Evaluating Hydrologic Response in Tile-Drained Landscapes: Implications for Phosphorus Transport.

Phosphorus (P) loss in agricultural discharge has typically been associated with surface runoff; however, tile drains have been identified as a key P pathway due to preferential transport. Identifying when and where these pathways are active may establish high-risk periods and regions that are vulnerable for P loss. A synthesis of high-frequency, runoff data from eight cropped fields across the Great Lakes region of North America over a 3-yr period showed that both surface and tile flow occurred year-round, although tile flow occurred more frequently. The relative timing of surface and tile flow activation was classified into four response types to infer runoff-generation processes. Response types were found to vary with season and soil texture. In most events across all sites, tile responses preceded surface flow, whereas the occurrence of surface flow prior to tile flow was uncommon. The simultaneous activation of pathways, indicating rapid connectivity through the vadose zone, was seldom observed at the loam sites but occurred at clay sites during spring and summer. Surface flow at the loam sites was often generated as saturation-excess, a phenomenon rarely observed on the clay sites. Contrary to expectations, significant differences in P loads in tiles were not apparent under the different response types. This may be due to the frequency of the water quality sampling or may indicate that factors other than surface-tile hydrologic connectivity drive tile P concentrations. This work provides new insight into spatial and temporal differences in runoff mechanisms in tile-drained landscapes.

The Latitudes, Attitudes, and Platitudes of Watershed Phosphorus Management in North America.

Phosphorus (P) plays a crucial role in agriculture as a primary fertilizer nutrient-and as a cause of the eutrophication of surface waters. Despite decades of efforts to keep P on agricultural fields and reduce losses to waterways, frequent algal blooms persist, triggering not only ecological disruption but also economic, social, and political consequences. We investigate historical and persistent factors affecting agricultural P mitigation in a transect of major watersheds across North America: Lake Winnipeg, Lake Erie, the Chesapeake Bay, and Lake Okeechobee/Everglades. These water bodies span 26 degrees of latitude, from the cold climate of central Canada to the subtropics of the southeastern United States. These water bodies and their associated watersheds have tracked trajectories of P mitigation that manifest remarkable similarities, and all have faced challenges in the application of science to agricultural management that continue to this day. An evolution of knowledge and experience in watershed P mitigation calls into question uniform solutions as well as efforts to transfer strategies from other arenas. As a result, there is a need to admit to shortcomings of past approaches, plotting a future for watershed P mitigation that accepts the sometimes two-sided nature of Hennig Brandt's "Devil's Element."

Advancing the Sustainability of US Agriculture through Long-Term Research.

Agriculture in the United States must respond to escalating demands for productivity and efficiency, as well as pressures to improve its stewardship of natural resources. Growing global population and changing diets, combined with a greater societal awareness of agriculture's role in delivering ecosystem services beyond food, feed, fiber, and energy production, require a comprehensive perspective on where and how US agriculture can be sustainably intensified, that is, made more productive without exacerbating local and off-site environmental concerns. The USDA's Long-Term Agroecosystem Research (LTAR) network is composed of 18 locations distributed across the contiguous United States working together to integrate national and local agricultural priorities and advance the sustainable intensification of US agriculture. We explore here the concept of sustainable intensification as a framework for defining strategies to enhance production, environmental, and rural prosperity outcomes from agricultural systems. We also elucidate the diversity of factors that have shaped the past and present conditions of cropland, rangeland, and pastureland agroecosystems represented by the LTAR network and identify priorities for research in the areas of production, resource conservation and environmental quality, and rural prosperity. Ultimately, integrated long-term research on sustainable intensification at the national scale is critical to developing practices and programs that can anticipate and address challenges before they become crises.

Decreasing Phosphorus Loss in Tile-Drained Landscapes Using Flue Gas Desulfurization Gypsum.

Elevated phosphorus (P) loading from agricultural nonpoint-source pollution continues to impair inland waterbodies throughout the world. The application of flue gas desulfurization (FGD) gypsum to agricultural fields has been suggested to decrease P loading because of its high calcium content and P sorbing potential. A before-after control-impact paired field experiment was used to examine the water quality effects of successive FGD gypsum applications (2.24 Mg ha; 1 ton acre each) to an Ohio field with high soil test P levels (>480 ppm Mehlich-3 P). Analysis of covariance was used to compare event discharge, dissolved reactive P (DRP), and total P (TP) concentrations and loadings in surface runoff and tile discharge between the baseline period (86 precipitation events) and Treatment Period 1 (42 precipitation events) and Treatment Period 2 (84 precipitation events). Results showed that, after the first application of FGD gypsum, event mean DRP and TP concentrations in treatment field tile water were significantly reduced by 21 and 10%, respectively, and DRP concentrations in surface runoff were significantly reduced by 14%; however, no significant reductions were noted in DRP or TP loading. After the second application, DRP and TP loads were significantly reduced in surface runoff (DRP, 41%; TP 40%), tile discharge (DRP, 35%; TP, 15%), and combined (surface + tile) discharge (DRP, 36%; TP, 38%). These findings indicate that surface application of FGD gypsum can be used as a tool to address elevated P concentrations and loadings in drainage waters.

Downstream approaches to phosphorus management in agricultural landscapes: regional applicability and use.

This review provides a critical overview of conservation practices that are aimed at improving water quality by retaining phosphorus (P) downstream of runoff genesis. The review is structured around specific downstream practices that are prevalent in various parts of the United States. Specific practices that we discuss include the use of controlled drainage, chemical treatment of waters and soils, receiving ditch management, and wetlands. The review also focuses on the specific hydrology and biogeochemistry associated with each of those practices. The practices are structured sequentially along flowpaths as you move through the landscape, from the edge-of-field, to adjacent aquatic systems, and ultimately to downstream P retention. Often practices are region specific based on geology, cropping practices, and specific P related problems and thus require a right practice, and right place mentality to management. Each practice has fundamental P transport and retention processes by systems that can be optimized by management with the goal of reducing downstream P loading after P has left agricultural fields. The management of P requires a system-wide assessment of the stability of P in different biogeochemical forms (particulate vs. dissolved, organic vs. inorganic), in different storage pools (soil, sediment, streams etc.), and under varying biogeochemical and hydrological conditions that act to convert P from one form to another and promote its retention in or transport out of different landscape components. There is significant potential of hierarchically placing practices in the agricultural landscape and enhancing the associated P mitigation. But an understanding is needed of short- and long-term P retention mechanisms within a certain practice and incorporating maintenance schedules if necessary to improve P retention times and minimize exceeding retention capacity.

Phosphorus concentration and loading reductions following changes in fertilizer application and formulation on managed turf.

Excess phosphorus, particularly in surface waters can lead to severe eutrophication. Identifying source areas, quantifying contributions, and evaluating management practices are required to address current and future water quality concerns. A before-after study was conducted from 2003-2010 on a sub-watershed of Northland Country Club Golf Course in Duluth, MN to demonstrate the impacts of two different phosphorus management approaches (Period 1: traditional application and timing using commercially available synthetic blends; Period 2: reduced rate, low dose applications, and organic formulations). Outflow median dissolved reactive phosphorus (DRP) and total phosphorus (TP) stream concentrations were significantly less in Period 2 compared to Period 1. There was no statistical difference in the mean TP loading in Period 1 (0.25 kg ha(-1) year(-1)) compared to Period 2 (0.20 kg ha(-1) year(-1)) or between the DRP loading in Period 1 (0.15 kg ha(-1) year(-1)) compared to Period 2 (0.09 kg ha(-1) year(-1)). However, by switching to organic phosphorus formulations and reducing application rates by greater than 75%, substantial reduction in DRP and TP concentrations was achieved. Based on these findings it is recommended that turf managers (parks and recreation to golf courses) explore the feasibility of altering their fertility management related to phosphorus by including organic formulations, low dose applications, and overall rate reductions. Additionally, it is recommended that the fertilizer industry develop and make more readily available commercial blends with lesser to zero amounts of phosphorus.

Stream water nutrient enrichment in a mixed-use watershed.

Eutrophic conditions, in both saline and freshwater systems, result from nutrient export from upstream watersheds. The objective of this study was to quantify the surface runoff losses of nitrate-nitrogen (NO3-N), total nitrogen (TN), dissolved reactive phosphorus (DRP), and total phosphorus (TP) resulting from prevailing practices on a managed golf course. Inflow and outflow discharge waters on a sub-area of Northland Country Club (NCC) located in Duluth, Minnesota were measured for both quantity and quality from April through November from 2003 to 2008. Nutrient losses were detectable throughout the year, had a seasonal trend, and routinely exceeded recommended levels to minimize eutrophication. The median outflow TN concentration (1.04 mg L⁻¹) was significantly greater (p < 0.05) than the median inflow (0.81 mg L⁻¹) concentration. Similarly, the median outflow TP concentration (0.03 mg L⁻¹) was significantly greater (p < 0.05) than the median inflow concentration (0.02 mg L⁻¹). Maximum recorded concentrations during the study period were 1.9 mg L⁻¹ NO3-N, 3.93 mg L⁻¹ TN, 0.34 mg L⁻¹ DRP, and 1.11 mg L⁻¹ TP. Mean annual export coefficients at NCC were 0.7 kg ha⁻¹ NO3-N (1.7% of applied), 4.43 kg ha⁻¹ TN (10.7% of applied), 0.14 kg ha⁻¹ DRP (2.6% of applied), and 0.25 kg ha⁻¹ TP (4.6% of applied). The findings of this study highlight the need for adopting conservation practices aimed at reducing offsite nutrient transport.

Chlorothalonil and 2,4-D losses in surface water discharge from a managed turf watershed.

Managed turf sites (golf courses) are the most intensively managed landscapes in the urban environment. Yet, long-term watershed scale studies documenting the environmental transport of agrichemicals applied to these systems are rare. The objective of this study was to quantify the surface discharge losses of two commonly applied pesticides (chlorothalonil and 2,4-D) resulting from prevailing practices on a managed golf course. Inflow and outflow discharge waters on a subarea of Northland Country Club located in Duluth, MN were measured for both quantity and quality from April through November from 2003 to 2008. The median chlorothalonil outflow concentration (0.58 microg L(-1)) was significantly greater (p < 0.05) than the inflow concentration, which was below the detection limit (0.07 microg L(-1)). Similarly, the median outflow 2,4-D concentration (0.85 microg L(-1)) was significantly greater (p < 0.05) than the inflow concentration (0.31 microg L(-1)). Chlorothalonil concentrations occasionally exceeded acute toxicity levels (7.6 microg L(-1)) reported for rainbow trout. No 2,4-D concentrations exceeded any human or aquatic species published toxicity level; however, the maximum measured 2,4-D concentration (67.1 microg L(-1)), which rarely occurred, did approach the 70 microg L(-1) maximum contaminant level (MCL) for that compound. Losses of both pesticides were detectable throughout the annual sampling period. Mean annual chlorothalonil loading was 10.5 g ha(-1) or 0.3% of applied, while mean annual 2,4-D loading was 4.9 g ha(-1) or 0.5% of applied. The findings of this study provide quantifiable evidence of agrichemical transport resulting from typical turfgrass management and highlight the need for implementation of best management practices to combat the offsite transport of agrichemicals used in professional turf management.

Nutrient load generated by storm event runoff from a golf course watershed.

Turf, including home lawns, roadsides, golf courses, parks, etc., is often the most intensively managed land use in the urban landscape. Substantial inputs of fertilizers and water to maintain turf systems have led to a perception that turf systems are a major contributor to nonpoint source water pollution. The primary objective of this study was to quantify nutrient (NO(3)-N, NH(4)-N, and PO(4)-P) transport in storm-generated surface runoff from a golf course. Storm event samples were collected for 5 yr (1 Apr. 1998-31 Mar. 2003) from the Morris Williams Municipal Golf Course in Austin, TX. Inflow and outflow samples were collected from a stream that transected the golf course. One hundred fifteen runoff-producing precipitation events were measured. Median NO(3)-N and PO(4)-P concentrations at the outflow location were significantly (p < 0.05) greater than like concentrations measured at the inflow location; however, median outflow NH(4)-N concentration was significantly less than the median inflow concentration. Storm water runoff transported 1.2 kg NO(3)-N ha(-1) yr(-1), 0.23 kg NH(4)-N ha(-1) yr(-1), and 0.51 kg PO(4)-P ha(-1) yr(-1) from the course. These amounts represent approximately 3.3% of applied N and 6.2% of applied P over the contributing area for the same period. NO(3)-N transport in storm water runoff from this course does not pose a substantial environmental risk; however, the median PO(4)-P concentration exiting the course exceeded the USEPA recommendation of 0.1 mg L(-1) for streams not discharging into lakes. The PO(4)-P load measured in this study was comparable to soluble P rates measured from agricultural lands. The findings of this study emphasize the need to balance golf course fertility management with environmental risks, especially with respect to phosphorus.

Nutrient flux in storm water runoff and baseflow from managed turf.

The urban landscape is comprised of many land uses, none more intensively managed than turfgrass; however, quantification of nutrient losses from specific land uses within urban watersheds, specifically golf courses is limited. Nitrate (NO(3)-N) and dissolved reactive phosphorus (DRP) were measured on a golf course in Austin, TX, USA from April 1, 1998 to March 31, 2003. NO(3)-N and DRP concentrations measured in storm flow were significantly greater exiting the course compared to those entering the course. Significant differences were also measured in baseflow NO(3)-N concentrations. The measured loading from the course was 4.0kg NO(3)-Nha(-1)yr(-1) (11% of applied) and 0.66kg DRPha(-1)yr(-1) (8% of applied). The resulting concentrations contributed by the course were 1.2mgL(-1) NO(3)-N and 0.2mgL(-1) DRP. At these levels, NO(3)-N poses minimal environmental risk. However, the DRP concentration is twice the recommended level to guard against eutrophication.

Impact of soil amendments on reducing phosphorus losses from runoff in sod.

Received for publication December 22, 2004. Research was initiated to study the interaction between soil amendments (lime, gypsum, and ferrous sulfate) and dissolved molybdate reactive phosphorus [RP(<0.45)] losses from manure applications from concentrated runoff flow through a sod surface. Four run-over boxes (2.2-m2 surface area) were prepared for each treatment with a bermudagrass [Cynodon dactylon (L.) Pers.] sod surface (using sod blocks) and composted dairy manure was surface-applied at rates of 0, 4.5, 9, or 13.5 Mg ha-1. The three soil amendments were then applied to the boxes. Two 30-min runoff events were conducted and runoff water was collected at 10-min intervals and analyzed for RP(<0.45). Results indicated that the addition of ferrous sulfate was very effective at reducing the level of RP(<0.45). in runoff water, reducing RP(<0.45) from 1.3 mg L(-1) for the highest compost rate with no amendment to 0.2 mg L(-1) for the ferrous sulfate in the first 10 min of runoff. Lime and gypsum showed a small impact on reducing RP(<0.45), with a reduction in the first 10 min to 0.9 and 0.8 mg L(-1), respectively. The ferrous sulfate reduced the RP(<0.45) in the tank at the end of the first runoff event by 66.3% compared with no amendment. In the second runoff event, the ferrous sulfate was very effective at reducing RP(<0.45) in runoff, with no significant differences in RP(<0.45) with application of 13.5 Mg ha(-1) compost compared with no manure application. The results indicate that the addition of ferrous sulfate may greatly reduce RP(<0.45) losses in runoff and has considerable potential to be used on pasture, turfgrass, and filter strips to reduce the initial RP(<0.45) losses from manure application to the environment.

Organisation of the mouse and human 5T4 oncofoetal leucine-rich glycoprotein genes and expression in foetal and adult murine tissues.

The human 5T4 oncotrophoblast leucine-rich glycoprotein may contribute to the process of placentation or metastasis by modulating cell adhesion, shape and motility. To understand better the role of 5T4 in development and cancer, the gene structure has been elucidated from both human and mouse genomic clones and mRNA expression has been studied in foetal and adult mouse tissues. The protein coding region is located within the second of two exons, the first exon comprising solely of 5'-untranslated region. Upstream there are no TATA or CAAT boxes, but there are a number of potential Sp1 binding sites. The murine and human proteins show a homologous domain organisation of the leucine rich repeats (LRR) and associated N- and C-terminal flanking regions, although the hydrophilic sequence which intervenes between the two LRR domains contains six additional amino acids in the mouse. The signal peptide, transmembrane region and cytoplasmic tail sequences are identical as are 6 out of the 7 potential N-linked glycosylation sites. Mouse 5T4 transcripts are abundant in placenta and also highly expressed in embryos while in adult tissues transcripts are restricted to brain and ovary. These patterns of expression and the genomic organisation are discussed in relation to possible function and other recently described LRR containing proteins.

Characterization of the gene encoding Mhp1 from Mycoplasma hyopneumoniae and examination of Mhp1's vaccine potential.

The gene encoding Mhp1, a 124 kDa protein from Mycoplasma hyopneumoniae, has been cloned, sequenced, and its product characterized. No significant homology to the gene or encoded polypeptide was found in the Genbank, NBRF, or PIR databases, though this protein appears similar to p97, a putative adhesin of M. hyopneumoniae described by Zhang et al. (Infect. Immun. 63, 1013-1019, 1995). Two repeated motifs were identified within the 3' end of the gene and encoded polypeptide. The mhp1 gene was fused to the glutathione S-transferase (GST) gene from Schistosoma japonicum, enabling high-level expression and purification of the protein. Both the authentic and recombinant proteins were recognized by sera from pigs infected with M. hyopneumoniae. In an induced-disease model in pigs, coughing was reduced in animals vaccinated with recombinant GST-Mhp1, although differences were not significant. Only minimal protection against lung lesion formation was provided, and again differences between the Mhpl-vaccinated and nonvaccinated groups were not significant.

Transformation of Mycoplasma capricolum and examination of DNA restriction modification in M. capricolum and Mycoplasma mycoides subsp. mycoides.

Plasmids pIK delta and pIK delta-erm have recently been developed as mycoplasmal cloning vectors. In this report, we demonstrate that these plasmids can replicate in Mycoplasma capricolum, a mycoplasmal species for which transformation had not previously been characterized. Both plasmids are stably maintained at a higher copy number than in their parental species, Mycoplasma mycoides subsp. mycoides. We have also examined the possibility of one or more restriction-modification systems affecting transformation frequencies in both species.

Cloning and characterization of the recA genes from Mycoplasma pulmonis and M. mycoides subsp. mycoides.

The RecA protein has a central role in DNA repair and is essential for homologous recombination in most eubacteria. Little is known about these critical processes in mycoplasmas. By using standard and inverse polymerase chain reactions (PCR) coupled with conventional cloning techniques, a series of overlapping fragments comprising the entire recA genes of Mycoplasma mycoides subsp. mycoides (Mm) and Mycoplasma pulmonis (Mp) were generated. Each gene was sequenced in its entirety. The recA genes of Mm and Mp would encode proteins of 345 amino acids (aa) and 339 aa, respectively. The mycoplasmal RecA proteins revealed strong conservation when compared with RecA sequences from other bacterial species.

Mycoplasmal cloning vectors derived from plasmid pKMK1.

Only two plasmids have been isolated and characterized from the entire genus Mycoplasma, which includes over 90 recognized species. Both of these plasmids were obtained from the same species, Mycoplasma mycoides subsp. mycoides. We have previously characterized one of these plasmids, pKMK1, as a preliminary step in developing mycoplasmal cloning vectors. In the present study, we have separately combined pKMK1 with two different Escherichia coli replicons and a tetracycline resistance (tetM) gene. One of the constructs, plasmid p2D4, was shuttled from E. coli to M. mycoides subsp. mycoides and back to E. coli with no deletions or rearrangements occurring in the plasmid. In the second construct, the E. coli replicon was deleted when the plasmid was transformed into M. mycoides subsp. mycoides. This derivative, designated plasmid pIK delta, is noteworthy in that it could be transformed into M. mycoides subsp. mycoides at a much higher frequency than the parental plasmid. A gram-positive bacterial erythromycin resistance determinant (erm) was cloned into both p2D4 and pIK delta. Resistance to erythromycin was stably maintained using both constructs, even in the absence of erythromycin selection, indicating that these plasmids will be useful mycoplasmal cloning vectors.

Nucleotide sequence of Mycoplasma mycoides subspecies Mycoides plasmid pKMK1.

To facilitate the development of mycoplasmal cloning vectors, we have determined the nucleotide sequence of pKMK1, a cryptic plasmid isolated from Mycoplasma mycoides subsp. mycoides. It is 1875 bp in length and contains two open reading frames (ORFs) that share homology with ORFs from members of a large family of gram-positive bacterial plasmids which replicate via a single-stranded DNA intermediate. Putative origins of replication and candidate cloning sites have been identified.

Plasmid transformation of Mycoplasma mycoides subspecies mycoides is promoted by high concentrations of polyethylene glycol.

The recent isolation and characterization of two plasmids from Mycoplasma mycoides subspecies mycoides has opened up new possibilities for studying mycoplasmal genetics. In order to facilitate the development of a genetic system in M. mycoides subsp. mycoides, parameters of polyethylene glycol (PEG)-mediated transformation were examined, as existing protocols prove very inefficient in this organism. The effects of PEG concentration, DNA concentration, presence of Ca2+ ions, and choice of buffers on the transformation of the Tn916-containing plasmid pAM120 into M. mycoides subsp. mycoides were examined. The stability of Tn916 in the M. mycoides subsp. mycoides chromosome was also evaluated. The optimal PEG concentration (53-62% (w/v)) in the transformation mixture was substantially higher than the PEG concentration reported to be optimal for transformation of other mycoplasmas (36% (w/v)). The PEG concentrations used here were also higher than the concentration used to promote transformation or fusion of gram-positive bacterial protoplasts. A necessity for the presence of Ca2+ ions for optimal transformation was shown, as was the possible involvement of cell culture growth stage. Our results demonstrate the need for expanding current transformation techniques for mycoplasmas. Studies also indicate that once Tn916 inserts into the M. mycoides subsp. mycoides chromosome, it can transpose to other sites at a relatively high frequency.

An investigation of the external physician search process.

As a basis for better understanding the health care consumer and identifying ways to segment the health care market, the authors report the results of an empirical investigation of the external search process patients undertake to find a physician. The impact of a patient's perceived illness severity on this process also is investigated. Implications of the findings are discussed.