【作者】 蒋朝晖；

【导师】 曾清如； Abdelwahid Mellouki；

【作者基本信息】 湖南农业大学 ， 生态学， 2013， 博士

【摘要】 大棚是个接近封闭的生态系统,其施用氮肥量大,氮肥的利用率低,与敞开体系相比挥发氮素不易扩散,各种环境问题易发生。为了提高氮肥使用效率,进行了各种尝试,如利用尿素包膜,或添加脲酶抑制剂、硝化抑制剂、聚合物、元素硫。通过实验室模拟和田间试验,在蔬菜大棚中单独施入尿素,或包膜,或加入硝化抑制剂双氰胺(DCD),分析了尿素在土壤中的氮素转化、测定了氨气、二氧化氮和臭氧等气体。研究了大棚内挥发性碳氢化合物的释放特征,获得了以下主要研究成果：1、通过室内模拟,不同尿素水平施入土壤一周后,随着施肥水平的的增大,pH值明显上升,NH4+-N浓度上升较大,N03--N浓度上升缓慢,土壤中有效态A1、Mn、Cu、Zn、Ca随着施肥水平的增大而下降。动态试验表明,土壤中五种元素(Al、Mn、Cu、Zn、Ca)随着pH升高,有效态含量逐渐降低,然后随pH降低而升高,其中Al受pH影响最大,当pH上升7.00以上时,有效态A1就很少了,试验发现Ca受pH影响最小。用二次方程Y=ax2+bx+c模拟这些元素含量与pH的关系,在pH4-8范围内,五种元素含量与pH呈负相关。2、通过室内模拟,研究了4个尿素品种(普通尿素、保水型控释尿素、德国缓释尿素、矿物改性保膜尿素)施入土壤后pH变化和氨气释放情况的差异。结果表明,德国缓释尿素pH下降速度最慢,而氨气挥发量最多,五周内在冲积性菜园土、红壤性菜园土、茶园土和北京菜园土中挥发NH3-N分别占总施N量的25.6%、16.7%、3.0%和34.4%。矿物改性包膜尿素pH下降最快,氨气挥发量最少,五周内在冲积性菜园土、红壤性菜园土、茶园土和北京菜园土中挥发NH3-N分别占总施N量的8.07%、5.19%、0.85%和13.0%。这是由于德国缓释尿素含硝化抑制剂双氰胺(DCD)；抑制硝化反应,pH下降缓慢,氨气挥发量大,矿物改性包膜尿素外面一层磷矿粉,能缓解尿素的溶解,降低氮的释放,减少氨气挥发,优于其它尿素品种。3、采用实验室人工气候箱培养的方法,研究了双氰胺在不同温度下对两种不同土壤(碱性菜园土和酸性菜园土)中氨挥发的影响,以及对尿素氮转化和)H值变化的影响。结果表明,在两种土壤中,随着温度的升高pH值和氨的挥发量都升高。碱性土壤氨的挥发量远远大于酸性土壤,在硝化抑制剂双氰胺的处理中,15℃时氨挥发总量增加了353.18%,25℃时增加了618.33%,35℃时增加了1080.46%。总体上土壤硝态氮的量随着温度的升高有下降的趋势。铵态氮的量是先增大后减小,随着温度的升高铵氮含量出现峰值的时间提前,约为一周。4、在长沙大棚田间试验四个不同氮肥处理：不施氮肥(T1)、施普通尿素(T2)、施矿物改性包膜尿素(T3)、硝化抑制剂双氰胺(DCD)+普通尿素(T4)中,利用被动采样器,进行了一个半月对NH3、N02和03的采样,氨气、二氧化氮和臭氧平均浓度从高到低的顺序分别是(μg/m3)：T4(31.66)>T2(25.93)>T3(23.52)>T1(7.96),T2(10.99)>T3(8.16)>T4(7.48)>T1(5.20),T2(75.05)>T364.20)>T4(63.85)>T1(49.02)。塑料大棚中施入氮肥后,发生了光化学反应,并且产生了有害气体的积累。双氰胺抑制铵根离子向硝酸盐的转化,增加了氨挥发和减少二氧化氮的生成。矿物改性包膜尿素减少了氨挥发和二氧化氮的生成,增加了氮素利用效率。极显著正相关(p<0.01)在大气温度与氨气和二氧化氮水平之间、土壤pH值与氨气和二氧化氮水平之间被证实。高纬度大棚中,银川其臭氧浓度是低纬度长沙的两倍。银川郊区臭氧日浓度在168.03到214.83μ g/m3之间变化,超过了160μ g/m3(国家一级标准),最大值214.83μ g/m3超过了200μ g/m3(国家三级标准)。5、用气相色谱并使用质谱检测器对非甲烷碳氢化合物进行分析,检测限在0.1μ g/m3以下。长沙市郊区温室大棚内外非甲烷碳氢化合物的平均浓度,大棚内的NMHC的浓度远远高于大棚外,棚内NMHC总浓度是132.53ppb,是棚外的4.44倍。棚内植物释放了大量异戊二烯,棚内大气中VOCs化学活性强于棚外,更易发生光化学反应。大棚内莴苣叶片中POD活性棚外大于棚内,说明了大棚施肥明显地抑制了POD活性,而棚外较高的POD抑制植株的生长,因此棚外莴苣生长矮小。特别是棚内施氮肥处理第二次测定中,POD活性异常低,受到严重抑制,此时棚内施氮肥处理第二次测定中MDA含量异常升高,远远高于同次测定的其它处理,表明此时莴苣已经受到了明显的环境胁迫作用,在塑料大这个特殊的环境中,施入氮肥后,发生了光化学反应,产生有害气体的积累,造成了对植物的伤害。更多还原

【Abstract】 Greenhouses almost were closed environment. In greenhouses environmental problems began to emerge as much use of nitrogen fertilizer and the low utilization rate of fertilizer and volatilization N not easy to go out. To optimize fertilizer N efficiency, various attempts have been made to coat or treat N fertilizers with urease inhibitors, nitrification inhibitors, polymers, and elemental S. we designed and conducted laboratory and field experiments to measure air concentrations of NH3, NO2and O3at vegetable fields with the application of urea alone or with coating or with nitrification inhibitor (dicyandiamide, DCD), to study about transformation of N. We studied release of the hydrocarbon in greenhouse.1. With simulation test, the results showed that soil pH and concentration of NH4+-N increased quickly, concentration of NO3--N increased slow by fertilizing different level of fertilization in soil, while soil available Al, Mn, Cu, Zn and Ca decreased sharply with the increasing level of fertilization after one week. The dynamic experiment revealed that the concentrations of5elements of Al, Mn, Cu, Zn and Ca by fertilizing urea in soil were more and more lower with the pH raising, and then they were more and more higher with the pH dropping. The influence on Al was the most important, when pH raising to over7.00, the concentration of exchangeable Al was much lower. The pH influence on Ca was not so considerable. In pH4-8, by formula Y=ax2+bx+c simulating the relationship of concentrations of these pH values and elements, concentrations of these elements were negatively correlated with pH values.2. With simulation test, we studied about change of pH and volatilization of ammonia by fertilizing four different types of urea (general urea, keep water controlled-release urea, Germany slow-release urea, mineral coated urea). The results showed that the fallen rate of pH by Germany slow-release urea was the slowest while the amount of ammonia volatilization was the biggest, in the five weeks the amount was25.6%in alluvial vegetable garden soil,16.7%in red vegetable garden soil,3.0% in tea garden soil,34.4%in Beijing vegetable garden soil. The fallen rate of pH by fertilizing mineral coated urea was the fastest while the amount of ammonia volatilization was the smallest, in the five weeks the amount was8.07%in alluvial vegetable garden soil,5.19%in red vegetable garden soil,0.85%in tea garden soil,13.0%in Beijing vegetable garden soil. Because there was inhibitor (DCD) in Germany slow-release urea, which controlled nitroreaction and the fallen velocity of pH was slow, the amount of ammonia volatilization was great. The mineral coated urea was coated ground phosphate rock and reduced nitrogen release, decreased ammonia volatilization and better than other urea.3. Incubation studies on the effect of dicyandiamide on ammonia volatilization in two different soils such as alkaline soil and acid soil, and on urea-nitrogen transformation and pH value’s change in two different soils show that in these two different soils, pH and ammonia content increased with the elevated temperature, and were higher in treatments with nitrification dicyandiamide than in no-NI control. The amount of ammonia volatilization in alkaline soil was much more than in acid soil, approximately353.18%,618.33%and1080.46%at the temperature of15,25and35℃in the dicyandiamide treatments, respectively. During the whole experiment, the amount of nitrifying nitrogen in soils was declined with the rising tempetature. The amout of ammoniacal nitrogen in soils was increased initially and then reduced, and the time of peak revealed earlier followed with the increased temperature, about one week.4.. With passive sampler techniques NH3, NO2and O3were measured from plastic greenhouse in Changsha suburban, China, over a one and a half month period. By four treatments (T) types (no N fertilizer T1, common urea T2, coated urea T3and common urea with nitrification inhibitor dicyandiamide (DCD) T4, the average concentrations (μg/m3) of NH3, NO2and O3emitted from high to low in order was: T4(31.66)> T2(25.93)> T3(23.52)> T1(7.96), T2(10.99)> T3(8.16)> T4(7.48)> T1(5.20), T2(75.05)> T364.20)> T4(63.85)> T1(49.02), respectively. This implied that photochemical reaction took place and there were accumulated harmful gases after applied N fertilizer in plastic greenhouse. DCD inhibit the conversion of ammonium to nitrate, and increase NH3volatilization and decrease NO2levels. The coated urea decreased the levels of NH3and NO2, and increased nitrogen use efficiency. Significant positive correlations (p<0.01) between temperature and NH3, NO2levels, between soil pH and NH3, NO2levels were found. The O3average concentration in higher latitude of Yinchuan suburban, China, was two times greater than that in Changsha suburban, China. The O3daily concentrations in Yinchuan suburban exceeded160μg/m3(i.e., China’s Grade Ⅰ standard), and the maximal value214.83μg/m3exceeded200μg/m3(i.e., China’s Grade Ⅲ standard).5. Reliable sampling and analysis methods were selected and optimized to meet the requirements of atmospheric nonmethane hydrocarbons measurement using gas chromatography equipped with a mass spectrometry. Method detection limits (MDLs) were found below0.1μg/m3nonethane hydrocarbons. The concentration of NMHC in greenhouse in Changsha suburb was132.53ppb, which were4.44times greater than that of outside. The plant releases much isoprene, and the strong chemical activity of VOCs in greenhouse was more prone to photochemical reaction. The activity of POD outside was greater than that in greenhouse, and fertilization in greenhouse significantly inhibits POD activity in lettuce leaves. Higher POD activity inhibits the growth of plant, so lettuce growth outside is smaller. Especially in second determination, POD activity in greenhouse nitrogen treatment is abnormally low and severely inhibited, while the content of MDA abnormally elevated, far higher than that in other treatments, and lettuce has been obvious environmental stresses, which implied there were accumulated harmful gases and photochemical reaction took place after N fertilizer application in special plastic greenhouse conditions.更多还原