Sand Sandy Soils • Low water • Large particles you can see holding capacity • Large spaces between particles – Susceptible to – Rapid water flow drought • Non cohesive • Small surface • Small surface area area – Low CEC – Infertile – Easily acidified

Silt Sandy soils • Small micro sand particles you can’t see – Rapid weathering - nutrient • Generally very release easy to use – Higher surface area equipment on – More nutrient retention • Low potential • Small spaces between for particles compaction – water retention • Non cohesive - can erode easily

Wind blown and alluvial parent Silty soils materials

• Generally primarily silt • Without vegetative cover – Sand is too heavy • ‘can melt like butter’ – Clay is too sticky • Can be excellent agricultural • Silt fences soils • Sedimentation ponds • Fertile – Good water retention – Nutrient availability

1 Clay Clayey soils • Tiny particles, require • Heavy soils special microscopes • Difficult tillage to see • Water holding • Very high surface capacity is high area – Water can be so – Very reactive tightly held to clay – High nutrient / water particles holding capacity – Not plant available • Cohesive - can • Slow drainage behave like plastic

Clay goes up, water goes down There is a system

• When you classify a soil, texture in the A horizon is major factor

Soil Texture Triangle 25% Clay 50% Sand 25% Silt How to you categorize? How to you categorize?

2 15% Clay 30% Sand 55% Silt 63% Clay 20% Sand 17% Silt How to you categorize? How to you categorize?

Aggregation is how soils Particle size doesn’t change are held together rapidly (in our lifetime) • Separates soil from dirt • Aggregation is something you can • “Dirt is soil out of place” influence • Granular • Crumb

• Organic matter from plants can do this Aggregates are: • Earthworms can do this- casts • Small particles or colloids that have • Well maintained soil will have good been glued together, usually by aggregation organic matter Sand Sand

Aggregates Aggregates

3 How do you measure Bulk Density aggregation • Mass per unit • Visible appearance volume of dry • Feel of the soil soil • Quantitative approach • How much will the soil weigh • Lighter the soil - the better the aggregation We are not weak

How do you calculate Particle density

• Known volume of soil • Known volume of soil • Dry • Dry/ remove pore space • Weigh • Weigh • Weight / adjusted volume = PARTICLE DENSITY

• Weight / volume = BULK DENSITY

Remember What do the different 1m3 of soil is really about components weigh? half pore space • Air is negligible • Water is 1 Mg m3 but doesn’t count • Soil solids –Inorganic –organic

4 Inorganic fraction- Organic fraction- Generally 2.6- 2.75 Mg m3 Generally 0.2 Mg m3 2,200 pounds 200 pounds

Mineral Organic

Bulk density- largely a What the aggregates function of soil structure consist of In here Macropores

Macropores Flocculated clays

Micropores Fungal hyphae

Bulk densities 3 The greater the pore space (g/cm ) and organic matter- • Andisol 0.7 The lower the bulk density • Uncultivated loamy A 1.05 will be • Cultivated loamy A 1.5 • Dry vertisol 1.8 • Fragipans 1.85 • Concrete 2.45 • Soil I sampled in MO 3.0

5 Why do you care Growth is generally limited

• Root growth reduced due to • Bulk density greater than – Slow air movement – 1.45 Mg m3 in clays – Slow water movement –1.85 Mg m3 in sands – Gas build up Hard to push through Dense soil

Factors that increase bulk Same soil, from good to density bad structure • Agricultural practices – Tillage Number of Macropores – Equipment decreases

• Foot traffic Number of Micropores increases

Moldboard plow - lifts and Using conventional ag turns soil • Incorporate more air into soil – Break down organic matter • Plowing can break existing aggregates – Decrease number of macropores • Can lead to formation of a plow pan – Cemented layer as a result of compaction

6 Heavy equipment Conservation tillage - especially under improper Mulchtiller conditions Only a portion of the soil is disturbed

Conservation tiller

Mark Sheppard wants all the flotation he can get. He works anywhere from 25 to 35,000 acres around Loving, Texas, where much of the soil is sandy and easily disturbed. He needs the kind of low ground contact pressure and high flotation narrow tires can't provide. With Firestone Flotation 23° Center Rib tires up front and Firestone Flotation 23° DTs in back, he's riding high.

Use of organic amendments Heavy traffic

• Manures • Biosolids

• Crop residues No Growth • Composts

7 One reason trails exist

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