Soils, Nutrients and Fertilizers Part I Handouts: Soil Texture Triangle pH Nutrient Availability

Soil Diverse combination of weathered rock fragments and minerals, with decaying remains of plants and animals (organic matter). Dirt, on the other hand, is what is under you fingernails

Soil Profile Topsoil Sub soil Parent material O Horizon Organic material Topsoil Sub soil Second picture simplifies first picture. Second picture is what will be tested on Parent material

Soil Profile Neat soil profile from Discovery Channel. Second picture just showing that there are many different types of soil profiles and that Montana has many different soil profiles, so it is hard to speak specifics. This may be a time to describe the soils you have in your county.

Shows soil cuts. Important to know how deep your topsoil is and not to dig too deep and turn over the “B” layer. Really important in new construction. Make sure that the top soil is moved first and replaced last – in other words, make sure the contractor puts the soil back in the same layers that it came out.

An Ideal Soil 50% Pore Space 25% Air 25% Water 50% Solid Material 5% Organic Matter 45% Mineral Let’s look at organic matter

An Ideal Soil 50% Pore Space 25% Air 25% Water 50% Solid Material 5% Organic Matter 45% Mineral What is Humus? Degraded organic material in soil from decomposed plants, animals and other organisms Shows the amount of organisms, roots and humus in soil. Joke: it’s not Hummus! Definition of Humus

What’s in your soil? Organism Number in 1 lb soil Bacteria ~900 Billion Fungi ~450 Million Actinomycetes ~20 Billion Protozoa ~670 Million Total ~930 Billion Students don’t need to know all the amounts, just that soil contains billions of microbes

Microorganisms in the Soil Microorganisms do much of the “work” in the soil by breaking down nutrients and making them available to plants

45% mineral Sand, silt, and clay Sand is easily seen by the naked eye and is rough when moist between your fingers .05 to 2.0 mm in size Next three slides describe particle size, how it feels when wet rubbed between fingers, and how it feels when just moist

45% mineral Sand, silt, and clay Silt has a smooth and floury consistency and is hard to see with the naked eye .002 to .05 mm in size

45% mineral Sand, silt, and clay Clay cannot be seen by the naked eye. They are hard when dry and sticky when wet. .002 mm or less in size

Particle Size in Comparison Sand

Particle Size in Comparison Silt

Particle Size in Comparison Clay

Using the Soil Texture Triangle Fill a Mason jar 1/3 with soil. Add water until almost full. Add 2 drops detergent. Shake and let sit for 24 hours Introduction to Mason Jar texture test. Fill jar 1/3 full of soil, add water and a couple drops of laundry detergent to disperse the particles. Shake and let sit. Sand will settle out in 30 seconds. Silt will settle out in approx. two hours, clay may take up to 24 hours. Estimate or measure % of layers and use the soil triangle to determine soil type (shown on nest page)

What is the soil texture if you have 50% sand, 25% clay, and 25% silt? Soil texture triangle They need to add up to 100%! Soil texture is defined as the proportions of sand, silt and clay particles in a soil. Equal parts are LOAM. Texture affects drainage. Texture affects the type of plant that should / can be grown on a given soil.

Soil Properties - Texture Relative proportions of the different types of particles in the soil This looks like a 50% sand, 40% silt and 10% clay soil 10% Clay 40% Silt 50% Sand

50% sand 40% silt 10% clay soil Soil texture triangle

Soil texture triangle SANDY LOAM SILT LOAM Sandy loam and silt loams are best for most gardens. SANDY LOAM SILT LOAM

Texture Effects on Soil Properties Particle size (mm) Drainage water holding capacity Aeration Sand 2.0 excellent poor Silt 0.05 good Clay 0.002 Texture effects on soil properties.

An Ideal Soil What happens when you add water?

PERMANENT WILTING POINT SATURATION POINT FIELD CAPACITY SOIL PARTICLE WATER AIR AIR Blue is water. White is air. Brown is soil particles. Using a sponge as an example, saturation is when the sponge is dripping, field capacity is when the sponge is wet, yet you can extract water easily form the sponge, permanent wilting point is when the sponge is dry or slightly moist, yet it is hard to extract water. Field capacity is what is best for plant (equal amounts air and water).

Soil Properties - Structure How soil particles bind together. Influences: Water and air movement Biological activity Root growth Seedling emergence Just showing that depending on how a soil was formed and it’s texture, it has different structures

Tips in Working with Soils Working wet soil destroys its structure. If the soil sticks to the tools – it is too wet. Foot traffic compacts wet soil

Cation Exchange Capacity Indicates ability of soil to hold positively charged nutrients. Many essential plant nutrients carry positive charges. Example: Potassium (K+). A fertile soil has the capacity to attract and hold these nutrients. CEC is an index of soil fertility. Essential plant elements carry positively charged ions called cations (Ca+, Na+, K+ and Mg+ for example). A fertile soil has the capacity to attract and hold these nutrients. Most efficient are those with large surface areas, like CLAY. Clay particles called colloids have large surface areas that are negatively charged. OM also has colloidal properties. The higher the capacity for attraction of cations, the higher the CEC.

Cation Exchange Capacity Positively charged nutrient + + Negatively charged soil particle + + Negatively charged soil particle + Points on a soil particle are negatively charged (red). Most nutrients are positively charged (white) More surface area = more nutrients available for plant. Clay has more surface area than sand. + + + Negatively charged soil particle + + +

Texture Effects on Soil Properties Particle size (mm) Drainage water holding capacity Aeration Sand 2.0 excellent poor Silt 0.05 good Clay 0.002 Remember this graph…

Texture Effects on Soil Properties Particle size (mm) CEC Drainage water holding capacity Aeration Sand 2.0 low excellent poor Silt 0.05 med good Clay 0.002 high Add CEC. CEC = cation exchange capacity, the ability of soil to attract and hold cations. LOW = low soil nutritional status. Soils with large surface areas, such as clay and organic matter, have more CEC and surface area and therefore are generally more fertile.

Basic or “alkaline” soils pH Increasing acidity Increasing alkalinity Neutral Acidic Soils Basic or “alkaline” soils Most soils range form 4.5 to 9.0 pH. Unfortunately, most Montana soils are higher in pH. Testing pH from a garden test kit is relatively accurate. Most plants grow best just below neutral…Why? Next slide Soils 2 3 4 5 6 7 8 9 10 11 12 Most Montana soils

pH affects nutrient availability 7 +/- 1 appears to be safe for most nutrient elements in the soil. Montana soils are usually alkaline, which means that iron is unavailable, resulting in chlorosis.

Tips in Working with Soils It is very hard to change the pH of soil Sulfur will decrease pH – Slightly Lime will increase pH – Slightly Trying to alter garden soil alkalinity with “acidifying” liquid fertilizers is a lost cause. Understanding your soil pH will help you determine what nutrients you may need to incorporate

Questions so far?