Effects of difference in fertilization treatments on nitrification activity in tea soils

Abstract

It is generally recognized that the nitrification activity in acid soils is very low. Indeed, nitrification in mineral soils has been found to be negligible at pH values below 5.0 (Dancer et al. 1973; Nyborg and Hoyt 1978). However, it was reported that autotrophic nitrification occurred in some tea soils at pH levels far below 5.0 (Walker and Wickramasinghe 1979; Hayatsu and Kosuge 1993). An acidophilic ammonia-oxidizing bacterium has been recently isolated from strongly acidic tea soils in Japan (Hayatsu 1993). On the other hand, fertilization has-been considered to be an important factor influencing nitrification in agricultural soils. For example, several studies have shown that the addition of ammoniacal fertilizer to soils can lead to the increase of the populations of Nitrosomonas (McLaren 1971; Ardakani et al. 1974). Liming of acidic soils also tends to stimulate the nitrification activity (Dancer et al. 1973; Nyborg and Hoyt 1978). Although nitrification has been studied in a wide variety of agricultural soils, there is little information available on nitrification in tea soils. The effect of fertilization on nitrification in tea soils is poorly documented.