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A field and laboratory study of nitrite accumulation under arable soil conditions was carried out using a considerable number of nitrogen fertilizers applied at various seasons of the year. The results show that nitrite will accumulate under neutral or alkaline soil conditions provided the rate of fertilization is heavy enough to produce a considerable concentration of the ammonium ion. Under field conditions, especially where the soils are not warm enough for rapid biological activity, the nitrite produced may persist for several months. For example, nitrite accumulating from urea applied in January (43 ppm N as NO2) persisted into May (31 ppm N). Amounts of nitrite up to 90 ppm N were produced under favorable conditions. More nitrite was produced from urea than any other nitrogen fertilizer. This is considered due to the high ammonia and pH conditions resulting from application of this material. In none of the field studies was there any evidence of nitrite accumulation from denitrification though occasionally heavy fertilization with nitrate fertilizer supplemented with straw was immediately followed by heavy rains or irrigation. From these studies, it appears that wherever two conditions occur, namely, fairly high ammonium concentrations and neutral or alkaline soil conditions, more or less nitrite accumulation may be expected.

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