Adding compost to your garden soils is a great way to improve water retention and drainage and add nutrients. Making your own compost is the best way to produce large quantities at home, however, an uncovered compost pile can leach nutrients, especially nitrogen and phosphorus, creating pollution runoff.
Research from the Rodale Institute in Emmaus, Pennsylvania, has shown that adding amendments such as clay and gypsum to your compost pile can reduce this leaching and help retain nutrients.
Researchers built three 20-cubic-yard compost piles: one containing only manure; one containing manure and leaves; and one containing manure, leaves, clay, gypsum, and humic acid. They then monitored the nutrient loss after heavy rains. The manure-only pile lost 18 pounds of ammonium nitrogen and 74 pounds of phosphorus. The leaf and manure compost pile lost 18 ounces of nitrogen and 3 pounds of phosphorus. The pile with amendments lost 19 ounces of nitrogen and only 1.9 pounds of phosphorus. Thus, amending the compost resulted in a 90 percent reduction in nitrogen runoff and a 75 percent reduction in phosphorus runoff compared to the manure-only pile. Also, the amended compost piles matured three months sooner than the other piles.
The amended piles consisted of 14 cubic yards of leaves, 4 cubic yards of manure, 2 cubic yards of clay, 110 pounds of humic acid (leonardite coal dust), and 90 pounds of gypsum. Home gardeners can use similar ratios of the materials to make their own smaller piles.
For more information about this research, go to: Rodale Institute .