United States Department of Agriculture Soil Survey Field and Natural Resources Laboratory Methods Conservation Service Manual National Soil Survey Soil Survey Investigations Report No. 51 Center Kellogg Version 2 Soil Survey Laboratory Issued 2014 Cover photos: Upper left.—Sampling of a pedon of Banister soil in Iredell County, North Carolina. This series is classified as fine, mixed, active, mesic Aquic Hapludalfs. Upper right.—Measuring saturated hydraulic conductivity (Ksat) by Amoozemeter (Ksat Inc., Raleigh, North Carolina) for a pedon of Talos soil at White Sands Missile Range, New Mexico. This series is classified as fine, mixed, superactive, thermic Calcic Argigypsids. Lower left.—Slaking of plinthite in a Btvx2 horizon from a pedon of Dothan soil. This series is classified as fine-loamy, kaolinitic, thermic Plinthic Kandiudults. Lower right.—Chemical analysis of soil samples using the HACH Kit (HACH Co., Loveland, Colorado). (Photo credits: upper left and lower left, John Kelly (retired), NRCS, Raleigh, NC; upper right, Philip Schoeneberger, NRCS, National Soil Survey Center (NSSC), Lincoln, Nebraska; lower right, Soil Survey Staff, NRCS, NSSC, Lincoln, Nebraska). Citation: Soil Survey Staff. 2014. Soil Survey Field and Laboratory Methods Manual. Soil Survey Investigations Report No. 51, Version 2.0. R. Burt and Soil Survey Staff (ed.). U.S. Department of Agriculture, Natural Resources Conservation Service. Trade names are used in this manual solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee of the product by USDA nor does it imply an endorsement by USDA. SOIL SURVEY FIELD AND LABORATORY METHODS MANUAL Soil Survey Investigations Report No. 51 Version 2.0 Compiled and Edited by Rebecca Burt Kellogg Soil Survey Laboratory National Soil Survey Center Natural Resources Conservation Service U.S. Department of Agriculture Lincoln, Nebraska Issued 2014 CONTENTS CONTENTS .......................................................................................................... iii NONDISCRIMINATION STATEMENT ................................................................ xvi PREFACE ........................................................................................................... xvii CONTRIBUTORS ............................................................................................... xxi ACKNOWLEDGEMENTS ................................................................................... xxii USER’S GUIDE ................................................................................................. xxiii 1. FIELD ASSESSMENT AND SAMPLING STRATEGIES .................................... 1 1.1 Soil Survey ................................................................................................... 1 1.1.1 Field Sample Collection and Preparation ............................................... 1 1.1.1.1 Site Selection ................................................................................... 1 1.1.1.2 Geomorphology ................................................................................ 1 1.1.1.3 Pedon ............................................................................................... 1 1.1.1.4 Water ................................................................................................ 1 1.1.1.5 Biological .......................................................................................... 1 1.2 Other Sampling Strategies ......................................................................... 21 1.2.1 Comparison Studies ............................................................................. 21 1.2.2 Chronosequence Studies ..................................................................... 21 1.2.3 Space-For-Time Studies ...................................................................... 21 1.2.4 Long-Term Experiments ...................................................................... 21 1.2.5 Long-Term Monitoring .......................................................................... 21 1.2.6 Short-Term Monitoring ......................................................................... 21 1.2.7 Composite Random Sampling ............................................................. 21 1.2.8 Diagonal and Zigzag Sampling ............................................................ 21 1.2.9 Benchmark Sampling ........................................................................... 21 1.2.10 Landscape Directed Sampling ........................................................... 21 1.2.11 Grid Sampling .................................................................................... 21 1.3 Field Assessment ....................................................................................... 23 1.3.1 Salinity, Sodicity, and pH ..................................................................... 23 1.3.1.1 Saline Soils .................................................................................... 23 1.3.1.2 Sodic Soils .................................................................................... 23 1.3.1.3 High pH Soils ................................................................................. 23 iii 1.3.1.4 Interactions, Salinity, Sodicity, and High pH ................................... 23 1.3.1.5 Sampling for Salinity, Sodicity, and High pH .................................. 23 1.3.2 Soil Fertility and Plant Nutrition ............................................................ 26 1.3.2.1 Soil Sampling as Basis for Fertilizer Applications ........................... 26 1.3.2.2 Plant Analysis as Basis for Fertilizer Applications .......................... 26 1.3.2.3 Remote Sensing for Crop Nitrogen Status and Plant Biomass ...... 26 1.4 Laboratory Sample Collection and Preparation .......................................... 28 1.4.1 Soils ..................................................................................................... 28 1.4.1.1 Field-Moist Preparation .................................................................. 28 1.4.1.1.1 Particles <2 mm ....................................................................... 28 1.4.1.2 Air-Dry Preparation ........................................................................ 28 1.4.1.2.1 Particles <2 mm ....................................................................... 28 1.4.1.2.2 Particles >2 mm ....................................................................... 28 1.4.1.2.2.1 Particle-Size Analysis ........................................................ 28 2. CONVENTIONS ............................................................................................... 33 2.1 Data Types ................................................................................................. 33 2.2 Size-Fraction Base for Reporting Data ....................................................... 33 2.2.1 Particles <2 mm ................................................................................... 33 2.2.2 Particles >2 mm ................................................................................... 33 2.3 Soil Sample Weight Base for Reporting Data ............................................ 33 2.3.1 Air-Dry/Oven-Dry Ratio ........................................................................ 33 2.3.2 Field-Moist/Oven-Dry Ratio ................................................................. 33 2.3.3 Correction for Crystal Water ................................................................ 33 2.4 Significant Figures and Rounding ............................................................... 34 2.5 Data Sheet Symbols ................................................................................... 34 3. SOIL PHYSICAL ANALYSES .......................................................................... 35 3.1 Soil Morphology .......................................................................................... 35 3.1.1 Color .................................................................................................... 36 3.1.1.1 Color Charts ................................................................................... 36 3.1.1.2 Ignition ............................................................................................ 38 3.1.1.3 Alkaline Solution ............................................................................. 40 3.1.1.4 Dispersion ..................................................................................... 40 3.1.1.5 Hydrogen Peroxide........................................................................ 40 iv 3.1.2 Structure and Consistence ................................................................... 40 3.1.2.1 Soil Morphology Index .................................................................... 40 3.1.2.2 Singleton Blade and Modified Singleton Blade ............................... 44 3.1.2.3 Near-Surface Subzones ................................................................. 46 3.1.2.4 Horizon Examination ...................................................................... 47 3.1.2.4.1 Ped Faces ................................................................................ 48 3.1.2.4.2 Pores and Other Voids ............................................................. 51 3.1.2.4.3 Packing .................................................................................... 51 3.1.2.4.4 Other Structural Features......................................................... 51 3.1.3 Podzol and Podzolic Soil Development