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The extent of gene flow in Caribbean marine communities has been investigated primarily in taxa from coral reef habitats, particularly in corals and reef fishes. Results from empirical population genetic studies in those taxa have indicated the presence of an east–west genetic break between 67° and 70°W longitude, and isolation of populations in the Bahamas. Hydrodynamic modelling has further suggested the presence of four connectivity regions that may contribute to genetic isolation. In this study we test for the presence of genetic structure in two gastropods (Cenchritis muricatus and Echinolittorina ziczac) from poorly sampled rocky-intertidal habitats, using mitochondrial sequence data. Significant genetic structure was found in C. muricatus (Snn = 0.29, P< 0.001; Fst = 0.022, P< 0.001), but not in E. ziczac (Snn = 0.17, P= 0.48; Fst = 0.022, P= 0.48), in spite of similar larval life histories. The pattern of differentiation does not match a simple east–west model in either species, nor a four-region model, nor do the Bahamas show evidence of isolation. However, the genetic differentiation of Bonaire from other sites that is observed in C. muricatus and E. ziczac is consistent with the previously observed isolation of this location in the trochid gastropod Cittarium pica. [ABSTRACT FROM PUBLISHER]

A new soil extractant (H3A-1) with the ability to extract ammonium (NH4) nitrogen (N), nitrate (NO3) N, and phosphorus (P) from soil was originally developed and tested against 32 soils (Haney et al. 2006). H3A-1 is composed of organic acid root exudates, which are naturally occurring, and lithium citrate. In this study, H3A-1 was modified to reduce the extractable iron and aluminum and improve the nutrient extracting relationships with other well-known soil extractants. Correlations show improved relationships with NO3, NH4, PO4, P, potassium, calcium, and zinc when compared to the original H3A-1 as well as standard soil-test methods [Olsen, potassium chloride (KCl), water, Mehlich 3, Bray 1, ammonium acetate (NH4 OAc), and diethylenetriaminepentaacetic acid (DTPA)]. The modifications were tested against the results from the North American Proficiency Testing (NAPT) database, which included 60 soils, varying in pH, organic carbon, and clay content. [ABSTRACT FROM AUTHOR]

Soil microbial activity is greatly affected by soil water content. Determining the appropriate moisture content to rewet soils that have been dried in preparation for laboratory incubations to determine microbial activity can be laborious and time-consuming. The most common methods used achieve sufficient moisture content for peak microbial respiration are gravimetric water content, soil matric potential, or percentage of water-filled pore space (WFPS). Alternatively, a fast, simple, and accurate way to ensure that a given soil receives the appropriate amount of water for peak soil microbial respiration is to rely on natural capillary action for rewetting the dry soil. The capillary method is related to the gravimetric method for water uptake and has a strong correlation with WFPS. A microbial respiration test was conducted to compare rewetting methods. The 24-h carbon dioxide (CO2) / carbon (C) results were very similar and strongly correlated using the gravimetric method and the capillary method for rewetting dried soil. [ABSTRACT FROM AUTHOR]

The coastal South American species Cyprinodon dearborni contains two lineages distinct at both mitochondrial and nuclear loci. One appears to be a long-term South American endemic, whereas the other is a more recent colonizer related to the widespread Cyprinodon variegatus. [ABSTRACT FROM AUTHOR]

Inositol hexakisphosphate kinase 2 (IP6K2), a member of the inositol hexakisphosphate kinase family, functions as a growth suppressive and apoptosis-enhancing kinase during cell stress. We created mice with a targeted deletion of IP6K2; these mice display normal embryogenesis, development, growth and fertility. Chronic exposure to the carcinogen 4-nitroquinoline 1-oxide (4-NQO, a UV-mimetic compound) in drinking water resulted in fourfold increased incidence of invasive squamous cell carcinoma (SCC) formation in the oral cavity and esophagus of the knockout (KO) mice compared to the wild-type (WT) littermates. Paradoxically, KO mice displayed relative resistance to ionizing radiation and exhibit enhanced survival following 8–10 Gy total body irradiation. Primary KO fibroblasts displayed resistance to antiproliferative effects of interferon-β and increased colony forming units following ionizing radiation. Radioresistance of KO fibroblasts was associated with accelerated DNA repair measured by comet assay. Direct microinjection of 5-PP-Ins(1,2,3,4,6)P5 (the enzymatic product of IP6K2), but not InsP6 (the substrate of IP6K2) induced cell death in SCC22A squamous carcinoma cells.Oncogene (2009) 28, 2383–2392; doi:10.1038/onc.2009.113; published online 11 May 2009 [ABSTRACT FROM AUTHOR]

The measurement of soil carbon dioxide (CO2) respiration is a means to gauge biological soil fertility. Test methods for respiration employed in the laboratory vary somewhat, and to date the equipment and labor required have limited more widespread adoption of such methodologies. A new method to measure soil respiration was tested along with the traditional alkali trap and titration method. The new method involves the Solvita gel system, which was originally designed for CO2 respiration from compost but has been applied in this research to soils with treatments of increasing dairy manure compost. The objectives of this research are to (1) examine the relationship between the CO2 release after 1 day of incubation from soils amended with dairy manure compost that have been dried and rewetted as determined using the titration method and the Solvita gel system, and (2) compare water-soluble organic nitrogen (N), as well as carbon (C), N, and phosphorus (P) mineralization after 28 days of incubation with 1-day CO2 release from the titration method and Solvita gel system. One-day CO2 from both titration and the Solvita gel system were highly correlated with cumulative 28-day CO2 as well as the basal rate from 7-28 days of incubation. Both methods were also highly correlated with 28-day N and P mineralization as well as the initial water-extractable organic N and C concentration. The data suggest that the Solvita gel system for soil CO2 analysis could be a simple and easily used method to quantify soil microbial activity and possibly provide an estimate of potential mineralizable N and P. Once standardized soil sampling and laboratory analysis protocols are established, the Solvita method could be easily adapted to commercial soil testing laboratories as an index of soil microbial activity. [ABSTRACT FROM AUTHOR]

An evaluation of soil quality, which integrates biological, chemical and physical processes, would be beneficial to regulators as well as mining companies when making reclamation decisions. Coal mining regulations require that industry perform soil sampling and submit laboratory results in order to determine pre-mine and reclaimed soil quality. A rapid and accurate biological soil quality method, such as one-day CO2 (1-day CO2) analysis, can be used to determine soil microbial activity which is related to the soils' ability to sustain nutrient cycling. Our objective in this study was to compare native and reclaimed soils from surface-mine operations in order to assess the effectiveness of the 1-day CO2 method as a tool for determining biological soil quality. Soil samples were taken from sites that visually had poor and well-vegetated reclaimed areas of a surface-mine operation as well as an undisturbed native site. Chemical, physical and biological indicators were compared to 1-day CO2 analysis for microbial activity. Results indicate that the biological soil quality indicators as summarized by 1-day CO2 analysis are a more sensitive indicator of soil health on the reclaimed soils tested than chemical analysis alone. One-day CO2 analysis can be a useful additional tool for regulators and mining companies when assessing the soils ability to sustain plant growth and evaluate reclamation success. [ABSTRACT FROM AUTHOR]

The pelagic larval stage of most coral reef fishes might allow extensive dispersal or, alternatively, some level of local recruitment might be important. Molecular markers can be used to obtain indirect estimates of dispersal to evaluate these alternatives, yet the extent of gene flow among populations is known for only a small number of species. The use of such markers must take into account the properties of the markers and the demographic history of the population when making inferences about current gene flow. In the Caribbean bluehead wrasse, Thalassoma bifasciatum, previous studies have found both substantial levels of local recruitment, in studies interpreting otolith microchemistry and, conversely, a lack of genetic differentiation inferred from mitochondrial DNA (mtDNA) restriction-fragment length polymorphism (RFLP) data and allozymes. However, if subtle differentiation exists, larger sample sizes and highly variable markers may be required to discern it. Here we present results from mitochondrial control region sequence and microsatellite data that indicate a lack of genetic differentiation at both small and large spatial scales. However, historical processes, such as changes in population size, may have affected the current distribution of genetic variation.Heredity (2007) 98, 294–302. doi:10.1038/sj.hdy.6800940; published online 31 January 2007 [ABSTRACT FROM AUTHOR]

A new soil extractant (H 3 A) with the ability to extract NH 4 , NO 3 , and P from soil was developed and tested against 32 soils, which varied greatly in clay content, organic carbon (C), and soil pH. The extractant (H 3 A) eliminates the need for separate phosphorus (P) extractants for acid and calcareous soils and maintains the extract pH, on average, within one unit of the soil pH. The extractant is composed of organic root exudates, lithium citrate, and two synthetic chelators (DTPA, EDTA). The new soil extractant was tested against Mehlich 3, Olsen, and water for extractable P, and 1 M KCl and water‐extractable NH 4 and NO 2 /NO 3 . The pH of the extractant after adding soil, shaking, and filtration was measured for each soil sample (5 extractants×2 reps×32 soils=320 samples) and was shown to be highly influential on extractable P but has no effect on extractable NH 4 or NO 2 /NO 3 . H 3 A was highly correlated with soil‐extractable inorganic N (NH 4 , NO 2 /NO 3 ) from both water (r=0.98) and 1 M KCl (r=0.97), as well as being significantly correlated with water (r=0.71), Mehlich 3 (r=0.83), and Olsen (r=0.84) for extractable P. [ABSTRACT FROM AUTHOR]

Abstract Zooplankton of the family Bosminidae have a unique paleolimnological record in many Holarctic lakes that provides a near continuous record of morphological change for thousands of years. If this morphological change could be interpreted reliably, then a rarely achieved direct observation of macroevolution would be feasible. We tested paleolimnological predictions derived from morphological variation found in the genus Eubosmina using mtDNA and nuclear DNA sequence variation from geographically distant Holarctic sites. The mtDNA and nDNA trees were congruent but genetic divergence was inversely associated with morphological divergence. The three most genetically divergent groups belonged to Eubosmina longispina , whose phylogeography and genetic divergence was consistent with glacial vicariance. The genetic evidence also supported the hypothesis that at least two Nearctic species were recent European introductions. Finally, the genetic evidence was consistent with paleolimnology in the finding of several proposed species undergoing rapid morphological evolution and being post-glacially derived from European E. longispina . The results suggested that lacustrine bosminids are susceptible to geographic speciation processes, and that morphological interpretation of diversity in paleolimnology can be markedly improved by genetic studies. [ABSTRACT FROM AUTHOR]

On-farm adoption of agricultural conservation practices or management alternatives depends on conservation ethic, social pressure, regulatory attention, and perceived impact on yield and economic return. Although agro-economic and environmental impacts are assumed to conflict, little research has been conducted to address potential tradeoffs and provide a scientific basis for decision-making. Thus, this 16-year evaluation of adaptive nutrient management was conducted in the Texas Blackland Prairies ecoregion on six fields with structural conservation practices already in place. Each field was randomly selected to receive either commercial fertilizer or poultry litter at rates of 4.5 to 13.4 Mg ha-1. Two major nutrient management adaptations were made (i.e., soil test nitrogen [N] rate recommendations in 2009, and reduction of fallow period length and cover cropping during prolonged fallow periods in 2013). Important results included (1) soil test recommendations that consider historical crop yields reduced N application 25% to 38% for low rates of poultry litter, but did not reduce profits; (2) interannual variability of economic and weather conditions contributed to the lack of statistically significant differences in profit, although profit reduction for high nutrient rate treatments was clear; and (3) litter application, especially at rates in excess of crop phosphorus (P) needs, also increased runoff P losses by 1 to 1.4 kg ha-1 indicating the need for careful management of organic nutrient sources. Results of this long-term study showed that maintaining or increasing economic return does not have to be sacrificed to improve environmental impacts, which is an important consideration as producers make on-farm management decisions. [ABSTRACT FROM AUTHOR]

Water quality experts have suggested that no-till induces phosphorus (P) stratification, which may exacerbate soluble P (SP) runoff from agricultural fields, contributing to eutrophication. Conservationists have been concerned about increased SP loading to Lake Erie, which has been partially blamed on adoption of no-till and the concomitant P stratification of no-till soils. This study was conducted to provide better insight into the potential link between P stratification from no-till soils and P losses via runoff with the objective of exploring P fertilization strategies on P stratification and P runoff from a corn (Zea mays L.)–soybean (Glycine max L.) rotation. Plots were established with nine treatments, including unfertilized, diammonium phosphate (DAP) applications, monoammonium phosphate (MAP) applications, surface applied, injecting fertilizer or tilling fertilizer in, and the use of cover crops. Fertilizer applications were made at 24.4 kg P ha−1 (21.8 lb P ac−1) every other year or at 9.6 kg P ha−1 (8.7 lb P ac−1) every year. Disking, which was intended to minimize P stratification, resulted in the greatest stratification, with significantly higher water SP and Mehlich 3 P in the 0 to 5 cm (0 to 2 in) soil layer compared to the other treatments. There were no differences in SP or total P (TP) runoff from rainfall simulations between fertilizer source (MAP versus DAP) or fertilizer rate (annual versus biennial). The highest SP concentrations observed were from DAP applied to cover crops at the high application rate (24.4 kg P ha−1 applied every other year). This may suggest cover crops are not the ideal practice to decrease SP losses from agricultural fields. Incorporation of fertilizer reduced SP but increased erosion and could potentially increase TP loss. Injecting liquid fertilizer (polyphosphate [Poly]) at the time of planting resulted in lower SP and TP loads than surface applied fertilizers. We encourage other researchers to confirm these results at the field-to-watershed scale to ensure there are not unintended consequences of adopting this fertilization strategy. Further, fertilizer dealers, crop consultants, and farmers should be encouraged to consider liquid fertilizer applications as one option to minimize P losses. [ABSTRACT FROM AUTHOR]

Conservation planners need simple yet accurate tools to predict sediment and nutrient losses from agricultural fields to guide conservation practice implementation and increase cost-effectiveness. The Texas Best Management Practice Evaluation Tool (TBET), which serves as an input/output interpreter and vastly simplified interface for the Soil and Water Assessment Tool (SWAT), was developed to predict mean annual runoff, sediment, nitrogen (N), and phosphorus (P) losses from agricultural fields in Texas under a variety of management scenarios and conservation practices. The Texas Best Management Practice Evaluation Tool was developed to provide a scientific basis for decision making, evaluation, and reporting in state and federal conservation programs. A rigorous, data-intensive calibration and validation process was employed in TBET development. First, hydrology outputs were calibrated with basin scale streamflow data from 20 US Geological Survey sites. Then, runoff, sediment, total N, and total P outputs were calibrated and validated with measured field scale data (260+ site years). Even without calibration,TBET was able to make "good" to "very good" predictions of mean annual runoff and total P losses according to commonly applied model evaluation methods. Calibrated TBET predictions of sediment and total N losses were not as accurate but were still "satisfactory." These much-improved results relative to those of often applied tools such as P Indices are very encouraging since the design goals of simple operation and accurate predictions for diverse Texas conditions with only readily available inputs were certainly met. Thus, TBET meets an important need by providing accurate, science-based estimates of conservation practice benefits at the field scale. [ABSTRACT FROM AUTHOR]

Abstract: Hydrogen peroxide vapor has been proposed as a sterilant/decontaminant for usage in buildings and transportation vehicles including emergency vehicles, buses, trains and aircraft. Although the efficacy of the process has been demonstrated, questions regarding the compatibility of vaporized hydrogen peroxide treatments with the many diverse materials of construction have been raised. This paper presents results on the embrittlement of high strength AISI 4340 steel as a result of condensation of the vapor during exposure to vaporized hydrogen peroxide. Notched four point bending samples of AISI 4340 steel were tested using the standard test methods of ASTM F519-06 to quantify susceptibility to hydrogen embrittlement in this aggressive service environment. No embrittlement effects were observed for samples exposed to strictly vapor phase hydrogen peroxide for concentrations up to 1000ppm H2O2 and exposure times of 4.8h. Higher concentrations of 1300 and 1600ppm H2O2 led to the condensation of the vapor throughout the process chamber and brittle fracture of samples. These results were confirmed by examination of the fracture surfaces of samples using scanning electron microscopy. Samples that were not considered embrittled possessed dimpled fracture surfaces consistent with ductile failure. Embrittled samples exhibited inter-granular fractures along prior austenitic grain boundaries near the root of the notch – a common characteristic of hydrogen embrittlement. [Copyright &y& Elsevier]

Application of litter and other organic by-products to agricultural land off site of animal production facilities has created both environmental concerns and agro-economic opportunities, but limited long-term, field-scale data are available to guide management decisions. Thus, the objective of this study was to determine the water quality effects of repeated annual poultry litter application as a cropland and pasture fertilizer. Eight years of data collected on ten field-scale watersheds indicated several significant water quality differences based on litter rate (0.0 to 13.4 Mg ha-1 [0 to 6 ton ac-1]) and land use (cropland and pasture). On cropland fields, increasing litter rates (with corresponding decreases in supplemental inorganic nitrogen [Ni) increased runoff orthophosphate phosphorus (PO4-P) concentrations but reduced extreme high nitrate nitrogen (NO3-N) concentrations. Whereas run off PO4-P concentrations were somewhat similar between land uses, NO3-N concentrations were much lower in pasture runoff because of supplemental inorganic N application, reduced nutrient uptake potential, and faster litter mineralization on cropland. Although considerable variability was observed, intra-annual runoff NO3-N and PO4-P concentrations generally exhibited curvilinear decay based on time since fertilizer application. In spite of repeated annual litter application and buildup of soil phosphorus (P) at high litter rates, few long-term trends in N and P runoff were evident due to the dynamic interaction between transport and source factors. These results support several practical implications, specifically: (1) combining organic and inorganic nutrient sources can be environmentally friendly and economically sound if application rates are carefully managed; (2) high runoff N and P concentrations can occur from well-managed fields, which presents difficulty in regulating edge-of-field water quality; and (3) change in the animal industry mindset to view by-products as marketable resources could mitigate environmental problems, provide alternative fertilizer sources, and enhance animal industry revenue opportunities. [ABSTRACT FROM AUTHOR]

The size of the harmful algal blooms in western Lake Erie is strongly correlated with agricultural phosphorus (P) loading from tributaries. Despite farmers' efforts to reduce sediment-bound P loadings and fertilize using current guidance, the media and public have singled them out as the culprit in Lake Erie re-eutrophication. In this paper, two farmer surveys were used to evaluate if farmers in the Lake Erie region follow P fertilizer recommendations, and we also review historic and current P management guidance provided by the scientific community and agricultural industry. The majority (56% to 80%) of farmers apply P fertilizers at or below the current fertility recommendations. Wholesale agronomic changes (e.g., no-tillage adoption, crop cultivar advances, and fertilizer application and formulation) have occurred since current fertilizer recommendations were developed. Although crop P uptake mechanisms have not changed, these agronomic changes have altered P cycling in soil and water. Based on these results, it is time that the scientific community and agricultural industry acknowledge that our current guidance may be contributing to eutrophication. We must ask whether or not we have (1) developed appropriate fertility guidance, (2) developed and recommended appropriate practices to protect water quality, (3) adequately considered "the law of unintended consequences" in conservation recommendations, and (4) focused too much on short-term economic outcomes while disregarding environmental quality. Improved understanding, reconsideration of traditional recommendations, and wider farmer adoption of the most effective practices are needed to develop a sustainable agricultural system in the Western Lake Erie Basin that produces needed commodities while preserving ecosystem integrity. [ABSTRACT FROM AUTHOR]

Excess nutrient loading from numerous sources (e.g., agricultural and urban runoff, treatment plant discharge, and streambank erosion) continues to adversely impact water resources, and determination of the cause(s) of accelerated nutrient enrichment has become a contentious and litigious issue in several US regions. This paper addresses one fundamental question: What are acceptable levels of nutrients in runoff from agricultural fields? It focuses on the field scale where farmers and ranchers make management decisions. Not answering this question limits the effectiveness of on-farm management and policy alternatives to address agriculture's contribution. To answer the question, some might suggest "direct comparison"with reference site data, existing criteria/standards, or measured data compilations. Alternatively, "indirect assessments"using soil test phosphorus (P) levels, P indices, field-scale models, or certainty programs might be suggested. Thus, to provide a scientific basis for policy debate and management decisions related to nutrient runoff from agricultural fields, we evaluated "direct comparisons"with measured data from case studies and evaluated "indirect assessment"alternatives. While acknowledging that scientific challenges and practical realities exist for each alternative, we concluded that certainty programs offer the most promise for ensuring acceptable nutrient runoff, and that field-scale models linked with watershed decision support tools are the most promising for assessing impacts on downstream water quality. Recognizing the reality that some nutrient loss is unavoidable from natural and anthropogenic sources, agriculture, industry, and municipalities are each encouraged to commit to implementing enhanced management where needed to minimize their sector's contribution to excess nutrients in our nation's waters. [ABSTRACT FROM AUTHOR]

The application of poultry litter to agricultural land has become a topic of interest for policy makers due to public concern about its effects on water quality. The Soil and Water Assessment Tool (SWAT) version 2005 is designed to assess nonpoint and point sources of pollution. In this study, six subwatersheds in Texas (HUC-8; 12070101) are used to evaluate the model's ability to simulate water quality at a small scale. Each of these subwatersheds randomly received poultry litter rates of 0.0 to 13.4 Mg ha-1. Monthly and daily data from 2002 were used for calibration purposes, while 2000, 2001, 2003, and 2004 were used for validation. The SCS runoff curve number for moisture condition II (CN2) and the soil evaporation compensation factor (ESCO) parameters were found to be more sensitive than the surface runoff lag time (SURLAG) and initial soil water content expressed as a fraction of field capacity (FFCB). The monthly and daily runoff model simulations for the six subwatersheds resulted in calibration Nash-Sutcliffe efficiency (NSE) values of 0.59 and 0.53 and validation NSE values 0.82 and 0.80, respectively. The monthly and daily R² runoff values for the six subwatersheds resulted in calibration values of at least 0.60 and 0.53 and validation R² values of 0.86 and 0.81, respectively. The observed trends included SWAT's overestimation of runoff in the dry periods and underestimation in the wet periods. The monthly NSE and R² values for sediment and nutrient losses were generally above 0.4 and 0.5, respectively. Paired t-tests for the monthly manually adjusted parameter simulation of sediment, organic N and P, NO3-IV, and soluble P for the 2000-2004 period losses showed that their respective SWAT means were not significantly different from the measured values (α = 0.05), except for NO3-N losses for the Y10 subwatershed (p-value 0.042). The control subwatershed's measured and simulated water quality results were significantly different (α = 0.05) from the treated subwatersheds, most likely due to the amount of inorganic N present. Almost all of the subwatersheds that had poultry litter applied resulted in higher sediment, organic N, organic P, and soluble P losses than the control subwatershed upon averaging thee monthly validation values. High NO3-N losses may have been a function of poultry litter and commercial fertilizers being applied before a large rainfall event occurred. The subwatersheds that received smaller amounts of commercial fertilizer and/or poultry litter lost more sediment, organic N, and organic P than the subwatersheds that received the higher litter and/or fertilizer treatments. Overall, the SWAT simulated the hydrology and the water quality constituents at the subwatershed scale more adequately when all of the data were used to simulate the model, as evidenced by statistical measures. [ABSTRACT FROM AUTHOR]

The scientific community has not established an adequate understanding of the uncertainty inherent in measured water quality data, which is introduced by four procedural categories: streamflow measurement, sample collection, sample preservation/storage, and laboratory analysis. Although previous research has produced valuable information on relative differences in procedures within these categories, little information is available that compares the procedural categories or presents the cumulative uncertainty in resulting water quality data. As a result, quality control emphasis is often misdirected, and data uncertainty is typically either ignored or accounted for with an arbitrary margin of safety. Faced with tile need for scientifically defensible estimates of data uncertainty to support water resource management, the objectives of this research were to: (1) compile selected published information on uncertainty related to measured stream, flow and water quality data for small watersheds, (2) use a root mean square error propagation method to compare the uncertainty introduced by each procedural category, and (3) use the error propagation method to determine the cumulative probable uncertainty in measured streamflow, sediment, and nutrient data. Best case, typical, and worst case "data quality" scenarios were examined. Averaged across all constituents, the calculated cumulative probable uncertainty (±%) contributed under typical scenarios ranged from 6% to 19% for streamflow measurement, from 4% to 48% for sample collection, from 2% to 16% for sample preservation/storage, and from 5% to 21% for laboratory analysis. Under typical conditions, errors in storm loads ranged from 8% to 104% for dissolved nutrients, from 8% to 110% for total N and P, and from 7% to 53% for TSS. Results indicated that uncertainty can increase substantially under poor measurement conditions and limited quality control effort. This research provides introductory scientific estimates of uncertainty in measured water quality data. The results and procedures presented should also assist modelers in quantifying tile "quality" of calibration and evaluation data sets, determining model accuracy goals, and evaluating model performance. [ABSTRACT FROM AUTHOR]

Phosphorus (P) indices were developed to address nonpoint source P losses from agricultural fields; however, only limited information on P index performance at the field- and watershed-scale is available. Evaluation of P indices is necessary to provide the basis of modification and improvement of their usefulness as P management tools. In this study, the ability of the Texas P index to estimate P loss potential was evaluated by comparison with measured annual P loads over three years on four new pasture and six new cultivated litter application sites in the Texas Blackland Prairie. The Arkansas and Iowa P indices were also evaluated. The Texas and Iowa versions were able to provide reasonable estimates of P loss potential as illustrated with significant linear relationships (p <0.01) between P index values and measured annual P loads. In general, the P index values, Mehlich 3 soil test P, and poultry litter application rate were better correlated with dissolved P concentrations and loads (r² ranged from 0.12 to 0.91) than with total P and particulate P loads (r² ranged from 0.00-0.31). A major source of error in P index load estimations was their inability to capture variability in annual soil erosion. This source of error was dramatically reduced by using measured erosion instead of estimated annual average erosion (average r² values increased from 0.24 to 0.58). While these results illustrate a potential for the P Indices to make relative P loss assessments, research on incentives to prevent buildup of soil P levels, linkages between P levels in soils and receiving waters, and other important issues related to the use of P indices is warranted. [ABSTRACT FROM AUTHOR]