Using data calibration to reconcile outputs from different survey methods in long-term or large-scale studies.

Understanding the impact of management interventions on the environment over decadal and longer timeframes is urgently required. Longitudinal or large-scale studies with consistent methods are best practice, but more commonly, small datasets with differing methods are used to achieve larger coverage. Changes in methods and interpretation affect our ability to understand data trends through time or across space, so an ability to understand and adjust for such discrepancies between datasets is important for applied ecologists. Calibration or double sampling is the key to unlocking the value from disparate datasets, allowing us to account for the differences between datasets while acknowledging the uncertainties. We use a case study of livestock grazing impacts on riparian vegetation in southeastern Australia to develop a flexible and powerful approach to this problem. Using double sampling, we estimated changes in vegetation attributes over a 12-year period using a pseudo-quantitative visual method as the starting point, and the same technique plus point-intercept survey for the second round. The disparate nature of the datasets produced uncertain estimates of change over time, but accounting for this uncertainty explicitly is precisely the objective and highlights the need to look more closely at this very common problem in environmental management, as well as the potential benefits of the double sampling approach.

Nutrient capture in an Iowa farm pond: Insights from high-frequency observations.

Shallow constructed ponds are abundant landscape features in the midwestern United States, suggested as an edge of field best management practice (BMP) in voluntary nutrient reduction strategies. The efficacy of such features is highly uncertain, however, and previous studies have lacked sufficient temporal resolution to determine N and P removals during critical periods of transport. We utilized high-frequency in-situ measurements and flow-weighted grab sampling to determine water and nutrient budgets for a typical constructed "farm pond" in central Iowa situated within the Iowa Southern Drift Plain. Our monitoring approach yielded insight into in-stream nitrogen processing and the relative importance of transport-vs. supply-limited N delivery. Diel patterns in NO3-N observed during early Spring, prior to canopy closure, revealed that in-stream primary production and NO3-N assimilation can influence downstream N delivery in a stream with nitrate pollution (mean annual NO3-N of nearly 5 mg/L). Analysis of discharge-concentration hysteresis for NO3-N showed a shift from transport to supply limitation for NO3-N delivery over the growing season, influenced by antecedent moisture, with wet antecedent conditions leading to supply limitation. Significant NO3-N removal (64% of 19.8 kg/ha inputs) occurred within the 4.2 ha pond (230 ha watershed), but total N removal was much lower (36% removal of 22.3 kg/ha inputs). The lower total N removal highlights the importance of both particulate N and dissolved organic N and ammonia export to the N budgets of hypereutrophic small ponds. Total P removal in the pond was only 8% of 2.3 kg/ha inputs, likely due to internal loading of recent and legacy sedimentary P within the pond. High-flow events dominated N and P inputs, during which removal efficacy of the pond was significantly diminished. Poor process performance during critical moments may partially explain lower than expected water quality improvements post-BMP implementation. Accordingly, shifting hydroclimatic regimes (e.g., frequency of intense rainfall events) will impact the efficacy of small ponds and other edge of field BMPs for nutrient reduction.

Native Riparian Plant Species Dominate the Soil Seedbank of In-channel Geomorphic Features of a Regulated River.

Flow regulation impacts on riparian vegetation composition, often increasing the prevalence of exotic and terrestrial plant species. Environmental flows may benefit native riparian vegetation via the promotion of plant recruitment from riparian soil seedbanks, but this is dependent on an intact native seedbank. Thus, we assessed the composition of the soil seedbank of different riverine geomorphic features to determine its potential response to environmental flows. Soil seedbank samples were taken from channel bars, benches and floodplains at six sites along the Campaspe River, Australia, a heavily regulated river that receives environmental flows. These geomorphic features represent a gradient in elevation and thus flooding frequency from frequently flooded (bars) to infrequently flooded (floodplain). Seedbank samples were 'grown out' in a glasshouse, and seedlings identified and classified according to taxa, flood tolerance and origin (native or exotic). We identified 6515 seedlings across all geomorphic features and sites, with monocots most abundant. Soil seedbank composition varied between geomorphic features. Overall, seedling abundances were greater for in-channel features (bars and benches) than floodplains, but taxa richness did not vary likewise. Soil seedbanks of in-channel features were dominated by flood tolerant and native taxa, while flood intolerant and exotic taxa were generally associated with floodplains. The dominance of native flood tolerant taxa in the soil seedbanks of in-channel geomorphic features suggest these seedbanks can play an important role in the resilience of native riparian plant communities. Moreover, environmental flows are likely to play a positive role in maintaining native riparian plant communities given such conditions.

Use of real-time sensors for compliance monitoring of nitrate in finished drinking water.

Across the Midwestern United States, Public Water Systems (PWSs) struggle with high levels of nitrate in source waters from intense agricultural activity. Leveraging a sensor network deployed across Iowa surface waters, we evaluated the potential of the Hach Nitratax SC Plus, which uses UV-light absorption to quantify dissolved nitrate-nitrite (NOx-N) down to 0.1 mg-N L-1, for real-time monitoring of NOx-N in drinking water. For six different PWSs over multiple years, we compare NOx-N levels in source waters (surface and groundwater under surface influence) to those measured via traditional methods (e.g., ion chromatography (IC)) for US EPA compliance monitoring. At one large PWS, we also evaluated sensor performance when applied to near-finished drinking water (filter effluent). We find good agreement between traditional analytical methods and in situ sensors. For example, for 771 filter effluent samples from 2006-2011, IC analysis averaged NOx-N of 5.8 mg L-1 while corresponding sensor measurements averaged 5.7 mg L-1 with a mean absolute error of 0.23 (5.6%). We identify several benefits of using real-time sensors in PWSs, including improved frequency to capture elevated NOx-N levels and as decision-support tools for NOx-N management.

Hydrograph separation of subsurface tile discharge.

Baseflow is an important component of streamflow and watershed hydrologic budgets, yet quantifying the baseflow fraction of tile drainage has rarely been reported. In this study, we used two common hydrograph separation methods (local minimum method, recursive digital filter) to separate the discharge hydrographs from three drainage district tiles located in Iowa. Based on data collected from 2009 to 2013, annual baseflow ranged from 116 to 162 mm and comprised approximately 60% of the annual discharge. Baseflow was greatest during June (average of 34% of annual baseflow) and the March through August period produced 86% of the total annual baseflow. We found that the two methods of hydrograph separation produced similar results but the digital filter method was less erratic in estimating baseflow fraction. Study results can be used to better quantify hydrologic pathways in tiled landscapes and improve the design, implementation, and evaluation of nutrient reduction strategies.

Effectiveness of a newly reconstructed floodplain oxbow to reduce NO3-N loads from a spring flood.

Enhancing NO3-N processing in floodplains offers opportunities to achieve water quality improvements in agricultural watersheds but few studies have quantified the effectiveness of newly reconstructed oxbows to reduce loads delivered from floods. In this study, we evaluated NO3-N retention during a spring storm water runoff event in a newly reconstructed oxbow (<1 year old) located along Morgan Creek in eastern Iowa. A 30-h flood connected the oxbow to the creek for approximately nine hours and delivered 14.7 kg of NO3-N into the oxbow. Using a NO3-N sensor, oxbow NO3-N concentrations were observed to increase from 0.7 to 5.3 mg/l after the flood event, but decreased to background conditions over the next 21 days. We estimated NO3-N retention to be 0.30 g N m-2 d-1 and the NO3-N retention efficiency to be 74.2% for the single flood event. The NO3-N mass reduction in the oxbow intersected with predicted mass reduction from a first-order denitrification decay model after 21 days which suggests that denitrification was largely responsible for the observed NO3-N decrease. However, the effectiveness of the oxbow for reducing watershed-scale N loads appears to be limited, since the oxbow is located in a low-nutrient floodplain and would only retain NO3-N loads when delivered to the oxbow via flooding. Study results suggest that oxbows provides valuable ecosystem services during non-flooding periods and are activated for NO3-N load reduction during floods.

Iowa Stream Nitrate, Discharge and Precipitation: 30-Year Perspective.

We evaluated Iowa Department of Natural Resources nitrate (NO3-N) and US Geological Survey hydrological data from 1987 to 2016 in nine agricultural watersheds to assess how transport of this pollutant has changed in the US state of Iowa. When the first 15 years of the 30-year water-quality record is compared to the second 15 years (1987-2001 and 2002-2016), three different metrics used to quantify NO3-N transport all indicate levels of this pollutant are increasing. Yield of NO3-N (kg ha-1) averaged 18% higher in the second 15 years, while flow-weighted average concentrations (mg L-1) were 12% higher. We also introduced the new metric of NO3-N yield (g ha-1) per mm precipitation to assess differences between years and watersheds, which averaged 21 g NO3-N ha-1 per 1 mm of precipitation across all watersheds and was 13% higher during the second half of the record. These increases of NO3-N occurred within a backdrop of increasing wetness across Iowa, with precipitation and discharge levels 8 and 16% higher in the last half of the record, indicating how NO3-N transport is amplified by increasing precipitation levels. The implications of this are that in future climate scenarios where rainfall is more abundant, detaining water and increasing evapotranspiration within the cropping system will be necessary to control NO3-N losses. Land use changes that include use of cover crops, living mulches, and perennial plants should be expanded to improve water quality and affect the water balance within agricultural basins.

Nitrate uptake in an agricultural stream estimated from high-frequency, in-situ sensors.

Real-time, continuous, in situ water quality sensors were deployed on a fourth-order Iowa (U.S.) stream draining an agricultural watershed to evaluate key in-stream processes affecting concentrations of nitrate during a 24-day late summer (Aug-Sep) period. Overall, nitrate-nitrogen (NO3-N) concentrations declined 0.11 mg L-1 km-1, or about 1.9% km-1 and 35% in total across 18 km. We also calculated stream metabolic rates using in situ dissolved oxygen data and determined stream biotic N demand to be 108-117 mg m-2 day-1. From this, we estimate that 11% of the NO3-N concentration decline measured between two in-situ sensors separated by 2 km was a result of biotic NO3-N demand, while groundwater NO3-N data and estimates of groundwater flow contributions indicate that dilution was responsible for 53%. Because the concentration decline extends linearly across the entire 18 km of stream length, these processes seem consistent throughout the basin downstream of the most upstream sensor site. The nitrate-dissolved oxygen relationship between the two sites separated by 2 km, calculations of biotic NO3-N demand, and diurnal variations in NO3-N concentration all indicate that denitrification by anaerobes is removing less NO3-N than that assimilated by aquatic organisms unable to fix nitrogen for their life processes, and thus the large majority of the NO3-N entering this stream is not retained or removed, but rather transported downstream.

Dissolution of anionic surfactant mesophases.

Linear and circular solvent penetration experiments are used to study the dissolution of anionic SLE3S surfactant mesophases in water. We show that a lamellar (Lα) phase in contact with water will transit through a series of cubic, hexagonal, and micellar phase bands with sharp interfaces identified from their optical textures. In both linear and circular geometries, the kinetics of front propagation and eventual dissolution are well described by diffusive penetration of water, and a simple model applies to both geometries, with a different effective diffusion coefficient for water Df as the only fitting parameter. Finally, we show a surprising variation of dissolution rates with initial surfactant concentration that can be well explained by assuming that the driving force for solvent penetration is the osmotic pressure difference between neat water and the aqueous fraction of the mesophase that is highly concentrated in surfactant counterions.

Orthophosphorus Contributions to Total Phosphorus Concentrations and Loads in Iowa Agricultural Watersheds.

Phosphorus (P) is delivered to streams as episodic particulate P and more continuous soluble P (orthophosphorus [OP]), and it is important to determine the proportion of each P form in river water to more effectively design remedial measures. In this study, we evaluated the annual mean ratios of OP to total P (TP) concentrations and loads in 12 Iowa rivers and found systematic variation in the ratios. The OP/TP ratios were >60% in two tile-drained watersheds of the Des Moines Lobe and in a shallow fractured bedrock watershed in northeast Iowa, whereas in southern and western Iowa, OP contributions to TP were <30%. Higher OP/TP ratios were associated with greater row crop intensity in the watershed and a greater proportion of baseflow in the river. Orthophosphorus contributions from croplands would be greater in watersheds characterized by widespread tile drainage and well-drained soils, whereas cropland TP export would be dominated by particulate P in dissected till plains with poorly drained soils. Understanding the dominant form and transport pathway of P from agricultural areas in a watershed is seen as an important first step in determining appropriate conservation practices to reduce P loads.

Use Alkalinity Monitoring to Optimize Bioreactor Performance.

In recent years, the agricultural community has reduced flow of nitrogen from farmed landscapes to stream networks through the use of woodchip denitrification bioreactors. Although deployment of this practice is becoming more common to treat high-nitrate water from agricultural drainage pipes, information about bioreactor management strategies is sparse. This study focuses on the use of water monitoring, and especially the use of alkalinity monitoring, in five Iowa woodchip bioreactors to provide insights into and to help manage bioreactor chemistry in ways that will produce desirable outcomes. Results reported here for the five bioreactors show average annual nitrate load reductions between 50 and 80%, which is acceptable according to established practice standards. Alkalinity data, however, imply that nitrous oxide formation may have regularly occurred in at least three of the bioreactors that are considered to be closed systems. Nitrous oxide measurements of influent and effluent water provide evidence that alkalinity may be an important indicator of bioreactor performance. Bioreactor chemistry can be managed by manipulation of water throughput in ways that produce adequate nitrate removal while preventing undesirable side effects. We conclude that (i) water should be retained for longer periods of time in bioreactors where nitrous oxide formation is indicated, (ii) measuring only nitrate and sulfate concentrations is insufficient for proper bioreactor operation, and (iii) alkalinity monitoring should be implemented into protocols for bioreactor management.

Soybean Area and Baseflow Driving Nitrate in Iowa's Raccoon River.

Improved understanding of the drivers of stream nitrate is necessary to improve water quality. This is particularly true for Iowa, a large contributor to Mississippi River Basin nitrate loads. Here, we focus on the Raccoon River at Des Moines, Iowa, and develop statistical models to describe the monthly (from March to August) nitrate concentrations in terms of eight drivers representing monthly climate, monthly hydrology, and yearly cropping practices. We consider six two-parameter distributions, linear and nonlinear dependencies between the predictors, and the distributions' parameters. Model selection was performed by penalizing more complex models. Our results show that the Weibull and Gumbel distributions are the only two selected distributions. Baseflow and the previous year's soybean [ (L.) Merr.] area were the two predictors most often identified as important. Our modeling results imply that increases in soybean area have led to increasing nitrate concentrations. Moreover, nitrate concentrations are related to baseflow in a nonlinear way, with effects strongest when baseflow is near or below the average condition. Additional relevant predictors were precipitation and, to a lesser extent, temperature. We conclude that best management practices and improved conservation targeting soybean in a corn ( L.)-soybean rotation will improve water quality in this artificially drained system.

Assessing the relation of USDA conservation expenditures to suspended sediment reductions in an Iowa watershed.

From 1936 to 2010, U.S. Department of Agriculture (USDA) agencies spent $293.7 billion (value adjusted for inflation at the 2009 level) on conservation programs. Of these expenditures, $75.2 billion (26%) were allocated for technical assistance (TA; it is related to costs associated with USDA field staff providing their expert advice to farmers) and $218.5 billion (74%) for financial assistance (FA; monetary incentives for farmers to adopt conservation programs). A major environmental goal of these programs was to reduce soil erosion and sediment leaving the land. In this study, we correlate expenditures on FA and TA programs to a unique long (1937-2009) record of total suspended solids (TSS) and sediment load (SL) for the Raccoon River at Van Meter, Iowa. Study results suggest that three predictors (rainfall, TA and FA) are important in explaining the temporal changes in annual TSS and SL and provide evidence that USDA expenditures helped reduce TSS and SL in the Raccoon River. TA was more effective than FA in reducing TSS levels in the watershed. Our empirical model represents an initial, broad-scale attempt to correlate conservation expenditures to a specific water quality outcome, although more work is needed to disentangle the impacts associated with other unexplored factors.

Nitrate-nitrogen export: magnitude and patterns from drainage districts to downstream river basins.

Alteration of the prairie pothole ecosystem through installation of subsurface tile drains has enabled the U.S. Corn Belt to become one of the most agriculturally productive areas in the world but has also led to increased nitrogen losses to surface water. The literature contains numerous field plot studies but few in-depth studies of nitrate exports from small, tile-drained catchments representative of agricultural drainage districts. The objectives of this study were to quantify hydrology and nitrate-nitrogen (NO-N) export patterns from three tile-drained catchments and the downstream river over a 5-yr period, compare results to prior plot-, field-, and watershed-scale studies, and discuss implications for water quality improvement in these landscapes. The tile-drained catchments had an annual average water yield of 247 mm yr, a flow-weighted NO-N concentration of 17.1 mg L, and an average NO-N loss of nearly 40 kg ha yr. Overall, water yields were consistent with prior tile drainage studies in Iowa and the upper Midwest, but associated NO-N concentrations and losses were among the highest reported for plot studies and higher than those found in small watersheds. More than 97% of the nitrate export occurs during the highest 50% of flows, at both the small catchment and river basin scale. Findings solidified the importance of working at the drainage district scale to achieve nitrate reductions necessary to meet water quality goals. They also point to the need for implementing strategies that address both hydrology and nitrogen supply in tile-drained landscapes.

Pyrimidone-based series of glucokinase activators with alternative donor-acceptor motif.

Glucokinase activators are a class of experimental agents under investigation as a therapy for Type 2 diabetes mellitus. An X-ray crystal structure of a modestly potent agent revealed the potential to substitute the common heterocyclic amide donor-acceptor motif for a pyridone moiety. We have successfully demonstrated that both pyridone and pyrimidone heterocycles can be used as a potent donor-acceptor substituent. Several sub-micromolar analogs that possess the desired partial activator profile were synthesized and characterized. Unfortunately, the most potent activators suffered from sub-optimal pharmacokinetic properties. Nonetheless, these donor-acceptor motifs may find utility in other glucokinase activator series or beyond.

Carbon export from the raccoon river, iowa: patterns, processes, and opportunities.

Farmed landscapes are engineered for productivity, and research suggests they contribute a disproportionate share of inorganic C to the Mississippi River and Gulf of Mexico. Here we use alkalinity and total organic C (TOC) measurements collected from the Raccoon River of Iowa to (i) evaluate inorganic and organic C concentrations and export patterns, (ii) compare current trends to historical conditions, and (iii) link C transport processes to current land use management. Export of inorganic C averaged 106,000 Mg per year and contributes 90% of the C flux from the basin. Alkalinity concentrations are unchanged from 1931 to 1944 levels (∼53 mg L C), but inorganic C loads have doubled due to increasing discharge. Carbonate-rich glacial deposits and agricultural lime provide a large source of inorganic C, and results confirm that alkalinity export in the Raccoon Basin is transport limited. Although fertilization and tillage practices have possibly helped increase C fluxes over the last 70+ yr, the overriding factor on inorganic C export is discharge. Discharge control over C export provides an opportunity for agriculture in terms of quantifying C sequestration for potential C trading. Controlling water flux through soils can limit inorganic C export similar to practices such as reduced tillage and managed rotations.

How paired is paired? Comparing nitrate concentrations in three iowa drainage districts.

Quantifying the effectiveness of perceived best management practices (BMPs) at the field and landscape-scale is difficult, so paired watershed studies are used to detect water quality improvements. We evaluated concentrations of NO-N discharged from three tiled Iowa watersheds during a 4-yr period to assess their suitability for a paired watershed approach. Our objectives were to evaluate similarities in physical characteristics, concentration patterns, and correlation among the three paired sites and perform a minimum detectable change (MDC) analysis on paired site configurations. The study results demonstrate that concentration variability within and between sample sites affected correlation among the paired basins, even though the physical characteristics of the basins are quite similar. Restricting comparisons to the active tile drainage period (March-July) improved correlations. The lack of a suitable correlation will impair the ability to detect changes expected to result from BMP implementation. The MDC for NO-N concentration change detection varied from 6.9 to 12.9% and averaged 8% for the best control-treatment pair. To ensure that conservation resources are being used effectively, implemented BMPs should focus on practices capable of achieving at least this magnitude of change. These practices may include reduced fertilizer applications, adoption of cover crops, and land use change.

Dissolved inorganic and organic carbon export from tile-drained midwestern agricultural systems.

While carbon is a critically important natural element cycling through the soil profile of agricultural systems, few studies have examined the flux of dissolved organic carbon (OC) and inorganic carbon (IC) through artificially-drained cropped fields. In this study, we monitored eight tile outlets, nine groundwater wells and the receiving stream during a March to November period in 2018 to quantify subsurface IC and OC flux from tiles and groundwater to a perennial stream from a single cropped field in north-central Iowa. Results showed that carbon export from the field was dominated by IC losses through subsurface drainage tiles that were 20× higher than dissolved OC concentration in tiles, groundwater and in Hardin Creek. IC loads from tiles comprised approximately 96 % of the total carbon export. Detailed soil sampling within the field quantified TC stocks to a 1.2 m depth (246,514 kg/ha), and based on the maximum annual rate of IC loss from the field (553 kg/ha per year), we estimated that approximately 0.23 % of the TC content (0.32 % of the TOC content and 0.70 % of the TIC content) of the shallow soils was lost in a single year. Loss of dissolved carbon from the field is likely offset by reduced tillage and additions of lime. Study results suggest that attention should be given to improved monitoring of aqueous total carbon export from fields for accurate accounting of carbon sequestration performance.

Metabolomics of forage plants: a review.

BACKGROUND: Forage plant breeding is under increasing pressure to deliver new cultivars with improved yield, quality and persistence to the pastoral industry. New innovations in DNA sequencing technologies mean that quantitative trait loci analysis and marker-assisted selection approaches are becoming faster and cheaper, and are increasingly used in the breeding process with the aim to speed it up and improve its precision. High-throughput phenotyping is currently a major bottle neck and emerging technologies such as metabolomics are being developed to bridge the gap between genotype and phenotype; metabolomics studies on forages are reviewed in this article. SCOPE: Major challenges for pasture production arise from the reduced availability of resources, mainly water, nitrogen and phosphorus, and metabolomics studies on metabolic responses to these abiotic stresses in Lolium perenne and Lotus species will be discussed here. Many forage plants can be associated with symbiotic microorganisms such as legumes with nitrogen fixing rhizobia, grasses and legumes with phosphorus-solubilizing arbuscular mycorrhizal fungi, and cool temperate grasses with fungal anti-herbivorous alkaloid-producing Neotyphodium endophytes and metabolomics studies have shown that these associations can significantly affect the metabolic composition of forage plants. The combination of genetics and metabolomics, also known as genetical metabolomics can be a powerful tool to identify genetic regions related to specific metabolites or metabolic profiles, but this approach has not been widely adopted for forages yet, and we argue here that more studies are needed to improve our chances of success in forage breeding. CONCLUSIONS: Metabolomics combined with other '-omics' technologies and genome sequencing can be invaluable tools for large-scale geno- and phenotyping of breeding populations, although the implementation of these approaches in forage breeding programmes still lags behind. The majority of studies using metabolomics approaches have been performed with model species or cereals and findings from these studies are not easily translated to forage species. To be most effective these approaches should be accompanied by whole-plant physiology and proof of concept (modelling) studies. Wider considerations of possible consequences of novel traits on the fitness of new cultivars and symbiotic associations need also to be taken into account.

The design and synthesis of indazole and pyrazolopyridine based glucokinase activators for the treatment of type 2 diabetes mellitus.

Glucokinase activators represent a promising potential treatment for patients with Type 2 diabetes. Herein, we report the identification and optimization of a series of novel indazole and pyrazolopyridine based activators leading to the identification of 4-(6-(azetidine-1-carbonyl)-5-fluoropyridin-3-yloxy)-2-ethyl-N-(5-methylpyrazin-2-yl)-2H-indazole-6-carboxamide (42) as a potent activator with favorable preclinical pharmacokinetic properties and in vivo efficacy.