北方风沙区砾石对堆积体坡面径流及侵蚀特征的影响

为了研究砾石对工程堆积体降雨侵蚀规律的影响,采用室内人工模拟试验,以土质堆积体(砾石质量分数为0)为对照,研究了10%、20%和30%砾石质量分数堆积体边坡在模拟降雨条件下的径流水力特征、产沙过程及侵蚀动力机制。结果表明:1)产流0~6 min,砾石促进堆积体坡面细沟间径流流动;产流12~30 min后,砾石阻碍堆积体坡面细沟径流流动;2)含砾石堆积体坡面粗糙度增大,水流流态变缓,水流速度降低,且均以层流为主。较土质堆积体而言,30%砾石质量分数堆积体坡面阻力系数增大88.8%~288.4%,弗汝德数降低28.9%~41.8%,水流速度降低0~45.8%;3)径流含沙量随产流历时经历快速降低-平稳过渡-波动上升3个阶段,土质及10%砾石质量分数堆积体高含沙水流现象频发,且随雨强增大,重力坍塌次数增加,重力侵蚀程度增强。20%、30%砾石质量分数堆积体发生高含沙水流的几率约为0。相对土壤流失比与砾石质量分数呈极显著负指数函数关系;4)土壤剥蚀率与各侵蚀动力参数均可用简单线性函数关系描述,单位径流功率是描述风沙区土质和10%砾石质量分数工程堆积体侵蚀产沙的最优因子,径流功率是刻画20%、30%砾石质量分数工程堆积体土壤侵蚀参数更为合理的因子。结果可为全国范围工程堆积体土壤侵蚀模型的建立提供科学依据。     

坡面径流水蚀动力参数室内试验及模糊贴近度分析

为了确定何种水蚀动力参数能更好地描述径流剥蚀土壤的过程,该文在坡度为3°～30°和流量为2.5～6.5 L/min范围内采用变坡土槽径流冲刷试验,对土壤水蚀动力过程进行了系统模拟,并运用模糊贴近度的分析方法,系统地研究了坡面水蚀动力参数(单宽径流能耗、水流剪切力、水流功率和单位水流功率)与土壤剥蚀率之间的贴近程度。研究结果表明:流量相同时,单宽能耗与土壤剥蚀率贴近程度最大,水流功率次之,且单宽能耗和水流功率分别与土壤剥蚀率呈线性关系,该研究说明单宽能耗和水流功率能较好地描述径流剥蚀土壤过程。     

坡面土壤剥蚀率与水蚀因子关系室内模拟试验

为了确定影响十壤剥蚀率的丰要侵蚀因子,该文采用变坡土槽在较大坡度(9°～24°)和流量(2.5～6.5 L/min)范围内进行了径流冲刷试验,运用逐步回归法,系统地分析了土壤剥蚀率与坡度和流量、水流剪切力、水流功率、单位水流功率和单宽能耗各因子之间的关系,建市了基于水流功率和坡度的土壤剥蚀率二元线性公式(R2=0.977).结果表明,土壤剥蚀率和各水蚀因子都显著相关,土壤剥蚀率与坡度和流量呈幂函数关系(R2=0.77),土壤剥蚀率与水流剪切力呈幂函数关系(R2=0.908),土壤剥蚀率随着水流功率的增加呈线性增加(R2=0.945),土壤剥蚀率和单宽能耗呈线性关系(R2=0.91),土壤剥蚀率与单位水流功率呈三次方关系(R2=0.52);坡度和水流功率是影响土壤剥蚀率的土要凶素.     

集中水流内红壤分离速率与团聚体特征及抗剪强度定量关系

为明确红壤结构特征与抗剪强度对坡面土壤分离能力的影响,选取8种典型红壤为研究对象,通过团聚体稳定性分析,饱和抗剪强度测定,和室内模拟冲刷试验,就各参数间定量关系进行了初步探讨。研究结果表明:团聚体稳定性特征参数As集合了红壤团聚体破碎的主要机制,与不同水流剪切力中红壤分离速率有较好的相关性;红壤饱和抗剪强度(σs)与集中水流内临界水流剪切力(τc)呈较好的线性关系。基于WEPP细沟侵蚀模型,将团聚体稳定性特征参数As代替可蚀性因子Kc,饱和抗剪强度(σs)代替临界水流剪切力(τc),得出新的预测方程。结果显示预测方程能准确的预测坡面集中水流内红壤分离速率(R2=0.887 1)。该结果为深入研究红壤侵蚀机理提供了新思路,对完善侵蚀物理过程模型具有重要的意义。     

紫色土细沟剥蚀率对近地表水流作用的响应

近地表水流的存在会加剧土壤侵蚀过程,剥蚀率是土壤侵蚀预报模型的重要物理参数,其对近地表水流的响应值得进一步研究.采用限定性细沟模拟冲刷试验,探讨不同工况条件(3个近地表水流饱和深度5,10,15 cm;3个坡度5°,10°,15°;3个流量2,4,8 L/min)下紫色土细沟剥蚀特征.结果表明:不同近地表水流饱和深度下...     

Stability analysis of aggregates in relation to the hydrophobicity of organic manure for Sri Lankan Red Yellow Podzolic soils

Aggregate slaking is linked with rapid pressure buildup within aggregates. Soil water repellency may help hamper the pressure buildup within aggregates by reducing their wetting rates. We examined the effects of animal manure in improving aggregate stability, the hydrophobic effects of green manure, and the possibility of using organic manure mixtures to increase the aggregate stability for Sri Lankan red yellow podzolic soils using model aggregates. Almost all the cow dung (CD) added samples showed extremely low percentages of water stable aggregates (%WSA) demonstrating rapid destruction of aggregates. Although the addition of ≥ 10% goat dung (GD) improved the %WSA, aggregate floating occurred, showing the risk of aggregate floating with runoff water. Addition of 5% GD would be an acceptable solution if the %WSA can be improved. Casuarina equisetifolia L. leaves (CE) was found to be a hydrophobic green manure. Although addition of ≥ 5% CE increased the %WSA up to about 90%, aggregate floating occurred. The possibility of improving %WSA using 1–2% hydrophobic green manure in organic manures mixtures was tested. Samples with 5% GD + 2% CE manure mixture showed the highest and the most stable %WSA without showing aggregate floating. Additions of compost and poultry litter were found not to be effective in improving aggregate stability with or without CE. Strong or higher water repellency was not observed in any of the samples with manure mixtures, showing that the addition of 1–2% hydrophobic CE would not induce detrimental effects of water repellency. There was no clear correlation between %WSA and the hydrophobicity of soils. However, the %WSA can be considered to show a tendency to increase with increasing hydrophobicity, because the %WSA was very high in samples with hydrophobic CE, the %WSA increased when mixed with 1–2% CE, and samples with highest water drop penetration time (WDPT) among all the manure mixtures showed the highest %WSA.     

Soil degradative effects of slope length and tillage methods on alfisols in western Nigeria. III.Soil physical properties

Effects of six slope lengths, 60 m to 10 m with 10-m increments, on soil physical properties were evaluated for plough-based conventional till and no-till seedbed preparation on field runoff plots for three consecutive years from 1984 to 1987. Soil physical properties measured included texture, bulk density, infiltration capacity, and soil moisture retention characteristics. Conventional till treatment caused a rapid increase in soil bulk density and penetration resistance, and decrease in available water capacity and equilibrium infiltration rate. Gravel content increased with cultivation duration. Soil bulk density of 0–5 cm depth was 1·20 Mg m⁻³ for 1984, 1·39 Mg m⁻³ for 1985 and 1·46 Mg m⁻³ for 1986 for conventional till; and 1·13 Mg m⁻³ for 1984, 1·33 Mg m⁻³ for 1985, and 1·27 Mg m⁻³ for 1986 for the no-till treatment. The penetration resistance of the no-till treatment was relatively low and increased with cultivation duration. Mean penetration resistance for 0–5 cm depth was 2·2 kg cm⁻² in 1984, 2·71 kg cm⁻² in 1985, and 3·79 kg cm⁻² in 1986. The available water capacity decreased in both tillage methods without any consistent trends with regard to slope length. The equilibrium infiltration rate declined drastically for long slopes and conventional till methods. The data support the conclusion that these soils should be managed with short slope lengths and a no-till method of seedbed preparation. © 1997 John Wiley & Sons, Ltd.     

番茄果实品质和叶片保护酶对水肥水平的响应

通过3个土壤相对含水量（W1,50%～60%; W2,7～0%80%; W3,90%～100%）和3个施肥水平（F1,N 0.187 g/kg+ P2O5 0.131 g/kg; F2,N 0.267g/kg+ P2O5 0.187 g/kg; F3,N 0.347 g/kg+ P2O5 0.243 g/kg）共9个处理的盆栽试验,研究了番茄结果期果实品质、叶片保护酶及叶绿素含量的变化规律,旨在为番茄结果期合理的水肥管理提供理论依据。结果表明: 在整个结果期,W1F2处理有利于提高果实品质; W2F2处理下果实中的渗透物质（游离氨基酸）保持着较高水平,且叶片保护酶活性较高,丙二醛含量低; W2F3处理的叶片叶绿素含量保持较高水平,W2F2处理番茄果实单株产量高。相关分析表明: 果实品质与超氧化物歧化酶、叶绿素含量呈正相关,而与丙二醛含量呈负相关; 游离氨基酸含量与过氧化物酶活性、脯氨酸含量呈显著正相关,而与丙二醛含量呈显著负相关。综合分析,番茄结果期较优的水肥组合为N 0.267g/kg+P2O5 0.187g/kg和70%80%的土壤相对含水量。     

反求根系吸水速率方法的检验与应用

土壤含水率剖面实测时间间隔T与实测点间距SI是影响平均根系吸水速率反求方法的2个主要因子。通过数值实验，首先探讨分析了T和SI的不同取值条件下，平均根系吸水速率模拟值的误差效应，从实际应用角度出发，若设定平均根系吸水速率的最大绝对误差≤0.0015 d^-1，总体相对误差≤15%，则T和SI的选取最好能限制在如下范围之内：5 d≤T<15 d，SI<20 cm。应用上述检验分析结果，对两种水分胁迫条件下土柱实验中苗期冬小麦的根系吸水进行了模拟分析，结果表明：持续的水分胁迫将显著地降低冬小麦根系的吸水速率，抑制其根系的生长；当上部土层水分供应不足时，小麦的自我调节功能可导致根系扩大其吸水范围，向下部土层生长。     

高速公路不同边坡土壤保持措施对土壤侵蚀速率影响分析

研究郑州西南绕城高速公路边坡不同土壤保持工程措施,在一定植被盖度(90%、70%、50%、30%、10%)下,不同降雨强度对土壤侵蚀速率的影响。按照区组试验设计,对郑州西南绕城高速公路小拱架、方形网状、未实施工程措施的三种类型边坡在不同降雨强度下产生的土壤侵蚀速率进行了测定。建立一定盖度下,土壤侵蚀速率与降雨强度关系15种模型。利用模型和降雨强度区间的不定积分计算不同工程类型的土壤保持效率。结果表明:三种类型边坡,土壤侵蚀速率随降雨强度呈幂函数增加;小拱架、方形网土壤保持效率随盖度的增大而增大,当盖度为50%~70%时达到最大值,后随盖度的增大而减小。小拱架土壤保持效率平均为方形网防护的1.28倍。