地表管理与施肥方式对太湖流域旱地氮素流失的影响

Effect of Surface Management and Fertilization Mode on Nitrogen Runoff from Upland in Taihu Lake Region

太湖富营养化日益严重,其中农业非点源氮污染对太湖富营养化有着相当大的贡献,探明该地区农田土壤氮素随地表径流向水体迁移的形态与通量对水体富营养化治理具有重要的现实意义。采用田间试验方法,研究了太湖流域旱地氮素随地表径流排放特征。结果表明,常规管理下典型旱地氮向水体迁移的年负荷为12.66kg·hm-2左右,约占年施肥量的5.63%,其中硝态氮和颗粒态氮是径流损失的主要形式,分别约占总流失量的48.74%和38%左右。随着降雨的进行,NO-3-N浓度逐渐增大,而NH+4-N浓度逐渐降低,氮向水体迁移具有明显的季节特征,夏季和秋季为氮高负荷季节,6～11月占全年氮输出总量的83.4%。地表覆盖和氮肥深施均能有效地降低氮流失量,其中地表覆膜、秸秆覆盖、肥料条施及穴施分别可降低60.3%、59.8%、50.1%、52.4%的氮流失。

Nitrogen released from farmland is one of the major factors resulting in eutrophication of Taihu Lake. Understanding fluxes and chemical forms of nitrogen in surface runoff is important to control eutrophication of water body. The characteristics and the components of surface runoff from upland in the Taihu region were investigated and analyzed. By building up a pilot-plant and the experiment of natural rainfall, the effect of different surface managements and fertilizing modes on controlling the pollution of nitrogen from surface runoff was researched. The results showed that about 12.66 kg · hm^-2 of total nitrogen discharged from surface runoff into water body under the conventional management, which accounted for 5.63% of annual fertilizer N input. Nitrate-N and particle nitrogen are the main forms of N loss, which accounted for 48.73% and 38% of total nitrogen, respectively. With the rainfall processing, the concentration of nitrate-N rose gradually, but ammonium-N declined. The loss showed obviously seasonal characteristics, with the high loading in summer and autumn, accounting for 83.35% of total loads in the period of Jun-Nov. Surface coverage and deep placement of fertilizer can effectively lower the risk of nitrogen discharged into water body. Film coverage, straw coverage, drill and deep application of fertilizers can lower about 60.3%, 59.8%, 50.1% and 52.4% of nitrogen loss, respectively.