【作者】 赵长盛；

【导师】 胡承孝；

【作者基本信息】 华中农业大学 ， 植物营养学， 2009， 博士

【摘要】 农业生态系统中氮素的淋失是地下水硝态氮污染的主要来源之一,近十几年来受到国内外研究者的广泛关注。本文在总结国内外土壤中氮素转化和淋失的研究基础上,建立大型原状土柱,通过原状土柱试验、室内试验和大田试验,以武汉城郊典型菜地土壤黄棕壤和潮土为研究对象,以小白菜、辣椒、苋菜、菠菜、萝卜为供试蔬菜。深入探讨了氮肥施用对武汉城郊菜地土壤氮素转化和淋失的影响,揭示氮素转化和淋失规律,总结提出了武汉城郊菜地控制地下水硝态氮污染的原则和对策,为蔬菜的可持续生产和地下水硝态氮污染提供了科学依据。主要研究结果如下:1.利用大型原状土柱系统（黄棕壤）研究了武汉城郊菜地系统硝态氮淋失规律。结果表明:氮肥的大量施用显著增加了菜地土壤中硝态氮的淋失风险,是造成地下水硝态氮污染的主要原因之一。硝态氮平均淋失浓度（Y mg N/L）与氮肥施用量（x kgN/ha）（两年）符合二次相关:Y=9E-06x²+0.0014x+3.51（R²=0.99,P＜0.001）。即年施氮量为395.89kg N/ha和646.78kg N/ha时,达到国家饮用水控制标准10mg N/L和地下水源控制标准20mg N/L。降水是引起硝态氮淋失的主要原因,硝态氮淋失主要发生在降水较多的春夏两季,硝态氮淋失浓度高峰主要出现在秋冬季。氮肥施用量增加的同时增加了钙镁离子淋失量,硝态氮淋失量与钙镁淋失量之和呈极显著正相关关系。2.利用小型原状土柱试验对比了武汉城郊主要菜地土壤类型黄棕壤和潮土的硝态氮淋失规律。结果表明:在相同氮肥用量下,黄棕壤硝态氮淋失量要高于潮土,但潮土淋失浓度要高于黄棕壤。黄棕壤和潮土硝态氮淋失浓度（Y₁）和（Y₂）与氮肥施用量（x）（两年）符合二次相关:Y₁=5E-06x²+0.0044x+3.549（R²=0.981 P＜0.0001）;Y₂=4E-06x²+0.0062x+4.412（R²=0.980 P＜0.0001）。黄棕壤年氮肥施用量为393.13kgN/ha和722.22kg N/ha时,潮土年氮肥施用量为320.69kg N/ha和680.18kg N/ha时达到国家饮用水和地下水源硝态氮控制标准10mg N/L和20mg N/L。与大土柱相比,小土柱在低施氮量下模拟硝态氮淋失状况较好。3.以大田试验为主结合原状土柱试验,研究氮肥施用对蔬菜产量和硝酸盐含量的影响。随着氮肥施用量的增加,蔬菜产量先增加后降低,二者之间呈现显著二次相关。蔬菜硝酸盐含量随氮素施用量的增加而迅速增加,二者呈显著正相关关系,试验期间不同蔬菜硝酸盐含量顺序为:小白菜＞菠菜和萝卜＞辣椒,降低氮肥的施用量是减少蔬菜硝酸盐含量最主要的方法。在综合考虑蔬菜产量及硝酸盐含量的基瓷?不同蔬菜作物最佳施氮量范围为,秋季小白菜180kg N/ha-270kg N/ha,冬季菠菜40kg N/ha-80kg N/ha,春夏季早辣椒150kg N/ha-300kg N/ha,秋萝卜120kgN/ha-180kg N/ha。在相同状况下潮土蔬菜产量高于黄棕壤。4.在大型原状土柱上采用¹⁵N同位素和Br^-示踪方法,研究菜地氮肥施用对氮素的利用率及硝态氮淋失的影响。武汉城郊菜地土壤氮肥的施用主要以满足当季作物需要为主,后季作物对氮素的利用率低,当季作物氮素的利用率平均为3.82%,后季作物对氮素利用率总和仅为4.72%。结果还明表,当季蔬菜作物施用的氮肥对硝态氮淋失贡献较小,硝态氮的淋失主要发生在后续作物中。利用Br^-示踪表明,当水分淋失量为土壤田间持水量的2.22倍时,溴离子淋失完全。5.利用小型原状土柱与室内试验相结合研究黄棕壤和潮土的矿化规律。黄棕壤和潮土的净矿化速率随温度的升高而增加,在相同的温湿状况下潮土的矿化量要明显高于黄棕壤。黄棕壤和潮土的矿化势分别为74.63mg N/kg和123.45mg N/kg,分别占土壤全氮量的26.25%和24.21%。小土柱研究表明,春夏季土壤的矿化量与矿化速率要远高于秋冬季,试验期间黄棕壤和潮土矿化速率,春夏季为0.13mg N/kg/d和0.18mg N/kg/d,秋冬季二者相同均为0.02mg N/kg/d,试验后期秋冬季节土壤出现明显的氮素固持现象。6.研究武汉城郊菜地系统氮素的干湿沉降。试验表明通过降雨降尘输入的无机氮总量平均为29.58kg N/ha yr,湿沉降是大气氮素沉降的主要组成部分,约占总无机氮素沉降量的81.05%。春夏季氮素沉降通量要高于秋冬季节,铵态氮沉降量要高于硝态氮。试验期间降水pH值平均为4.47±0.59。7.提出了武汉城郊菜地减少硝态氮淋失策略。（1）减少氮肥施用量,黄棕壤年氮肥施用量不得超过722.22kg N/ha,潮土不得超过680.18kg N/ha;（2）减少秋冬季氮肥的施用量,并在越冬前种植蔬菜或闲填作物;（3）将深根系蔬菜与浅根系蔬菜轮作,种植生长期长的蔬菜作物并减少耕作次数:（4）在主要降雨季节减少灌溉量与灌溉次数,推广节水灌溉措施:（5）根据不同蔬菜的需肥规律及土壤状况推广蔬菜测土配方施肥,提高氮肥的利用率;（6）施用硝化作用抑制剂。8.利用PVC材料结合凡士林填充建设的原状土柱,完全能够满足研究农业生态系统中氮素的转化和淋失研究需要。更多还原

【Abstract】 Nitrate leaching from ago-ecosystem is an important contributor of nitrate contamination of water resources,which has been extensively concerned by researchers of home and abroad for the recent decade.Based on the research of soil nitrogen transformation and nitrate leaching,we built large undisturbed soil columns and combined with the indoor cultivation and field trial to research the nitrogen and nitrate leaching of the Wuhan surbub vegetable soil.The test soils were two typical soil types （yellow-soil and fluvo-aquic soil） from Wuhan surbub,and vegetables of capsicum （Capsicum annuum L.）,amaranth（Amaranthus mangostanus L.）,radish（Raphanus sativus L.）,spinach（Spinacia oleracea L.） and Chinese cabbage（Brassica Chinensis L.） were planted seasonly.The study reveals the nitrogen transformation and nitrate leaching law,sums up principles and measure of controlling nitrate groundwater pollution in Wuhan surbub,and provides a scientific base for the sustainable production of vegetables and control of nitrate groundwater pollution.The main results are as followed.1.The study of vegetable soil nitrate leaching in Wuhan surbub by large undisturbed soil core lysimeters（yellow-brown soil） revealed that much application of nitrogen significantly increased nitrate leaching risk and it was the main reason of nitrate groundwater pollution.The equation between the average nitrate concentration（Y mg N/L） and nitrogen application（x kg N/ha）（two years） were:Y=9E-06x²+0.0014x+3.51 （R²=0.99,P＜0.001）.That is,when nitrogen application amount are 395.89 kg N/ha/yr and 646.78 kg N/ha/yr,the nitrate concentration reach to the drinking water control 10 mg N/L and groundwater control 20 mg N/L.Rainfall was the main reason for nitrate leaching,and nitrate leaching occurs mainly in spring and summer while the peak nitrate-N occurs mainly in autumn and winter.Nitrogen application increased the amount of calcium and magnesium leaching,and there is significant positive correlation between nitrate leaching and the leaching of calcium and magnesium2.The comparison of nitrate leaching law of yellow-brown soil and Fluvo-aquic soil by small undisturbed soil core lysimeters shows that the yellow-brown soil nitrate leaching loss was higher than fluvo-aquic under the condition of the same amount of nitrogen application while the nitrate concentration was higher than yellow-brown soil. The equation between the nitrate concentrations yellow-brown soil（Y₁） and Fluvo-aquic （Y₂） and nitrogen application（x） are:Y1=5E-06x²+0.0044x+3.55（R²=0.98 P＜0.0001）Y²=4E-06x²+0.0062x+4.41（R²=0.98 P＜0.0001）When the yellow-brown soil nitrogen application rate are 393.13 kg N/ha/yr and 722.22 kg N/ha/yr,and Fluvo-aquic soil 320.69 kg N/ha/yr and 680.18 kg N/ha/yr,the leachate nitrate concentration reach to the drinking water control 10 mg N/L and groundwater control 20 mg N/L.The small undisturbed soil core lysimeters simulates nitrate leaching better than the large one under the low nitrogen application.3.This paper studied the effect of nitrogen application on yield and nitrate content of vegetables by the combination of field and undisturbed soil trial.With the increase of the nitrogen application,the vegetable yield increased firstly,then decreased.They are significant positive correlation.The vegetable nitrate content increased with the nitrogen application and there is significant positive correlation between them.The vegetable nitrate content during the trail period is Chinese cabbage＞spinach and capsicum＞radish. The decrease of nitrogen application is the main method of reducing nitrate content of vegetables.Considering the yield and nitrate content of vegetables,we suggest that the optimum nitrogen application are 180 kg N/ha-270 kg N/ha,40 kg N/ha-80 kg N/ha,150 kg N/ha-300 and 120 kg N/ha-180 kg N/ha for autumn Chinese cabbage,winter spinach, spring and summer capsicum and autumn radish,respectively.The yield of vegetable in fluvo-aquic soil is higher than in yellow-brown soil on the same condition.4.The paper studied the effect of nitrogen application on vegetable soil nitrate leaching and vegetable nitrogen use efficiency in large undisturbed soil column using ¹⁵N and Br^- tracer.The result shows that nitrogen application was mainly used for the season vegetable,and was less absorbed by the post-seasons vegetable.The season vegetable average nitrogen use efficiency was 31.82%,and the post-seasons vegetable was only 4.72%.Besides,nitrogen application on the season vegetable contributes little to the nitrate leaching,which mainly occurs on the post-seasons vegetable.The use of Br^-showed that the Br^- leach completely when the leachate was 2.22 times than the field water capacity.5.The paper combined the small undisturbed soil column with field trials,the yellow-brown and fluvo-aquic soil mineralization law was studied.The soil net mineralization rates increase with the temperature.The fluvo-aquic soil mineralization rate was higher than yellow-brown soil.The mineralization potential of Yellow-brown soil and fluvo-aquic were 74.63 mg N/kg and 123.45 mg N/kg,respectively,and accounting for soil total nitrogen of 8.58%and 9.56%.Small undisturbed soil core lysimeters research showed that vegetable soil mineralization in spring-summer was higher than in autumn-winter.The yellow-brown soil mineralization rates were 0.13 mg N/kg/d and 0.02 mg N/kg/d in spring-summer and in autumn-winter seasons,respectively, and the fluvo-aquic were 0.18 mg N/kg/d and 0.02 mg N/kg/d.6.Research the atmospheric deposition of vegetable systems in Wuhan surbub.The results show that the average inorganic nitrogen input through atmospheric deposition was 29.58 kg N/ha/yr.Wet deposition was the main component of atmospheric deposition, and it occupies 81.05%of the total inorganic input.The atmospheric deposition in spring-summer was higher than in autumn-winter,and ammonium deposition was higher than nitrate.The average pH value was 4.47±0.59 during the trial period.7.In the paper,we proposed strategies to reduce nitrate-N leaching of vegetable soil in Wuhan suburb.（1） Reduce the nitrogen application,and the nitrogen applied no more than 722.22 kg N/ha/yr and 680.18 kg N/ha/yr in yellow-brown soil and fluvo-aquic soil, respectively;（2） Reduce the nitrogen applied amount in autumn-winter,and planted the vegetable or free filling crops before winter;（3） Rotate deep and shallow vegetable crops, choose long growing season vegetable crops and reduce farming;（4） Reduce the irrigation volume and frequency in the main rainfall seasons,and promote water-saving irrigation;（5） Promote vegetable fertilization soil testing technology to improve nitrogen use efficiency;（6） Applicate nitrification inhibitors.8.The use of PVC and Vaseline materials building the undisturbed soil core lysimeters fully meet the research need of the nitrogen transformation and leaching in agro-ecosystems.更多还原