Study On The N₂O Emission From Tea Garden Soils

N2O is a greenhouse gas and participates in the destruction of stratospheric ozone. Soil is the most important source of the N2O. N2O is naturally produced through soil microbial processes mainly by nitrification and denitrification.The major factors influencing emission process of nitrous oxide in soil include soil water content, nitrogen fertilizer application, soil organic matter content and soil pH, etc. Certainly, quantifying the N2O production in the tea garden soil by nitrification and denitrification is essential to understand the nature and law of N2O production. It can provide theoretical basis and technical means for reasonable fertilization in tea garden. It could also reduce environmental pollution and make sustainable development in tea production.Using forest and vegetable soils as the controls, three tea garden soils, namely high, middle and low production tea garden soils ,were collected to study N2O emission under laboratorial incubation conditions. There were two treatments: (I) control soils without addition of any chemicals; (II) N treatment, adding 200mg N in form of (NH4)2SO4 per kg soil. The soils were continuously incubated at 25℃for 14 days. After 0, 1, 3, 7 and 14d incubation, the air in head space of the incubation bottles were collected, respectively, for measuring N2O concentrations. The effects of soil moisture content and N addition on N2O emission were also studed. Using 10% C2H2 to distinguish the contribution of nitrification and denitrification for N2O emission was also conducted. The main results are as follows:1. The high tea production soil in a group with natural soils had the highest mean N2O emission rate during 14 days incubation period. It reached to 11.26 mgN/kg.d, significantly higher than other four soils. However, in the other group with N addition vegetable soil had the highest N2O emission rate, very significantly higher than tea and forest soils. The N2O emission rate in N added soils was higher than in natural soils.2.The N2O emission rate of the soils except low tea production soil, was increase with the increase of soil moisture content. Low tea production soil had the most N2O emission rate at 80% of WHC. For high, middle tea production soils and vegetable soil, there was a significant interaction between soil moisture content and N addition. N addition to high moisture content soils could stimulate the N2O emission.3.The nitrification rate in high production tea garden and forest soils were low, resulting in the N2O emission was mainly due to denitrification. However, the nitrification rate in vegetable soil was high, resulting in the N2O emission was mainly from nitrification.