茶园土壤NO_3^--N含量与净硝化速率的研究

NO_3^--N Concentration and Net Nitrification Rate in Tea Soils

调查采集了我国130个茶园的土壤,用0.5 mol/L的K2SO4提取法和实验室恒温培养法分别测定了土壤NO3--N含量和净硝化速率。结果表明,茶园土壤NO3--N含量在0～286.8 mg/kg之间,平均为41.7 mg/kg,40.8%的土样低于20 mg/kg;土壤NO3--N浓度的高低主要取决于施氮量,与土壤净硝化速率相关性不显著,与pH呈二次方程关系:Y=738.0-289.9X+28.8X2(r2=0.2033,P<0.001)。土壤净硝化速率在-6.08～6.54 mg/kg.d之间,平均为1.62 mg/kg.d,变异系数高达119%;其中,10%的土壤净硝化速率低于零,表明这些土壤处于氮固定化状态中;土壤净硝化速率与施氮量呈显著正相关,与pH呈反函数方程关系:Y=10.14-33.96/X(r2=0.253,P<0.001)。文章对茶园土壤中NO3-积累、硝化作用与pH的关系等进行了讨论。

An investigation of NO3——N concentration and net nitrification rate in 130 tea soil samples was conducted.The net nitrification rate was measured by laboratory incubation method.The results showed that the NO3——N concentration ranged from 0 to 286.8 mg/kg with a mean of 41.7 mg/kg.Among all the samples,40.8% of the soils were less than 20 mg/kg in NO3——N concentration.Soil NO3——N concentration had a significant relationship with N application rate,but no obvious relation with soil net nitrification rate.A quadratic equation Y=738.0-289.9X＋28.8X2（r2=0.2033,P0.001） was established between NO3——N concentration（Y） and pH（X）.Soil net nitrification rate ranged from-6.08 to 6.54 with a mean of 1.62 mg/kg？d,and coefficient of variation（CV） was as high as 119%.10% of the soil samples were below 0 in net nitrification rate,indicating net immobilization of nitrate happened in these soils.Net nitrification rate was positively and significantly related with N application rate.And an inverse function Y=10.14-33.96/X（r2=0.253,P0.001）was found between net nitrification rate（Y） and soil pH（X）.Why nitrate accumulated in tea soils and relationship between nitrification and pH was discussed.