Dr. Darraugh used to work for ChemLawn developing fertilizer and studying grass. CLC is located north of I-270 off Route 23, but tests soil samples from all over the world and right here in Central Ohio.
According to Dr. Darraugh, plants grown in soil with correct fertility will outgrow insects and diseases. Too little or too many nutrients will stress plants. When dropping off a soil sample, be sure to indicate what you plan to grow so that you will be provided with fertilizer recommendations. Different plants have different needs and recommendations cannot be made in a vacuum.
In general, Central Ohio soil has lots of lime because of all of the limestone left during the ice ages. Lime consists of calcium carbonate, which is alkaline (i.e., with a high pH). Eastern Ohio and Franklin County have more acidic soil than western Franklin County. Central Ohio soils are likely to be deficient in Phosphorus than Nitrogen or Potassium. Accordingly, he spent most of his time discussing Phosphorus (P), which is a controversial component of fertilizer and responsible for algae blooms in Ohio lakes.
Phosphorus is banned in many states unless you have a soil test showing that your land is phosphorus deficient. Phosphorus is critical for new plants to develop roots and for the plant’s metabolism (so that it can develop fruit, etc.) However, lawn grass does not need equal amounts of nitrogen and phosphorus, so low phosphorus fertilizers are perfectly sufficient. Excessive phosphorus runs off into storm water (see the tie-in with the Conservation District presentation?) and contaminates our creeks and lakes, so gardeners should be circumspect. Good sources of phosphorus include bone meal (6-12-2), turf seed fertilizer (20-27-5 OR 18-24-12), and the materials used in the infamous pink slime hamburger, etc. It can be difficult to effectively raise phosphorus level in soil, so it should be done gradually over a few years.
Dr. Darraugh explained that plants also need oxygen, which they absorb through their roots which are exposed to air in the spaces in dirt. Accordingly, water-logged soils fill those gaps with water instead of air and suffocate plants. That is why it is important to have good drainage and to not use too much compost (which holds onto water more than regular soil). Conversely, clay soils are too compact and don’t hold much oxygen, so it is important to mix it in with compost. Oxygen is needed to help the plant absorb nitrogen.
The amount of nitrogen (N) in the soil is constantly changing with rainfall. If you have too much nitrogen, you’ll have more plant than flowers or fruit with your tomatoes. Accordingly, start withholding nitrogen from your tomatoes when it starts to flower. In contrast, peppers and leafy vegetables can tolerate high amounts of nitrogen. Good sources of nitrogen include Ammonium sulfate (i.e., percentages of 20-0-0) is also a soil acidifier and can be found in packages that promote azaleas. Urea (46-0-0), and Blood meal (15-0-0) are also good sources. http://www.omri.org/ will tell you organic sources of fertilizers.
If your soil is deficient in Potassium (K), you can get some through muriate (0-0-60) or sulfate (0-0-50) of Potash, green sand (0-0-3) or sunflower seed ash (0-0-12).
Many plants (like red maples, oaks, holly, etc.) are deficient in manganese, not iron. You can improve the Mn level through Main Event Manganese (that is available locally at Advanced Turf Solutions or High Manganese Combo (which can be purchased through John Deere Landscape Stores). Apply the liquid to the soil and not the plant (which should be washed with clear water if you splash some on the plant).
You can increase the amount of Magnesum (Mg) through Espsom Salt.
Dr. Darraugh believes you can have too much organic matter because it can lead to water-logged soils. He doesn’t recommend peat moss because it does not degrade and has no nutritional value. (I, however, like it because it inexpensively lowers pH). He pointed out that horse manure is high in potassium, weeds and salts.
CLC will also test for lead if asked for an extra fee. It normally costs $45, but he will charge a community garden only $28. Nutrient soil tests were $15 last year. CLC Labs is at 325 Venture Drive in Westerville. Dr. Darraugh can be reached at 888-1663.