【作者】 金雪霞；

【导师】 黄耀； 范晓晖；

【作者基本信息】 南京农业大学 ， 环境工程， 2004， 硕士

【摘要】 本论文采用室内培养试验对南京郊区6对菜地土和水稻土，3对菜地土和旱作粮地土的土壤氮素矿化、硝化和反硝化作用特征进行了研究。菜地土分别为附近相同类型水稻土（稻麦轮作体系）和旱作粮地改种为蔬菜约20年的土壤。矿化和硝化试验中称量10g风干土在65％或100％田间持水量（FC，Field capacity），28℃条件下培养。矿化试验不加氮肥，而硝化试验加200mgN／kg的尿素。在研究反硝化作用的试验中，将10g风干土在100％FC或淹水，28℃条件下培养，其施肥处理为加200mgN／kg硝酸钾。此外还对南京郊区3对菜地土和水稻土（马肝土）的N₂O排放和氮素反硝化损失进行了测定，将20g风干土在100％FC，28℃条件下培养21天，施肥处理为加100mgN／kg尿素。 在南京雨花区武警农场（土壤pH5.4）和栖霞区东阳科技站（土壤pH7.7）先后于2002和2003年进行了秋季小青菜和秋冬季大白菜田间试验，采用密闭室通气法测定氨挥发；用乙炔抑制-土柱培养法测定反硝化损失，不加乙炔培养则测定土壤N₂O排放。小青菜试验设对照、低氮和高氮3个处理，尿素氮总用量分别为0，75和150 kgN／hm²，2施肥处理分基肥和追肥施用，比例为0.6：0.4。大白菜试验设对照、缓释尿素、低氮和高氮4个处理，尿素氮总用量分别为0，180，300和600 kgN／hm²，缓释尿素全部作为基肥施用，低氮和高氮两处理分基肥和两次追肥施用，比例为0.25：0.25：0.50。 培养试验的结果表明，在65％FC条件下，6个菜地土的矿化率（矿化氮量／全氮量×100）均低于相应水稻土；而3个菜地土的氮素矿化量和矿化率都高于相应的旱作粮地土壤。与相同类型水稻土相比，大多数菜地土pH较低，故其硝化作用相对较弱；与相同类型旱作粮地土相比，大多数菜地土pH较高，故其硝化作用相对较强。不同水分条件下培养的结果表明，水稻土和改制的菜地土在100％FC条件下的矿化和硝化速率比在65％FC条件下的高，而旱作粮地土和改制的菜地土则相反。5个供试菜地土的反硝化率均低于相同类型的水稻土；3个供试土壤中只有1个菜地土的反硝化率低于旱作粮田土。另一试验结果表明，3对供试土壤中，2个菜地土培养21天排放的N₂O总量与反硝化损失总量均显著高于相同类型的水稻土（P＜0.05）。3对供试土壤施尿素后反硝化损失均未显著增加。施肥和不施肥处理，土壤N₂O排放累积量和反硝化损失累积量随时间t的变化均符合修正的Elovich方程y=bln（t）+a。 田间试验的结果表明，小青菜试验地土壤pH值低，无论是施用基肥还是劫巴后氛挥发均低（< 0.4%）.在大白菜试验中，施用基肥后当天降大雨，3个施氮肥处理均没有氛挥发;施用第1次追肥后第2一4天降了小雨，3个处理的氨挥发损失率分别为0.52%、5.39%和7.7%;第2次追肥后天气一直晴朗，氛挥发率则为0.45%、21.7%和30.3%。大白菜整个生长期间3个施氮处理的氛挥发总损失率分别为0.97%、且 .1%和17 .1%。以上结果表明，土壤PH、施肥后的降雨量和氮肥施用量都对土壤氛挥发有不同程度的影响，而施用缓释尿素能有效地减少氛挥发.另外，小青菜田间试验的结果表明:土壤充水空隙率（WFPS，wa ter一Fx一led Pore Spaee）是土壤N20排放的重要影响因子。N20排放和反硝化损失与土壤WFPs均呈极显著正相关。在24天内，菜地土壤不施与施氮肥的反硝化损失和N20排放都低，N20量为反硝化总量的49.0一79.7%。该试验中施用氮肥没有增加反峭化损失。更多还原

【Abstract】 Characteristics of nitrogen(N) mineralization, nitrification and denitrification in six pairs of soils grown with vegetables and food crops (irrigated paddy rice - upland winter crops), three pairs of soils grown with vegetables and upland food crops in Nanjing suburbs, respectively, were investigated by incubation experiments in laboratory. The soils grown with vegetables had been converted from food crops around 20 years ago. Mineralization and nitrification incubation experiments were conducted under 65%FC(field capacity) or 100%FC and 28 C, and for nitrification study 200mgN/kg of urea was added to the soil. In denitrification experiments, the soils were incubated with and without KNO3 at a rate of 200mgN/kg under 100%FC or waterlogged and 28 C. Moreover, N2O emission and denitrification loss in three pairs of soils with and without 200mgN/kg of urea were investigated under 100%FC and 28 C.Field experiments with green cabbage (Xiao Qing Cai) in 2002 and Chinese cabbage in 2003 were conducted in Nanjing suburbs. Ammonia volatilization was measured by an enclosure method, and N2O emission and denitrification loss were measured by without and with acetylene inhibition-soil core incubation technique, respectively. In the green cabbage field experiment, 3 treatments were control, low rate N and high rate N with a total application rate of 0, 75 and 150 kgN/hm2, respectively. N was applied as basal and top dressing in the ratio of 0.60 to 0.40. In the Chinese cabbage field experiment, 4 treatments were control, slow-released urea, low rate N and high rate N with a total application rate of 0, 180, 300 and 600 kgN/hm2, respectively. In the slow-released urea treatment, whole amount of N was applied as basal dressing. In the other 2 N treatments, N was applied as basal and 2 top dressing in the ratio of 0.25:0.25:0.50.Results from laboratory show that at 65%FC incubation, ration of mineralized N to total soil N in six vegetable soils were lower than those of the corresponding paddy soils. Amounts of mineralized N and ration of mineralized N to total soil N in vegetable fieldswere higher than those in upland soils grown with food crops, hi comparison with the corresponding paddy soils, nitrification rates in soils of vegetable fields were lower due to the lower soil pH value in most cases. On the contrary, in comparison with the corresponding upland soils, nitrification rates in soils of vegetable fields were higher. Moreover, mineralization and nitrification rates from paddy soils and the corresponding vegetable soils incubated by 100%FC were higher than those by 65%FC. In contrast, mineralization and nitrification rates from upland soils and the corresponding vegetable soils incubated by 100%FC were lower than those by 65%FC. Results show that denitrification rates in all of 5 vegetable soils were lower than those of the corresponding paddy soils, and denitrification rate in one of three vegetable soils was lower than the corresponding upland soil. Results from another incubation experiment show that N2O emission and denitrification loss from two of three vegetable soils were significantly higher than those of the corresponding paddy soils after incubation of 21 days (P<0.05) . The amounts of the denitrification loss were not significantly increased by application of nitrogen fertilizer in the three pairs of soils. The relation between the accumulated N2O emission or denitrification loss and the incubation time, in the three pairs of soils either with or without applied nitrogen, was matched with the revised Elovich equation of y=bln(t)+a.Results from field experiment show that ammonia loss was very low after either basal or top dressing to the green cabbage due to the low soil pH of 5.4. In Chinese cabbage field, no ammonia volatilization occurred after basal dressing due to a heavy rainfall after fertilization even though the soil pH is 7.7. There was small amount of rainfall during 2-4 days after 1st top dressing, and ammonia volatilization was 0.52%, 5.39% and 7.7% of applied N for the slow-released urea, lo更多还原