【作者】 郝桂娟；

【导师】 任天志；

【作者基本信息】 中国农业科学院 ， 作物栽培与耕作学， 2009， 博士

【摘要】 本研究采用定量分析与定性分析相结合的方法对大兴安岭东麓旱作丘陵区耕地土壤化学性状和物理性状演变特征、环境质量演变特征、耕地土壤侵蚀的形成与演变,以及耕地质量演变的驱动因素与影响进行了系统的分析研究,提出了该区耕地可持续利用的技术措施和区域农业可持续发展的典型模式与对策等。研究结果如下:(1)经过20多年的演变,大兴安岭东麓旱作丘陵区耕地土壤有机质含量平均下降23.8%;土壤全氮含量下降31.9%;土壤碱解氮含量降低12%以上;土壤速效钾含量下降24.7%。土壤中交换性钙、交换性镁、有效硫、有效硅等中量元素含量较为丰富。微量元素中锌、铜、铁、锰等含量丰富。硼和钼呈现缺乏,缺乏面积分别占总耕地面积的87.2%和78.2%。(2)与20多年前相比,研究区耕地物理性状逐步恶化,主要表现在土壤结构变劣、容重增加、腐殖质层厚度和有效土层厚度减少、障碍层的形成、地表砾石含量增多。该区耕地出现了明显的次生障碍层,形成5～10cm的犁底层并不断加厚变硬,并形成一个地表砾石层。目前地表砾石度大于5%的面积比20多年前增加近20倍;耕地中有1/3～1/2以上的土壤分布在薄体和薄层暗棕壤上,该土壤腐殖质层较薄(<20cm),土体砾石含量高(>30%),砾石层位浅,一般20cm就出现大量砾石。而且随着坡度的升高,种植年限的延长,表层土壤砾石含量显著增加。(3)研究区耕地土壤综合污染指数均小于0.7,达到Ⅰ级标准,符合绿色食品产地土壤环境条件。因自然因素成土母质和成土过程不同,各类型耕地土壤重金属元素的汞、铬、砷、铅、铜含量有一定差异,但土壤镉含量的差异较小。该区土壤pH值在4.8～7.1之间,平均为6.0,呈微酸性～中性,各土类间pH值变化不大。研究区的河水和地下水都达到了农田灌溉水质标准的极限值,符合农田灌溉和绿色食品生产的水质标准。(4)按照全国土壤侵蚀类型区划,研究区属于东北黑土区的低山丘陵区,存在不同程度的侵蚀现象,主要分为水力侵蚀、冻融侵蚀两种类型,其中水力侵蚀占耕地侵蚀的99.8%。与第二次土壤普查期间比较,现有耕地面积比20多年前增加了3.3倍,耕地土壤侵蚀强度由微度发展到轻度。耕地土壤二级以上的明显侵蚀面积由12.2万hm2增加到52.7万hm2,增加了4.3倍;平均侵蚀模数由第二次土壤普查前的小于500 t/km2.年,增加到1935.7 t/km2.年;沟壑密度由0.06 km/km2增加到1.87 km/km2;30%左右的耕地因土壤侵蚀已经产生严重或比较严重的水土流失。耕地自开垦以来,表土层流失厚度总量为3～16.8cm,平均为8.4cm,年均流失厚度为0.2～1.1cm,严重地区个别年度表土层的流失量达5cm以上。其中暗棕壤表土层的总流失厚度为11.3cm,占腐殖质层厚度的51.3%;黑土土类的总流失厚度为9.5cm,占该土类腐殖质层厚度的28.83%;草甸土流失厚度为4.4cm,占该土类腐殖质层厚度的6.2%。根据土壤侵蚀程度分级标准,黑土土类的土层厚度占A层的6.2%,属轻度侵蚀;暗棕壤的侵蚀厚度占A层的51.8%,属中度侵蚀;草甸土土类的侵蚀厚度占A层的4.4%,属轻度侵蚀。研究区的总体侵蚀厚度为8.4cm,占A层的17.8%,属于轻度侵蚀程度。耕地土壤受侵蚀后,一方面造成水土流失,物理性状恶化,另一方面还存在养分流失的问题。平均每年流失土壤总量为916.7万t,流失有机质总量为42.5万t,流失的N、P、K养分相当于40%高浓度含量的复合肥5.9万t,是该地区年均化肥施用量的1.4倍。(5)耕地土壤<0.01mm颗粒含量、孔隙度、团聚体含量、田间持水量随坡度增大而减小,容重随坡度增大而增大。土壤有机质、全氮、有效磷、有效钾、有效铜、有效锰、有效硼、有效硅,随着坡度的升高明显下降;土壤有效铁、有效钼、有效硫含量,随着坡度的升高而增加;随着坡度升高酸性增强。降水的季节性分布不均、蒸发量的上升加重土壤侵蚀;气温的变化和灾害性天气频率的增加也导致耕地质量向退化方向演变。在人为因素中,不合理的垦荒种植,难以改变的小型四轮拖拉机表土翻耕方式,不科学的肥料使用、管理方式,以及人口增长和经济社会发展的负面影响,都促使耕地质量在演变中逐步形成退化。(6)提出了分区改良、合理布局、防止水土流失、科学施肥培肥地力、改革耕作制度等耕地可持续利用的技术措施和建立耕地可持续利用的立法机制、开发保育监督机制、政府专题议事规则、加强人才培养,发展区域特色经济等政策建议。针对研究区的实际,提出区域农业可持续发展的典型配套模式。更多还原

【Abstract】 Based on the method of quantitative and qualitative analysis, this study was conducted to investigate the change of soil fertility characteristics, soil physical properties, soil environmental quality, soil erosion status of hilly dryland in the east of Great Xingan Mountains, and then the reasons for those changes were comprehensively investigated. At last, the technical and strategically pathways were put forward for sustainable utilization and agricultural sustainable developmental model in this area. The results were list as follows:(1) Compared with the parameters at 20 years ago in the studied regions, the soil organic matter content decreased 23.8%, soil total nitrogen content decreased 31.9%., alkali-hydrolysable nitrogen content decreased more than 12%, and soil available potassium decreased 24.7%. Soil medium elements and microelements remain consistently, such as exchangeable calcium, exchangeable magnesium, available sulfur, available silica and zinc, copper, iron, manganese, while 87.2% and 78.2% of the soils were short of boron and molybdenum, respectively.(2) The soil physical properties had a trend of depravation in the recent 20 years in the studied area, which representing in the decrease of soil structure quality, the increase of soil bulk density, the decline of humus and availability soil layer, the form of obstacle layers and the increase of surface gravel contents. Secondary soil obstacle layers were formed in the studied 20 years, which resulted in a surface gravel layer and a 5~10cm hard ploughpans. The surface areas with gravel contents≥5% were increased by 20 times compared with 20 years ago. One third to half of the farmland were distributed in thin dark-brown soil, which has thinner humus layer (<20cm) and higher gravel content (>30%) and the gravel appeared under ground 20cm in general. With the increasing of the slope and cultivation years, the gravel content in soil surface increased significantly.(3) The integration pollution index of soil in studied areas were below 0.7 in general, which reached to theⅠclass standard, belonging to soil standard for green food production. Due to the different of natural factors and soil parent material and soil pedogenesis process, soil heavy metals such as mercury, chromium, arsenic, lead, copper contents in different types of soils had certain differences while soil cadmium contents had no such obvious difference. Soil pH values in the areas were on the average of 6.0, between 4.8~7.1, was slightly acidic to neutral response. The water quality from river and ground had reached the limits of quality standards for irrigation in the studied areas, which accorded to the water quality standards use for green food production.(4) In term of the national divisions of soil erosion type, the studied areas belonged to north-eastern hilly areas of black soil zone. There were different degrees of erosion, which mainly fall into two categories including water erosion and freeze-thaw erosion. Water erosion accounted for 99.8% of arableland erosion in this area. Freeze-thaw erosion only accounted for part of areas which called "land split" (2~5cm in width, 5~50cm in depth ) in the near Great Xingan Mountains forest due to the formation of frozen-thawed 20 years ago, while the area enlarged to 3.3 times more than before. The soil erosion intensity of arableland turned to micro-developed from mild. The soil erosion area above second class increased from 12.2×104 hm2 to 52.7×104 hm2, which increasing 4.3 times; The average soil erosion modulus were increased by 1935.7 t/km2/year from less than 500 t/km2/year. Gully density were increased by 1.87 km/km2 from 0.06 km/km2; 30% of the arableland has been subjected to serious soil erosion. The total thickness of soil loss for the 3~16.8cm, with an average of 8.4cm, an average annual loss of thickness 0.2~1.1cm, serious areas of individual annual soil loss amounted to more than 5cm since the reclamation of land, in which 11.3cm thickness soil layer was loss in dark brown soil, accounting for 51.3% of humus layer; 9.5cm thickness soil was loss in black soil, accounting for 28.8%of humus layer thickness; 4.4cm thickness soil was loss in meadow soil, accounting for humus layer thickness by 6.2% of the same soil type. In terms of the classification standards of the degree of soil erosion, black soil layer thickness accounts for 6.2% level of Class A, which is mild erosion; dark brown soil erosion accounts for 51.8% of A level, which is moderate erosion; meadow soil erosion thickness accounted for 4.4% of A level, which is slightly eroded. The overall erosion of the study area is a thickness of 8.4cm, accounting for 17.8% of A level, with a degree of slight erosion. Investigation of the studies showed that soil erosion resulted in, both deterioration of physical properties and nutrient loss. Average annual soil loss of the total amount is 9,167,000 t. The loss of organic matter reached 425,000 t. The loss of N, P, K nutrients equivalent to 59,000 t compound fertilizers with 40% content, 1.4 times of the total amount of chemical fertilizer use in this areas.(5) The soil particles <0.01mm content, porosity, aggregate content, field capacity decreased with the increase of slope, while bulk density increased with the slope. Soil pH value, organic matter, total nitrogen, available phosphorus, available potassium and effective copper, effective manganese, boron, silicon decreased with the increasing of slope, while soil available iron, molybdenum and efficient sulfur content increased with the slope. The seasonal uneven precipitation and evaporation increasing resulted in the worse of soil erosion; The temperature change and the increase of the frequency of severe weather also led to the degradation of arableland. Unreasonable cultivation, the small four-wheel tractor tillage system, and unscientific fertilization system, as well as the negative effects result from population growth and economic and social development were all led the degradation of soil quality.(6) Based on the analysis of natural and human activity factors which affected soil quality, the technical methods to sustainable utilization of cultivated land resources including district improvement, rational distribution, preventing soil erosion, rational fertility fertilization, reforming the faming systems were proposed. In addition, we also put forward corresponding strategic step such as enhancing legislative work to protect arable land, establishing the monitoring mechanisms for the conservation of farmland development of study area, and put the eco-environment restoration of farmland into the agenda of government, the establishment of Great Xingan Mountains green resources conservation areas, and developing the characteristics economic of the studied area. Finally, regional agriculture sustainable development patterns in the studied area were proposed.更多还原