Studies On Soil Soluble Organic Nitrogen And Its Key Influencing Factors In Tea Plantations

Soil soluble organic nitrogen (SON) plays a vital role in ecosystem N cycling processes and is controlled by a number of biotic and abiotic factors. This study examined the subtropical tea ecosystems with the same soil parent material and soil type of two different genotypes-Oolong tea(huangdan) and Green tea(fuyun6) in Fujian.Using H₂O(room temperature),H₂O(70℃)and KCl(2mol/l)extraction-high catalytic oxidation method to carry out the soluble organic nitrogen concentrations and its infuencing factors at the 0-15cm and 15-30cm layers in tea plantations-establish at diffierent slope positions. In order to reveal the characteristics of soil soluble organic nitrogen and its key influencing fators in tea plantations of different genotypes. The main results show as follows:1. Concentrations of Soil SON under tea plantations of different genotypes in H₂O (room temperature), H₂O (70℃) and KCl (2mol/L) extracts both at the 0-15cm and the 15-30cm layer showed KCl2 mol/L > H₂O (70℃) >H₂O.The differences about concentrations of SON among different tea plantations beteeen the different extraction efficiencies were significant or highly significant difference.2. Concentrations of Soil SON under tea plantations of different genotypes in different extraction efficiencies show some of the differences. Concentrations of Soil SON under tea plantations of different genotypes in different extraction efficiencies at the 0-15cm soil layer respectively were higher than the 15-30cm soil layer. Huangdan plantation soil SON concentrations in H₂O (room temperature), H₂O (70℃) and KCl (2mol/L) extracts under 0-15cm layer were respectively higher 9.62%,17.93% and 11.64% than 15-30cm layer,at the same time,showed the significant or highly significant vertical differences. Fuyun6 plantation soil SON concentrations in H₂O (room temperature), H₂O (70℃) and KCl (2mol/L) extracts under 0-15cm layer were respectively higher 36.57%,46.23% and 25.54% than 15-30cm layer,at the same time,showed the significant or highly significant vertical differences.3. Concentrations of soil SON under the huangdan plantation in H₂O (room temperature) and H₂O (70℃) extracts were significantly higher in the lower slope than in the upper slope and middle slope at the 0-15cm depth,which were respectively higher 43.16%,12.94% and 29.98%,7.87%.while the concentrations of soil SON in KCl (2mol/L) extracts in the middle slope were respectively higher 26.64% and 0.4% than the upper slope and middle slope. Concentrations of soil SON under the fuyun6 plantation at the 0-15cm depth were different from the huangdan plantation. Concentrations of soil SON under the fuyun6 plantation in H₂O (room temperature), H₂O (70℃)and KCl(2mol/L) extracts were significantly higher in the middle slope than in the upper slope and lower slope at the 0-15cm depth. The differences in concentrations of SON beteeen the middle slope and upper slope were highly significant difference,while the differences beteeen the middle slope and lower were no significant difference. Concentrations of soil SON in H₂O (room temperature), H₂O (70℃)and KCl(2mol/L) extracts across different slope positions and the tea plantations at 0-15cm depth were similar to the 15-30cm depth.4. Concentrations of Soil SON in H₂O (70℃) extracts under huangdan plantation ranged from 23.63-27.75mg/kg, significantly higher 17.44% than in the fuyun6 plantation,at the same time, showed the significant differences. Concentrations of Soil SON in KCl(2mol/L) and H₂O (70℃)extracts were similar. Concentrations of Soil SON in KCl(2mol/L) extracts under huangdan plantation ranged from 45.42-49.00mg/kg, which were higher 7.88% than in the fuyun6 plantation,at the same time, showed the significant differences.5. Based on the grey system theory,the result showed that we could divide the influencing factors into two groups:the first group was the key factors which including soil protease activity,organic C,soil microbial biomass,asparaginase activity and total N. The correlation coefficients they had all higher than 0.750. Although the familiar degree was different between SON and the five influencing factors ,they were the key factors of affecting SON under tea plantantion.The second group was the normal factors which including clay(%),silt(%) , sand(%) and pH.The correlation coefficients of this group were all lower than 0.734, and sand(%) had the lowest correlation coefficients which was 0.623.