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.

Nitrous oxide emissions from soybean in response to drained and undrained soils and previous corn nitrogen management.

While corn (Zea mays L.)-soybean (Glycine max. Merr.

Simulated nitrous oxide emissions from multiple agroecosystems in the U.S. Corn Belt using the modified SWAT-C model.

Agriculture is a major source of nitrous oxide (NO) emissions into the atmosphere. However, assessing the impacts of agricultural conservation practices, land use change, and climate adaptation measures on NO emissions at a large scale is a challenge for process-based model applications. Here, we integrated six NO emission algorithms for the nitrification processes and seven NO emission algorithms for the denitrification process into the Soil and Water Assessment Tool-Carbon (SWAT-C).

In situ N-N O site preference and O concentration dynamics disclose the complexity of N O production processes in agricultural soil.

Arable soil continues to be the dominant anthropogenic source of nitrous oxide (N O) emissions owing to application of nitrogen (N) fertilizers and manures across the world. Using laboratory and in situ studies to elucidate the key factors controlling soil N O emissions remains challenging due to the potential importance of multiple complex processes. We examined soil surface N O fluxes in an arable soil, combined with in situ high-frequency measurements of soil matrix oxygen (O ) and N O concentrations, in situ N labeling, and N O N site preference (SP).

Temporal assessment of N-cycle microbial functions in a tropical agricultural soil using gene co-occurrence networks.

Microbial nitrogen (N) cycling pathways are largely responsible for producing forms of N that are available for plant uptake or lost from the system as gas or leachate. The temporal dynamics of microbial N pathways in tropical agroecosystems are not well defined, even though they are critical to understanding the potential impact of soil conservation strategies. We aimed to 1) characterize temporal changes in functional gene associations across a seasonal gradient, 2) identify keystone genes that play a central role in connecting N cycle functions, and 3) detect gene co-occurrences that remained stable over time.

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.

Modeling nitrous oxide mitigation potential of enhanced efficiency nitrogen fertilizers from agricultural systems.

Agriculture soils are responsible for a large proportion of global nitrous oxide (NO) emissions-a potent greenhouse gas and ozone depleting substance. Enhanced-efficiency nitrogen (N) fertilizers (EENFs) can reduce NO emission from N-fertilized soils, but their effect varies considerably due to a combination of factors, including climatic conditions, edaphic characteristics and management practices. In this study, we further developed the DayCent ecosystem model to simulate two EENFs: controlled-release N fertilizers (CRNFs) and nitrification inhibitors (NIs) and evaluated their NO mitigation potentials.

The role of alanine synthesis and nitrate-induced nitric oxide production during hypoxia stress in Cucurbita pepo nectaries.

Floral nectar is a sugary solution produced by nectaries to attract and reward pollinators. Nectar metabolites, such as sugars, are synthesized within the nectary during secretion from both pre-stored and direct phloem-derived precursors. In addition to sugars, nectars contain nitrogenous compounds such as amino acids; however, little is known about the role(s) of nitrogen (N) compounds in nectary function.

Global Research Alliance N O chamber methodology guidelines: Flux calculations.

A critical step in determining soil-to-atmosphere nitrous oxide (N O) exchange using non-steady-state chambers is converting collected gas concentration versus time data to flux values using a flux calculation (FC) scheme. It is well documented that different FC schemes can produce different flux estimates for a given set of data. Available schemes differ in their theoretical basis, computational requirements, and performance in terms of both accuracy and precision.

Global Research Alliance N O chamber methodology guidelines: Introduction, with health and safety considerations.

Non-steady-state (NSS) chamber techniques have been used for decades to measure nitrous oxide (N O) fluxes from agricultural soils. These techniques are widely used because they are relatively inexpensive, easy to adopt, versatile, and adaptable to varying conditions. Much of our current understanding of the drivers of N O emissions is based on studies using NSS chambers.

Measurements and Models to Identify Agroecosystem Practices That Enhance Soil Organic Carbon under Changing Climate.

A the anticipated impacts of climate change is a pressing issue facing agriculture, as precipitation and temperature changes are expected to have major effects on agricultural production in many regions of the world. These changes will also affect soil organic matter decomposition and associated stocks of soil organic C (SOC), which have the potential to feed back to climate change and affect agroecosystem resiliency. This special section brings together multiple efforts to assess effects of climate change on SOC stocks around the globe in grassland, pasture, and crop agroecosystems under varying management practices.

Urea Amendment Decreases Microbial Diversity and Selects for Specific Nitrifying Strains in Eight Contrasting Agricultural Soils.

Application of nitrogen (N) fertilizers, predominantly as urea, is a major source of reactive N in the environment, with wide ranging effects including increased greenhouse gas accumulation in the atmosphere and aquatic eutrophication. The soil microbial community is the principal driver of soil N cycling; thus, improved understanding of microbial community responses to urea addition has widespread implications. We used next-generation amplicon sequencing of the 16S rRNA gene to characterize bacterial and archaeal communities in eight contrasting agricultural soil types amended with 0, 100, or 500 μg N g of urea and incubated for 21 days.

Nitrogen Management Affects Nitrous Oxide Emissions under Varying Cotton Irrigation Systems in the Desert Southwest, USA.

Irrigation of food and fiber crops worldwide continues to increase. Nitrogen (N) from fertilizers is a major source of the potent greenhouse gas nitrous oxide (NO) in irrigated cropping systems. Nitrous oxide emissions data are scarce for crops in the arid western United States.

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).

Plastic Biofilm Carrier after Corn Cobs Reduces Nitrate Loading in Laboratory Denitrifying Bioreactors.

Nitrate-nitrogen (nitrate-N) removal rates can be increased substantially in denitrifying bioreactors with a corn ( L.) cob bed medium compared with woodchips; however, additional organic carbon (C) is released into the effluent. This laboratory column experiment was conducted to test the performance of a postbed chamber of inert plastic biofilm carrier (PBC) after corn cobs (CC) to extend the area of biofilm colonization, enhance nitrate-N removal, lower total organic C losses, and reduce nitrous oxide (NO) production at warm (15.

Corn Nitrogen Management Influences Nitrous Oxide Emissions in Drained and Undrained Soils.

To date, no studies have evaluated nitrous oxide (NO) emissions of a single versus a split-nitrogen (N) fertilizer application under different soil drainage conditions for corn ( L.). The objective of this study was to quantify season-long cumulative NO emissions, N use efficiency, and soil N dynamics when corn received a recommended N rate as single or split-N application in Minnesota soils with and without tile drainage over two growing seasons.

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.

Evaluation of Intensive "4R" Strategies for Decreasing Nitrous Oxide Emissions and Nitrogen Surplus in Rainfed Corn.

The "4R" approach of using the right rate, right source, right timing, and right placement is an accepted framework for increasing crop N use efficiency. However, modifying only one 4R component does not consistently reduce nitrous oxide (NO) emissions. Our objective was to determine if N fertilizer applied in three split applications (Sp), by itself or combined with changes in N source and rate, could improve N recovery efficiency (NRE) and N surplus (NS) and decrease NO emissions.

Nitrous Oxide Fluxes, Soil Oxygen, and Denitrification Potential of Urine- and Non-Urine-Treated Soil under Different Irrigation Frequencies.

Despite increased use of irrigation to improve forage quality and quantity for grazing cattle ( Linnaeus), there is a lack of data that assess how irrigation practices influence nitrous oxide (NO) emissions from urine-affected soils. Irrigation effects on soil oxygen (O) availability, a primary controller of NO fluxes, is poorly understood. It was hypothesized that increased irrigation frequency would result in lower NO emissions by increasing soil moisture and decreasing soil O concentrations.