1. Soils Texture and Structure and the Nature of Soil Soils Rock!!!

2. Definitions Clods Loam Peds Permiability Soil structure Soil Texture Soil Workability Texture Triangle Water Holding Capacity

3. What’s In Soil 50% Pore Space (25% air 25% H2O) 45% Minerals (Sand, Silt, Clay) 5 % Organic Matter

4. Soil Texture Sand-large particles Silt-Medium Particles Clay-Small Particles

5. Texture is important because it affects Water holding capacity-how well the soil holds available water Permeability-the ease in which air and water may pass through the soil Soil workability-the ease with which soil may be tilled and the timing of working soil after a rain Ability of plants to grow-some crops like carrots and onions have difficulty growing in fine textured soils

6. How do we determine texture? Lab method –The soil is measured in a lab by separating the three major parts (sand, silt, and clay) Field method –This method involves taking a sample in the field and spraying it with water and forming a ribbon in your hand. This method is more technically known as the ribbon method.

7. Lab Method When testing in the lab an accurate measurement can be made resulting in 12 different textural classes of soils –Silt –Silt loam –Silty clay loam –Loam –Sandy clay loam –Sand –Sandy loam –Sandy clay –Clay loam –Silty clay –Clay

8. The Ribbon Method When performing the ribbon method the measurement is not as accurate but 5 classifications gives one a pretty good idea what the soil is like –Fine-textured--ribbon forms easily and is long and flexible –Moderately fine-textured—a ribbon forms but it breaks into pieces ¾ to 1 inch long –Medium-textured—no ribbon forms. The sample breaks into pieces less than ¾ of an inch long –Moderately coursed-textured---no ribbon forms. The sample feels gritty and lacks smoothness. –Coarse-textured—no ribbon forms. It is composed almost entirely of gritty material

9. The Lab Method First put soil in a glass jar Then fill the jar with water Add soap Shake Let it sit over night and watch it separate. –Sand falls to the bottom, silt settles next, then comes clay and finally organic matter

10. After Using the Lab Method the Soil Triangle will show what the sample is

11. Soil Structure The arrangement of soil particles into aggregates of various sizes and shapes –Natural aggregates are peds –Clumps caused by tillage are clods

12. There are two steps that form structure 1) A clump of soil particles sticks loosely together through: –Plant roots surrounding the soil and separating clumps –Freezing and thawing of soil –Soil becomes wet and then dries –The soil is tilled –Fungal activity

13. 2) Weak aggregates are cemented to make distinct and strong. Clay, iron oxides, and organic matter may act as cements. When soil microorganisms break down plant residues, they produce gums that also glue peds together.

14. Soil structure is important for several reasons It improves soil tilth It improves permeability It resists the beating action of raindrops, minimizing the formation of crusts that reduce crop stands.

15. There are eight types of structures Granular-aggregates are small, non-porous and tightly held together Crumb-aggregates are small, porous, and strongly held together Platy-aggregates are flat or plate-like slowing percolation Prismatic or Columnar-aggregates are prism like that are very tall Blocky-aggregates are block-like with six or more sides Structureless- there is no structure –Single grain-no aggregates –Massive-soil particles cling together and form huge masses

17. Soil Profile