Evaluation of uncalibrated preferential flow models against data for isoproturon movement to drains through a heavy clay soil

The uncalibrated predictive ability of four preferential flow models (CRACK‐NP, MACRO/MACRO_DB, PLM, SWAT) has been evaluated against point rates of drainflow and associated concentrations of isoproturon from a highly structured and heterogeneous clay soil in the south of England. Data were available for four plots for a number of storm events in each of three successive growing seasons. The mechanistic models CRACK‐NP and MACRO generally gave reasonable estimates of drainflow over the three seasons, but under‐estimated concentrations of isoproturon over a prolonged period in the first season and over‐estimated them in the two remaining seasons. CRACK‐NP simulated maximum concentrations of isoproturon over the first two events of each of the three seasons of 156, 527 and 24.4 µg litre^?1, respectively, and matched the observed data (465, 65.1 and 0.65 µg litre^?1) slightly better than MACRO (69.1, 566 and 58.5 µg litre^?1). Automatic selection of parameters from soils information within MACRO_DB reduced the emphasis on preferential flow relative to the stand‐alone version of MACRO. This gave a poor simulation of isoproturon breakthrough and simulated maximum concentrations were 0, 50.1 and 35.1 µg litre^?1, respectively. The capacity model PLM gave the best overall simulation of total drainflow for the first two events in each season, but over‐estimated concentrations of isoproturon (967, 808 and 51.3 µg litre^?1). The simple model SWAT represented total drainflow reasonably well and gave the best simulation of maximum isoproturon concentrations (140, 80.2 and 8.2 µg litre^?1). There was no clear advantage here in using the mechanistic models rather than the simpler models. None of the models tested was able to simulate consistently the data set, and uncalibrated modelling cannot be recommended for such artificially drained heavy clay soils. © 2001 Society of Chemical Industry     

Effect of humic acid on growth and crop nutrient status of wheat on two different soils

The effect of plant-derived humic acid (PDHA) and coal-derived humic acid (CDHA) on wheat growth was tested on two alkaline calcareous soils in pots. Humic acid derived from plant and coal materials was applied at the rate 0 (control), 50 and 100 kg/ha to wheat in pots carrying two soils viz. clayey loam soil and sandy loam soil separately. Data was collected on plant growth parameters such as spike weight, grain and straw weight, and plant nutrients (macronutrients and micronutrients). Results showed that spike weight increased by 19%, 15%, and 26%, and 11% with application of PDHA at the rate of 50 and 100 mg/kg in clayey loam and sandy loam soil, respectively. Grain yield show an increase of 21% and 11% over control with application of PDHA and CDHA at the rate of 50 mg/kg on both soils, respectively, and 10% and 22% with application of PDHA and CDHA at the rate of 100 mg/kg on both soils.     

Potassium behavior and clay mineral composition in the soil with low effectiveness of potassium application

ABSTRACT

Increasing exchangeable potassium (ExK) content in soil to an appropriate level is important to mitigate the transfer of radioactive cesium to crops. We focused on a buckwheat (Fagopyrum esculentum Moench) field with a low ExK content, despite the application of K, in Fukushima Prefecture, Japan (Field A), following the Tokyo Electric Power Company Fukushima Dai-ichi (No. 1) Nuclear Power Plant accident in March 2011. We examined the relationship between K concentration and clay mineral composition in the soil of Field A and compared the findings with another field in Fukushima Prefecture (Field B) to clarify whether K applied to the soil was leached or remaining fixed. Pot experiments showed that K concentration in water seepage from pots following irrigation was significantly lower in pots from Field A than in those from Field B. Soil ExK content after soybean cultivation was lower in soils of Field A than those of Field B. These results indicate that K applied to Field A was fixed in the soil. Analysis of clay mineral composition confirmed the distinctive vermiculitic nature of Field A soils. This clay mineralogy would be associated with the higher K fixation ability of Field A than Field B soils. This study demonstrated that K fixation in vermiculite was a factor preventing the increase in ExK content from K application to Field A.     

云南省植烟土壤理化性状及其相关性研究

为进一步了解云南省植烟土壤理化性状分布特征及其关系,于2014年和2015年对云南省12个州(市)采集2 127份土壤样品进行测定分析.结果表明:1)云南省植烟土壤物理性粘粒质量分数平均50.91%,偏重壤土,pH值以及养分平均质量分数除有机质偏高外,均适宜优质烤烟生产.2)12个州(市)间植烟土壤的物理性粘粒和养分质量分数差异有统计学意义(p0.01),红河和文山物理性粘粒质量分数最高,保山和大理的有机质和速效氮质量分数最丰富,曲靖和昭通速效钾最丰富,昆明、楚雄和临沧有效硼最丰富,德宏和普洱的pH值和养分质量分数较低.3)文山43.08%和红河52.34%的土壤物理性粘粒质量分数大于60%,需适当调节土壤通透性;德宏66.67%,临沧54.78%和普洱53.69%的土壤pH值小于5.5,需调节土壤酸碱度;普洱58.40%和41.61%的土壤速效氮和速效磷质量分数缺乏,需增施氮肥和磷肥;各州(市)均存在35.41%~66.67%土壤速效钾质量分数缺乏,需增施钾肥;红河49.99%土壤有效硼质量分数缺乏,需增施硼肥;大理30.41%,曲靖20.80%和昭通16.66%的植烟土壤水溶性氯质量分数大于30mg/kg,应当适当控制含氯肥料施用.4)云南省植烟土壤有机质、速效氮、速效钾和有效硼质量分数与物理性粘粒质量分数的R2值较高(0.696 2~0.885 9),有机质和速效氮和有效硼质量分数存在随物理性粘粒质量分数升高而先升高再降低趋势,速效钾质量分数存在随物理性粘粒质量分数升高而升高的趋势.     

黏土对沙地土壤改良效果的微形态研究——以内蒙古科尔沁沙地为例

为了研究施加黏土后的沙地土壤微形态特征,说明其改良效果,对内蒙古科尔沁沙地土壤切片进行观察,并利用土壤切片图像处理分析系统和Image-Pro Plus 6.0软件进行处理和分析,提取基质、孔隙和粗骨颗粒等和土壤肥力状况相关的定量化数据进行分析及定性分析,结果表明:施加黏土后,出现了块状微结构和雏形团聚体;从基质比、毛管孔隙占比方面来说,底施处理效果更好,基质比在C2(3×10~5 kg/hm~2)处理水平比对照组提高了8.8%,毛管孔隙占比在C3(6×10~5kg/hm~2)处理水平提高了15%;就总孔隙百分比、粗骨颗粒磨圆度、粉粒百分比、粗骨颗粒平均粒径来说,表施处理效果比较好,C1(1.5×10~5 kg/hm~2)、C2(3×10~5 kg/hm~2)处理水平均有显著改善。结论:1)施加黏土后,沙地土壤结构与原始沙地的粒状微结构相比有一定的改善;2)短期底施处理下,C1和C2处理单元的基质比有所提高,毛管孔隙占比随着黏土施加量的增加而提高;粗骨颗粒特征方面,表施处理效果比底施效果要好;3)短期改良情况下,沙地土壤微结构并没有太大的变化,还是以粗骨颗粒为主,但改良后出现一些雏形团聚体,各量化指标均有不同程度的提高。     

川西粉质黏土-衬砌接触面冻结强度规律研究

为揭示川西灌渠粉质黏土-衬砌接触面间冻结强度规律,针对川西地区灌渠渠基土开展了冻结作用下冻结温度、冻结时间、初始含水率、法向荷载4种影响因素在不同条件下的剪切试验。结果表明:接触面间峰值抗剪强度与冻结温度、初始含水率变化呈负相关,与冻结时间、法向荷载变化呈正相关。此外,利用正交分析,揭示了4种因素对峰值抗剪强度影响的显著性,结果显示:法向荷载对峰值抗剪强度影响最显著,初始含水率、冻结温度次之,冻结时间影响不显著。试验成果可为川西灌渠冻胀稳定性及相关工程研究提供依据。     

中国福建省土壤的主要粘土矿物

The clay minerals of more than 200 soil samples collected from various sites of Fujian Province were studied by the X-ray diffraction method and transmission electron microscopy to study their distribution and evolution.Montmorillonite was found in coastal solonchak,paddy soils derived from marine deposit,lacustrine deposit and river deposit,and some lateritic red soil,red soil and yellow soil with a low weathering degree.Chlorite existed mainly in coastal solonchak and paddy soil developed from marine deposit.1.4nm intergradient mineral appeared frequently in yellow soil,red soil and lateritic red soil.The content of 1.4nm intergradient mineral increased with the decrease of weathering degree from lateritic red soil to red soil to yellow soil.Hydrous micas were more in coastal solonchak,paddy soils derived from marine deposit,lacustrine deposit and river deposit.and puple soil from purple shale than in other soils.Kaolinte was the most important clay mineral in the soils iun this province.The higher the soil weathering degree,the more the kaolinite existed.From yellow soil to red soil to lateritic red soil,kaolinite increased gradually,Kaolinite was the predominant clay mineral accompanied by few other minerals in typical lateritic red soil. Tubular halloysite was a widespread clay mineral in soils of Fujian Province with varying quantities.The soil derived from the paent rocks rich in feldspar contained more tubular halloysite.Spheroidal halloysite was found in a red soil and a paddy soil developed from olivine basalt gibbsite in the soils in this district was largely“primary gibbsite” which formed in the early weathering stage.Gibbsite decreased with the increase of weathering degree from yellow soil to red soil to lateritic red soil.Goethite also decreased in the same sequence while hematite increased.     

有机酸对高岭石, 针铁矿和水铝英石吸附镉的影响

Effects of organic acids （oxalic, acetic, and citric） on adsorption characteristics of Cadmium （Cd） on soil clay minerals （kaolinite, goethite, and bayerite） were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L^-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.     

土壤钾素转化的影响因素及其研究进展

土壤中各种形态的钾之间存在着动态的平衡,这些平衡受一定因素的影响。本文主要从粘土矿物类型、土壤水分状况、温度、pH、肥料施用以及陪伴离子等方面对土壤钾素转化的影响因素进行了综述,可以归纳为:①以2∶1型粘土矿物为主的土壤吸附K 的结合能较小,易解吸;而以1∶1型粘土矿物为主的土壤吸附K 的结合能较大,吸附的K 不易解吸。②土壤干湿变化对钾素转化的影响因速效钾含量的高低而有明显的区别。③在0~40℃温度范围内,增温能使交换性钾离子减少,而水溶性钾离子浓度则相应增加。④pH对土壤钾素转化的影响比较复杂。⑤氮肥中的NH4 因与K 离子具有相似的离子半径和水化能而对土壤钾素的有效性产生显著的影响。最后展望了钾素转化领域未来的发展方向和研究热点。     

土壤入渗过程中空气压力变化规律的研究

用测压入渗仪对重粉质粘土进行了模型试验，同时根据试验结果，分析研究了垂直—维均匀土壤内气阻压力的变化规律。