砂粒含量对土壤水分蓄持能力影响模拟试验研究

通过人工配制不同质地土壤,测定土壤水分特征曲线,研究了土壤中砂粒含量对其水分蓄持能力的定量影响.结果表明:(1)砂粒含量对土壤水分蓄持能力有较大影响.土壤持水能力随砂粒含量增加递减,表征土壤持水能力的水分特征曲线Gardner模型参数及表征土壤饱和含水量的Van Genuchten模型参数均随砂粒含量增加逐渐减小.(2)砂粒含量对土壤比水容量有较大影响,试验土壤在任一吸力水平下的比水容量值均随其砂粒含量增加递减.(3)试验土壤饱和含水量与砂粒含量呈线性关系,田间持水量、凋菱系数与砂粒含量都呈开口向下抛物线右半段的关系.(4)试验土壤有效水、迟效水含量随砂粒含量增加递减,二者与砂粒含量均呈开口向下抛物线右半段的关系.易效水含量与砂粒含量呈开口向上抛物线关系.     

黏粒质量分数对土壤水分蓄持能力影响的模拟试验

通过人工配制不同质地土壤,测定土壤水分特征参数,研究土壤中黏粒质量分数对其水分蓄持能力的定量影响。结果表明：1）黏粒质量分数对土壤水分蓄持能力有较大影响,土壤持水能力随黏粒质量分数增加而递增。2个水分特征曲线模型——Gardner模型及van Genuchten模型中,表征土壤持水能力的参数均随黏粒质量分数增加而增大。2）黏粒质量分数对土壤比水容量有较大影响,试验土壤在任一水吸力水平下的比水容量值均随其黏粒质量分数增大而增大。3）试验土壤饱和含水量、田间持水量分别与黏粒质量分数呈指数、对数正相关,凋萎系数与黏粒质量分数呈指数正相关。4）试验土壤有效水、迟效水含量随黏粒质量分数增加呈先升高后降低趋势,二者与黏粒质量分数均呈抛物线关系,最高点分别出现在黏粒质量分数为35.9%和35.8%处,易效水含量与黏粒质量分数相关性不显著。研究结果可为黄土区土壤水分蓄持机制进一步研究提供一定理论依据。     

生物质炭对旱地红壤理化性状和水力学特性的影响

[目的]研究生物质炭对旱地红壤基本理化性质及水分特征曲线的影响,为红壤地区土壤改良提供依据。[方法]分层测定不同生物质炭施用量水平下的土样容重、孔隙度和有机碳含量,采用原状土压力膜法分层测定土壤的水分特征曲线。[结果]施用生物质炭能显著降低土壤的容重,提高土壤的孔隙度及有机碳含量,且随着施用量的增加,土壤容重逐渐降低,孔隙度及有机碳含量逐渐提高;随着生物质炭施用量的增加,土壤饱和含水量、田间持水量和有效水含量逐渐增加,凋萎系数逐渐减小,施用生物质炭30t/hm2的土壤处理饱和含水量、田间持水量和有效水含量最高;生物质炭施用量与土壤饱和含水量、田间持水量和有效水含量呈极显著正相关关系,与凋萎系数呈极显著负相关关系。[结论]施用生物质炭能显著提高红壤田间持水量和有效水含量。     

东北黑土区土壤侵蚀对土壤持水性的影响

为探究不同侵蚀程度对土壤持水性的影响,采用压力膜法对表土分别被侵蚀剥离0,10,20,30,40,50,60,70cm,3次重复,共计48个试验小区的土壤田间持水量、凋萎湿度进行测定,计算其土壤有效水含量。结果表明:随土壤侵蚀程度增加凋萎湿度呈微弱上升趋势,田间持水量和土壤有效水含量逐渐降低。土壤侵蚀70cm时,田间持水量降低7%,有效水含量降低11%。随侵蚀程度增加,土壤有机质含量下降。土壤田间持水量、有效水含量与土壤有机质含量呈正相关,与容重呈负相关。     

太湖地区主要水稻土的土壤水分参数研究

太湖地区主要水稻土类型的水分参数研究结果表明 ,水稻土 4个土层的土壤水分特征曲线基本一致。土壤的饱和含水量、田间持水量、凋萎系数和土壤有效水的含量均从土壤上层到下层呈降低的趋势 ;土壤的非饱和导水率与负压水头之间呈负相关的指数曲线变化 ,当负压水头达到 10 k Pa时 ,非饱和导水率降低到最小值 ,且基本趋于稳定 ;非饱和土壤水扩散率变化于 1.1× 10 - 3～ 1.886× 10 - 3cm2 / min之间 ,非饱和土壤水扩散率随含水量也呈指数曲线变化。     

石油烃污染对土壤持水特征及水分有效性的影响

石油烃污染土壤已经成为我国一个严重的环境问题,污染后的土壤理化性质发生改变,直接影响土壤的持水特性及水分有效性,确定石油烃污染对土壤持水特征和水分有效性的影响及其程度可为揭示石油烃污染对土壤性质的影响提供新的科学认识。通过人工配置柴油和原油不同污染浓度污染的黄绵土,利用离心机法测定土壤水分特征曲线,分析了土壤的持水特征与水分有效性。结果表明:(1)不同浓度柴油与原油污染土壤后,水分特征曲线均位于未污染土壤的下部,其中原油污染的影响更甚。(2)水分特征曲线van Genuchten模型参数θ_s、θ_r随着污染浓度的增加呈现指数衰减,参数α值呈幂函数减小、n值出现随污染浓度对数增加的特点。(3)土壤的饱和含水量、田间持水量以及凋萎含水量均随柴油、原油污染浓度的增加出现下降趋势,表观土壤有效含水量随污染浓度表现出先降后升的U字形的变化模式。无论原油还是柴油污染土壤,均会影响土壤的持水特征和水分有效性,影响的大小与石油烃的类型和浓度密切相关。     

砾石对丘陵紫色砾质土持水性的影响

通过红棕紫泥、灰棕紫泥、棕紫泥原状土和扰动土的持水性实验,研究了砾石对丘陵紫色砾质土持水性的影响.结果表明,在考虑砾石的情况下,原状土饱和含水量减少0.70%～10.70%,田间持水量减少2.07%～4.33%;砾石含量＜10%,饱和含水量和田间持水量与砾石含量关系不明显;砾石含量＞10%,饱和含水量和田间持水量随砾石含量减少而增加;在0～30 kPa吸力段,原状土和扰动土的持水能力、幂函数拟合式的α值、原状土物理性黏粒含量、扰动土比水容量都随砾石含量减少而增大;原状土的比水容量随砾石含量减少而减小.     

生物炭添加对皖南旱地土壤物理性质及水分特征的影响

为明确生物炭添加对皖南旱地典型土壤供水能力的影响,采用室内模拟实验,研究了3种生物炭(竹炭、稻炭和烟炭)及3种添加比例(2%,5%,10%)对皖南旱地土壤物理性质及水分特征的影响。结果显示:土壤容重随生物炭添加量的增加而减小,土壤总孔隙度、毛管孔隙度、吸湿系数、凋萎湿度、饱和持水量及田间持水量随生物炭的添加而呈增加的趋势,竹炭2%、5%和10%添加处理及稻炭与烟炭5%和10%添加处理在降低土壤容重、增加孔隙度、吸湿系数、凋萎湿度、饱和持水量和田间持水量较对照有差异显著(P0.05)。随着生物炭添加量的增加,土壤有效水分范围进一步增大,速效水与中效水含量增加,提高了土壤对作物的供水能力;同时,生物炭在一定程度上减少了水分蒸发,提高了土壤的保水保湿能力。因此,合理施用生物炭对改善土壤供水能力有着重要作用,在我国南方红壤旱地中有很强的适用性。     

几种常用绿地改良材料对土壤水分特征的影响

分析了几种常用绿地土壤改良材料及其不同配比对土壤水分特征曲线和水分常数的影响,结果表明:利用RETC软件对各配比土壤水分特征曲线van Genuchten方程的参数拟合效果较好,R2均大于0.99;随着砂粒含量的增加,土壤田间持水量降低,土壤中水分有效性比例增加,但砂粒粒径对土壤水分常数影响不显著;绿化植物废弃物能提高土壤田间持水量和有效水含量,降低土壤凋萎含水量;绿化植物废弃物还能提高有效水占田间持水量的比例,以20%绿化植物废弃物的用量为最大,为49.59%;聚丙烯酰胺(PAM)虽然能提高土壤田间持水量,但阻碍土壤水分的释放,降低土壤水分的有效性;脱硫石膏可以增加土壤田间持水量和水分的有效性。综合而言,以70%土、10%砂、20%绿化植物废弃物和0.5 kg/m~3脱硫石膏的配比相对最佳。     

容重对土壤饱和水分运动参数的影响

通过石蜡固定容重方法测定了4种土壤不同容重下的饱和重量含水量与饱和导水率，分析了容重对这两个土壤饱和水分运动参数的影响。结果表明：饱和重量含水量随容重的增加而减小，与容重成反比关系．饱和导水率随着容重的增加呈现幂函数形式递减。这些结果将为构建变容重土壤水分运动创新性理论体系提供适当的定量关系，有利于实现土壤水资源的合理利用。     

容重对土壤水分入渗能力影响模拟试验

通过人工改变土壤颗粒级配,配制典型砂壤、中壤、黏壤,并设置不同容重水平,用土柱积水入渗模拟了土壤容重对其入渗能力的影响,为土壤改良和促进天然降水转化利用提供理论依据。结果表明,容重对土壤入渗能力有较大影响。试验土壤入渗能力随容重增大递减,3种典型土壤稳定入渗速率与容重均呈对数负相关,砂壤120 min累积入渗量与容重呈幂函数负相关,中壤、黏壤则呈线性负相关。考斯加科夫入渗模型中,表征初始入渗速率的参数随容重增大递减,表征入渗能力衰减速度的参数则随容重增大递增,说明土壤初始入渗能力随容重增大递减,入渗能力衰减速度随容重增大递增。     

基于主成分分析红壤有效含水量估算模型

季节性干旱是南方红壤地区农业可持续发展面临的关键科学问题，土壤有效含水量是评价土壤对植物给水能力的重要因子之一。该文以红壤为研究对象，在江西省采集了34个红壤样品，测定了土壤田间持水量、永久萎蔫系数、有机质含量、土壤容重、土粒密度和土壤质地组成(砂粒，粉砂粒和黏粒)的百分含量等土壤物理参数，并对这些因子进行主成分分析，建立经验回归模型，相关系数为0.87。结果表明：区域红壤有效含水量可以通过土壤物理参数估算，通过主成分分析等统计方法对于大面积估算土壤有效含水量是可行的。     

种植果树对土壤物理性状的双重效应

在渭北果区选择不同园龄(<10 年、10~20 年、>20 年)果园, 分层测定0~60 cm 土层土壤容重、土壤坚实度、土壤含水量以及表层土壤团聚体组成等物理性状, 进一步分析了果园土壤物理性状随园龄的变化特征。结果表明: 土壤容重在0~30 cm 土层随园龄增长而降低; 在30 cm 以下土层随园龄增长而增加, 超过了健康园艺土壤的质量标准1.30 g·cm^-3; 与休闲农田相比, 种植果树可降低10~30 cm 土层土壤容重; 但30 cm 以下土层土壤坚实度急剧增大, 接近或达到了限制根系延伸的土壤质量标准1 000 kPa; 与休闲农田相比, 种植果树对于降低17.5~27.5 cm 土层的坚实度具有明显作用。果园表层土壤团聚体状况整体较差, 水稳性优势团聚体直径为0.5~0.25 mm, >0.25 mm 水稳性团聚体含量随园龄增加而增大, >20 年果园比<10 年果园高1 倍。种植果树对表层土壤具有明显的保护和改善作用, 却在深层发生着紧实化和坚硬化过程。果树对土壤物理状况的双重效应体现在对0~30 cm 土层土壤结构具有改善作用, 对30 cm 以下土层土壤结构有破坏作用。果园土壤“深层的隐蔽性退化过程”影响着果树根系健康生长, 应当给予极大关注。     

砂姜黑土钙质结核剖面分布特征及其对土壤持水性的影响

钙质结核是砂姜黑土重要的成土特征,直接影响土壤结构和水分运移,但目前关于钙质结核对土壤持水性作用机制的研究主要集中在实验室尺度,而且报道较少。基于此,该研究在田间尺度上研究了钙质结核剖面垂直分布特征及其对土壤持水性的影响。结果表明:钙质结核主要分布在20cm以下的土层,其含量和粒径均随土层深度的增加呈现增大趋势,80～100 cm土层钙质结核质量分数可达11.42%。2～5、5～8、8～30 mm的钙质结核饱和含水率分别为0.25、0.22和0.20 cm3/cm3,均远低于土壤饱和含水率。土壤饱和含水率、田间持水量和萎蔫点均随钙质结核含量的提高而逐渐降低。但是含钙质结核土层土壤有效持水量与钙质结核含量呈现显著正相关关系,钙质结核有利于改善砂姜黑土黏重的土壤质地。研究结果可为深入了解砂姜黑土水分运动规律及中低产田改良提供理论依据。     

利用计算机断层扫描技术研究土壤改良措施下土壤孔隙

为探明不同土壤结构改良措施（秸秆覆盖、免耕、有机肥、保水剂）对土壤孔隙特征及分布的影响,采用计算机断层（computed tomography,CT）扫描法定量分析了土壤孔隙的数目、孔隙度及孔隙在土壤剖面上的分布特征。结果表明：不同措施均提高了土壤总孔隙数、大孔隙数及0.13～1.0 mm孔隙数,且其孔隙度也相应提高。同时孔隙成圆率也得到了改善。各处理中以有机肥和免耕处理效果较佳,其次为保水剂和秸秆覆盖,对照最低。此外,不同措施显著提高了土壤的田间持水量和＞0.25 mm 水稳性团聚体含量,降低了土壤容重,且各处理中,仍以有机肥和免耕处理效果最佳,其田间持水量分别较对照提高了15.9%和16.4%,而土壤容重较对照降低了6.8%和8.8%。相关分析表明：田间持水量、容重和＞0.25 mm水稳性团聚体含量与土壤总孔隙度和大孔隙度呈显著或极显著正相关;而土壤容重对于总孔隙度和大孔隙度及孔隙成圆率呈显著负相关。     

秸秆不同还田方式对土壤入渗特性及持水能力的影响

通过入渗试验及对土壤水分特征曲线的测定,对比研究了秸秆在经过粉碎、氨化及与无机土壤改良剂混合3种措施处理后加入土壤中对土壤入渗特性及持水特征的影响。结果显示：长秸秆处理加入土壤后显著降低土壤入渗能力;粉碎氨化后的秸秆较对照处理及粉碎秸秆处理能显著增加土壤稳定入渗率、土壤累积入渗量,同时在经过30 d培养后土壤体积质量较对照低7.13%;无机土壤改良剂（氢氧化铁）能显著提高土壤稳定入渗率和累积入渗量,但在减小土壤体积质量、增加土壤孔隙度作用方面不如氨化秸秆处理显著,同时当秸秆与其混合加入土壤时未对土壤改良效果起到正交互作用;各种处理土壤持水能力差异不明显,但粉碎并氨化措施处理过的秸秆在中低吸力段均表现出较高的土壤持水能力,这对于提高旱区农田蓄水保墒抗旱能力有重要意义。     

Water erosion risk assessment and impact on productivity of a Venezuelan soil

Soil losses affect the physical, chemical and biological soil properties and as a consequence reduce soil productivity. Erosion reduces or eliminates root-explorable soil depth and crop available water, selectively decreases the nutrient and organic matter content, and exposes soil layers with unsuitable characteristics for crop growth. Yield is hence assumed to be a function of root growth, which in turn is a function of the soil environment. In order to evaluate the water erosion impact on soil properties and productivity, a study was carried out on a Typic Haplustalfs soil, with sorghum (Sorghum bicolor (L) Moench), located in Chaguaramas in the Central Plains of Venezuela. Four different study locations with the same soil type, with slopes ranging from 3% to 6% and with different levels of erosion were selected: Chaguaramas I (slightly eroded), Chaguaramas II, (moderately eroded), Chaguaramas III (moderately eroded), and Chaguaramas IV (severely eroded). A sorghum–livestock farming system was introduced 30 years ago. Secondary tillage with a disc harrow (without mulch on the topsoil) was applied for seedbed preparation. Fertilizers and pesticides were applied uniformly over the entire fields. Soil samples from each horizon were analysed for particle size distribution, water retention, bulk density, pH and organic matter content. The relative production potential was estimated using the Productivity Index developed by Pierce et al. [Pierce, F.C., W.E. Larson, R.H. Dowdy and W.A. Graham. 1983. Productivity of soils: assessing long-term changes due to erosion. Journal of Soil and Water Conservation. 38 39–44.], and adapted to the methodology proposed by Delgado [Delgado F. 2003. Soil physical properties on Venezuelan steeplands: applications to conservation planning. The Abdus Salam International Centre for Theoretical Physics. College on Soil Physics. 11 pp.] for Venezuelan soil conditions. The Productivity Index (PI) could estimate the tolerable rate of soil productivity loss. A soil erosion risk was assessed by the Erosion Risk Index (ERI) taking into account the soil hydrological characteristics (infiltration–runoff ratio), rainfall aggressiveness and topography (slope). The Productivity Index (PI) and the Erosion Risk Index (ERI) were used to classify the lands for soil conservation priorities, for conservation requirements and for alternative land uses. The results showed that: (a) the Productivity Index (PI) decreased with increasing level of erosion, (b) the Productivity Index (PI) was mainly affected by changes in available water storage capacity, bulk density and pH, (c) the erosion risk (ERI) was strongly affected by slope gradient and rainfall aggressiveness, (d) the areas were classified as critical lands and super-critical lands, with high to very high soil conservation requirements, depending on the level of soil erosion.     

Water erosion risk assessment and impact on productivity of a Venezuelan soil

Soil losses affect the physical, chemical and biological soil properties and as a consequence reduce soil productivity. Erosion reduces or eliminates root-explorable soil depth and crop available water, selectively decreases the nutrient and organic matter content, and exposes soil layers with unsuitable characteristics for crop growth. Yield is hence assumed to be a function of root growth, which in turn is a function of the soil environment. In order to evaluate the water erosion impact on soil properties and productivity, a study was carried out on a Typic Haplustalfs soil, with sorghum (Sorghum bicolor (L) Moench), located in Chaguaramas in the Central Plains of Venezuela. Four different study locations with the same soil type, with slopes ranging from 3% to 6% and with different levels of erosion were selected: Chaguaramas I (slightly eroded), Chaguaramas II, (moderately eroded), Chaguaramas III (moderately eroded), and Chaguaramas IV (severely eroded). A sorghum–livestock farming system was introduced 30 years ago. Secondary tillage with a disc harrow (without mulch on the topsoil) was applied for seedbed preparation. Fertilizers and pesticides were applied uniformly over the entire fields. Soil samples from each horizon were analysed for particle size distribution, water retention, bulk density, pH and organic matter content. The relative production potential was estimated using the Productivity Index developed by Pierce et al. [Pierce, F.C., W.E. Larson, R.H. Dowdy and W.A. Graham. 1983. Productivity of soils: assessing long-term changes due to erosion. Journal of Soil and Water Conservation. 38 39–44.], and adapted to the methodology proposed by Delgado [Delgado F. 2003. Soil physical properties on Venezuelan steeplands: applications to conservation planning. The Abdus Salam International Centre for Theoretical Physics. College on Soil Physics. 11 pp.] for Venezuelan soil conditions. The Productivity Index (PI) could estimate the tolerable rate of soil productivity loss. A soil erosion risk was assessed by the Erosion Risk Index (ERI) taking into account the soil hydrological characteristics (infiltration–runoff ratio), rainfall aggressiveness and topography (slope). The Productivity Index (PI) and the Erosion Risk Index (ERI) were used to classify the lands for soil conservation priorities, for conservation requirements and for alternative land uses. The results showed that: (a) the Productivity Index (PI) decreased with increasing level of erosion, (b) the Productivity Index (PI) was mainly affected by changes in available water storage capacity, bulk density and pH, (c) the erosion risk (ERI) was strongly affected by slope gradient and rainfall aggressiveness, (d) the areas were classified as critical lands and super-critical lands, with high to very high soil conservation requirements, depending on the level of soil erosion.