Nitrapyrin and Etradiazole Effects on Nitrification and Grain Sorghum Production 1

Nitrification inhibitors offer the potential to improve efficiency of N applications when climatic and soil conditions are favorable for leaching and/or denitrification. Grain sorghum [ Sorghum bicolor (L.) Moench] was grown in five field experiments at three locations during 1976, 1977, 1978, and 1979, with two nitrification inhibitors and three N sources. Four of these five experiments received supplemental irrigation water. Soil textures at experimental locations were sandy, silt, and clay loams and pH's ranged from 5.2 to 7.8. Nitrification inhibitors evaluated were nitrapyrin and etradiazole. Sources of N were anhydrous ammonia and urea in 1976, urea and urea‐ammonium‐nitrate (UAN) solution in 1977, and UAN hi 1978 and 1979. Treatments consisted of 0.56 kg/ ha of nitrapyrin and multiple rates of etradiazole applied with varying rates of N. Soil samples were taken from selected experiments at varying time intervals and analyzed for urea‐, NH 4 +− , NO 3 − , and/or NO 3 − ‐N depending on the year and experiment. Field plots were harvested with a conventional combine and yields were analyzed statistically to assess beneficial effects of treatments. Soil N forms were altered by nitrification inhibitors at various tune intervals during the growing seasons. However, the changes observed did not lead to increased efficiency of applied N or to an increase in yield of grain sorghum. It was concluded that little if any benefit can be derived from nitrification inhibitors in grain sorghum production in Oklahoma.