(1) (1) (4) (2) (2) Quiz 3 - Answers 1.) T FConservation tillage refers to methods of preparing the soil for planting that are more likely to disturb or move soil than conventional tillage. 2.) T F One thing soil color helps to identify is the moisture regime of a soil. 3.) a. What textural class is a soil with 10% clay and 60% sand? sandy loam b. What % silt would this soil have? 30% silt c. Can you change a soil’s textural class by adding organic matter? No d. Why or why not? Soil texture is a property referring only to the mineral particles; therefore organic matter plays no part in determining a soil’s textural class. 4.) What is the % pore space of a typical mineral soil having a Db of 1.05 Mg/m3?60.4% pore space 5.) What did you learn about bulk density from the Sharratt article? Some possible answers: In areas of compaction, bulk density can be higher. Bulk density did not account for a thinner A horizon. The effects of compaction causing greater bulk density can last for 100 yrs.
CO2 flux REVIEW:Processes of Soil Formation OM additions, OM transformations, weathering Clay transfers Additions Organic C Dust Removals CO2 Weathering products Transfers Clay Organic matter Carbonate Transformations Plants to SOM Primary silicates to secondary silicates, carbonates Clay and carbonate transfers Leaching
Soil Horizon Nomenclature Based on interpretation of dominant soil forming processes affecting that horizons Names based on presumed changes relative to parent material (t=0) Universal with some variance Originated by Russians in 19th Century
Example A Bt Btqm BC
Chapter 3:Soil Classification “It is embarrassing not to be able to agree on what soil is. In this the pedologists are not alone. Biologists cannot agree on a definition of life and philosophers on philosophy.” -Hans Jenny from The Soil Resource: Origin and Behavior
Classification • Pedon: the smallest volume that can be called “a soil” • Polypedon: two or more contiguous pedons, also called “soil individual” • Landscape: region, tract of land Figure 3.1
Classification • Genetic horizon: soil layers resulting from soil-forming processes (pg. 73) • presence or absence help classify soil • Diagnostic horizon: soil layers having specific soil characteristics indicative of certain classes of soils • at surface: “epipedon” • below surface: “diagnostic subsurface horizon” Figure 3.4