Soil acidification of alfisols influenced by nitrate and ammonium nitrogen level in tea plantation

Nitrogen is an important fertilizer in tea production, but it is also an important factor in tea garden soil acidification. The relationship between absorption and transport of different forms of nitrogen in the tea plant and soil acidification is still unknown. In order to explore the different characteristics of absorption, utilization and distribution of nitrogen, stable isotope 15N tracer technique was used to measure the absorption, utilization and allocation of nitrate nitrogen (NO3-15N) and ammonium nitrogen (NH4-15N) under the same nitrogen application amount of tea tree seedlings as experimental materials. The results showed that the tea seedlings had the same pattern of nitrogen application: tissue nitrogen content increased after fertilization, remarkable rising at 7 d and the absorption speed increased quickly after 28 d, finally reached its maximum at 56 d. The nitrogen use efficiency of two nitrogen sources in two kinds of soil varied not significantly. The maximum NUE of NO3-15N reached 12.66%, and at the same time NH4-15N utilization rose up to 11.54%. According to the absorption of soil nitrogen and nitrogen fertilizer in the two kinds of soil, it is concluded that the soil nitrogen cannot meet the growth needs of tea tree and extra nitrogen supply was required. The declined soil pH indicated that fertilizer should be used in moderation, which can not only satisfy the growth of tea tree but also to restrict soil acidification.