茶园土壤的氮迁移特性

The migration characteristics of soil nitrogen in tea plantations

土壤氮素在降雨条件下淋失到深层土壤甚至进入地下水,不仅导致土壤肥力下降,同时还会造成地下水污染。本研究采用原状土柱室内模拟方法,通过模拟当地强降雨淋滤,研究了西双版纳州大渡岗普洱茶产区5年、20年、33年和56年茶园以及周边森林的0~20 cm和0~40 cm土壤层TN、NO_3^--N、NH_4^+-N和可溶性土壤有机氮(DON)的迁移变化,以及土壤p H变化对氮迁移的影响。结果表明:0~20 cm、0~40 cm土层的茶园土壤,TN迁移通量均随植茶年限的增加而增加(P<0.05),茶园年龄每延长一年,通过20 cm深的土层向下迁移下渗的TN通量将增加235.13 mg·m^(-2),而通过40 cm深的土层TN迁移通量则增加151.24 mg·m^(-2);0~40 cm土层的NO_3^--N迁移通量与茶园植茶年限显著正相关(P<0.05);0~20 cm土层的DON迁移通量与茶园植茶年限显著正相关(P<0.05);而NH_4^+-N迁移量不随植茶年龄变化而变化(P>0.05);茶园40 cm土层内的TN、DON和NH_4^+-N下渗迁移主要发生在0~20 cm,而NO_3^--N的迁移则主要发生在20~40 cm;40 cm土层的茶园土壤氮素以DON损失最多,其次为NO_3^--N,NH_4^+-N损失量最少;未发现茶园土壤p H对氮素迁移变化产生影响(P>0.05)。

Soil nitrogen migrates into deeper soil layer even into groundwater in the conditions of rainfall,which results in not only the degradation of soil fertility,but also the pollution of groundwater. In this study,soil samples of 0-20 cm and 0-40 cm depths were collected from Puer Tea plantations with different cultivation ages of 0（ i.e. forest）,5,20,33,and 56 years old respectively in Dadugang Town,Xishuangbanna. Undisturbed soil columns were used to study the migration characteristics of TN,NO_3^--N,NH_4^＋-N,DON and the influence of soil p H on nitrogen migration by simulating local heavy rainfalls indoors. The results showed that TN migration fluxes increased with the increase of tea planting age in the soil layers of 0- 20 cm and 0- 40 cm（ P〈0.05）. The migration increased by 235.13 mg·m^（-2）through 20 cm soil layer,and 151. 24mg·m^（-2）through 40 cm soil layer for each additional year of tea cultivation. A significant positive correlation between NO_3^--N migration flux and cultivation age of tea plantation was observed in the layer of 20-40 cm（ P〈0.05）,and the same pattern was found between DON migration flux and tea planting age in the layer of 0-20 cm（ P〈0.05）. However,NH_4^＋-N loss fluxes did not change with tea planting age（ P〉0.05）. While the migration of TN,NH_4^＋-N,DON in tea plantations occurred mainly in the layer of 0-20 cm,most of NO_3^--N migration existed in the 20-40 cm layer. The soil nitrogen mainly migrated in the form of DON through 40 cm soil layer,followed by NO3--N,and NH_4^＋-N the least. No evident effects of soil p H on nitrogen migration was observed in our study（ P〉0.05）.