A Soil, Mulch, and Compost Guide
Soil is so much more than just dirt. Most Southern soils have sand, silt, and clay. Depending on the particle size, there are different classifications:
Soil Particle Size
Sand: Very coarse: 1.0-2.0mm
Very fine: .05-.10mm
Clay: less than .002mm
Most gardening guides use terms like “for loamy soils” or “best in silty clay”. Ever wondered that those terms really meant? Soil composition is determined by the percentage of the above particles in the soil sample.
Sandy soils: more than 35% sand, less than 15% silt and clay
Coarse sand: more than 35% very coarse or coarse sand, less than 50% fine or very fine sand
Medium sand: more than 35% coarse and medium sand, less than 50% fine or very fine sand
Fine sand: more than 50% fine or very fine sand
Very fine sand: more than 50% very fine sand
Loam soils: less than 20% clay, 30-50% silt, 30-50% sand
Sandy loam: 20-50% silt and clay
Coarse sandy loam: more than 45% very coarse and coarse sand
Medium sandy loam: more than 25% very coarse or coarse sand and medium sand, less than 35% very fine sand
Fine sandy loam: more than 50% fine, less than 25% very coarse or coarse sand and medium sand
Very fine sandy loam: more than 35% very fine sand
Silt loam: less than 20% clay, more than 50% silt
Clay loam: 20-30% clay
Sandy clay loam: less than 30% silt, 50-80% sandy, 20-30% clay
Silty clay loam: 20-50% silt, 20-50% sand, 20-30% clay
Clay soils: more than 30% clay, less than 50% silt, less than 50% sand
Sandy clay: 30-50% clay, less than 20% silt, 50-70% sand
Silty clay: 30-50% clay, 50-70% silt, less than 20% sand
How to Test Your Soil
One of the easiest ways to test your own soil is to wait until two days after a rain and scoop a ball of earth, about the size of a golf ball, and squeeze. If the ground is gritty it is sandy soil; smooth, it is silty; and slippery, it is clay. Open up your hand: if it will not hold together at all it is sandy soil; if it crumbles slowly it is loamy soil; and if it sticks together it is clay soil. There are much more proper ways to have soil tests done, but in a pinch this is a quick way to test your own garden soil. For the best and most accurate results, have your soil sent in for a proper test.
Need some good basic potting soil but don’t like the results you get (or spending all that cash) on the pre-made potting soils? Below are some favorite recipes for 5 different potting soil formulas and one famous international mix. See which one works best for you.
Potting Soil Recipes
A) 1 part perlite, 1 part peat moss, 1 part vermiculite
B) 1 part garden soil, 1 part peat moss, 1 part builder’s sand
C) 1 part soil, 1 part milled sphagnum moss, 1 part peat moss
D) 1 part peat moss, 1 part sieved compost
E) 2 parts soil, 1 part compost, 1 part perlite
John Innes Compost (Famous British mix):
7 parts composted loam, 3 parts peat moss, 2 parts coarse sand, 1 ½ parts ground limestone, 8 ½ parts fertilizer (2 parts hoof and horn meal, 2 parts super phosphate, 1 part sulfate of potash) OR 12 parts 5-10-10 fertilizer.
Guide to Mulches
Ever wonder why mulch is really there? Is it decorative, or really useful? Most serious gardeners know that it is a key to great style, good soil, and less weeds. Summer mulching is good for attracting worms, slowing water evaporation and weed growth, nourishing the soil and keeping it moist. Winter mulching is mostly to keep the soil from deep freezing and to keep roots from heaving out from too much freezing/thawing cycles. The following is a guideline to the different types of mulches.
Bark chips: Long lasting, but expensive. Try to get larger pieces as it will last longer. Spread bark chips 2 inches deep and add nitrogen to the soil before you mulch.
Shredded bark: Long lasting, but expensive. Spread 3 inches deep and add nitrogen to the soil before you mulch.
Buckwheat hulls: These will last approximately two years. Spread 2 inches deep.
Cocoa bean hulls: A short-lived chocolate smell, and expensive. This is good for formal gardens. Spread 2 inches deep.
Compost: A nourishing mulch, but not a weed barrier. Spread 1-2 inches deep.
Ground corncobs: Inexpensive. Spread 3-4 inches deep and add nitrogen to the soil before you mulch.
Cottonseed hulls: Good weed suppressor. Spread 3-4 inches deep and add nitrogen to the soil before you mulch.
Hay/Straw: Lightweight, will compact in the garden over time. This may contain weed seeds in the hay; most straw is weed-seed free. Spread 4-6 deep inches in the summer; 8-12 inches in the winter.
Shredded leaves: Weed suppressor. Good winter mulch and used in naturalistic woodland gardens. Spread 2-3 deep inches in summer; 6-8 in winter.
Peanut hulls: Lightweight. Spread 2-3 deep inches deep.
Pine needles: Lightweight, but long lasting. Use around acid loving plants like azaleas. Spread 3-4 inches deep.
Sawdust: Cheap, acidic mulch. Spread 2-3 inches deep and add nitrogen to the soil before mulching.
Stone, gravel, marble chips: Must use over black plastic to be a weed suppressor. This mulch is best around trees and shrubs. Spread 2-3 inches deep.
Wood chips: Long lasting, this decomposes faster than bark. Spread 2-3 inches deep and add nitrogen to the soil before you mulch.