EFFECTS OF THIOUREA, ETHYL URETHANE AND SOME DITHIOCARBAMATE FUNGICIDES ON NITRIFICATION IN FOX SANDY LOAM

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Abstract
Nitrification in Fox Sandy Loam was studied using the soil percolation technique. The formation of nitrate from ammonium sulphate was inhibited for about 20 days by 1.6 × 10−3moles of thiourea/kgm. of soil, for 8 days by 1.6 × 10−2moles of ethyl urethane/kgm. of soil, for 25 and 17 days by 2.1 × 10−4moles of manzate and zineb/kgm. of soil respectively, and for 28 days by 3.5 × 10−4moles of ferbam/kgm. of soil. Thiourea and ethyl urethane were less effective inhibitors of the nitrification of ammonia added as ammonium carbonate, possibly because of the more alkaline pH in percolates containing this salt. The four dithiocarbamate fungicides caused a lag in nitrification of 150 days when added to percolation units at a concentration of 2.1 × 10−3moles/kgm. of soil.The investigations indicated that treatment of soil with ferbam inhibited the nitrite-oxidizing bacteria as well as the ammonium-oxidizing organisms.