Browsing by Subject "phosphorus"
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Item A water quality assessment of the import of turfgrass sod grown with composted dairy manure into a suburban watershed(Texas A&M University, 2005-02-17) Richards, Chad EdwardConcentrated animal feeding operations (CAFOs) have caused water quality concerns in many rural watersheds, sometimes forcing the State of Texas to conduct Total Maximum Daily Load (TMDL) assessments of stream nutrients such as nitrogen (N) and phosphorus (P). One suggested Best Management Practice (BMP) is the export of phosphorus (P) through turfgrass sod produced with composted dairy manure from an impaired rural watershed to an urban watershed. The manure-grown sod releases P slowly and would not require additional P fertilizer for up to 20 years in the receiving watershed. This would eliminate P application to the sod and improve the water quality of urban streams. The Soil and Water Assessment Tool (SWAT) was used to model a typical suburban watershed that would receive the transplanted sod. The objective of the modeling was to determine the water quality changes due to the import of sod transplanted from turf fields and grown with composted dairy manure. The SWAT model was calibrated to simulate historical flow and sediment and nutrient loading to Mary's Creek. The total P stream loading to Mary's Creek was lower when manure-grown sod was imported instead of commercial sod grown with inorganic fertilizers. Yet, flow, sediment yield, and total N yield increased equally for both cases at the watershed outlet. The SWAT simulations indicate that a turfgrass BMP can be used effectively to import manure P into an urban watershed and reduce in-stream P levels when compared to sod grown with inorganic fertilizers.Item Chemical fractionation and solubility of phosphorus in dairy manure-amended soils as a predictor of phosphorus concentration in runoff(Texas A&M University, 2007-04-25) Harstad, Laura ElizabethNutrient over-loading in many dairy manure-amended soils in the dairy producing areas of Texas has led to environmental problems as such eutrophication of local surface water bodies. One of the nutrients contributing to eutrophication problems is phosphorus (P). This project focused on fractionation and solubility of selected P forms in an effort to determine a relationship with P found in runoff from dairy manureamend soils. Ten soils (5 calcareous, 5 noncalcareous) were collected from the dairy producing areas of Texas. Triplicate soil samples were analyzed for 0-5 cm and 5-15 cm depths. An acid-base extraction method was used to determine total P (TP), inorganic P, and organic P. Sequential extractions were used to determine the loosely-bound P, iron (Fe) phosphates, aluminum (Al) phosphates, reductant soluble P, occluded apatite P, and calcium (Ca) phosphates for calcareous and noncalcareous samples. The ammonium oxalate method was used to determine extractable Fe, Al, and silicon (Si). Potassium chloride extraction was used to determine soluble Ca, Al, Fe, Mg, and P. A weak NaOH extract was used to determined the amount of bioavalible P. Dissolved P in runoff events and soil pH were collected in a previous study. Calcareous and noncalcareous soils displayed varying concentrations of P indifferent fractions and with separate comparisons, stronger relationships could be achieved. It was also determined that KCl soluble Mg could be used as a predictor for dissolved and total P in runoff for calcareous soils (r2??????s ranging from 0.865 to 0.928 and 0.801 to 0.886, respectively). Ammonium oxalate extractable Al also yielded high correlations in calcareous soils for dissolved and total P in runoff (r2 ranging from 0.798 to 0.991 and 0.766 to 0.973, respectively). In noncalareous soils, pH resulted in a less correlated relationship with dissolved P (r2 = 0.600). This study shows that there are simple and effective ways of predicting dissolved and total P in runoff to improve best management practice recommendations for manure-amended soils.Item The effect of nutrient limitations on the production of extracellular polymeric substances by drinking-water bacteria(2013-05) Evans, Ashley Nichole; Kirisits, Mary JoBiological filtration (biofiltration) of drinking-water is gaining popularity due the potential for biodegradation of an array of contaminants not removed by traditional drinking-water processes. However, previous research has suggested that biomass growth on biofilter media may lead to increased headloss, and thus, greater energy and water requirements for backwashing. Research has suggested that the main cause of headloss might be due to extracellular polymeric substances (EPS) rather than the bacterial cells themselves. As EPS production has been shown to increase under nitrogen- and phosphorus-limited or -depleted conditions, the goal of this research was to add to the body of knowledge regarding biofiltration by studying the relationship between EPS production and nutrient limitations in drinking-water. Batch experiments with a synthetic groundwater were run with a mixed community of drinking-water bacteria under nutrient-balanced (a molar carbon to nitrogen to phosphorus ratio [C:N:P] of 100:10:1), nutrient-limited (e.g., C:N:P of 100:10:0.1), and nutrient-depleted conditions (C:N:P of 100:0:1 or 100:10:0). After 5 days, growth was measured as the optical density at 600 nanometers (OD600), and the concentrations of free and bound carbohydrates and proteins, the main components of EPS, were measured. In batch experiments with 2.0 and 0.2 g/L as carbon (mixture of acetic acid, mannitol and sucrose) increases in EPS production per OD600 and decreases in growth were noted under nutrient-depleted conditions. When the same experiments were conducted with a pure culture of Bacillus cereus, bound polysaccharides normalized to OD600 increased under nitrogen- and phosphorus-depleted conditions. Since previous research suggested that Bradyrhizobium would be an important player in EPS production in drinking-water biofilters, similar batch experiments were conducted with Bradyrhizobium. However, due to experimental challenges with Bradyrhizobium japonicum USDA 110, differences in EPS production under nutrient limitations could not be reliably assessed. Additional work is required with Bradyrhizobium. Recommendations for future work include the replication of these batch conditions in steady-state chemostats containing biofilm attachment media and in bench-scale columns. Additionally, future work should include experiments at carbon concentrations as low as 2 mg/L to match typical carbon concentrations in drinking-water biofilters.Item Evaluation of organophosphate insecticides on performance of transgenic and conventional cotton(Texas A&M University, 2005-08-29) Hundley, Christopher AlanGenetically modified cotton (Gossypium hirsutum L.) acreage has increased dramatically over the last six years. Reports of variable results in fiber quality and yield have arisen in these cultivars. Some changes in production practices have occurred coincident with the introduction of transgenic technology, such as reduced use of broad-spectrum insecticides, including organophosphates (OP) that could potentially influence the growth and yield of cotton. One factor that might affect these parameters is the difference in the amount of foliarly-applied phosphorus (P) between an OP and non-phosphate (NP) insecticide regime. Therefore, a study was conducted to investigate selected growth characteristics, yield, and fiber quality of genetically modified and conventional cotton as influenced by OP and foliar phosphorus (FP) applications. A four replication strip-plot experimental design was utilized with cultivar serving as the whole plot and insecticide regime as the sub-plot. Three cultivars of the same recurrent parent (ST4892BR, ST4793R, and ST474) were planted in 2001 and 2002 under irrigated conditions in Burleson County, TX on a Weswood silty clay loam (fine-silty, mixed, thermic Fluventic Ustochrept). The insecticide regime consisted of NP, NP+FP, and OP treatments. The FP was applied at P2O5 weight equivalent to the P component in the concurrent OP application. ST4892BR had greater lint yield than ST4793R and ST474. The yield increase can be explained through plant mapping analysis which showed ST4892BR producing larger bolls and greater boll numbers. In addition, evaluation of fruiting distribution showed ST4892BR contained more lint on sympodial branches 6 through 10. The insecticide regime effect on lint yield resulted in higher yield (P=0.08) for the NP+FP regime. Examination of yield components revealed NP+FP increased second position bolls, predominantly at sympodial branches 6 through 10. Leaf tissue analysis revealed increased levels of P for the OP and NP+FP over that of the NP insecticide regime, which indicates a potential for plants to acquire P from OP insecticides. Furthermore, the considerable yield response to small amounts of FP is not clearly understood. While conclusive evidence exists regarding cultivar yield differences, this study does not provide sufficient evidence to conclude that OP insecticides influence growth, yield, or fiber quality characteristics of these cotton cultivars.Item Genetic Variability for Low Phosphorous Tolerance in Cowpea(2014-04-18) Alexander, Tulle WAs a result of rising fertilizer prices and environmental concerns, efforts are being made to develop crop varieties with better nutrient acquisition and use efficiencies to ensure higher yields and sustainability, especially in the semi-arid tropics and sub-tropics where soils are inherently low in nitrogen and phosphorus. Cowpea does not require additional nitrogen fertilizer because of its ability to biologically fix nitrogen, but it needs phosphate application. However, preliminary studies have shown that some cowpea genotypes have the ability to extract bound phosphorus from low-P soils and from rock phosphate. Therefore, a project was initiated at Texas A&M University to develop high yielding cowpea varieties with enhanced acquisition and efficient utilization of phosphorus from low-P soils and rock-P. This study was conducted to screen 12 selected cowpea varieties under low-P soil, with rock- phosphate application. One-kg pots were filled with 1000 g of low-P soil (< 4 ppm) collected from Nacogdoches, TX, and amended with five phosphorus treatments ? no added phosphorus, 200, 400, and 600 ppm rock-phosphate and Normal-P (Hoagland?s solution). Pots with No-P and rock-phosphate treatments were treated with a modified (P-free) Hoagland?s solution. The Normal-P treatment received unmodified Hoagland?s solution. Pots were arranged in a completely randomized design with three replications and planted with three seeds which were thinned to a single plant per pot after emergence. Pots were watered every second day to field capacity with reverse-osmosis purified water. The experiment was terminated 42 days after planting and dry weights of plants from each pot were recorded. Major varietal differences were observed for biomass production in the low-P and rock-P treatments. Some of the promising cowpea varieties are IT97K-1069-6, IT98K-476-8, TX 2028-1-3-1 and Big John which performed well regardless of phosphorus treatment. California Blackeye #50, Dan Ila, IAR-48, and IT00K-1148 performed poorly in low-P soils, but exhibited significant growth response with addition of rock-P.Item Phosphorus reduction in dairy effluent through flocculation and precipitation(Texas A&M University, 2005-02-17) Bragg, Amanda LeannPhosphorus (P) is a pollutant in freshwater systems because it promotes eutrophication. The dairies in the North Bosque and its water body segments import more P than they export. Dairies accumulate P-rich effluent in lagoons and use the wastewater for irrigation. As more P is applied as irrigation than is removed by crops, P accumulates in the soil. During intense rainfall events, P enters the river with stormwater runoff and can become bio-available. Reducing the P applied to the land would limit P build up in the soil and reduce the potential for P pollution. Since wastewater P is associated with suspended solids (SS), the flocculants, poly-DADMAC and PAM, were used to reduce SS. To precipitate soluble P from the effluent, NH4OH was added to raise the pH. Raw effluent was collected from a dairy in Comanche County, TX, and stored in 190-L barrels in a laboratory at Texas A&M University. Flocculant additions reduced effluent P content by as much as 66%. Addition of NH4OH to the flocculated effluent raised the pH from near 8 to near 9, inducing P precipitation, further reducing the P content. The total P reduction for the best combination of treatments was 97%, a decrease from 76 to 2 mg L-1. If this level of reduction were achieved in dairy operations, P pollution from effluent application would gradually disappear.Item Sustainable Management of Biogeochemical Cycles in Soils Amended with Bio-Resources from Livestock, Bioenergy, and Urban Systems(2011-10-21) Schnell, Ronnie WayneBioresources are generated in a variety of environments and each presents unique risks and benefits associated with land application. Bioresources from livestock, urban and bioenergy systems were selected and evaluated through field, greenhouse and laboratory studies of potential risk and benefits of recycling to agricultural and urban landscapes. The waste stream, including feedstock sources and treatment processes, affects composition and properties of bioresources and effects on biogeochemical cycles of amended soils. Variation of decomposition and nutrient mineralization rates among bioresources used to amend soil for turfgrass and forage reflected variation among contrasting feedstock sources and treatments prior to application. During turfgrass establishment, plant available nitrogen and nitrogen mineralized from a bioresource from livestock waste streams, (Geotube! residual solids, supplied N in excess of crop uptake potential and contributed to leaching loss of N. In contrast, N mineralization rates from bioresources generated during methane production from dairy manure (manure solids) were not sufficient to maximize crop production, necessitating N fertilizer application. In addition to variation of composition, bioresource effects on crop productivity and environmental quality vary among management practices and between forage and turfgrass cropping systems. Large application rates of bioresources increase soil nutrient concentration and potential crop productivity, but contribute to increased nutrient loss in drainage and surface runoff. Yet, incorporation or Alum treatment of bioresources will reduce runoff loss of dissolved P and protect water quality without sacrificing crop productivity. Alum treatment of bioresources prior to land application effectively reduced runoff loss of dissolved P to levels observed for control soil. For situations in which large, volume-based bioresource rates are top-dressed or incorporated, export of applied nutrients environmental impacts were compared between forage and turfgrass systems. Starting during the initial year of production, annual export of applied N and P in Tifway bermudagrass sod was greater than export through forage harvests of Tifton 85. Low forage yield limited N and P export from Tifton 85 during the year of establishment, but increased forage yield during the second year increased export of manure N and P to levels more comparable to sod. As variation between compost sources, turfgrass and forage production systems, and application methods indicated, effective management of bioresources is necessary to balance benefits and risk in cropping systems. Integrated assessment of bioresource composition and crop-specific management of application method and rate will enable sustainable bioresource cycling and crop productivity.Item The role of iron oxyhydroxides in phosphorus chemistry of some East Texas forest soils(Texas A&M University, 2006-10-30) Hass, AmirForest soil phosphorus (P) chemical behavior was evaluated in some mid-rotation fertilized loblolly pine (Pinus taeda L.) plantations in East Texas, that differed in their site drainage characteristics. Forest floor mass and carbon content in the forest floor were determined. Total P (PT) in the forest floor, and total and Mehlich-1 P and citratedithionite (CD) and acid ammonium-oxalate (AAO) extractable P, Al, Fe, and Mn within the mineral soil upper 100 cm were determined. Colorimetric determination of AAOand CD-extractable P by the molybdenum blue ascorbic acid method, without the use of pre-digestion, was assessed by an automated continuous flow injection system. Phosphorus distribution between different operationally defined solid phases and its relationships with CD and AAO extractable Mn, Al, Fe among depth, site, drainage class and treatment were evaluated. Soil P forms were highly correlated with iron oxides across sites, drainage classes, treatments, and depth intervals with significant differences in P content and distribution in the soil profile and solid phases among drainage classes. Soil P distribution patterns differed among drainage classes, yet it followed the distribution of the iron oxides. Iron oxide??????s role as a sink for soil P was higher in the well-drained compared to the poorly drained sites. Amorphous phases of iron oxides were higher in the poorly drained sites and dominated the role of iron oxides as a sink for P under the poor drainage conditions. Fertilization resulted in significantly higher forest floor mass, P content in the forest floor, and total P (PT) and CD-extractable P (Pd) in the soils?????? upper 10 cm. The treatment effect on P in the forest floor, and on PT and Pd in the upper 10 cm of the mineral soil was equivalent to 6, 19, and 11% of the applied P, respectively. AAO-extractable P was highly correlated with Mehlich-1 P in the fertilized plots. Treatment and site drainage class effects on P accumulation in the different solid phases in the mineral soil and in the forest floor and the potential contribution of these pools to P availability in subsequent rotations, following clearcutting, are discussed.Item Urban Sodicity in a Humid Subtropical Climate: Impact on Biogeochemical Cycling(2012-10-19) Steele, Meredith KateUnderstanding the mechanisms of non-point source carbon and nutrients in urban watersheds will help to develop policies to maintain surface water quality and prevention of eutrophication. The purpose of this dissertation is to investigate the impact of sodium on carbon and nutrient leaching from the two main contributors; soil and leaf litter, and calculate the sodium exports in a humid subtropical urban river basin. The first chapter reviews the current literature on urbanization in watersheds. Chapter II quantifies the carbon and nutrient in intact soil core leachates and in water extractable solution from urban soils collected from 33 towns and cities across the state of Texas. Chapter III investigates the impact of sodicity and salinity on water extractable organic carbon and nitrogen from vegetation. Chapter IV investigates the export of sodium and chloride from the upper Trinity River basin. The results derived from this study indicate that sodium exports are elevated in urban watersheds and further that sodium in irrigation water elevates the loss of carbon and nutrients from both watershed soil and senesced vegetation and that this may contribute to high concentrations in urban freshwaters.