RESPONSE OF SOIL MOISTURE AND PH TO THE TOPICAL APPLICATION OF POWDERED LIMESTONE

Acid deposition has severely affected the soils and waters of the Adirondack region in New York. Atmospheric pollution from industrial areas in the American Midwest causes harmful concentrations of sulfates and nitrates to be released to the atmosphere. Their subsequent precipitation as acids over the northeastern US have caused reductions in the pH of soil and soil moisture, and have led to the reduction of the base cation calcium in soils. The loss of calcium from soils and soil moisture is a concern because of its vital role as both an acid neutralizer and an important nutrient in aquatic and terrestrial life. As calcium levels remain low, the ability of the soils to buffer against acid deposition will only decline.

In order to study the ability of soils to recover from acid deposition in the Adirondacks five research sites were selected in the Town of Webb and have undergone three topical applications of powdered limestone. The limestone addition was intended to increase calcium concentrations and pH in the soils and soil moisture. These sites also have control plots to compare the natural fluctuations of pH and calcium with any observed changes in the experimental plots. The applications of limestone occurred in the fall of 2005, and the spring and fall of 2006 at a rate of 10 metric tones per hectare per application. After the initial addition, there was an increase in soil pH in all five sites followed by a plateau. All shallow soil horizons displayed higher pH levels than deeper horizons. The soil moisture pH increased in the experimental plots for which data exists whereas the pH showed no change for control plots. Soil moisture collection devices showed varying results. Wick lysimeters, which sample mobile water in macropores, have shown higher calcium concentrations in the experimental plots than in the control plots following the first application. Then the experimental plots experienced a gradual decrease in calcium concentrations. This trend occurred again after the second application. Porous cup lysimeters, which sample immobile water in micropores, show an increase in calcium concentration for shallow horizons. These results indicate that calcium does not move passively through the soil zone with mobile water, but instead interacts with solid phases of the soil, probably via cation exchange and/or adsorption.