Testing soil pH with the gang
Will Wischhusen, far right, and the Botanical Training Group in Great Neck
I spent the morning visiting with the good folks in the Botanical Training Program at North Shore University Hospital's Vocational Training Center. The group, led by Will Wischhusen, comprises aspiring gardeners preparing for careers in the horticulture world.
We talked about soil pH, explored types of liming materials, discussed macronutrients and then played in the dirt, literally.
The group's eight members took turns testing two soil samples -- one from a neglected area in my backyard, the other from directly outside the building on Northern Boulevard in Great Neck. Both were surprisingly nonacidic, with readings of approximately 7.0 to 7.2.
That's some sweet soil, and unless you're planting ericaceous plants like blueberries, azaleas or rhododendrons, it's absolutely perfect. But what if your soil is more acidic, as much of Long Island soil is?
Your first course of action when planting a new area should be to get a soil test. The Cornell Cooperative Extension has walk-in counters located in Eisenhower Park in Nassau and in Riverhead in Suffolk. They'll test your sample for $5. You also can buy a test kit at most nurseries. The advantage to using the extension's service, though, is that it comes with recommendations for adjusting the pH, if necessary.
To get started: Dig down 4 inches and scoop up about 1/4 cup of soil from the area(s) you'd like to have tested. Place it in a zippered plastic bag and run a test.
The pH scale runs from 0 to 14. Readings of less than 7 indicate acid (sour) soil; higher than 7, alkaline (or sweet). Optimum pH depends on what you're planting. Pieris (andromeda), gooseberry, hemlock, creeping juniper, magnolia, pinoaks, white pines and potatoes -- in addition to azaleas, rhododendrons and blueberries -- thrive in more acidic soils. But most common garden plants require a neutral pH of around 7.0, or slightly below. So the next step is determining what pH suites your garden. (For a list of pH preferences of different plants, check out the Cornell Cooperative Extension of Nassau County fact sheet on soil acidity).
Once you know your plants' needs and your soil's reading, you can adjust the pH accordingly, if necessary. That's important because if the pH is off, nutrients won't be available to your plants. They might be in the soil, but they'll be locked up.
Most soil on Long Island is naturally acidic because of the amount of rain we get and because of our humid summers, so lowering pH usually isn't warranted.
Raising soil pH can be accomplished by adding calcium and magnesium to the soil. Both elements are present in limestone. Look for dolomitic limestone or dolomite; calcitic limestone is mostly calcium and contains only a very small amount of magnesium.
Liming materials are available in different particle sizes, which determine the speed of absorption. Like anything else, you get what you pay for. Pelletized lime is the Rolls Royce of amendments. It's fast acting and easy to spread but the most expensive of the group. Hydrated lime also is very fast, but caustic. Pulverized lime is fine and dusty and works fairly fast. Granular is slow acting and inexpensive. Your budget, obviously, but also the size of the area you're treating will determine the type of lime you purchase. If you have a small area and can afford it, go for the pelletized lime. If you're working on a acre of land, let your wallet be your guide.
Lowering soil pH is a very slow process and needs to be repeated ad nauseum. It's a never-ending uphill battle, but if you're growing ericaceous plants, you might have to consider it. Frankly, if my soil weren't suitable for acid-loving plants, I'd plant something else rather than mess with this stuff, but there are instances where it might be necessary, like if your plants are suffering from iron chlorosis (indicated by dark green veins on yellowing leaves.)
Elemental sulfur and ammonium sulfate are two elements used to lower soil pH. Ammonium sulfate also adds lots of nitrogen, which will run off and pollute groundwater something awful, but it gives instantaneous results, so people tend to prefer it. Sulfur can take weeks or months to become effective.
Use extreme care when messing with either of these. If they contact leaves, rinse immediately to avoid burns. And whatever you do, don't over-apply them.
We talked about macronutrients and micronutrients, fertilizers and how some freaky things can end up in drinking water.
In all, I'd say my morning was pretty alkaline.
