USDA-ARS National Soil Dynamics Laboratory 2 articles published in JoVE Engineering Measurements of Soil Carbon by Neutron-Gamma Analysis in Static and Scanning Modes Galina Yakubova1, Aleksandr Kavetskiy1, Stephen A. Prior1, H. Allen Torbert1 1National Soil Dynamics Laboratory, Agricultural Research Service, United States Department of Agriculture Here, we present the protocol for in situ measurement of soil carbon using the neutron-gamma technique for single point measurements (static mode) or field averages (scanning mode). We also describe system construction and elaborate data treatment procedures. Environment Design and Operation of a Continuous 13C and 15N Labeling Chamber for Uniform or Differential, Metabolic and Structural, Plant Isotope Labeling Jennifer L Soong1, Dan Reuss1, Colin Pinney1, Ty Boyack1, Michelle L Haddix1, Catherine E Stewart2, M. Francesca Cotrufo1,3 1Natural Resource Ecology Laboratory, Colorado State University, 2Soil Plant Nutrient REsearch, USDA-ARS, 3Department of Soil and Crop Sciences, Colorado State University This method explains how to build and operate a continuous 13C and 15N isotope labeling chamber for uniform or differential plant tissue labeling. Representative results from metabolic and structural labeling of Andropogon gerardii are discussed.