Deposition and Transformation of Nitrogen By the Pre-Plant Soil Fumigant Ethanedinitrile.

Ethanedinitrile (EDN) is being examined as a pre-plant soil fumigant for use in high-value vegetable crops. The degradation products of EDN are ammonium (NH⁴⁺), NH³, CO², and HCO^2-. It is currently unknown at what quantities these degradation products are being released into the soil at a given rate of EDN. Two experiments were conducted at the North Florida Research and Education Center in Quincy, Florida. Treatments consisted of 300, 400, and 500 lb/ac EDN applied via two mole shanks 10 inches below the soil surface and immediately covered with totally impermeable film mulch. Two 18-inch soil samples were taken in each experimental plot at 0, 1, 2, and 3 weeks after fumigation (WAF) to determine the deposition of nitrogen at each rate. These samples were separated by the top, middle, and bottom 6 inches and analyzed for soil pH, NH⁴⁺, nitrate (NO^3-), and total kjeldahl nitrogen (TKN). Following the initial 4 weeks of sampling, data was collected to determine the transformation of ammonium to nitrate for an additional 6 weeks for the 400 lb/ac EDN treatment. Two 12-inch soil samples were collected each week with the top and bottom 6 inches being separated and analyzed. Results from these experiments revealed significant increase of pH, TKN, and NH⁴⁺ in the top 6 inches of soil following fumigation with EDN. NH⁴⁺ and pH began to decrease 7 WAF, whereas TKN decreased sharply at 6 and 4 WAF in the spring and fall, respectively. Ammonium deposition was inconsistent between spring and fall seasons but was 120 lb/ac during the spring. It remains unclear how much nitrogen will be deposited after EDN application, but it is clear that if adopted, pre-plant nitrogen fertilization practices will need to be adjusted.