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.

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.

Dissolved phosphate concentrations in Iowa shallow groundwater.

Regional groundwater phosphorus (P) concentrations are rarely reported, and it is important to develop a better understanding of background concentrations in shallow groundwater to help develop strategies to mitigate environmental risks. In this study, results collected from 17 different Iowa-based studies conducted from 2006 to 2019 and a total of 210 discrete locations of water table dissolved phosphate (DPO4 3- ) measurements are summarized (a) to assess the occurrence, range, and statistical distribution of groundwater DPO4 3- concentrations in Iowa and (b) to evaluate statewide patterns of DPO4 3- concentrations related to land use or land cover and landscape position. The DPO4 3- concentrations ranged from 0.02 to 1.56 mg L-1 and averaged 0.15 ± 0.19 mg L-1 with a median value of 0.10 mg L-1 (95% confidence interval of 0.08-0.11 mg L-1 ). Although minor variations were observed among land cover class and landscape position, concentrations exhibited uniformity across the state, likely attesting to the legacy of P from historical agricultural management. Median concentrations are higher than typical water quality criteria used to assess risk to surface water systems, implying that simply discharging groundwater DPO4 3- to streams, rivers, and lakes would be sufficient to cause environmental degradation.

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.

Livestock manure driving stream nitrate.

Growth and consolidation in the livestock industry in the past 30 years have resulted in more total farm animals being raised on fewer Iowa farms. The effects of this on stream water quality at the landscape scale have largely gone unexplored. The main objective of this work was to quantify the effects on stream nitrate levels of livestock concentration in two western Iowa watersheds relative to seven other nearby watersheds. To achieve this objective, we used data on high-frequency nitrate concentration and stream discharge, commercial nitrogen fertilizer use, and manure-generated nitrogen in each watershed. Our analysis shows much higher stream nitrate in the two watersheds where livestock concentration has been greatest, and little difference in commercial fertilizer inputs with the widespread availability of manure N. Reducing N inputs and better management of manure N, including analysis of crop N availability in soil and manure, can reduce uncertainty regarding fertilization while improving water quality.

Quantifying the contribution of tile drainage to basin-scale water yield using analytical and numerical models.

The Des Moines Lobe (DML) of north-central Iowa has been artificially drained by subsurface drains and surface ditches to provide some of the most productive agricultural land in the world. Herein we report on the use of end-member mixing analysis (EMMA) models and the numerical model Soil and Water Assessment Tool (SWAT) to quantify the contribution of tile drainage to basin-scale water yields at various scales within the 2370 km2 Boone River watershed (BRW), a subbasin within the Des Moines River watershed. EMMA and SWAT methods suggested that tile drainage provided approximately 46 to 54% of annual discharge in the Boone River and during the March to June period, accounted for a majority of flow in the river. In the BRW subbasin of Lyons Creek, approximately 66% of the annual flow was sourced from tile drainage. Within the DML region, tile drainage contributes to basin-scale water yields at scales ranging from 40 to 16,000 km2, with downstream effects diminishing with increasing watershed size. Developing a better understanding of water sources contributing to river discharge is needed if mitigation and control strategies are going to be successfully targeted to reduce downstream nutrient export.

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.

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 and the Gulf of Mexico.

The main objective of this work was to quantify and update the U.S. Midwest agricultural state of Iowa's contribution of nitrate-nitrogen to the Mississippi River stream network against the backdrop of the ongoing problem of Gulf of Mexico hypoxia. To achieve this objective, we used stream nitrate and discharge data collected from 1999 until 2016 at 23 Iowa stream sites near watershed outlets, along with publicly-available data for sites downstream of Iowa on the Missouri and Mississippi Rivers. Our analysis shows that Iowa contributes between 11 and 52% of the long-term nitrate load to the Mississippi-Atchafalaya Basin, 20 to 63% to the Upper Mississippi River Basin, and 20 to 89% to the Missouri River Basin, with averages of 29, 45 and 55% respectively. Since 1999, nitrate loads in the Iowa-inclusive basins have increased and these increases do not appear to be driven by changes in discharge and cropping intensity unique to Iowa. The 5-year running annual average of Iowa nitrate loading has been above the 2003 level for ten consecutive years, implying that Gulf hypoxic areal goals, also based on a 5-year running annual average, will be very difficult to achieve if nitrate retention cannot be improved in Iowa. An opportunity exists for land managers, policy makers and conservationists to manifest a positive effect on water quality by targeting and implementing nitrate reducing-practices in areas like Iowa while avoiding areas that are less likely to affect Gulf of Mexico hypoxia.

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.

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.

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.

Defining the Added Value of 99mTc-MIBI SPECT/CT to Conventional Cross-Sectional Imaging in the Characterization of Enhancing Solid Renal Masses.

PURPOSE: This study investigates whether the addition of preoperative Tc-MIBI SPECT/CT can increase the degree of diagnostic confidence in the differentiation of benign from malignant enhancing renal masses. PATIENTS AND METHODS: Patients were recruited as part of an institutional review board-approved prospective clinical trial. Forty-eight patients with clinical stage T1 solid renal masses who underwent a Tc-MIBI SPECT/CT before partial or radical nephrectomy were evaluated. Conventional CT and MRI, which were approximately performed within 8 weeks before Tc-MIBI, were retrospectively retrieved. Based on a 5-point scale (1 = definitely benign, 5 = definitely malignant), 2 blinded readers recorded their degree of confidence for each lesion using conventional imaging before and after reviewing the Tc-MIBI uptake ratios. Surgical pathology was considered as the reference standard. RESULTS: Additional review of Tc-MIBI SPECT/CT uptake ratios increased diagnostic confidence in the differentiation of solid renal masses in 14/48 lesions (29.2%). In 9 lesions, the addition of Tc-MIBI changed the initial confidence levels of malignancy toward benign diagnosis. Postsurgical pathology confirmed the diagnosis of benign histology (oncocytoma/hybrid oncocytic-chromophobe tumors) in 7 and chromophobe renal cell carcinoma (behave as indolent) in 2 of these lesions. Tc-MIBI increased the confidence level toward malignancy in 5 cases; all were confirmed as RCC on surgical pathology. The area under the receiver operative characteristic curve was 0.60 for conventional imaging alone and 0.85 after reviewing Tc-MIBI (P for difference = 0.03). CONCLUSIONS: Preoperative Tc-MIBI SPECT/CT enhances the performance of conventional imaging, improving the characterization of benign histologies and lowering the possibility of misclassification.

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.

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.

Transcript profiling of fructan biosynthetic pathway genes reveals association of a specific fructosyltransferase isoform with the high sugar trait in Lolium perenne.

Lolium perenne cultivars with elevated levels of fructans in leaf blades (high sugar-content grasses) have been developed to improve animal nutrition and reduce adverse environmental impacts of pastoral agricultural systems. Expression of the high sugar trait can vary substantially depending on genotype×environment (G×E) interactions. We grew three potential high sugar-content and a control cultivar in three temperature regimes and quantified water soluble carbohydrates (WSCs) and the expression of all functionally characterised L. perenne fructan pathway genes in leaf tissues. We also analysed the distribution, expression and sequence variation of two specific isoforms of Lp6G-FFT (fructan: fructan 6G-fructosyltransferase). Our study confirmed a significant G×E interaction affecting the accumulation of fructans in the high sugar-content cultivar AberDart, which accumulated higher levels of high DP (degree of polymerisation) fructans in blades compared to the control cultivar only when grown at 20°C (day)/10°C (night) temperatures. The cultivar Expo on the other hand accumulated significantly higher levels of high DP fructans in blades independent of temperature. Fructan levels in pseudostems were higher than in blades, and they increased markedly with decreasing temperature, but there was no consistent effect of cultivar in this tissue. The expression of the high sugar trait was generally positively correlated with transcript levels of fructosyltransferases. Presence and expression of only one of the two known 6G-FFT isoforms was positively correlated with high fructan biosynthesis, while the second isoform was associated with low fructan concentrations and positively correlated with fructan exohydrolase gene expression. The presence of distinct 6G-FFT sequence variants appears to be associated with the capacity of high sugar-content grasses to accumulate higher fructan levels particularly at warmer temperatures. These findings might be exploited for the selection and breeding of 'warm-effective' high sugar-content grasses to overcome some of the limitations of current high sugar-content ryegrass cultivars.