Nitrification Inhibition by Nitrapyrin and Volatile Sulfur Compounds

Abstract

AbstractNitrification inhibitors can slow the rate of nitrification in soils and reduce nitrogen losses under some soil‐climatic conditions. Carbon disulfide (CS2) and compounds which produce CS2 have slowed nitrification in laboratory studies, but these compounds have not been tested extensively in the field. Therefore, field studies were conducted on irrigated corn (Zea mays L.) in 1978 and 1979 to evaluate inhibition of nitrification by CS2 at 5.6, 11 and 22 kg ha−1, sodium trithiocarbonate (STC) at 11 and 22 kg ha−1, ammonium dithiocarbamate (ADTC) at 11 and 22 kg ha−1, and potassium ethyl xanthate (KEtX) at 5.6 and 11 kg ha−1 as compared to nitrapyrin (2‐chloro‐6‐(trichloromethyl)‐pyridine) at 5.6 kg ha−1. Anhydrous ammonia was knifed 15 to 20 cm deep on 60 cm spacings at rates of 84, 168, and 252 kg N ha−1. All materials were evaluated on a Eudora fine sandy loam (Fluventic Hapludoll, coarse, silty mesic) in 1979 and CS2 and STC were evaluated on the same soil in 1978 and on two additional soils in 1979: a Pratt loamy fine sand (Psammentic Haplustalf, sandy, mixed, mesic) and a Crete silty loam (Pachic Argiustoll, fine, montmorillonitic, mesic). The performance of STC and CS2 in 1978 and 1979 indicated that these materials were not effective in inhibiting nitrification under the conditions that existed at the locations where they were applied. ADTC and KEtX were not effective inhibitors of nitrification, although they were only tested at one location in 1979. Nitrapyrin was effective in inhibiting nitrification in all studies. However, it resulted in an increase in corn yield only once—the fall N application on the Pratt loamy fine sand. The lack of yield response was attributed to the absence of conditions conducive for losses of nitrate nitrogen.