Quality Control for Types of Soil Tests

Fertility and pH

• The most fundamental of soil tests, fertility and pH testing measures essential nutrition content and relative acidity. In order to increase test results' accuracy, test at the end of the growing season or before planting, but never right after working lime, compost or fertilizer into the soil. Before gathering soil samples, scrape the area clean of all leaves and debris that could skew the results. Use a chrome-plated or stainless steel shovel or trowel to gather soil samples; galvanized, bronze or brass tools can contaminate samples. Dig a small, 4-inch-deep hole to collect a soil sample for lawns, a small, 6- to 8-inch-deep hole for vegetable and flower gardens and a small hole that is 6 to 10 inches deep for shrubs and trees. Collect a sample from six to eight areas, placing all the samples into a clean, plastic bucket and thoroughly mixing them before testing.

Temperature

• An underappreciated assessment, testing soil temperature helps you plant seeds under the most favorable conditions, decreasing seed rot and boosting germination rates. Get a reading by using any thermometer that can measure a temperature as low as 45 degrees Fahrenheit. Placing the thermometer at a seed’s planting depth, ensure good soil contact and leave it in the ground for two minutes -- long enough for the thermometer to reach temperature equilibrium. On a sunny day, shade the thermometer to prevent sunlight from falsely affecting the reading. If you use a glass thermometer, first probe the soil with a screwdriver before inserting the thermometer to prevent breaking the thermometer.

Moisture

• Particularly in dry locations, growers should know the level of moisture in soil before sowing large swaths of seeds. Just as seeds need proper soil temperature for good germination, they rely on water absorption to increase respiration and start growth. Collect three soil samples from different locations in your garden by using a soil probe or shovel. Digging to a depth of 2 feet, collect two separate samples, one from the first foot of soil and another from the second foot. Keeping the samples separate, place each in a zip-style plastic bag immediately after collection; exposure to warm air can dry soil and skew test results. The samples should be placed in a cooler until you are ready to test them.

Water Infiltration

• Water moving easily through soil’s air pockets allows for good root penetration and provides much-needed oxygen to plants, bacteria and microorganisms. Soil’s infiltration rate can be tested with a large coffee can that has its bottom removed. Being careful not to cut yourself on the can’s sharp edges, use a permanent marker to make one mark every inch on the inside of the can, starting 3 inches from the can's bottom. Pound the can into the soil until the first mark is at soil level. After filling the can to the top with clean water, measure how far the water drops every minute for 10 minutes. Dividing the total number of inches drained by 10 gives you the infiltration rate for that site. Perform the same test at several other sites for a more accurate view of your soil.