Soil texture and irrigation influence the transport and the development of Pasteuria penetrans, a bacterial parasite of root-knot nematodes     

K.R Dabiré 《Soil biology & biochemistry》2004,36(3):539-543

The transport of the spores of Pasteuria penetrans was studied in three contrasted textured soils (a sandy, a sandy-clay and a clay soils), cultivated with tomato, inoculated with juveniles of Meloidogyne javanica and watered with 25 or 150 mm day⁻¹. One month after inoculation of the nematodes, 53% of the spores inoculated were leached by water flow in the sandy soil but only 14% in the sandy-clay soil and 0.1% in the clay soil. No nematodes survived in the clay soil, while the population was multiplied both in the sandy and in the sandy-clay soils. But juveniles of M. javanica were more infected by P. penetrans in the sandy-clay soil than in the sandy soil. Comparing different combinations of bare soils containing 1.1-57% of clay showed that the best spore percolation and retention balance occurred in soils amended with 10-30% clay. However, the spore recoveries decreased when the soil was enriched with more than 30% clay. The role of clay particles on the extractability of spores and on their availability to attach to the nematode cuticle in the soil is discussed.  相似文献   

土壤固定态铵的影响因素   总被引：14，自引：3，他引：14       下载免费PDF全文

廖继佩  林先贵  曹志洪  张杨株 《土壤》2003,35(1):36-40

本文研究了有机质、全氮、有机氮、粘粒、CEC、溶液中铵浓度、水分、温度等影响土壤固定态铵含量的因素。结果表明,固定态铵与<0.01lmm的粘粒呈显著正相关,但与<0.00lmm的粘粒、有机质、全氮、有机氮、CEC相关性很差。通过拟合Langmuir方程可知河沙泥的最大固铵量为357.2mgN/kg,这与359mgN/kg相近。无论是潮沙泥还是紫泥田,固定态铵含量均有:30oC>20oC,30oC>40oC。除了黄泥田外,紫泥田,河沙泥和潮沙泥三种土壤的固定态铵含量均有:长期淹水>干湿交替8次>长期干燥。  相似文献   

Persistence of soil compaction due to high axle load traffic. I. Short-term effects on the properties of clay and organic soils     

Laura Alakukku 《Soil & Tillage Research》1996,37(4):211-222

Short-term effects of high axle load traffic on soil total porosity and pore size distribution were examined in field experiments on a clay (Vertic Cambisol) and an organic soil (Mollic Gleysol) for 3 years after the heavy loading. The clay soil had 48 g clay (particle size less than 2 μm) per 100 g in the topsoil and 65 g per 100 g in the subsoil. The organic soil consisted of well-decomposed sedge peat mixed with clay below 0.2 m depth down to 0.4–0.5 m and was underlain by gythia (organic soil with high clay content). The experimental traffic was applied with a tractor-trailer combination in autumn 1981. The trailer tandem axle load was 19 Mg on the clay and 16 Mg on the organic soil. There were three treatments: one pass with the heavy axle vehicle, with wheel tracks completely covering the plot area, four repeated passes in the same direction, and a control treatment without experimental traffic. During loading, the clay was nearly at field capacity below 0.1 m depth. The organic soil was wetter than field capacity.

One and four passes with the high axle load compacted both soils to a depth of 0.4–0.5 m. On the clay soil the total porosity was reduced by the heavy loading nearly as much as macroporosity (diameter over 30 μm) to 0.5 m depth. On the organic soil, macroporosity was reduced and microporosity (under 30 μm) increased in the 0.2–0.5 m layer by the heavy loading. Total porosity did not reveal the effects of compaction on the organic soil. The compaction of the clay below 0.1 m persisted for 3 years following the treatment despite annual ploughing to a depth of 0.2 m, cropping and deep cracking and freezing. Likewise, in the subsoil (below 0.2 m) of the organic soil, differences in pore size distribution persisted for a period of at least 3 years after the heavy loading.  相似文献   

三江平原白浆土发生学特性   总被引：1，自引：1，他引：1  

邢宝山  M. J. Dudas  张之一  徐琪 《土壤学报》1994,31(1):95-104

本文对三江平原三个典型白浆土剖面的理化性质、土壤微形态和矿物学性质的研究，探讨了白浆土的发生学特性。土体中Ｚｒ／Ｓｒ和Ｔｉ／Ｚｒ比率的变异系数表明，所研究的土壤剖面其成土母质岩性是连续的。典型白浆土具有一个松软的表土层、一个漂白层和一个相当厚的粘化淀积层。研究还表明，粘粒的悬浮迁移是白浆土的主要成土过程。表层和白浆层在成土过程中有Ｆｅ－Ｍｎ结核形成，且是原地形成的，其Ｆｅ、Ｍｎ明显源于原生矿物的风  相似文献   

电解质种类和浓度影响磷酸根解吸的机理研究     

何振立  袁可能  朱祖祥 《土壤学报》1992,29(1):26-33

本文研究了吸附性阳离子、电解质浓度和组成影响几种矿物和土壤吸附态磷的解吸的机理。结果表明,吸附性阳离子影响磷酸根解吸与离子桥有关。桥接静电场愈强,被束缚磷的释放就愈困难。电解质阳离子对磷酸根解吸的影响则取决于其对表面负电荷的屏蔽效应。阳离子电价高,屏蔽作用大,磷解吸就少。电解质浓度影响吸附态磷的解吸主要与表面电位的变化有关。当pH>PZC值时,提高电解质浓度降低表面负电位,从而减少磷的吸附;当pH<PZC时,提高电解质浓度则降低表面正电位,促进磷的解吸。磷酸根解吸盐效应零点(P_PZSE)值一般都介于土壤或矿物样品吸附磷酸根前后测得的两个PZC值之间。不同浓度电解质溶液中磷解吸量之差与吸附层电位变化量(△ψ_x)呈正相关。  相似文献   

地基土液化特性的试验研究     

牛琪瑛  张素姣 《山西农业大学学报(自然科学版)》2002,22(2):175-177

本文通过室内动三轴对不同级配、不同粘土矿物成分、不同粘粒含量、不同干重度的重塑土所进行的系统试验 ,得出不论所含何种粘土矿物、也不论干重度及粗颗粒级配如何抗液化强度均在粘粒含量为 9%左右最低的变化规律。  相似文献   

华南某些低地粘性土粘粒矿物学和化学组成及其数学表征     

黄瑞采  潘根兴  程明焰 《南京农业大学学报》1987,(1)

本文是对我国热带亚热带7个低地粘性土的粘粒部分的矿物学和化学组成的分析资料及其计算机数学分析结果。这些土壤的粘粒矿物学组成有很大差异,但都有相当量的高岭石剖面中存在脱硅富铝趋势。主组元分析和因子分析表明,粘粒部分化学元素的赋存状态基本上可分为硅酸盐矿物组和氧化物组。粘粒矿物学和元素组成特点的差异,主要决定于母质的起源特性,而并非决定于气候。但利用条件对耕层土壤的粘粒的矿物学和元素组成有明显的影响,作为水耕成土过程的特点,铁铝发生了分异运动。此外,主组元分析和因子分析是分析土壤中多种组分相互联系的良好方法。  相似文献   

粘盘层的粘化和水分特征与林木生长的关系     

马焕成  丁瑞兴 《西南林学院学报》1992,12(1):17-23

本文通过分析含粘盘层土壤的水分和粘化特征,认为粘盘层影响林木生长的因素有三:①土壤过分紧实粘重,大孔隙少,极细孔隙多,使根系不易下扎;②由于水分不易下渗,使表层水分过多,常造成表层滞水、包浆等还原现象,易造成铁、锰的中毒;③粘盘层土壤的无效水多,有效水少,使林木出现生理干旱。此外,还对这种土壤的改造提出了一些看法。  相似文献   

Dependence of soil respiration on soil moisture, clay content, soil organic matter, and CO₂ uptake in dry grasslands     

J. Balogh  K. Pintér  D. Cserhalmi  Z. Nagy 《Soil biology & biochemistry》2011,43(5):1006-1013

The effects of abiotic and biotic drivers on soil respiration (R_s) were studied in four grassland and one forest sites in Hungary in field measurement campaigns (duration of studies by sites 2-7 years) between 2000 and 2008. The sites are within a 100 km distance of each other, with nearly the same climate, but with different soils and vegetation. Soil respiration model with soil temperature (T_s) and soil water content (SWC) as independent variables explained larger part of variance (range 0.47-0.81) than the Lloyd and Taylor model (explained variance: 0.31-0.76). Direct effect of SWC on R_s at much smaller temporal and spatial scale (1.5 h, and a few meters, respectively) was verified.Soil water content optimal for R_s (SWC_opt) was shown to significantly (positively) depend on soil clay content, while parameter related to activation energy (E₀) was significantly (negatively) correlated to the total organic carbon content (TOC) in the upper 10 cm soil layer. Dependence of model parameters on soil properties could easily be utilized in models of soil respiration. The effect of current (a few hours earlier) assimilation rates on soil respiration after removing the effect of abiotic covariates (i.e. temperature and water supply) is shown. The correlation maximum between the R_s residuals (R_{s_res}, from the R_s (SWC, T_s) model) and net ecosystem exchange (NEE) was found at 13.5 h time lag at the sandy grassland. Incorporating the time-lagged effect of NEE on R_s into the model of soil respiration improved the agreement between the simulated vs. measured R_s data. Use of SWC_opt and E₀ parameters and consideration of current assimilation in soil respiration models are proposed.  相似文献   

鄂西山地土壤胶体阳离子交换量与其固相组成的关系   总被引：3，自引：0，他引：3  

贺纪正  李学垣 《中国农业科学》1992,25(1):68-74

 本文研究了鄂西天宝山、武当山、星斗山等山地土壤胶体的阳离子交换量（CEC）与其固相组成的关系。结果表明：⑴随海拔升高，土壤胶体中有机质含量、无定形铁铝含量增加；粘土矿物中，1∶1型矿物减少，2∶1型矿物增多，14埃矿物含量趋于增加，而且在暗黄棕壤及山地棕壤中主要为14埃过渡矿物。⑵土壤胶体阳离子交换量与其固相组成的多元逐步回归方程为：CEC=25.01+3.23(Fed-Feo)+1.68(O.M.)-8.13(Alc)，(R#+2=0.785，n=23)。据此估计的有机质和无机组分对胶体阳离子交换量的相对贡献分别为31%和69%。⑶粘土矿物组合中含有较多蛭石，或主要为14埃过渡矿物且伴生少量蛭石时，土壤胶体阳离子交换量较高；而以14埃过渡矿物为主且伴生少量绿泥石时，其阳离子交换量较低。⑷每百克有机质的表观阳离子交换量为119毫克当量，脱有机质处理前后胶体阳离子交换量的差值与处理前胶体有机质含量呈极显著正相关（r=0.918，n=23）。⑸柠檬酸钠处理前后胶体阳离子交换量的 增值与脱去的羟基铝量呈极显著正相关（r=0.814，n=23）；每脱去1克羟基铝，胶体表观阳离子交换量增加6.8毫克当量/100克土壤胶体。  相似文献