【作者】 沈月；

【导师】 依艳丽；

【作者基本信息】 沈阳农业大学 ， 土壤学， 2013， 博士

【摘要】 土壤酸化也是土壤退化的一种表现形式,其发生机制、时空演变规律及恢复重建等问题已经成为国内外土壤学、农学及环境化学界共同关心的热点问题。酸化给土壤带来的灾害已经严重威胁到人类的生存和发展空间。棕壤是辽宁省的主要耕作土壤类型,近几年来的研究表明由于不合理的耕作施肥,土壤pH值下降幅度较大,酸化机理有待深入研究。基于此,本研究以辽宁省不同地区代表性耕地棕壤为研究对象,与第二次土壤普查结果相比,分析了辽宁省耕地棕壤酸化现状；结合棕壤长期定位试验田研究了不同施肥处理下,棕壤酸度变化特点及盐基离子变化规律,并从矿物学角度深入研究了长期施肥对粘土矿物组成及相对含量的影响；研究了不同水氮耦合条件下土壤氮素转化特征,以及氮素转化与迁移对盐基离子迁移、淋失的影响,获得的主要结论如下：1.辽宁省不同地区间土壤酸度分布差异很大,表现在东部、北部、中部地区酸性耕地棕壤所占面积较大而南部和西部酸性耕地棕壤所占面积相对较小的趋势。其中辽东清原和宽甸地区酸性耕地棕壤面积所占比例较大,分别为21.91%和51.91%,辽西和辽南酸性耕地棕壤面积所占比例较小,均低于5%。与第二次土壤普查结果相比,各地区棕壤pH平均值显著降低。弱酸性、酸性耕地棕壤面积增加,而中性面积减少。2.不同区域土壤心土层的pH值差异较大,辽东宽甸地区剖面土壤心土层pH值较低,呈酸性,耕作以后表层土壤pH有所提高。清原、开原和沈阳剖面土壤心土层pH呈弱酸性,而耕层土壤pH值相对降低。随着pH值的降低,阳离子交换量呈现降低趋势,在pH6.6-7.0之间,盐基饱和度均达到70%以上,在pH4.6-5.5的范围内,盐基饱和度低于60%。3.长期不同施肥对土壤pH值影响较大,与不施肥相比,连续施用尿素(270kg N hm-2)27年土壤pH值下降1.31个单位,土壤缓冲容量降低3.87nmol kg-1pH unit-1。在氮肥的基础上配施磷钾肥可增加pH值的降低程度。有机、无机肥配施可缓解土壤酸化。配施有机肥75.6kg N hm-2时对施化肥引起的酸化抑制作用不显著,但是配施有机肥135kg Nhm对120kg N hm-2处理引起的酸化作用抑制显著。随着尿素施用量的增多,土壤交换性酸和交换性铝的含量呈增加趋势。年施尿素120、135、180和270kg N hm-2,相当于分别向上壤增加1320、1500、1980和3780kmol hm-2交换性酸。长期施用尿素显著降低了土壤酸碱缓冲性能,促进了伊利石的风化,显著降低了伊利石含量,而增加了1：1型粘土矿物高岭石的相对含量使土壤易发生酸化。4.尿素施入土壤后0-21天内,NH4+-N含量达到最大值,而N03--N含量则在21天之后逐渐上升。在没有淋洗作用的前提下,硝化速率的快慢影响了土壤酸化的进程。盐基离子的迁移-淋失结果降低了土壤盐基饱和度,这是土壤产生实质性酸化的真正原因。70%田间持水量上壤硝化作用强烈,最利于NH4+-N向N03--N的转化。其次为50%条件下的生成量。100%田间持水量条件培养下,延缓了硝化作用的进行,使硝化作用发生的时间滞后。5.在氮素转化初期,NH4+取代土壤胶体上的盐基离子,增加了盐基离子淋失的潜在威胁。NH4+的累积主要影响了盐基离子+前期淋失量,而后期的淋失量主要取决于N03-累积量。在氮素转化前30天,土壤pH值与NH4+-N含量呈显著丁正相关,而30-90天与NO3-N含量呈显著负相关。在0～45天内土壤盐基离子的淋失量逐渐升高,且淋出液pH值达到最高值。淋洗120天后,土壤0～10cm土层出现酸化趋势,施氮量越高,pH值降低幅度越大。氮肥施用量450mg kg-1的处理pH值与不施肥相比降低了0.51个单位,酸化现象显著。更多还原

【Abstract】 Soil acidification is one symptom of soil degradation either. The topics of acidification mechanism, objectivity of space-time evolution and reconversion have been the hot issues that concerned by soil scientist, agronomist and environmental chemist. The survival and development space of human seriously threatened by the disaster of soil acidification. Brown earth is the main type of cultivated soil. Recent research showed that pH of brown earth significantly decreased due to the unreasonable tillage and fertilization, and the mechanism of it needs further study. Based on this situation, the statues of brown earth in different areas had investigated in this study by comparing with the second soil census. The characteristics of soil pH and the rules of base cations changed in different fertilizer treatments had studied by means of the long-term experimental field. The constituent and relative amount of clay minerals in different fertilizer treatment was tested. The characteristics of nitrogen migration within different soil moisture content and nitrogen rate, effects of migration and leaching of nitrogen on base cations has been study, either. The main results were as follows.1. Significant differences of soil pH were in different districts of Liaoning province. The area of acid arable brown earth in the east, north and middle Liaoning province took the large part while the south and west were relatively small. The acid area of arable brown earth in Qingyuan and Kuandian districts, which in the east of Liaoning province took the large parts, the values were21.91%and51.91%, respectively. The area in west and south Liaoning province were small which both below5%. The brown earth pH significantly decreased comparing with the second soil census. Area of weak acid and acid both increased while the neutral area decreased.2. The significant differences of subsoil were in different districts. Subsoil pH in soil profile of Kuandian district, which is in the east of Liaoning province was lower than the other district and the pH was in the acid range. However, pH of this district increased after tillage. The subsoil pH of Qingyuan, Kaiyuan and Shenyang districts was weak acid while the topsoil pH of them was relatively delined. A decreasing trend was found in cation exchange capacity as pH decreased. Base saturation were more than70%while pH range were from6.6to7.0, however, base saturation were lower than60%while pH range were from4.6to5.5. 3. Significant affects of soil pH were found after long-term fertilization. The decreasing of1.31pH unit-1applying urea with the nitrogen rate of270kg N hm-2after27years tillage. The pH buffer capacity decreased3.87mmol kg-1pH unit-1. The reduce extent of pH was increased when adding phosphate and potassium fertilizer based on nitrogen fertilizer. The degree of soil acidification will be relieved when applying organic and inorganic fertilizer. A non-significant difference was found in restraining soil acidification of applying nitrogen fertilizer (120kg N hm-2) only while the organic rate was75.6kg N hm-2. However, the difference was significant when the organic fertilizer rate was increased to135kg N hm-2. The contents of exchangeable acid and exchangeable Al3+increased as the nitrogen rate increased.1320、1500、1980and3780kmol hm-2exchangeable acid will be add to soil with the nitrogen rate of120、135、180and270kg N hm"2. Soil pH buffer capacity was significantly decreased and the weathering of illite was accelerated, the content of illite was significantly decreased while the content of kaolinite,1:1type mineral, was increased after long-term applying urea which will easily lead to soil acidification.4. The maximum of NH4+-N was found in the first21days after applying urea to soil. However, the content of NO3--N increased after the incubation time of21days. The speed of nitrification rate controlled the process of soil acidification in no leaching condition. Declining of base saturation after migration and leaching was the mechanism of substantiality of soil acidification. NH4+-N easily transformed to NO3--N and nitrification was intensively when the soil moisture was70%. NO2--N production with soil moisture of50%was lower than that of70%. Nitrification rate delayed and the date of nitrification was hysteretic when soil moisture was100%.5. Base cations of soil colloid were replaced by NH4-at the beginning of nitrogen transformation, which will increase potential menace of base cations losses. Leaching amount of base cations were due to the accumulation of NH4+in the earlier stage, while the accumulation of NO3-was the main factor in the later period. A significant positive correlation was found between soil pH and NH4+-N in nitrogen transformation stages of the first30days, while a negative correlation was found between pH and NO3-N from30to90days incubation. Leaching amount of base cations increased gradually and pH of leachate showed the maximum value during the first45days. Acidification trend was found in topsoil of soil columns after120days leaching, reduction rate of pH increased as nitrogen rate increased. Significant acidification phenomenon was found in the nitrogen rate of450mg kg-1with pH decreased0.51unit-1comparing with control.更多还原