施肥方式与施用生物质炭对设施菜地氨排放的影响     

史冬伟  刘衎  孙志华  黄梓恩  梁琼  刘云  段碧华  石生伟 《土壤》2022,54(2):255-261

采用通气法对设施菠菜和黄瓜在施用生物质炭与翻耕措施下土壤氨气(NH3)排放进行观测,探索设施菜地NH3减排的有效途径.观测表明,设施菠菜与黄瓜土壤NH3排放主要发生在施肥后一周内.在施化肥氮总量300 kg/hm2条件下,设施菠菜不施生物质炭和表施生物质炭处理的NH3排放量分别占总氮投入量的8.00％和10.15％,而...  相似文献   

Wildfire disturbance and shallow landsliding in coastal British Columbia over millennial time scales: A numerical modelling study     

Yvonne Elizabeth Martin   《CATENA》2007,69(3):206-219

An algorithm for wildfire occurrence is introduced for incorporation into a numerical model of drainage basin evolution. Within the model, fire return intervals are determined using a stochastic rule set and fire sizes are assigned according to a pareto distribution. A Weibull distribution was fit to millennial-scale lake charcoal data for calibration of fire return intervals in this study, while data for the Olympic Peninsula were used to determine the fire size distribution. Loss of tree root strength resulting from stand-replacing wildfires has been found to be comparable to loss after timber harvesting. Hence, data for increased shallow landslide activity associated with logging were used to calibrate transport equations for years following wildfire incidence. A weathering relation is incorporated in the model, which drives the supply of sediment. When sediment supply is depleted in the model, the shallow landsliding module shuts off until new material is available for transport. Time since last fire analysis indicates that the Weibull parameters defined for the Clayoquot charcoal data produce results that are weighted too heavily towards recent fires. Sensitivity analysis was undertaken, suggesting alternative values may be more reasonable for further model runs. The introduction of a weighted probability factor for aspect, whereby south-facing slopes have a higher likelihood of fire initiation, was not found to significantly affect patterns of fire age in the landscape. Patterns of net topographic change after 6000 years of model run time indicate that greatest net erosion is found on steep, upper slopes, with the highest deposition occurring in hillslope hollows and low-order channels. Depositional grid cells in interfluves show a variable response to the inclusion of wildfire in the model. Net erosion occurs over a relatively low proportion of hillslope area, with wildfire model runs showing a strong erosional signal in these locations. For stream grid cells, the additional deposition due to the inclusion of wildfire in model runs is about 9–10% for 1st to 3rd order streams. Overall, deposition rates increase with decreasing stream order, reflecting greater hillslope/channel coupling in low-order streams.  相似文献   

Long-term effect of ploughing, and organic matter input on soil moisture characteristics of a Ferric Lixisol in Burkina Faso     

Korodjouma Ouattara  Badiori Ouattara  Ayemou Assa  P. Michel Sdogo 《Soil & Tillage Research》2006,88(1-2):217-224

Soil moisture characteristic curves were determined in long-term trials at the agronomic research center of Saria (latitude 12°16′ N, longitude 2°09′ W) in West-central Burkina Faso. The agronomic treatments combined soil tillage with organic and chemical fertilizers. The twin values for soil moisture and water potential showed that on ploughed plots, moisture content was higher at low suction and lower at high suction than the hand hoed plots. Moisture contents were higher for extreme suctions (pF < 1.5 and >3) on plots that received high dose of animal manure. The bush fallow plots behaved as a ploughed plot at low suction and like a hand hoed plot at the high suction. Field capacities were around 9.50% (g/g) and 8% (g/g), respectively, for hand hoed and ploughed plots, while the wilting points for both were of 5–6% (g/g). Organic matter input improved field capacity and soil water content at wilting point but not the useful available water (UAW). The UAW ≥10 mm on the fallow and the control, while it was <9 mm on the other treatments in 0–20 cm soil layer. Soil structural modifications induced by tillage and organic matter input explained these differences in soil hydrologic regime.  相似文献   

某有色冶炼场地浅层土壤重金属空间变异规律与分布特征   总被引：4，自引：0，他引：4  

牛真茹  齐硕  吴庭雯  陈鸿汉 《土壤通报》2016,(3):738-745

以某历史遗留有色金属冶炼堆渣场地为研究对象,按照网格法分别在0~20 cm、20~50 cm深度处采集土样,综合经典统计学与地统计学方法,研究场地周边浅层土壤特征污染物Zn、Cd的空间变异规律与分布特征。经典统计学分析结果表明,浅层土壤Zn、Cd含量普遍远超于当地背景值,均属中等空间变异性,服从对数正态分布,Zn与Cd之间存在极显著的正相关性,推测其迁移影响因素具有相似性;采用地统计学方法并借助Arc GIS与Surfer软件分别预测浅层土壤不同深度Zn、Cd空间分布特征,结果表明,0~20 cm处Zn空间相关性较弱且分布不均匀,其空间变异性主要是由降水淋溶渣堆或携带松散废渣沿西北侧较高地势向东南侧地势较低处流动引起;0~20 cm处Cd空间相关性中等,其空间变异特征是由于Zn与Cd的竞争吸附增强了Cd的迁移性所导致的;20~50 cm处Zn、Cd空间相关性均较强且分布均匀,表明浅层低渗透性粘土的阻滞作用显著降低了Zn、Cd含量,而地层岩性、成土母质等自然环境因素对污染物分布影响更大。上述结论可为场地地下水重金属的污染风险评估与污染控制等提供理论依据。  相似文献   

小波神经网络在白城地区浅层地下水埋深预测中的研究     

王宇  卢文喜  卞建民  侯泽宇 《节水灌溉》2014,(12)

针对白城地区浅层地下水位动态变化的复杂性和非线性,采用小波分析和人工神经网络相结合的小波神经网络模型(WA-ANN)对白城地区浅层地下水埋深进行分析和预报。将研究区5口井2002-2009年逐月的降水量、蒸发量、人工开采量和前期水位埋深4个因素作为输入层,地下水埋深作为输出层,建立浅层地下水埋深预测模型,并采用"后验差"法对模型精度进行检验。检验结果表明,WA-ANN模型能很好地模拟该区地下水埋深变化规律,且拟合和预报精度均较高,相对误差小于10%。2010年以后的预报结果显示研究区地下水位呈逐年下降趋势,预计到2015年将下降1m,应及时加以控制。同时,笔者希望本次研究能为浅层地下水埋深预测提供一种新的途径。  相似文献   

Comparison of soil water content and corn yield in furrow and conventional ridge sown systems in a semiarid region of China   总被引：2，自引：0，他引：2  

Y.H. Jin  D.W. Zhou  S.C. Jiang 《Agricultural Water Management》2010,97(2):326-92

Water deficits and unusually warm soil temperatures can adversely affect conventional ridge sown systems. Increasingly serious water and temperature issues associated with global climate change may be problematic in the future, particularly in semiarid regions. This study explored the soil water and crop yield benefits of switching the sowing location of corn from ridges to furrows. Experiments were conducted over three years. Corn was grown in shallow furrow (SF) and deep furrow (DF) sown treatments until the V8 stage (eight visible leaf collars). New ridges were then built over the existing furrows. Grain yield was found to be higher in the SF and DF sown treatments than in a conventional ridge sown treatment (CR), especially in drought years. Switching sowing position from ridge to furrow could increase corn yield, directly, by improving soil moisture early in the growing season and, indirectly, by stimulating the growth of resource-capturing organs (e.g., leaves and roots). This simple and efficient approach to crop production in semiarid climates may be practical for the management of numerous agricultural systems, particularly those that are resource-limited, with greater vulnerability to the effects of global climate change.  相似文献   

Type and time of autumn tillage with and without herbicides at reduced rates in southern Sweden: 1. Yields and weed quantity     

Ullalena Bostrm 《Soil & Tillage Research》1999,50(3-4)

Environmental as well as economic incentives support the use of integrated weed management (IWM) systems for crop production. In order to reduce the input of agrochemicals for weed control, it may be possible to combine reduced doses of herbicides with appropriate tillage strategies and still maintain acceptable weed population levels. The purpose of this study was to compare the efficiency of different tillage strategies, with and without herbicides at 50% of normal rates, on weed populations and crop yields. The influences of type and time of stubble cultivation, harrowing and mouldboard ploughing were followed in eight long-term field trials in southern Sweden from 1988 until the spring of 1994. The crop rotations were dominated by spring-sown oats (Avena sativa L.) and barley (Hordeum distichon L.). Although significant site-by-year-by-treatment interactions were found, certain trends in influences of tillage on weeds and yields were identified. Weed density and weight often decreased in the order: stubble cultivation without ploughing > solely ploughing > stubble cultivation succeeded by ploughing. Grain yields of oats and barley varied 6–50% among tillage systems and the highest yields were often obtained in plots where ploughing succeeded stubble cultivation. Effects of tillage on weeds or yields were usually not influenced by herbicide application. Although only subnormal herbicide rates were used, weed density and weight were mostly reduced by 70–90%, while yields increased by 10–20%. In the spring of 1994, 1 year after the last herbicide application, densities of annual broad-leaved weeds were 40–65% lower in plots previously treated by herbicides than in non-treated plots, and differences among tillage systems were still significant. This study shows the advantage of combining herbicides at reduced rates with stubble cultivation and ploughing.  相似文献   

蒙吉陕三省半干旱区退化草原改良配套技术研究   总被引：4，自引：0，他引：4  

马志广  陈敏  聂素梅  王育青  闫志坚  安渊  杨志伟 《草地学报》1999,7(2):95-105

本课题在内蒙古、吉林和陕西三省区八个试验点,经三十年的试验研究,总结出-套退化草原改良技术。试验结果表明,在干旱及半干旱草原地区影响牧草产量的最基本因素是土壤水份的缺乏。基于上述生态学原理,东北西部及内蒙古东部地区,在以根茎禾草为主的退化草原用浅耕翻法改良;在内蒙古高原中部以丛生禾草为主的典型草原用松土法改良;在内蒙古西部和陕北黄土高原撂荒地用补播法改良。新研制的9SSB－1.75型和9SF－2.45型两种草原松土补播机以及在肝“八五”期间研制的草原改良多用机均可在天然草原作业,使开沟、松土、播种、施肥和镇压-次完成,使用稀土、根瘤菌、保水剂研制成的种子丸在均可提高保苗率。目前推广面积15.5万公顷。1995年国家科委批准为国家级科技成果重点推广项目(96140601A)。  相似文献   

白洋淀流域浅层地下水硝酸盐分布及来源的区域分异特征   总被引：1，自引：1，他引：0  

王仕琴  檀康达  郑文波  马林  宋献方  唐常源  胡春胜 《中国生态农业学报》2021,29(1):230-240

白洋淀位于雄安新区规划的核心范围,地下水是白洋淀流域主要的用水水源。由于白洋淀上游工业、生活污水的排放和农田肥料过量施用等农业面源引起的硝酸盐污染来源多样,使得流域内地下水硝酸盐污染较为普遍。然而,目前对全流域尺度地下水硝酸盐分布特征及来源仍不明晰。本文在分析过去近10年地表水和地下水硝酸盐数据的基础上,于2016年12月采集了平原区浅层地下水样品,结合水化学和硝酸盐氮同位素,从全流域尺度解析浅层地下水硝酸盐污染分布的时空差异和不同来源氮对地下水硝酸盐影响的程度。研究表明：山区典型流域河谷沉积带地下水硝酸盐浓度高值主要受农村厕所粪污水和局地污水排放影响（最高达313 mg·L^-1）,而历史时期农田有机肥施用是近年来地下水硝酸盐普遍升高的原因;雨季降水淋滤作用使地下水硝酸盐浓度明显升高,硝酸盐超标率大于旱季的2倍以上。平原区地貌类型控制着不同来源地下水硝酸盐的空间分布和迁移转化。2016年12月平原区130个浅层地下水硝酸盐超标率为21.5%,从上游到下游不同地貌类型地下水硝酸盐浓度中值呈现下降趋势：洪积扇（42.4 mg·L^-1） > 冲洪积扇（24.1 mg·L^-1） > 冲洪积平原（6.0 mg·L^-1）和河道带（6.2 mg·L^-1）,而硝酸盐氮同位素中值呈现上升趋势：洪积扇（12.8‰）和冲洪积扇（11.3‰） < 冲洪积平原（16.7‰） < 河道带（20.9‰）,说明从上游到下游地下水硝酸盐反硝化作用增强。其中山前平原洪积扇和冲洪积扇地区渗透性较好,地下水硝酸盐超标率高达33.3%和34.0%,主要来源于污水和有机肥。湖泊洼淀区典型生活和工业污水河周边,地下水硝酸盐则存在工业、生活和化肥多污染源并存的特征,且随着地表治污措施的影响地表水和地下水硝酸盐浓度变化较大,污水侧渗导致河道周边地下水硝酸盐浓度较高,距河道较远含水层强烈的还原条件使地下水硝酸盐浓度降低（<10 mg·L^-1）,污染风险较低。鉴于以上不同区域地下水硝酸盐脆弱性程度和风险水平的差异,提出了对白洋淀流域上游山区、山前平原洪积/冲洪积扇区、湖泊洼淀污水影响区等硝酸盐脆弱区实施区域分异农田面源污染和水环境整治及管理的建议,为雄安新区水环境安全保障提供科学依据。  相似文献   

喀斯特石漠化区农业土地利用对浅层地下水质量的影响   总被引：6，自引：0，他引：6  

刘方  罗海波  刘元生  刘鸿雁  何腾兵  龙健 《中国农业科学》2007,40(6):1214-1221

 【目的】探讨农业土地利用过程中喀斯特浅层地下水化学变化及农业种植活动对地下水质量的影响。【方法】在贵州中部喀斯特石漠化地区对不同生态区（阔叶林区、农林交错区、旱作农业区、复合农业区）进行植被和土壤调查及浅层地下水和地表径流水的采样分析。【结果】喀斯特石漠化区生态模式从阔叶林生态系统-农林生态系统-旱作农业生态系统-复合农业生态系统方向的演替过程中，其浅层地下水的HCO3-、SO42-、Ca2+、Mg2+ 、Na+、K+ 、NH4+、Cl- 、PO43-、NO3-、Pb的含量发生了明显的变化，在以种植玉米为主的低复种指数地区表现为NH4+及Pb、Cd含量的增加，而在以种指玉米或水稻、疏菜或油菜的高复种指数地区则表现在NO3-、SO42-、NH4+及Pb、Cr和Cd含量的增加。【结论】高复种指数农业区地下水的化学组成发生了明显地变化，浅层地下水质量出现一定程度的下降；作物种植结构和施肥水平是影响地下水质量的重要因素，在喀斯特地区发展农业生产的同时要兼顾地下水资源的保护。  相似文献