Nitrogen Losses During Nitrification in Solutions and in Acid Sandy Soils

Abstract

Soil nitrogen balances involving lysimeter experiments and cropped and uncropped pot experiments have shown that in many cases such important nitrogen deficits were observed that there must be hitherto unknown or unsuspected pathways along which nitrogen escapes. In former experiments of the senior author it was shown that in acid soils, dressed with ammonium sulphate, nitrogen can be lost as N—O compounds during nitrification. In the present investigation more accurate determinations made it clear that when the pH of a liquid culture of nitrifying bacteria dropped below about 5.5 nitrogen was not only lost as N—O compounds, but to a greater extent as nitrogen gas, most probably by chemical reaction between the HNO2 formed during nitrification and the ammonia present in the solution. In pot experiments with acid sandy soils from different parts of the Netherlands, losses of up to 74% of the ammonium sulphate added were observed. An investigation was made of the conditions which promote or are essential for these losses. When the initial pH of the culture medium, be it a solution or soil, enables the nitrifying bacteria to develop and the buffer capacity is of such a magnitude that the pH drops below 5.5 during nitrification, volatilization is to be expected. As volatilization and ammonification often coincided, both processes seem to be linked in some way or another; volatilization, however, has also been observed in the absence of ammonification. These losses are not caused by evaporation of ammonia, in which case they should increase as the pH increases; the contrary happens, however, and the losses stop entirely when sufficient CaCO3 is added to keep the pH above 5.5. They are also not due to denitrification, as they do not occur when nitrogen is added as nitrate instead of ammonium sulphate. Also there are no losses when the soil is pasteurized, which proves that they originate in bacteriological processes.

Nitrite Instability in Three Manitoba Soils

“…These data suggested that chemical factors were affecting nitrite loss. The present investigation is a continuation of this study aimed at evaluating the extent to which nitrite is unstable in Lakeland (pH 8.0), Wellwood (pH 7.1) and Holland (pH 6.2) soils under conditions of minimum biological activity. Some factors that appezrr to be involved in nitrite instability are also reported and discussed.…”

Nitrate-bromide movement analysis under saturated field condition

“…Decomposition of NO^H at low pH value Gerretsen and Hoop (1957) Gaseous loss of nitrogen has been reported by many workers in the fields and laboratories. Meek et al (1969) increased the water content of a soil having a water saturation percentage of percent tô…”

Chemical transformations of nitrite in soils

“…Several investigators (Temple, 1914;Robinson, 1923;Madhok and Uddin, 1946;Gerretsen and de Hoop, 1957;Reuss and Smith, 1965) have reported detection of nitrogen dioxide as a product of nitrite decomposition in acidic soils, but Smith and Clark (1960) and Tyler and Broadbent (1960) were unable to detect nitrogen dioxide by gas chromatographic or mass spectrometric analysis of aerobic atmospheres above acidic soils treated with nitrite. Reuss and Smith (1965) have suggested that the failure of Smith and Clark (1960) and Tyler and Broadbent (1960) to detect NO2 could be due to use of experi mental systems that promoted absorption of this gas by moist soil.…”

“…Nitrite is reasonable stable in solutions having pH values greater than 5.5 (Allison and Doetsch, 1951; Gerretsen and de Hoop, 1957), but the nitrous acid formed in more acidic so lutions decomposes to yield nitric oxide. This decomposition reaction is usually represented as follows: 3HN02 = 2N0 + HNO3 + H2O…”

“…Interest in ammonium nitrite decomposition as a mechanism of N loss from soils was stimulated by Gerretsen and de Hoop (1957). They claimed that substantial amounts of N2 were evolved from slightly acidic buffer solutions containing nitrite and ammonium ions and that considerable loss of N as N2 occurred during nitrification of ammonium sulfate in acidic, sandy soils; and they concluded that N2 formation in these studies resulted from decomposition of ammonium nitrite.…”