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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. Top-down emission estimates, based on tall-tower and aircraft observations, indicate that bottom-up inventories severely underestimate regional and continental scale N2O emissions, implying that EFs may be biased low. Here, we measured N2O emissions from streams within the US Corn Belt using a chamber-based approach and analyzed the data as a function of Strahler stream order (S). N2O fluxes from headwater streams often exceeded 29 nmol N2O-N m-2.s-1 and decreased exponentially as a function of S. This relation was used to scale up riverine emissions and to assess the differences between bottom-up and top-down emission inventories at the local to regional scale. We found that the Intergovernmental Panel on Climate Change (IPCC) indirect EF for rivers (EF5r) is underestimated up to ninefold in southern Minnesota, which translates to a total tier 1 agricultural underestimation of N2O emissions by 40%.We show that accounting for zero-order streams as potential N2O hotspots can more than double the agricultural budget. Applying the same analysis to the US Corn Belt demonstrates that the IPCC EF5r underestimation explains the large differences observed between top-down and bottom-up emission estimates. [ABSTRACT FROM AUTHOR]

Agriculture must increase production for a growing population while simultaneously reducing its environmental impacts. These goals need not be in tension with one another. Here we outline a vision for improving both the productivity and environmental performance of agriculture in the U.S. Midwest, also known as the Corn Belt. Mean annual precipitation has increased throughout the region over the past 50 years, consistent with climate models that attribute the increase to a warming troposphere. Stream gauge data indicate that higher precipitation has been matched or exceeded by higher stream flows, contributing to flooding, soil loss, and excessive nutrient flux to the Gulf of Mexico. We propose increasing landscape hydrologie storage through construction of ponds and restoration of wetlands to retain water for supplemental irrigation while also reducing flood risks. Primary productivity is proportional to transpiration, and analysis shows that in the U.S. Midwest both can be sustainably increased with supplemental irrigation. The proposed strategy should reduce interannual yield variability by limiting losses due to transient drought, while facilitating adoption of cropping systems that "perennialize" the landscape to take advantage of the full potential growing season. When implemented in concert, these practices should reduce the riverine nitrogen export that is a primary cause of hypoxia in the Gulf of Mexico. Erosive sediment losses should also be reduced through the combination of enhanced hydrologie storage and increased vegetative cover. Successful implementation would require watershed-scale coordination among producers and landowners. An obvious mechanism to encourage this is governmental farm policy. [ABSTRACT FROM AUTHOR]

• We developed water budgets for 18 Long-Term Agroecosystem Research sites. • We estimated uncertainty of all the water budget components. • The average water budget uncertainty was 25% of precipitation. • Uncertainties were greatest for percolation and evapotranspiration. • LTAR sites span a 0.4 – 1.1 evaporative fraction and a 0.8 – 4.8 aridity index. Understanding the movement and storage of water within agricultural landscapes as functions of management and climate is essential for more efficient and sustainable water use. However, knowledge of water storage and fluxes on U.S. agricultural lands is largely incomplete. The Long-Term Agroecosystem Research (LTAR) network provides a unique and geographically diverse set of agricultural study sites in the United States. The objectives of this study were to: 1) characterize the hydrologic variability across the LTAR network; 2) identify data gaps in the water budgets across the LTAR network; and 3) identify opportunities to leverage the LTAR network to improve understanding of water budgets across agricultural landscapes. For each of the 18 LTAR sites, we developed water budgets on an average annual basis. Uncertainty propagation methods combined individual component uncertainties to calculate an overall water budget uncertainty. Datasets length ranged from three to 50 years. The network covers a range of precipitation from 240 to 1400 mm yr−1, evapotranspiration from 228 to 1080 mm yr−1, and surface runoff and subsurface flow from negligible to 560 mm yr−1. However, uncertainties of where all the water is going remained high, in part because soil water storage and downward movement of water were often neglected or measured for very short periods, resulting in average water budget uncertainty of 25% of the water inputs. More accurate measurement of the major inputs and outputs, and direct measurement of water content and percolation are key to understanding how agricultural lands affect terrestrial water budgets. [ABSTRACT FROM AUTHOR]

The article focuses on the use of aerial seeding as a means of increasing crop production in the U.S. Topics discussed include the benefits and limitations of aerial seeding, factors to be considered in employing aerial applicators and the economical aspect of the practice. Also presented are the alternative practices of seeding cover crops and areas in the U.S. that have seen an increase in aerial seeding.

Nutrient recycling is fundamental to sustainable agricultural systems, but few mechanisms exist to ensure that surplus manure nutrients from animal feeding operations are transported for use on nutrient-deficient croplands. As a result, manure nutrients concentrate in locations where they can threaten environmental health and devalue manure as a fertilizer resource. This study advances the concept of the "manureshed" – the lands surrounding animal feeding operations onto which manure nutrients can be redistributed to meet environmental, production, and economic goals. Manuresheds can be managed at multiple scales, for example, on farms with both animals and crops, among animal farms and crop farms within a county, or even among animal farms and crop farms in distant counties. With a focus on redistribution among counties, we classified the 3109 counties of the contiguous United States by their capacity to either supply manure phosphorus (P) and nitrogen (N) from confined livestock production ("sources") or to assimilate and remove excess P and N via crops ("sinks"). Manure nutrient source counties were identified in 40 of the 48 states, with a substantial concentration in the southern US. Source counties for manure P greatly outnumbered source counties for manure N (390 vs. 100), and 99 of the 100 manure N source counties were also source counties for manure P. Conversely, sink counties for manure N outnumbered sink counties for manure P (2766 vs. 2317). We used the P balances of the source and sink counties to delineate four manuresheds dominated by various combinations of confined hog, poultry, dairy, and beef industries. The four manuresheds differed in the transport distances needed to assimilate excess manure P from their respective source areas (from 147 ± 51 km for a beef dominated manureshed to 368 ± 140 km for a poultry dominated manureshed), highlighting the need for systems-level strategies to promote manure nutrient recycling that operate across local, county, regional, and national scales. • A "manureshed" encompasses the lands surrounding animal feeding operations onto which manure nutrients can be redistributed to meet environmental, production, and economic goals. • 3109 U.S. counties were classified as sources or sinks of manure nutrients. • Manure nutrient source counties were found in 40 states. • Manuresheds were delineated for major animal industries. • Manureshed differed in transport distances from 147 km to 368 km. [ABSTRACT FROM AUTHOR]

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. Additionally, geographic information system software was used with data from regulated Minnesota dairies to assess cropland assimilative capacities and transport needs surrounding large dairies. Manureshed requirements vary across regions, but increased import of feed and soil phosphorus accumulation constrain on-farm manure utilization across the United States. In Minnesota, a growing proportion of Jersey cattle and differences in continuous corn (Zea mays L.) vs. corn-alfafa (Medicago sativa L.) rotations contribute to the amount of land needed to absorb dairy manure nutrients. Farm-gate budgets reveal that N-based manuresheds can be contained within Idaho dairies, but P-based manuresheds extend beyond the farm. In New Mexico, relocation of surplus manure nutrients off the farm is common via informal networks, but incentives to strengthen these networks could ensure sustainable manureshed management. Evaluation of manureshed requirements in Pennsylvania is often complicated by the need for additional nutrient management planning and greater understanding of nutrient balances on the preponderance of small dairies. Nutrient imbalances with highly concentrated dairy production often lead to the need for manure transport off-farm. However, advances in herd and cropland management offer opportunities to improve on-farm nutrient efficiencies, and emerging networks and technologies promise to facilitate manure export when needed., (© 2022 The Authors. Journal of Environmental Quality © 2022 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.)

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. At the landscape scale, the land surface flux was estimated with a modified Bowen ratio technique using measurements made on a tall tower. The chamber data revealed a diurnal pattern for the plant CH4 flux: it was positive (an emission rate of 0.4±0.1 nmol m(-2) s(-1), average of soybean and corn, in reference to the unit ground area) during the day, and negative (an uptake rate of -0.8±0.8 nmol m(-2) s(-1)) during the night. At the landscape scale, the flux was estimated to be 14.8 nmol m(-2) s(-1) at night and highly uncertain during the day, but the available references and the flux estimates from the equilibrium methods suggested that the CH4 flux during the entire observation period was similar to the estimated nighttime flux. Thus, soybean and corn plants have a negligible role in the landscape-scale CH4 budget.