"No-Till" Farming Is a Growing Practice

Most U.S. farmers prepare their soil for seeding and weed and pest control through tillage—plowing operations that disturb the soil. Tillage practices affect soil carbon, water pollution, and farmers’ energy and pesticide use, and therefore data on tillage can be valuable for understanding the practice’s role in reaching climate and other environmental goals. In order to help policymakers and other interested parties better understand U.S. tillage practices and, especially, those practices’ potential contribution to climate-change efforts, ERS researchers compiled data from the Agricultural Resource Management Survey and the National Resources Inventory-Conservation Effects Assessment Project’s Cropland Survey. The data show that approximately 35.5 percent of U.S. cropland planted to eight major crops, or 88 million acres, had no tillage operations in 2009.Tillage, no-till, Agricultural Resource Management Survey, ARMS, U.S. crop practices, National Resources Inventory-Conservation Effects Assessment Project, NRI-CEAP, carbon baseline, carbon sequestration, Environmental Economics and Policy, Farm Management, Land Economics/Use, Resource /Energy Economics and Policy, Risk and Uncertainty,

Nonlinear Landauer formula: Nonlinear response theory of disordered and topological materials

The Landauer formula provides a general scattering formulation of electrical conduction. Despite its utility, it has been mainly applied to the linear-response regime, and a scattering theory of nonlinear response has yet to be fully developed. Here, we extend the Landauer formula to the nonlinear-response regime. We show that while the linear conductance is directly related to the transmission probability, the nonlinear conductance is given by its derivatives with respect to energy. This sensitivity to the energy derivatives is shown to produce unique nonlinear transport phenomena of mesoscopic systems including disordered and topological materials. By way of illustration, we investigate nonlinear conductance of disordered chains and identify their universal behavior according to symmetry. In particular, we find large singular nonlinear conductance for zero modes, including Majorana zero modes in topological superconductors. We also show the critical behavior of nonlinear response around the mobility edges due to the Anderson transitions. Moreover, we study nonlinear response of graphene as a prime example of topological materials featuring quantum anomaly. Furthermore, considering the geometry of electronic wave functions, we develop a scattering theory of the nonlinear Hall effect. We establish a new connection between the nonlinear Hall response and the nonequilibrium quantum fluctuations. We also discuss the influence of disorder and Anderson localization on the nonlinear Hall effect. Our work opens a new avenue in quantum physics beyond the linear-response regime.Comment: 39 pages, 7 figures, 1 tabl

Grassland to Cropland Conversion in the Northern Plains: The Role of Markets and Policy

Crop Production/Industries, Land Economics/Use,

AKARI IRC 2.5-5 um Spectroscopy of Infrared Galaxies over a Wide Luminosity Range

We present the result of a systematic infrared 2.5-5 um spectroscopic study of 22 nearby infrared galaxies over a wide infrared luminosity range (10 < log(L_IR / Lsun) < 13) obtained from AKARI Infrared Camera (IRC). The unique band of the AKARI IRC spectroscopy enables us to access both the 3.3 um polycyclic aromatic hydrocarbon (PAH) emission feature from star forming activity and the continuum of torus-dust emission heated by an active galactic nucleus (AGN). Applying our AGN diagnostics to the AKARI spectra, we discover 14 buried AGNs. The large fraction of buried AGNs suggests that AGN activity behind the dust is almost ubiquitous in ultra-/luminous infrared galaxies (U/LIRGs). We also find that both the fraction and energy contribution of buried AGNs increase with infrared luminosity from 10 < log(L_IR / Lsun) < 13, including normal infrared galaxies with log (L_IR / Lsun) < 11. The energy contribution from AGNs in the total infrared luminosity is only ~7% in LIRGs and ~20% in ULIRGs, suggesting that the majority of the infrared luminosity originates from starburst activity. Using the PAH emission, we investigate the luminosity relation between star formation and AGN. We find that these infrared galaxies exhibit higher star formation rates than optically selected Seyfert galaxies with the same AGN luminosities, implying that infrared galaxies could be an early evolutionary phase of AGN.Comment: 13 pages, 8 figures, accepted for publication in Ap