五川流域农业土壤反硝化作用测定及其调控措施

Denitrification Determination in soil of Wu Chuan Agricultural Catchment and the Control Measure

反硝化作用是土壤氮素转化的一个重要过程,为探明五川流域内的农业土壤的反硝化作用强度及其影响因素,利用乙炔抑制-原状土柱培养法对其进行测定。通过3次试验测定,发现五川流域农业土壤具有较强的反硝化作用强度,在种植季节,土壤平均反硝化作用强度为0.1kgN·hm-2·d-1,最高达到0.6kgN·hm-2·d-1,其中蔬菜地反硝化作用强于其他土地利用类型。反硝化作用同土壤的NO3-含量、含水量、温度以及pH都存在正相关关系,它们是流域土壤反硝化作用的主要影响因子。五川流域农业土壤经由反硝化作用氮损失量占流域平均施肥量的16%,高于国内其他地区。针对五川流域的环境和农业经济特点,提出了控制反硝化作用的措施:在温度较低的夜间进行施肥灌溉宜以防止氮肥损失,用农村富余的厩肥代替化肥以减轻反硝化作用的发生,同时加大节水灌溉力度。

Denitrification in soil is the main pathway of gaseous nitrogen loss in the catchments. In order to find out the denitrification flux in top-soil and the affecting factors in Wu Chuan catchment, the denitrification rate of top-soil was determined using the acetylene inhibitionintact soil core technique for 5 months. Three times of the denitrification experiment were carried out from Dec.15th 2005 to Apr.18th 2006, at the same time, the chemical and physical properties of the soils were also measured during every experiment. The soils in Wu Chuan catchment belong to typical Haplic red soil, with the chemical and physical properties suitable for denitrification and the organic matter, total N, NO3-N and pH of the soils being 9-25 g·kg^-1, 0.4%-7.9%, 1.5-6.8 g·kg^-1 and 4.9-5.7, respectively. The results indicated that denitrification of the soil showed temporal and spatial variations. The denitrification rate in uplands of the catchment was higher than that in any other places, and was enhanced when there were many rains and when the soil temperature was high. The flux of denitrification was mostly related with fertilization, soil moisture, air temperature and pH. Air temperature affected denitrification significantly. The gaseous N loss rate through denitrification represented about 16% of the fertilizer applied in the catchment scale. Also, the denitrification flux of the top-soil in Wu Chuan catchment was much higher than that in other places of China, and the denitrification rate of soils in south was higher than that in north. The soils in Wu Chuan catchment may be the source of atmospheric nitrous oxide gas. Since the high level of agricultural economic development in Wu Chuan catchment and the frequently used fertilizers, the flux of fertilizers is much higher than other agricultural region in China. Based on the environmental characteristics and agricultural economy in Wu Chuan catchment, the following control measures should be adopted： （1） fertilization and irrigation in the low-temperature night to prevent fertilizer loss; （2） utilization of livestock waste instead of fertilizer to inhibit denitrification; （3） popularizing economical irrigation to avoid reductive situation in the soil.