Combining stable isotopes and spatial stream network modelling to disentangle the roles of hydrological and biogeochemical processes on riverine nitrogen dynamics.

Intensive agricultural activities have significantly altered watershed hydrological and biogeochemical processes, resulting in water quality issues and loss of ecosystem functions and biodiversity. A major challenge in effectively mitigating nitrogen (N) loss from agricultural watersheds stems from the heterogeneity of N transformation and transport processes that complicates accurate quantification and modeling of N sources and sinks at the watershed scale. This study utilized stable isotopes of water and nitrate (NO) in conjunction with spatial stream network modeling (SSNMs) to explore watershed hydrology, N transformation, and sources within a mesoscale river network in the U.

The LTAR Cropland Common Experiment at Upper Mississippi River Basin-St. Paul.

The Soil and Water Management Research Unit of the USDA-Agricultural Research Service is located in St. Paul, MN, and conducts long-term research at the University of Minnesota Research and Outreach Center located at Rosemount, MN. As part of USDA's Long-Term Agroecosystem Research (LTAR) network, the croplands common experiment (CCE) at this location is focused on integration of a kura clover (Trifolium ambiguum M.

The LTAR Integrated Common Experiment at Upper Mississippi River Basin-Platteville.

Alternative agronomic practices are needed to address the various climatic, agronomic, edaphic, and water quality related challenges faced by the dairy farmers of the Driftless Area (DA) in the Upper Mississippi River Basin (UMRB). These practices should be innovative in nature, inclusive of regional stakeholders, and sustainable to meet the future food and climate related challenges of Wisconsin agriculture. Here, we outline our Integrated (grazing and cropland) Long-Term Agroecosystem Research Common Experiment at the University of Wisconsin-Platteville Pioneer Farm (UW-P PF) in the UMRB and describe our collaboration in this USDA network.

Hydrologic Connectivity Regulates Riverine NO Sources and Dynamics.

Indirect nitrous oxide (NO) emissions from streams and rivers are a poorly constrained term in the global NO budget. Current models of riverine NO emissions place a strong focus on denitrification in groundwater and riverine environments as a dominant source of riverine NO, but do not explicitly consider direct NO input from terrestrial ecosystems. Here, we combine NO isotope measurements and spatial stream network modeling to show that terrestrial-aquatic interactions, driven by changing hydrologic connectivity, control the sources and dynamics of riverine NO in a mesoscale river network within the U.

Proanthocyanidin biosynthesis in the developing wheat seed coat investigated by chemical and RNA-Seq analysis.

The composition of proanthocyanidins in the testa (seed coat) of bread wheat was analyzed by thiolysis of PA oligomers from developing grain and found to consist of (+)-catechin monomers, with a small amount of (+)-gallocatechin. The average chain length of soluble PA stayed relatively constant between 10 and 20 days post-anthesis, whereas that of unextractable PA increased over the same period, suggesting that increases in chain length might account for the insolubility of PAs from mature wheat grain. We carried out RNA-Seq followed by differential expression analysis from dissected tissues of developing grain from red- and white-grained near-isogenic lines differing in the presence of an active gene that encodes a MYB transcription factor involved in control of PA biosynthesis.

Envisioning the manureshed: Toward comprehensive integration of modern crop and animal production.

The specialization and intensification of agriculture have produced incredible gains in productivity, quality, and availability of agricultural commodities but have resulted in the separation of crop and animal production. A by-product of this separation has been the accumulation of manure regions where animal production is concentrated. Enter the "manureshed," an organizing framework for integrating animal and crop production where budgeting of manure nutrients is used to strategically guide their recycling and reuse in agricultural production systems where manure resources are of highest value.

Response of nitrous oxide emissions to individual rain events and future changes in precipitation.

Changing precipitation has the potential to alter nitrous oxide (N O) emissions from agricultural regions. In this study, we applied the Coupled Model Intercomparison Project Phase 5 end-of-century RCP 8.5 (business as usual) precipitation projections for the U.

Challenges and opportunities for manureshed management across U.S. dairy systems: Case studies from four regions.

The manureshed represents cropland needed to safely assimilate manure nutrients from an animal feeding operation. Dairy manuresheds can be contained on-farm but may need to involve additional farms that can assimilate excess nutrients. We present case studies reviewing challenges and opportunities to manureshed management in four major dairy-producing states using available information on local manuresheds.

Biases in open-path carbon dioxide flux measurements: Roles of instrument surface heat exchange and analyzer temperature sensitivity.

Eddy covariance (EC) measurements of ecosystem-atmosphere carbon dioxide (CO) exchange provide the most direct assessment of the terrestrial carbon cycle. Measurement biases for open-path (OP) CO concentration and flux measurements have been reported for over 30 years, but their origin and appropriate correction approach remain unresolved. Here, we quantify the impacts of OP biases on carbon and radiative forcing budgets for a sub-boreal wetland.

Top-Down Constraints on Methane Point Source Emissions From Animal Agriculture and Waste Based on New Airborne Measurements in the U.S. Upper Midwest.

Agriculture and waste are thought to account for half or more of the U.S. anthropogenic methane source.

Error characterization of methane fluxes and budgets derived from a long-term comparison of open- and closed-path eddy covariance systems.

Wetlands represent the dominant natural source of methane (CH) to the atmosphere. Thus, substantial effort has been spent examining the CH budgets of global wetlands continuous ecosystem-scale measurements using the eddy covariance (EC) technique. Robust error characterization for such measurements, however, remains a major challenge.

Source Partitioning of Methane Emissions and its Seasonality in the U.S. Midwest.

The methane (CH) budget and its source partitioning are poorly constrained in the Midwestern United States. We used tall tower (185 m) aerodynamic flux measurements and atmospheric scale factor Bayesian inversions to constrain the monthly budget and to partition the total budget into natural (e.g.

Feasibility of Recycling Excess Agricultural Nitrate with Electrodialysis.

One of the most serious environmental problems associated with agriculture is excessive nitrate N in waters leaving fields. It is a health hazard in drinking water and a primary cause of hypoxia in ocean waters receiving drainage from agricultural regions. Recent mitigation efforts have focused on techniques that promote denitrification-conversion of excess agricultural nitrate to N.

Nitrous oxide emissions are enhanced in a warmer and wetter world.

Nitrous oxide (NO) has a global warming potential that is 300 times that of carbon dioxide on a 100-y timescale, and is of major importance for stratospheric ozone depletion. The climate sensitivity of NO emissions is poorly known, which makes it difficult to project how changing fertilizer use and climate will impact radiative forcing and the ozone layer. Analysis of 6 y of hourly NO mixing ratios from a very tall tower within the US Corn Belt-one of the most intensive agricultural regions of the world-combined with inverse modeling, shows large interannual variability in NO emissions (316 Gg NO-N⋅y to 585 Gg NO-N⋅y).

Impact of Kura Clover Living Mulch on Nitrous Oxide Emissions in a Corn-Soybean System.

Nitrous oxide (NO), produced primarily in agricultural soils, is a potent greenhouse gas and is the dominant ozone-depleting substance. Efforts to reduce NO emissions are underway, but mitigation results have been inconsistent. The leguminous perennial kura clover ( M.

Metabolite Profiling of Sugarcane Genotypes and Identification of Flavonoid Glycosides and Phenolic Acids.

Sugarcane is an important agricultural crop in the economy of tropical regions, and Brazil has the largest cultivated acreage in the world. Sugarcane accumulates high levels of sucrose in its stalks. Other compounds produced by sugarcane are currently not of economic importance.

Indirect nitrous oxide emissions from streams within the US Corn Belt scale with stream order.

N2O is an important greenhouse gas and the primary stratospheric ozone depleting substance. Its deleterious effects on the environment have prompted appeals to regulate emissions from agriculture, which represents the primary anthropogenic source in the global N2O budget. Successful implementation of mitigation strategies requires robust bottom-up inventories that are based on emission factors (EFs), simulation models, or a combination of the two.

Quantifying nitrous oxide fluxes on multiple spatial scales in the Upper Midwest, USA.

This study seeks to quantify the roles of soybean and corn plants and the cropland ecosystem in the regional N2O budget of the Upper Midwest, USA. The N2O flux was measured at three scales (plant, the soil-plant ecosystem, and region) using newly designed steady-state flow-through plant chambers, a flux-gradient micrometeorological tower, and continuous tall-tower observatories. Results indicate that the following.

Global and time-resolved monitoring of crop photosynthesis with chlorophyll fluorescence.

Photosynthesis is the process by which plants harvest sunlight to produce sugars from carbon dioxide and water. It is the primary source of energy for all life on Earth; hence it is important to understand how this process responds to climate change and human impact. However, model-based estimates of gross primary production (GPP, output from photosynthesis) are highly uncertain, in particular over heavily managed agricultural areas.

Automated, low-power chamber system for measuring nitrous oxide emissions.

Continuous measurement of soil NO emissions is needed to constrain NO budget and emission factors. Here, we describe the performance of a low-power Teledyne NO analyzer and automated chamber system, powered by wind and solar, that can continuously measure soil NO emissions. Laboratory testing of the analyzer revealed significant temperature sensitivity, causing zero drift of -10.

The influence of plants on atmospheric methane in an agriculture-dominated landscape.

The primary objective of this study was to clarify the influence of crop plants on atmospheric methane (CH4) in an agriculture-dominated landscape in the Upper Midwest of the United States. Measurements were carried out at two contrasting scales. At the plant scale, CH4 fluxes from soybean and corn plants were measured with a laser-based plant chamber system.

Combined NMR and flow injection ESI-MS for Brassicaceae metabolomics.

High-throughput screening of large collections of plants, whether in the context of gene function analysis, quality trait selection, or metabolic engineering requires robust and rapid methodologies that provide maximum information with minimum sample pre-fractionation. Here, we present a protocol for high-throughput plant metabolomic analysis developed for Arabidopsis and generally applicable to plant green tissue, including other Brassicaceae. The methodology uses combined, flow injection electrospray mass spectrometry (FI-ESI-MS) and nuclear magnetic resonance (NMR) spectroscopy analysis.

Glycosyl transferases in family 61 mediate arabinofuranosyl transfer onto xylan in grasses.

Xylan, a hemicellulosic component of the plant cell wall, is one of the most abundant polysaccharides in nature. In contrast to dicots, xylan in grasses is extensively modified by α-(1,2)- and α-(1,3)-linked arabinofuranose. Despite the importance of grass arabinoxylan in human and animal nutrition and for bioenergy, the enzymes adding the arabinosyl substitutions are unknown.