琼南地区稻菜轮作土壤氮素含量的动态变化

Dynamic Changes of the Soil Nitrogen Content in Rice-Vegetable Rotation Area in South Hainan

采用定点取样与实地调研相结合的方法进行多点重复监测,研究了海南琼南地区不同稻菜轮作模式下农田氮素含量的动态变化,客观评价了农业施肥对环境污染的风险.结果表明:稻菜轮作后,土壤表层的全氮、碱解氮含量下降,土壤深层的全氮、碱解氮含量增加;土壤表层和深层的硝态氮含量都增加.0~30 cm土层茄子田的土壤全氮含量最高,豆角田最低;地瓜叶田的土壤碱解氮、铵态氮、硝态氮含量都最高,含量最少的蔬菜田分别是茄子、菜心田、菜心田.150~180 cm的土壤深层,菜心田的土壤全氮含量最高,地瓜叶田最低、小白菜田次之;地瓜叶田的碱解氮的含量最高,茄子田最低;豆角田硝态氮、铵态氮含量最高,菜心田的硝态氮最低、地瓜叶田的铵态氮含量最低.小白菜田在60~90cm土层,土壤硝态氮最高,豆角田在60~90 cm土层土壤铵态氮的含量最高,菜心田在30~60 cm铵态氮的含量最高.地瓜叶对于耕层内土壤氮的吸收能力最强,茄子最弱.蔬菜植株内硝酸盐含量均在限量范围内,地下水的硝态氮含量均达到Ⅲ类水质标准.根据不同轮作模式下土壤氮素的累积现状,优化氮肥施用对于提高作物产量和氮肥利用率具有重要意义.

In the experiment, repeated multipoint monitoring was conducted to investigate the dynamic change of farmland nitrogen content under different rice-vegetable rotation modes in Southern Hainan area with the method combining spot sampling and field research. Meanwhile the environmental pollution risk of agricultural fertilization was objectively evaluated. The results showed that after rice-vegetable rotation, the contents of total nitrogen and effective nitrogen decreased in surface soil while increased in deep soil, and nitrate nitrogen contents in both surface and deep soil increased. For the soil layer within the depth of 0-30 cm, soil total nitrogen content was the highest in eggplant field, the lowest in cowpea field; The contents of effective nitrogen, ammonium nitrogen and nitrate nitrogen were the highest in sweet potato field, the lowest in eggplant field and Chinese flowering cabbage field. For the deep soil layer within the depth of 150-180 cm, soil total nitrogen content was the highest in Chinese flowering cabbage field, the lowest in sweet potato field, and the second lowest in pakchoi field; The effective nitrogen content was the highest in sweet potato field, the lowest in eggplant field; The contents of nitrate nitrogen and ammonium nitrogen were the highest in cowpea field, and the lowest in Chinese flowering cabbage field; And the ammonium nitrogen content was the lowest in sweet potato field. For the soil layer with the depth of 60-90 cm, soil nitrate nitrogen content was the highest in pakchoi field, while soil ammonium nitrogen content was the highest in cowpea field. Chinese flowering cabbage field showed the highest content of ammonium nitrogen in the soil layer within the depth of 30-60 cm. Sweet potato showed the strongest absorption capacity to the soil nitrogen in plough layer, while eggplant showed the weakest absorption capacity. Nitrate contents in all vegetable plants were within the specified amount range, while nitrate nitrogen contents in underground water met Class Ⅲ water quality standard. It is of great significance to improve crop yields and nitrogen fertilizer use efficiency by optimizing nitrogen fertilizer application according to the accumulation conditions of soil nitrogen under different rotation modes.