Because saturated buffers are a new conservation practice, there has been no large-scale assessment of their potential to aid in meeting water quality goals. Publicly available data were used in a stepwise fashion within a geographic information system to estimate the total stream length suitable for saturated buffer implementation across the US Midwest region and the resulting potential nitrate loading reduction from widespread saturated buffer implementation. Approximately 37,760 km of streams (or 75,520 km of stream bank) was deemed suitable to host a saturated buffer, and 3.85 million ha of drained land has the potential to drain to a saturated buffer. These results suggest that implementing saturated buffers widely could result in a 5 to 10% reduction of the estimated N load from midwestern tile-drained land. Saturated buffers can be an important component of plans to achieve water quality goals.

There are few peer-reviewed studies documenting saturated buffer annual nitrate (NO 3 ) removal or that have assessed the federal practice standard design criteria.Drainage flow, NO 3 , and dissolved reactive phosphorus (DRP) were monitored at three saturated buffers in Illinois, USA, for a combined 10 site-years. Nitrate loss reduction averaged 48 ± 19% with removals of 3.5-25.2 kg NO 3 -N ha −1 annually.Median DRP concentrations at all sampling locations were at the analytical detection limit of 0.01 mg L −1 . The current design paradigm (i.e., USDA practice standard) prescribes there should be no flow bypassing the saturated buffer at flow rates that are ≤5% of the peak drainage system flow rate. The drainage coefficient-based and Manning's equation-based peak flow estimates were higher and lower, respectively, than the observed annual peaks in all years. This illustrated inherent uncertainty introduced early in the design process, which can be further compounded by dynamic in-buffer hydrology. The percentage of the observed peak flow rate at which bypass initiated ranged across an order of magnitude between sites (4.4-8.1% of peak flow rate at one site and 42-49% of peak at another) despite the buffers providing relatively similar NO 3 removal. Bypass at one site (SB2) was related to the concept of "antecedent buffer capacity filled," which was defined as the 5-d average water depth in the middle control structure chamber expressed as a relative percentage of the bypass stop log height. This design flow analysis serves as a call to further evaluate predictive relationships and design models for edge-of-field practices. INTRODUCTIONSaturated buffers (also called "saturated riparian buffers") are an edge-of-field mitigation technique for nitrate (NO 3 ) treatment in subsurface agricultural drainage. In this practice, a control structure is used to re-route drainage water laterally underground within the noncropped riparian buffer zone. A perforated distribution tile connected to the control structure allows the water to become hydrologically reconnected to the Abbreviations: DRP, dissolved reactive phosphorus; SB, saturated buffer.

Prairies have been important living systems in various ecosystems. These complex living systems play a vital role both biologically and ecologically in the environment and support a large amount of wildlife. Prairie restoration is an ecologically friendly way to restore prairie land that was lost due to various reasons. This study evaluated a native prairie and a restored prairie to assess the influence of prairie restoration on soil hydraulic properties. Samples were collected from two prairie sites, a continuous no-till site (NT), a longterm timothy grass site (TM) and a row-crop (RC) field. Prairie Fork (RP) was restored in 1997, and the native prairie (Tucker prairie (NP) has never been tilled. NT and TM are located at historical Sanborn field in Columbia, and the row-crop field is located at Centralia, Missouri. All sites have Mexico silt loam (fine, Smectitic, mesic, Vertic Epiaqualfs) soil series. Soil cores (76 × 76 mm) from six replicate locations from each treatment were sampled to a 60 cm depth at 10 cm intervals. Samples were analyzed for bulk density, saturated hydraulic conductivity (Ksat), soil water retention and pore size distribution. In-situ saturated hydraulic conductivity was also measured at each location using a constant head permeameter by subsurface soil horizons with five replications. RETC computer program version 6.02 was used for parameter estimation. Bulk density was significantly lower for the NP site, and the RP site was significantly higher than NP. Bulk density was significantly lower for the first depth (0-10 cm) for all the sites and the second and third depths (10-20 cm and 20-30 cm) had the highest values. The in-situ Ksat was lower than all other treatments for the RP site when averaged across soil horizons while the Ksat it was significantly higher for the first horizon. NP had significantly higher laboratory measured Ksat when averaged across all depths and it was almost 4 times higher than RP. The first depth (0-10 cm) of all sites had significantly higher Ksat other depths and the sixth depth (50 -60 cm) showed the lowest Ksat. NP had the highest macroporosity and fine-mesoporosity, while RP had the highest microporosity. NP had significantly higher water retention at saturation while RP had the highest water retention for soil water pressure of -33 kPa, -100 kPa and -1500 kPa. Soil water retention was significantly higher in NP for -0.4 kPa to -10 kPa soil water pressures, and at -20 kPa NP, RP and RC had significantly higher retention. NP treatment had higher soil water content than the other sites for the first (0 -10 cm), second (10 -20 cm), third (20 -30 cm) and sixth (50 -60 cm) depths at soil water pressures less than -20 kPa. The fourth (30 -40 cm) and fifth (40 -50 cm) depths of RP had higher soil water content at all soil water pressures. The soil water characteristics for all sites and depths were well described by the van Genucheten relationship with r2 > 0.90. The n values for all treatments were less than two. RP showed significantly higher alpha values fo...

Bioenergy could help limit global warming to 2°C above pre‐industrial levels while supplying almost a fourth of the world's renewable energy needs by 2050. However, the deployment of bioenergy raises concerns that adoption at meaningful scales may lead to unintended negative environmental consequences. Meanwhile, the full consolidation of a bioenergy industry is currently challenged by a sufficient, resilient, and resource‐efficient biomass supply and an effective conversion process. Here, we provide a comprehensive analysis of how stable isotope approaches have accelerated the development of a robust bioeconomy by advancing knowledge about environmental sustainability, feedstock development, and biological conversion. We show that advances in stable isotope research have generated crucial information to (1) gain mechanistic insight into the potential of bioenergy crops to mitigate climate change as well as their impact on water and nutrient cycling; (2) develop high‐yielding, resilient feedstocks that produce high‐value bioproducts in planta; and (3) engineer microbes to enhance feedstock conversion to bioenergy products. Further, we highlight knowledge gaps that could benefit from future research facilitated by stable isotope approaches. We conclude that advances in mechanistic knowledge and innovations within the field of stable isotopes in cross‐disciplinary research actions will greatly contribute to breaking down the barriers to establishing a robust bioeconomy.

Abstract. Dependable flow rate measurements are necessary to calculate flow volumes and resulting nutrient loads from subsurface drainage systems and associated conservation practices. The objectives of this study were (1) to develop appropriate weir equations for a new stainless steel-edged 45° V-notch weir developed for AgriDrain inline water level control structures and (2) to determine if the equation was independent of flow depth in the structure. Weirs for 15 cm (6 in.) and 25 cm (10 in.) inline water level control structures were placed at three heights in each structure: at the base, 48 cm from the base, or 97 cm from the base, and the height of the nappe above the weir crest was recorded over a range of flow rates. The resulting data were fitted to equations of the form Q = aHb where Q is the flow rate, H is the height of the nappe above the weir crest, and a and b are fitted parameters. There were no significant differences in the fitted parameters across the two structure sizes or across the three weir placements. The fitted equation for these new stainless steel-edged V-notch weirs was Q = 0.011H2.28 with Q in liters per second and H in centimeters, and Q = 1.44H2.28, with Q in gallons per minute and H in inches. These equations can be used for measuring flow through AgriDrain in-line structures, although in-house weir calibration is highly recommended for specific applications, when possible. Keywords: Drainage, Flow monitoring, Subsurface drainage, V-notch weir, Weir calibration.