不同植物轮作提取深层土壤累积硝态氮的效果

Mining the Accumulated Nitrate from Deep Soil Layers by Rotation with Different Crops

【目的】利用不同植物轮作,通过生物修复耗竭深层土壤剖面的累积硝态氮,从而控制集约化粮田过量施氮造成的硝酸盐淋洗。【方法】通过田间试验,比较小麦-玉米轮作、休闲-玉米、小麦-休闲、紫花苜蓿连作、紫花苜蓿+苇状羊茅间作、黑麦-苋菜轮作、黑麦-高丹草轮作、黑麦-甜高粱轮作对土壤剖面硝态氮累积和淋洗的降低效果。【结果】紫花苜蓿、高丹草、黑麦1—2 m土体根系占0-2 m土体总根系的比例最高;黑麦-苋菜、黑麦-高丹草和黑麦-甜高粱处理具有较高的年吸氮量(330-390 kgN·hm-2);与小麦-玉米传统轮作相比,夏季休闲增加了土壤硝态氮淋洗。经过1年的田间试验,5个修复植物处理0—1 m、1—2 m的硝态氮累积量分别降低124.3和81.2 kgN·hm-2,其中苋菜、甜高粱、高丹草对深层土壤中硝态氮的消减作用较大;甜高粱、高丹草、苋菜种植下1 m处土壤溶液中硝态氮浓度一直处于最低水平,平均仅8.6 mg·L-1。【结论】在本试验条件下,黑麦-高丹草轮作是一年内提取深层土壤累积硝态氮效果最好的种植模式。

[ Objective ] This study aimed to use plants in cropping systems for bioremediation, depleting nitrate nitrogen in deep soil profile to control nitrate leaching caused by excessive nitrogen fertilizer application. [Method] Different treatments were designed in a plot experiment, including conventional wheat-maize rotation system, fallow-summer maize system, winter wheat-fallow system, rye-amaranth rotation system, rye-sorghum hybrid sudan grass rotation system, rye-sweet sorghum rotation system, alfalfa continuous cropping and alfalfa＋fescue inlercropping. The effects of each cropping system on the decrease of accumulation and leaching of soil nitrate nitrogen was analyzed. [Result] The results show that alfalfa, sorghum hybrid sudan grass and rye had the highest percentage of roots in 1-2 m soil profile. Annual plant N uptake under rye-amaranth, rye-sorghum hybrid sudan grass and rye-sweet sorghum treatments were the highest, about 300-390 kgN.hm-2. Fallow in summer season increased nitrate leaching from 0-1 m soil profile. After the first year＇s remediation, all the five treatments significantly reduced nitrate accumulation in 0-1 m and 0-2 m soil profile, decresed 124.3 kgN.hm^-2 and 81.2 kgN.hm^-2 respectively. Sorghum hybrid sudan grass, sweet sorghum and amaranth were more effective in decreasing nitrate nitrogen accumulation in deep soil layers. Nitrate concentration in soil solution under rye-sweet sorghum, rye-sorghum hybrid sudan grass and rye-amaranth systems was in the lowest level, averaged only 8.6 mg·L^-1 [Conclusion] According to the first year＇s results, rye-sorghum was the best cropping system to decrease the accumulated nitrate in deep soil layers and further control nitrate pollution.