A battery of specialists congregating at an industry meeting affords a rare opportunity for acquiring a collection of information in one fell swoop. So you can bet I was there at the opening bell for the start of the 15th annual Maryland Turfgrass Conference and Trade Show, sponsored by Maryland Turfgrass Council, at the Baltimore Convention Center and Festival Hall a few weeks ago.
Although the sessions were geared to professionals, they nevertheless contained ideas one might be able to build on and apply at home.
In his talk on managing turf to increase drought tolerance and reduce water use, Dr. Marj J. Carroll, an assistant agronomy professor at the University of Maryland, explained that if you knew how much moisture had evaporated from your soil each day, you could avoid over-watering (and thus wasting a precious resource) by replacing only the amount that was lost.
Plants should be given only as much water as they need, he said. Grass can lose up to an inch of water before becoming stressed. Clay soil usually takes about 3 days in summer and about 8 days in spring and fall to lose an inch of water.
Dr. Carroll noted that many newspapers, especially in the arid West, publish daily reports of the amount of water lost to evaporation to let farmers know the degree to which crops might be drying out. The figures, furnished by local weather stations, are obtained by measuring the amount of water lost from a special receptacle called a Class A evaporation pan. The steel pan, 4 feet in diameter and 10 inches deep, is set on a wooden pallet surrounded by grass.
The same information, Dr. Carroll says, is pertinent in the management of turfgrass. You can make a rough estimate of conditions in your own yard, Dr. Carroll says, by setting on the ground a one-pound coffee can (4 inches in diameter) and filling it to the top with water. Dip out and reserve 7 ounces of the water (7 fluid ounces equal 1 inch of water) and mark on the can the level of the remaining water. Pour back the water you removed. The receding of the water naturally to the 7-ounce line indicates that the time has come to water.
Dr. Carroll suggests setting out a "bunch" of empty tuna-fish cans under sprinklers to check how much water has been received.
During an intermission, I asked Dr. Tom Turner, an associate professor of agronomy and turfgrass extension specialist at the University of Maryland, to explain the differences in types of lime. Lime, as you may know, is used among other things to reduce the acidity of the soil and raise the pH to a more neutral level. The basic constituent of lime is calcium carbonate.
The variations occur through processing. As Dr. Turner explained it, pulverized or agricultural limestone, the cheapest form, is ground the most finely, to a powdery consistency.
Other kinds of lime are burnt lime or quicklime (calcium oxide), which is further refined by heating, and hydrated lime or slaked lime, obtained by mixing quicklime with water. Hydrated and burnt lime are caustic, Dr. Turner warns, and shouldn't be used by homeowners on lawns.
Dolomitic limestone contains calcium carbonates and magnesium carbonates. These elements help to improve soils with such deficiencies. Calcitic limestone incorporates calcium carbonates but not magnesium.