Interaction of Dwell, a nitrification inhibitor, with nitrogen source, soil properties and plant growth.

Abstract

A greenhouse experiment was conducted to study the effectiveness of Dwell, a nitrification inhibitor, on the efficiency of two fertilizers applied to three Arizona soils, Anthony sandy loam, Laveen loam, and Vinton loamy sand. Tomato plants Lycopersicum esculentum cultivar Row Pak were used as an index plant. These plants were grown in soil columns of 10 cm internal diameter and 50 cm in length, containing 4,500 g of soil. Two fertilizers, urea and ammonium sulfate (AS), were applied at two rates: 112 and 224 kg N/ha. The nitrification inhibitor Dwell was applied also at two rates: 0 and 1.27 kg/ha⁻¹ of active ingredient. The active ingredient in the chemical is 5- ethoxy -3- (trichloromethyl)-1, 2,4- thiadizole. Both fertilizers and Dwell were added to the soils using two methods: (1) uniform mixtures, in which the fertilizer and Dwell were mixed with the top 500 cm³ soil volume in the columns, and (2) banded fertilizers and Dwell, in which a soil paste, made by mixing 10 ml of 0.02% Dwell solution with the volume of 50 cm³ soil, was added to the required amount of the fertilizer to soil column about 7cm below the soil surface. This factorial designed experiment was arranged in a randomized complete block with three replications of each treatment. Plants were allowed to grow for 67 days after transplanting to the soil columns. At the end of the experiment, samples from two depths (0 to 18 cm and 18 5o 40 cm) were analyzed for NH₄, NO₃, and organic N. Dry matter yield and N content of plants were also determined. Results showed that Dwell was effective in improving N efficiency, as determined by yield and N content of plants, with all three soils and with both fertilizers. Higher yields were obtained when AS was used in all soils. Higher response to Dwell, but lower yields, were observed in urea treatments as compared to AS treatments. Dwell resulted in yield increase of 139 and 60% with urea in Vinton and Laveen soils, respectively, while with AS, the increases were 74 and 11%. The lowest response to Dwell occurred with the Anthony soil. Generally, higher yield was obtained when AS was thoroughly mixed and when urea was banded. Yield and N content in plants grown in these soils were in the following order: Laveen > Anthony > Vinton. Dwell was effective with both N rates, particularly with the high N rate of urea. Incubation studies showed that Dwell was effective in retarding nitrification for about 10 days. Accordingly, Dwell seems to have had no residual effect on soil nitrogen.