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 O Horizon Organic material Topsoil Sub soil Parent material 1
Soil Profile An Ideal Soil 50% Pore Space 25% Air 25% Water Water 50% Solid Material 5% Organic Matter 45% Mineral Mineral 45% 25% Air 25% Organic Matter 5% 2
50% Pore Space 25% Air 25% Water An Ideal Soil 50% Solid Material 5% Organic Matter 45% Mineral What is Humus? Degraded organic material in soil from decomposed plants, animals and other organisms Organism Bacteria Fungi What s in your soil? Number in 1 lb soil ~900 Billion ~450 Million Actinomycetes Protozoa Total ~20 Billion ~670 Million ~930 Billion Microorganisms in the Soil Microorganisms do much of the work in the soil by breaking down nutrients and making them available to plants 3
Sand is easily seen by the naked eye and is rough when moist between your fingers 45% mineral Sand, silt, and clay.05 to 2.0 mm in size 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 Clay cannot be seen by the naked eye. They are hard when dry and sticky when wet. 45% mineral Sand, silt, and clay.002 mm or less in size 4
Particle Size in Comparison Sand Particle Size in Comparison Silt Particle Size in Comparison Clay 5
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 Soil textur re triangle What is the soil texture if you have 50% sand, 25% clay, and 25% silt? 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 50% Sand 40% Silt 6
Soil textur re triangle 50% sand 40% silt 10% clay soil re triangle Soil textur SANDY LOAM SILT LOAM Texture Effects on Soil Properties Particle size (mm) Drainage water holding capacity Aeration Sand 2.0 excellent poor excellent Silt 0.05 good good good Clay 0.002 poor excellent poor 7
An Ideal Soil Water 25% Mineral 45% Organic Matter Air 5% 25% What happens when you add water? SATURATION POINT SOIL PARTICLE FIELD CAPACITY PERMANENT WILTING POINT WATER AIR AIR Soil Properties Structure How soil particles bind together. Influences: Water and air movement Biological activity Root growth Seedling emergence 8
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. Positively charged nutrient Cation Exchange Capacity Negatively charged soil particle Negatively charged soil particle Negatively charged soil particle 9
Texture Effects on Soil Properties Particle size (mm) Drainage water holding capacity Aeration Sand 20 2.0 excellent poor excellent Silt 0.05 good good good Clay 0.002 poor excellent poor Texture Effects on Soil Properties Particle size (mm) CEC Drainage water holding capacity Aeration Sand 2.0 low excellent poor excellent Silt 0.05 med good good good Clay 0.002 high poor excellent poor Soils with large surface areas, such as clay and organic matter, have more CEC and surface area and therefore are generally more fertile. ph Increasing acidity Acidic Soils Neutral Increasing alkalinity Basic or alkaline soils Soils 2 3 4 5 6 7 8 9 10 11 12 Most Montana soils 10
ph affects nutrient availability 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? 11