, or commercial fertilizer for 5 years. Organic amendments with higher concentrations of Fe, Al, and Ca had lower relative P solubility/availability. Phosphorus solubility in the Kempsville fine sandy loam, having far lower native P binding capacity, was more affected by Fe, Al, and Ca applied with the organic amendments. The concentration of P in runoff from the compost treatments was higher; however, infiltration was increased and runoff decreased so the mass loss of P and sediment was lower. Improved soil physical properties associated with compost applications aid to limit P runoff.
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    Community Decision Making Aids for Improved Pasture Resources in the Madiama Commune of Mali
    El Hadj, Meriem (Virginia Tech, 2004-11-29)
    The lack of forage resources in the Sahelian region of Mali is a major constraint to food production and food sufficiency. Madiama commune is located in northern Mali, in the Niger Delta region. Three separate experiments were conducted to investigate ways to improve pasture resources and productivity. The first experiment (2003) was designed to investigate the influence of sheep grazing tethered at two different residual heights on botanical composition, forage biomass and animal performance. Young sheep weighing approximately 18-24 kg were tethered for a certain period of time depending on residual canopy height. Two treatments 3 or 6 cm residual height were each replicated 4 times. Animals were rotated based on canopy height and each tethered animal followed an 8 paddock rotation. Measurements included forage biomass, plant diversity, animal performance, and botanical composition. The forage species found on these pastures were primarily Schoenfeldia gracilis, Panicum laetum, Setaria palludefusca, Eragrostis turgida, Eragrostis tremula, Zornia glauchidiata, Tephrosia pedicellata, and Cynodon spp. Accumulated seasonal forage biomass increased while forage quality declined as the growing season progressed. Treatment had only a slight effect on animal weight gains (1 to 3kg season-1). These results suggest that residual height may not affect livestock gain. The second experiment was designed to investigate the potential of Cassia tora (C. tora) which is an invasive weed in the region as a supplemental feed for livestock. Cassia tora was harvested within the Madiama commune and ensiled with or without additives (water and or honey/sugar) for 60 or 90 days. Harvest occurred at the vegetative stage in year 1 and mature growth stage in year 2. Prior to placing the chopped material in the bags for ensiling, sub-samples of fresh C. tora were obtained for dry matter (DM) and chemical analysis (NDF, ADF, CP, IVDMD and TDN). In year 1, the ensiled material/fresh material across treatments and locations had NDF varying from 48 to 56 %/ 56 to 57%, ADF from 34 to 41 %/40 to 42%, CP from 9 to 10 %/9 to 23%, and IVDMD from 53 to 64 %/52 to 54%. In year 2, CP averaged twice as much as year 1 with significantly less fiber probably due to the fact that harvest occurred at the vegetative stage. Addition of water or sugar/honey improved the nutritive values of the ensiled material. These results suggest that C. tora can be a reliable feed source during the dry season. A greenhouse experiment was conducted using various P sources (Tilemsi phosphate rock (TPR), North Carolina phosphate rock (NCPR), Aluminum phosphate (AlP), Iron phosphate (FeP), and Triple superphosphate (TSP) and rates (0, 20, 40, 60, and 80 mg P kg-1 soil). Plants were grown for 10 wks, harvested and separated into above and below ground plant parts. The root and plant material were dried, ground and analyzed for elemental P. The result showed variable P solubility and uptake by the plant. Overall, addition of P resulted in an increase in above ground biomass as well as root mass compared with the untreated control. Field and greenhouse experiments showed that in the Sahel region of Africa where feed resources are scarce 8 out of 12 months a year, anything we can do to increase pasture resources and animal productivity while maintaining a healthy ecosystem, could improve the quality of life in the community.
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    Effects of Feeding Phytase Enzyme and HAP Corn on Solubility of Phosphorus, Copper, and Zinc in Turkey Manure and Manure-Amended Soils
    Lawrence, Christophe L. (Virginia Tech, 2000-04-28)
    Manure from turkey poults on five diets were extracted both fresh (wet) and after drying. Soils amended with wet manure were also extracted. Phosphorus, Cu, and Zn were extracted with 0.01 M CaCl₂ and acidic Mehlich III extractant (Zn in soil extracts was not evaluated). Dietary treatments were (1) normal phytic acid (NPA) corn and 0.135% inorganic P (NPA diet); (2) NPA corn, 600 units phytase enzyme, and 0.135% inorganic P (NPA+Phyt diet); (3) High available phosphorus (HAP) corn and 0.135% inorganic P (HAP diet); (4) HAP corn, 600 units phytase, and 0.135% inorganic P (HAP+Phyt diet); (5) NPA corn and 0.345% inorganic P (NPA+P diet). The NPA+P diet was similar to conventional diets being fed commercially. The NPA+Phyt diet was similar to alternative, phytase-amended diets being fed commercially. Feeding the alternative NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet reduced total P in manures by 40%, but increased the percentage of total manure P extracted with 0.01 M CaCl₂ from fresh excreta (P < 0.05). Soils amended with wet NPA+Phyt, HAP, and HAP+Phyt manures released 29 to 49% more water-soluble P than soils amended with NPA+P manure on an equal-P basis (P < 0.05). Feeding the NPA+Phyt diet instead of the NPA+P diet did not affect the percentage of total P manure extracted by Mehlich III from wet excreta, while feeding the HAP and HAP+Phyt diets increased the percentage of total manure P soluble in Mehlich III (P < 0.05). Soils amended with wet NPA+Phyt manure did not release more Mehlich III-extractable P than soils amended with NPA+P manure on an equal-P basis. Soils amended with wet HAP and HAP+Phyt manures released more Mehlich III-extractable P than soils amended with NPA+P manure on an equal-P basis (P < 0.05). Treatment-induced differences in extractability of manure and soil P appeared to be caused by a higher proportion of P in calcium phosphate form in the NPA+P manure. Drying manures prior to extraction generally heightened differences in solubility of P between the NPA+P and other manures. Feeding the alternative NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet did not affect total Cu levels in manure or the percentage of total Cu extracted from manure with 0.01 M CaCl₂. After soils were treated with manure on an equal-Cu and equal-N basis, soils amended with NPA+Phyt, HAP, and HAP+Phyt manures released more water-soluble Cu than NPA+P-amended soils (P < 0.05). Under P-based manure management, soils amended with the three alternative manures released 92 to 108% more water-soluble Cu than NPA+P-treated soils (P < 0.05). Extractable Cu increased so dramatically because conversion to the alternative diets boosted total manure loadings by 67%. Mehlich III extraction of soils amended with manure on an equal-N and -Cu basis indicated no effect of manure type on Cu availability. Feeding the NPA+Phyt, HAP, and HAP+Phyt diets instead of the NPA+P diet did not affect total Zn levels in excreta, but caused at least a five-fold increase in the percentage of total manure Zn extracted by 0.01 M CaCl₂ from fresh excreta (P < 0.05). Feeding the NPA+Phyt, HAP, and HAP+Phyt diets did not alter the percentage of total manure Zn extracted by Mehlich III from wet excreta.
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    Evaluation of Phosphorus Transport and Transformations in GLEAMS 3.0
    Vincent, Amelia A. (Virginia Tech, 2006-02-21)
    The overall goal of this research was to improve simulation of soil phosphorus (P) transport and transformations in GLEAMS 3.0, a non-point source model that simulates edge-of-field and bottom-of-root-zone loadings of nutrients from climate-soil-management interactions to assess management alternatives. The objectives of this research were to identify the state of the science for P transport and transformations, determine appropriate relationships for inclusion in GLEAMS, and determine if modifications to GLEAMS improved predictions of P loss in runoff, sediment, and leachate. The state of the science review revealed numerous equations available to predict dissolved P loss in runoff and leachate from a soil's nutrient status. These equations use a single variable to predict P loss and were developed for site-specific conditions based on empirical data. Use of these equations in GLEAMS is not reasonable as transport factors must also be considered when predicting P loss. Results from the sensitivity analysis showed that GLEAMS prediction of leached P were extremely sensitive to changes in the P partitioning coefficient (CPKD). Runoff PO₄-P output was slightly to moderately sensitive, sediment PO₄-P was moderately sensitive to sensitive, and sediment organic P was moderately sensitive to changes in CPKD whereas plant uptake of P was insensitive to slightly sensitive. The weakness of GLEAMS to estimate CPKD has been documented. Upon further investigation, it was determined that CPKD was highly over-estimated in GLEAMS as compared to measured values found during the literature review. Furthermore, this over-estimation caused under-estimation of the P extraction coefficient (BETA P); the value of BETA P remained constant at 0.10 and did not vary over the simulation period. Expressions for CPKD and BETA P were modified in GLEAMS. Data from three published studies (Belle Mina, Gilbert Farm, and Watkinsville) were used in the analyses of three modifications to GLEAMS: GLEAMS BETA P, GLEAMS CPKD, and GLEAMS BETA P+CPKD. GLEAMS BETA P investigated the change in BETA P as a function of soil clay content, GLEAMS CPKD attempted to improve GLEAMS' estimation of CPKD, and GLEAMS BETA P+CPKD assessed the combined effects of changes to BETA P and CPKD. Over the respective study periods, GLEAMS over predicted runoff PO₄-P for Belle Mina by 193 to 238% while under-predicting runoff PO₄-P at Gilbert Farm by 41% and Watkinsville by 81%. Sediment P was over-predicted by GLEAMS for Belle Mina by 225 to 233% and Gilbert Farm by 560%, while sediment P was under-predicted by 62% at Watkinsville. Leached PO₄-P was both over- and under-predicted by GLEAMS; Belle Mina was the only data set with observed leached P values. Simulation results from the model changes were inconclusive. There was no clear evidence supporting use of one model over another. Modifications increased predicted dissolved P in runoff and leachate, while decreasing predicted sediment-bound P in runoff. The original GLEAMS model best predicted runoff and leached PO₄-P at the Belle Mina sites. GLEAMS CPKD was the best predictor of runoff PO₄-P and sediment P at Gilbert Farm. GLEAMS BETA P+CPKD best predicted runoff PO₄-P at Watkinsville. Overall, the proposed improvements to GLEAMS did not improve GLEAMS predictions. In conclusion, GLEAMS should not be used for quantitative estimates of hydrology, sediment, and nutrient loss for specific management practices. As recommended by the GLEAMS model developers, GLEAMS should only be used to predict relative differences in alternative management systems. It is recommended that future research focus on developing a better correlation between CPKD, clay mineralogy and content, and organic matter content, as CPKD has been identified as a vital component of the GLEAMS P sub-model that requires further examination.
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    Influence of Phytase and High Available Phosphorous Corn Diets on Solubility and Plant Uptake of P, Cu, and Zn in Poultry Manure and Manure-Amended Soils
    Stanley, Lori Hillman (Virginia Tech, 2001-01-08)
    Poultry manure is a useful nutrient source but recently it has raised environmental concern due to possible P movement from P saturated soils to waterbodies. This study was conducted to determine the effects of using phytase and high available phosphorous corn diets on the solubility and plant uptake of P, Cu, and Zn in poultry manure and soils amended with manure. Five diet treatments were used in the study: 1) normal phytic acid corn and 0.135% inorganic P (NPA), 2) normal phytic acid corn, 600 units phytase, and 0.135% inorganic P (NPA+Phytase), 3) normal phytic acid corn and 0.345% inorganic P (NPA+P), 4) high available phosphorous corn and 0.135% inorganic P (HAP), 5) high available phosphorous corn, 600 units phytase, and 0.135% inorganic P (HAP+Phytase). The NPA+P diet and NPA+Phytase diets are most similar to the conventional and alternative phytase supplemented diets currently used commercially. Three Virginia soils (Groseclose, Cecil, Mahan) were amended with manure from the diet treatments at rates of 25 and 50 g/kg and P and Cu were extracted with 0.01 M CaCl2 and Mehlich III extractant after incubation periods of 6 and 12 months. Corn was grown in a greenhouse experiment using these same Virginia soils and sand amended with 8.96 Mg/ha poultry manure from each of the five diet treatments. Poultry manure was nonsequentially extracted for determination of P, Cu, and Zn fractions. Comparing the alternative NPA+Phytase, HAP, and HAP+Phytase treatments to the conventional NPA+P treatment on an N- (nitrogen) basis all reduced both CaCl2 and Mehlich III-soluble P concentrations (P<0.05). Comparing these same treatments on a P-basis increased P extracted with CaCl2 24, 26, and 37%, respectively, and P extracted with Mehlich III P 5, 4, and 9%, respectively (P<0.05). The alternative NPA+Phytase and HAP+Phytase treatments increased water-soluble Cu compared to the conventional NPA+P on both a N- and P-basis, while no differences were observed in Mehlich III solubility between these treatments (P<0.05). The alternative NPA+Phytase treatment did not differ in Pand Cu in corn tissue or plant uptake when compared to the NPA or NPA+P (N- or P-basis) treatments. No difference in Zn in corn tissue was observed between these treatments on a N-basis, while NPA+Phytase was higher on a P-basis. Plant uptake of Zn was higher in the NPA+Phytase treatment compared to the NPA+P treatment on both a N- and P-basis. Addition of phytase reduced P solubility from all reagents except for CaCl2 (P<0.05). Replacing the conventional NPA+P treatment for the alternative NPA+Phytase treatment resulted in higher Cu concentrations for all reagents except for K-pyrophosphate and nitric acid. This same replacement increased Zn extracted by water, CaCl2, and CaNO3, while it reduced Zn extracted by HCl, acetic acid, PbNO3, K-pyrophosphate, and NH4-oxalate in the light. The use of phytase decreased P solubility from manure amended soils when treatments are compared on an equal N-basis, and increased P solubility when compared on an equal P-basis. No effect on plant uptake of P or Cu occurredfrom the NPA+Phytase treatment.
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    Land Application of Broiler and Turkey Litter for Farming Operations Without a DEQ Permit
    Marsh, Lori S.; Mullins, Gregory L.; Habersack, Mathew James; Collins, Eldridge R. Jr. (Virginia Cooperative Extension, 2009)
    This publication is intended to provide guidance on land-applying poultry litter in an environmentally-sound manner.
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    Management of Alum-Treated Poultry Litter
    Warren, Jason George (Virginia Tech, 2005-12-13)
    Previous research has shown that treatment of poultry litter with alum is an effective management strategy to reduce phosphorus (P) solubility in litter thereby reducing potential P losses to surface runoff after surface applications. However, limited data are available evaluating alum-treated poultry litter (ATPL) environmental impact in cultivated systems and how its application will affect crop production. In addition little is known as to how its application affects various P fractions or exchangeable Aluminum (Al) content in treated soils. Two, 3-yr field trials with corn (Zea mays L.) were used to show that, when applied at rates based on current litter management strategies, ATPL resulted in yields similar to those achieved through applications of non-treated poultry litter (NPL). These trials also showed that ATPL applications resulted in lower soil P status and decreased P losses in surface water runoff compared to application of NPL. A 4-yr field trial with fescue (Festuca arudinacea) also showed no significant differences in productivity when comparing ATPL and NPL. This trial was utilized to evaluate the distribution of P in soils receiving ATPL. Soil analysis data showed that ATPL applications result in decreased water-extractable P (H2O-P) and that this decrease was associated with an elevation in NaOH extractable organic soil P. A laboratory incubation was utilized to evaluate the short and long-term impact of ATPL application on soil pH, exchangeable soil Al and H2O-P. Data from this incubation confirmed that the relationship between soil pH and exchangeable Al is not adversely affected by ATPL applications. Also, variations in the H2O-P content of soils treated with two different ATPL sources could not be associated with differences in Al:P ratio or soluble P content of the two litters, providing evidence that additional characteristics also control P availability after incorporation in soil.
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    Manure Spreader Calibration for Rear-discharge Equipment -- Handling Solid and Semi-solid Manures and Poultry Litter
    Marsh, Lori S.; Mullins, Gregory L.; Ambler, Scott; Heidel, Richard D. (Virginia Cooperative Extension, 2009)
    Discusses calibration methods of manure spreaders.
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    The Mid-Atlantic nutrient management handbook
    Abaye, Azenegashe Ozzie; Basden, Thomas J.; Beegle, Douglas B.; Binford, Gregory D.; Daniels, W. Lee; Duiker, Sjoerd Willem; Haering, Kathryn C.; Evanylo, Gregory K.; Hansen, David J.; Mullins, Gregory L.; Taylor, Richard W. (Virginia Cooperative Extension, 2006)
    This revised handbook was developed to incorporate the advances in the understanding of managing soils, crops, and nutrients for the protection of surface and ground water that have occurred since the original manual was published, and to broaden the scope of the manual to cover the entire Mid-Atlantic region
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    The Mid-Atlantic Nutrient Management Handbook
    Haering, Kathryn C.; Abaye, Azenegashe Ozzie; Basden, Thomas J.; Beegle, Douglas B.; Binford, Gregory D.; Daniels, W. Lee; Duiker, Sjoerd W.; Mullins, Gregory L.; Taylor, Richard W. (Virginia Cooperative Extension, 2015-06-09)
    This handbook is a revision and update of a nutrient management training manual for Chesapeake Bay watershed published in 2000. This handbook includes the latest information on managing soils, crops and nutrients in order to better protect surface and ground water in the Mid-Atlantic region.
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    Nitrogen Regime Influence on Nutrient and Sediment Surface Runoff During Vegetative Establishment of Bermudagrass
    Beasley, Jeffrey S. (Virginia Tech, 2002-01-07)
    Bermudagrass (Cynodon dactylon (L.) Pers.) is a popular turfgrass used throughout the Southeast. Bermudagrass is established primarily as sprigs on large acreage sites. Currently, the industry standard practice (ISP) of fertilization during bermudagrass sprig establishment is 48.8 kg N ha⁻¹ wk⁻¹. This fertilizer rate can be excessive on morphologically immature sprigs in the initial weeks of establishment, thus making the possibility of offsite surface runoff N events more likely. Two experiments were conducted in 2000 and 2001 where sprigs were established at 2, 4, 6, 8, and 10 weeks prior to applying simulated rainfall (WPRS) following N fertilization rates of the ISP or a lower initial N (LIN) rate of 12.2 kg N ha⁻¹ wk⁻¹ the first four weeks and then 48.8 kg N ha⁻¹ wk⁻¹ until full establishment. At the tenth week all treatments were subjected to rainfall simulation at 63.5 mm hr⁻¹. Once surface runoff was induced, rainfall continued for thirty minutes during which time runoff samples were taken every five minutes and analyzed for sediment losses, N concentrations in the nitrate and ammonium forms, and phosphorus losses as dissolved reactive P (DRP). Experimental results indicate an ability to curb N losses through surface runoff during the initial weeks of sprig establishment following the LIN with only modest delays in sprig establishment. Sprigs established for the same time period, under the ISP or LIN, were very similar in growth, release of surface runoff, and sediment losses during runoff events.
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    Nutrient and Bacterial Transport From Agricultural Lands Fertlized With Different Animal Manures
    Mishra, Anurag (Virginia Tech, 2003-12-04)
    The increase of animal agriculture coupled with excess manure production, and the reduced availability of land has led to the over application of animal manure on agricultural fields. The excessive application of manure is responsible for nutrient and bacterial pollution of downstream waterbodies. Manure application based on the crop phosphorus (P) requirements has been recommended as a viable method to reduce nutrient pollution. A plot scale study was conducted to measure the loss of nutrients and bacterial transport in runoff from cropland treated with poultry litter, dairy manure and inorganic fertilizer according to the P requirements of the crop. Three simulated rainfall events were conducted 1, 2 and 35 days after planting of corn. Highest P and N concentrations were observed in the runoff from plots treated with poultry litter, followed by dairy manure and inorganic fertilizer. The poultry litter treated plots exhibited highest concentrations of bioavailable P in the runoff, compared to all other treatments. The P from poultry litter treated plots was also mostly in the soluble form, which underscores the need to control the runoff from cropland in order to decrease the P losses from the poultry litter treated fields. The edge of the field nutrient concentrations observed in this study were high enough to cause severe to moderate eutrophication problems in downstream waterbodies unless they are diluted. In general, nutrient concentrations were lower during the second simulated event, compared with those from the first event. A significant reduction in the nutrient concentrations of runoff was observed from the second to the third simulated event for all the treatments. This reduction was attributed to the loss of nutrients by natural rainfall-runoff events during the time period between the second and the third simulated rainfall event, plant uptake of nutrients, sorption and leaching processes. The indicator bacteria analyzed in the present study were fecal Coliform (FC), Escherichia Coli (E.Coli) and Enterococcus (ENT). The bacterial concentrations reported in the runoff for the first and second simulated events were 104 to 105 times higher than the federal and state limits for primary contact recreation waters. No significant effect of treatments was observed on the bacterial concentrations in runoff. The highest concentrations were observed for FC, followed by ENT and EC in the runoff. The ratio of bacteria removed in runoff to the bacteria applied also followed the above trend. The concentrations of bacteria generally increased from the first to second simulated event; unlike the nutrients. However, the bacterial concentrations dropped significantly from second to the third simulated rainfall event to the levels lower than those designated for primary contact recreation water limits. This reduction was attributed to the washing away of bacteria by the heavy rainfall-runoff events in the period between second and third simulated rainfall events and the die-off of bacteria. The results reported from this study suggest that the manure application based on crop P requirements can also be a significant source of nutrient pollution and should be coupled with other best management practices (BMPs) also to reduce nutrient pollution. The results also suggest that the manure treated cropland can be a source for significant indicator bacterial pollution and appropriate BMPs are required to mitigate their effect.
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    Phosphate Reactivity in Long-Term Manure Amended Soils in the Ridge and Valley of Virginia
    Gala, Caron E. (Virginia Tech, 2006-01-17)
    Phosphorus (P) released in overland flow is related to P form, soil solution P concentration and the release rate of P from soil. Models relating soil test P (STP) to water soluble P (WSP) and the degree of P saturation (DPS) to STP are used in Virginia to estimate P loss potential. Typically the reservoir of biologically available P in eastern soils has been attributed to P sorbed onto surface sites of non-crystalline aluminum (Al) and iron (Fe) oxides, extractable in ammonium oxalate. More recently, soils with a long-term history of manure application have exhibited properties that indicate calcium (Ca) may also be limiting P, especially in soils impacted by poultry manure. Accurate estimation of P loss potential is critical for justification of long-term management approaches. To evaluate the accuracy of model estimation of P loss potential and P source, we evaluated the (i) soil chemical properties, (ii) soil solution equilibria, (iii) inorganic speciation, and (iv) P desorption capacity of soils impacted over a long period of time by poultry litter (broiler and layer), dairy manure and commercial fertilizer applications. Soil chemical properties were measured with various extractions, while soil solution was measured in samples equilibrated at field capacity. Inorganic material was analyzed using scanning electron microscopy with electron dispersive capacities. Phosphorus desorption capacity was determined by calculating the rate of P release into a 0.01 M NaCl batch reactor. Out of the said analysis, we found that Al and Ca were the primary soil chemical elements limiting soil test P extractability and release. Soils with a high P sorbing capacity (PSC), that were not yet saturated, retained the most total soil P over a 60 hr. batch release experiment. Phase diagrams show that all soils were supersaturated with respect to common Al-, and Fe â P minerals. Saturation indices calculated with Visual Minteq were correlated with the degree of P saturation, and suggested that as the DPS increased, formation of less soluble Ca -P minerals occurs. The soils found to be supersaturated with respect to tri-calcium phosphate (TCP) and octa-calcium (OCP) had the highest P release rate coefficients for both the first (k1) and second (k2) phases of release. Scanning electron microscopy with electron dispersive analysis (SEM-EDS) found that for some manure impacted soils, Al formed associations with P that are stable over a large soil to solution ratio. Additionally, it appears that as non-crystalline Al becomes saturated with P, Ca-P forms may act as an additional reservoir of P in soils with a long-term history of poultry manure application.
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    Phosphorus Losses From Simulated Dairy Land Uses of Management Intensive Grazing and Concentrated Animal Feeding Operations
    Johnston, Michael Rhodes (Virginia Tech, 2004-04-21)
    Dairy grazing systems have been promoted as an environmentally friendly alternative to concentrated animal feeding operations (CAFOs). However, questions remain regarding the amount of phosphorus (P) loss from pasture-based dairies. Therefore, the goal of this study was to quantify P losses via runoff from grazing dairy systems and CAFO hay production. Four land use treatments were simulated on runoff release plots planted in two forage treatments. Land use treatments were management intensive grazing (MIG) and CAFO hay production to which manure was applied; grazing and CAFO hay production without manure application served as controls. The forage treatments were orchardgrass (Dactylis glomerata) and broad-leafed forage (buckhorn plantain [Plantago lanceolata], red clover [Trifolium pretense], and alfalfa [Medicago sativa]). The four land use treatments and two forage treatments had four replications for a total of 32 (4 land use treatments e n2 forage treatments e n ¤ nreplications) runoff release plots. Thirty minutes of runoff was collected from each runoff release plot during six rainfall simulation series. Grab samples of runoff were collected and analyzed for dissolved reactive phosphorus, total phosphorus, and total suspended solids. Particulate P (PP) was determined indirectly by subtracting dissolved reactive P (DRP) from total P (TP). No distinction was observed between DRP concentrations from simulated MIG plots and simulated CAFO plots for the duration of the study. However, a clear divergence of TP concentrations from CAFO hay plots with manure from all other land uses was observed during simulation series 1. DRP concentrations for all land uses were fairly consistent for the duration of the study with the exception of simulation series 2. All land uses had DRP concentrations that would be considered of concern (> 1.0 ppm DRP) by the US-EPA during simulation series 4 and 5. The elevated TP concentrations and mass losses from CAFO hay plots with manure were primarily due to PP losses. Thus, it was concluded that MIG has less potential for P loss than CAFO hay production. Broad-leafed forage had significantly higher DRP, PP, and TP losses than orchardgrass on CAFO hay with manure. However, no significant difference was found between forage types on MIG plots. Thus, either forage could be planted in grazing land without a significant difference in P losses.
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    Phosphorus Losses in Runoff from Virginia Soils
    Penn, Chad John (Virginia Tech, 2004-07-23)
    Previous research shows that dissolved P losses in runoff are well related to soil test P (STP), thus, various P loss prediction models incorporate the use of a STP vs. runoff DRP relationship. However, the relationship between STP and runoff DRP will vary based on soil type due to differences in soil properties. The purposes of the first two studies were to (i) investigate the effect of soil mineralogy on P sorption behavior and dissolved P in runoff and (ii) determine if any simple soil test extractions could indirectly take into account this effect of mineralogy. Nine soil types from the Virginia Piedmont, Coastal Plain, and Ridge and Valley were collected and used in a rainfall simulation study. Phosphorus retention among separated clay fractions and whole soils were related to Al bearing minerals such as hydroxy-interlayered vermiculite (HIV), gibbsite, and amorphous Al. Samples dominated by kaolinite retained very little P. Application of these results to runoff data showed that soil types with a HIV:kaolinite ratio > 0.5 caused significantly less DRP in runoff for a given soil WSP level compared to soils with a ratio < 0.5. The second study showed that the soil P vs runoff DRP relationships varied between physiographic provinces. Generally, the Coastal Plain soils resulted in a higher runoff DRP concentration for a given soil P level compared to Piedmont and Ridge and Valley soils. However, soil M3-P/Al resulted in one relationship with DRP for all three groups of soils. Results from the incubation study suggested that Al related P is more easily desorbed into solution compared to Fe related P. The final study demonstrated that phytase enzyme and high available P corn supplements in poultry diets can reduce manure WSP and total P. Results from the runoff study showed that DRP losses were related to sediment losses which consisted of > 90% manure particles. Manure particles were directly deposited into the collection container followed by desorption of P based upon the WSP content of that manure type. The results emphasized best management practices that prevent direct loss of manure particles from soil into surface waters.
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    Phosphorus runoff potential of different sources of manure applied to fescue pastures in Virginia
    Hollmann, Marcus (Virginia Tech, 2006-08-07)
    Version 2.0 of the P Index for Virginia uses coefficients describing the risk of P losses for different manure sources applied to fescue pasture that have not been verified on Virginian soils. In the first experiment, four sources of manure (dairy slurry, piggery waste, beef solids, and poultry litter) and triple superphosphate (TSP) were applied iso-nitrogenously to pasture plots (1.5 m2, 10% slope) with 31 ppm Mehlich 1-P soil test. The P treatments were amended in spring at a rate of 62.7 kg P2O5/ha and compared against a no-P-amended control. Forage was cut and removed monthly (n=5). Five rainfall simulations (65-70 mm/h) were conducted at three occasions (June, August, and October); the soil moisture was below field capacity at two events. Continuous surface runoff was collected for 30 min from each plot in accordance with the protocol of the National P Research Project. Data were statistically analyzed using Proc Mixed of SAS with rain event or cutting used as the repeated measure. Runoff concentrations of total P (TP) and dissolved reactive P (DRP) did not vary by treatment. The control showed less TP (0.126 mg/l) and DRP (0.068 mg/l) concentration than all other treatments (ranges 0.190 to 0.249 mg TP/l and 0.129 to 0.182 mg DRP/l) in runoff during the first event (40 d after treatment). The control had the lowest (0.118 mg/l) and TSP the highest (0.248 mg/l) TP concentration during the second event 24 h later. Samples taken at 5-min intervals during the second simulation showed a significant decrease in TP and DRP concentrations over time for all treatments but the control. Treatments did not affect edge-of-the-field losses of TP, DRP, or TKN. Soil test P and water-extractable P measured after the fifth and final rainfall simulation did not correlate to P concentrations in runoff. Forage yields and their N and P concentrations were not impacted. Results indicated a decreasing impact of manure, spring-applied to fescue pasture, on runoff P concentrations throughout the season. Highest TP concentrations were found during the first pair of simulated rainfalls from the TSP treatment. In a second experiment, indoor runoff boxes were used to simulate management intensive rotational grazing. Commercial fertilizer TSP and manure application increased runoff TP concentration from 0.146 mg/l to 0.245 mg/l and DRP concentration from 0.105 mg/l to 0.183 mg/l. Runoff P did not differ between organic or inorganic P treatments, possibly due to the small area of the boxes. However, application of manure increased runoff TKN overall, with a linear decrease as the time increased between application and rain simulation.
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    Phosphorus, Agriculture & The Environment
    Mullins, Gregory L. (Virginia Cooperative Extension, 2009)
    Discusses potential environmental impacts of phosphorus, the functions of phosphorus in plants and animals, and the soil phosphorus cycle. Notes methods for controlling phosphorus losses to surface waters
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    Phosphorus, agriculture & the environment
    Mullins, Gregory L. (Virginia Cooperative Extension, 2000)