Evaluation of Adsorption Isotherm Models for Potassium Adsorption under Different Soil Types in Wolaita of Southern Ethiopia

Adsorption isotherm is essential for predicting its mechanisms, which are important for potassium (K) fertilizer application and to recommendation appropriate rates for acidic soils. Thus, the objective of this study was to evaluate K adsorption characteristic of the selected soils by comparing different adsorption models with soil properties of the soil in different districts (Sodo Zurie, Damot Gale, Damot Sore and Boloso Sore) in the Wolaita Zone of Southern Ethiopia. Four adsorption isotherms are: Langmuir, Freundlich, Temkin, and Van Huay were used to describe adsorption processes. Composite surface (0-20 cm) depth soil samples from four districts sites were collected. The results revealed that the K adsorption data coincide with both models with (r² = 0.99). However, Freundlich model was better in describing K adsorption than the other model. The adsorption maxima(ad_(max), distribution coefficient, buffer capacity (BC), and adsorption capacity(a_(capacity) values of soils ranged from -333 to334.5,0.54 to78.7,159.9 to 389.3, and 327 to 417mg Kkg^-1 respectively, these results showed that Sodo Zurie, Bolos Sore and Demote Sore were effective model parameters. Van Huay a_(capacity) 417mg Kkg^-1 while the bonding energy constant Langmuir is -0.075mg Kkg^-1 in Bolos Sore soil compared to other soils, which were found to be more valuable in discriminating between high K adsorption soils. Correlation between some soil properties with ad_(max) were positively a highly correlated with clay, pH, organic carbon (OC) and exchangeable potassium with r² = 0.92**, 0.93**, 0.95** and 0.96 ** respectively, but negatively correlated with bonding energy with r²= -0.79, -0.80,-0.77 and -0.72 respectively, while calcium carbonate (CaCO3) was very highly correlated with ad_(max) r²= 0.99***). The Freundlich constant, Temkin BC, and Van Hauy a_(capacity) were correlated with CaCO3 content soils with r²=0.12,-0.01,and 0.12,respectively, while slope (1/n) was significantly negatively correlated with soil cation exchange capacity (CEC), CaCO₃, clay contents and exchangeable K and Mg²⁺ with r²= 0.04, -0.67, -0.78, -0.69, and –0.69, respectively. These findings reveal the extent of K depletion in the soils of Wolaita providing a baseline for K rates required for crop production and validation of all models through real-time experiments in the field; this is recommended before the models are used on a large scale basis.     

几种不同类型土壤有机碳库容大小及周转研究

通过土壤样品的室内培养,运用三库一级动力学理论,分析了沼泽土、草甸土、普通黄棕壤和棕色石灰土4种土壤有机碳库容大小、各碳库平均周转时间及分解动态。结果表明,4种土壤剖面表层和中层有机碳含量分别为8.48~24.53 g/kg,4.02~16.77 g/kg;活性碳占总有机碳含量的0.99%~5.01%,1.31%~1.91%,平均周转时间分别为8.8~14.3 d,10.4~16.5 d;缓效性碳占总有机碳含量的15.88%~59.04%,20.43%~48.36%,平均周转时间分别为1.3~29.1 a,3.6~21.3 a;惰性碳占总有机碳含量的39.97%~79.11%,50.31%~77.66%。不同类型土壤三库有机碳含量均是上层明显大于中层,培养3个月,表层和中层土壤有机碳累计分解量分别达到了165.99~2 429.57 mg/kg,108.04~743.02 mg/kg,4种土壤有机碳分解速率大小顺序:沼泽土>草甸土>棕色石灰土>普通黄棕壤,与活性碳的百分比含量成正相关关系。对培养期间土壤有机碳累计释放量进行拟合,发现三次方程(Y=b0 b1x b2x2 b3x3)能很好地描述其变化趋势,相关性均达到极显著水平(P<0.01)。     

应用等温吸附曲线判断水稻土供硅能力 Ⅰ等温曲线方程参数与水稻相对产量的关系

选取低浓度系列平衡液进行等温吸附解吸试验,并结合田间试验的效果,研究了不同水稻土对硅的吸附解吸特征及其与土壤理化性质水稻土供硅能力之间的关系。结果表明:在低浓度梯度条件下,直线方程y=bx-a可以很好地描述土壤对硅的吸附过程。水稻相对产量与a之间存在着极显著的幂指数函数正相关关系,所以,a可以作为评价水稻土供硅能力的指标。     

兴宁县石马河流域土壤侵蚀类型

本文通过定点观测研究,根据侵蚀力类型与地貌形态,将该地土壤侵蚀划分为:面状侵蚀、沟状侵蚀和崩岗侵蚀。一、面状侵蚀为:由雨滴打击地面、紊动地面径流产生的击溅侵蚀。由于地形和植物等的影响。片蚀实以细沟状侵蚀为主,并通过水量平衡方程、植被和产沙关系,对径流小区水量平衡,植被对片蚀的影响,小区产流、产沙状况作了探讨。二、沟状侵蚀为坡面和崩岗壁面集流作用的结果。三、流水和重力共同作用产生崩岗侵蚀。本文对崩岗侵蚀中面状流水作用区,重力-流水作用区,流水搬运-沉积区的发育过程,以及泥沙冲淤变化作了分析论述。     

对我省水土保持"三区"划分谈几点看法

针对已划定的福建省水土流失重点防治区和我市部分县（市）水土流失重点防治区的现状，参照部颁参考标准及有关“三区”划分的资料，结合我市多年来水土保持工作的开展情况，就“三区”划分方法谈谈看法，目的是促使我省“三区”划分更具合理性，科学性和可操作性。     

黄土丘陵草地土壤营养元素含量迁移及分布

系统研究黄土丘陵草地土壤理化性质、草地和农地营养元素迁移与富集,以及土壤养分剖面分布特征的基础上,试验结果表明:黄绵土、灰钙土及黑垆土为黄土丘陵区主要土壤类型;（2）黑垆土与黄绵土土壤颗粒组成含量差异较大,黑垆土成壤过程有隐粘化现象;（3）黑垆土表层及深层养分含量普遍高于黄绵土;（4）土壤养分在坡面与土壤剖面呈指数分布,土壤有效N、P、K含量北坡>西南>南坡;（5）提高草地生产力,防治土壤肥力退化的根本途径是增加草地养分输入,（6）提高豆科牧草对土壤深层养分的利用,可实现“生物聚肥”效应,培肥土壤。     

三峡库区主要森林植被类型土壤渗透性能研究

对三峡库区11种主要森林植被类型114块临时样地土壤渗透指标及物理性质进行测定和比较。结果表明：（1）各森林植被类型林地A层土壤渗透速率和孔隙度均高于B层,土壤渗透速率与土壤孔隙度之间存在显著相关关系。（2）不同森林植被类型林地各层次土壤稳渗速率存在差异。常绿阔叶林地各层土壤的稳渗速率最高,A、B层分别达到8.72 mm/min,8.52 mm/min,其后依次为杉木林、针叶混交林等,马尾松林最低,A、B层分别仅为2.22 mm/min和1.13 mm/min。（3）不同土壤种类的相同层次土壤稳渗速率存在显著差异,紫色土稳渗速率最高,A,B层分别为6.48 mm/min,3.25 mm/min,其后为山地棕壤、山地黄棕壤,最低为山地黄壤,其A、B层稳渗速率分别为1.98 mm/min,1.65 mm/min。（4）砂土A、B层均具有最高的非毛管孔隙,分别达到10.54%,8.28%,其稳渗速率均为最高,A、B层稳渗速率分别为7.16 mm/min,5.66 mm/min,显著高于其他质地土壤。（5）森林土壤的渗透特性和孔隙度受植被、土壤种类及质地等多种因素的影响,建立了利用多指标进行林地土壤渗透速度和孔隙度预测的多元线性模型。研究结果可为探讨森林对流域水文过程的调节机制及科学评价三峡库区森林植被水源涵养功能奠定基础。     

三峡库区主要森林植被类型土壤渗透性能研究

对三峡库区11种主要森林植被类型114块临时样地土壤渗透指标及物理性质进行测定和比较。结果表明:(1)各森林植被类型林地A层土壤渗透速率和孔隙度均高于B层,土壤渗透速率与土壤孔隙度之间存在显著相关关系。(2)不同森林植被类型林地各层次土壤稳渗速率存在差异。常绿阔叶林地各层土壤的稳渗速率最高,A、B层分别达到8.72 mm/min,8.52 mm/min,其后依次为杉木林、针叶混交林等,马尾松林最低,A、B层分别仅为2.22 mm/min和1.13 mm/min。(3)不同土壤种类的相同层次土壤稳渗速率存在显著差异,紫色土稳渗速率最高,A,B层分别为6.48 mm/min,3.25 mm/min,其后为山地棕壤、山地黄棕壤,最低为山地黄壤,其A、B层稳渗速率分别为1.98 mm/min,1.65 mm/min。(4)砂土A、B层均具有最高的非毛管孔隙,分别达到10.54%,8.28%,其稳渗速率均为最高,A、B层稳渗速率分别为7.16 mm/min,5.66 mm/min,显著高于其他质地土壤。(5)森林土壤的渗透特性和孔隙度受植被、土壤种类及质地等多种因素的影响,建立了利用多指标进行林地土壤渗透速度和孔隙度预测的多元线性模型。研究结果可为探讨森林对流域水文过程的调节机制及科学评价三峡库区森林植被水源涵养功能奠定基础。     

Combination of Different Extractants to Assess Binding Forms of Some Elements in Soil Profiles

Abstract

Three different chemical extractants were evaluated as to their extraction efficiency for copper (Cu), zinc (Zn), lead (Pb), aluminium (Al), iron (Fe), chromium (Cr), manganese (Mn), potassium (K), magnesium (Mg), and calcium (Ca) on forest soil profiles from the Romanian Carpathians. The extractants were hot 14 M nitric acid (HNO₃), 0.05 M hydrochloric acid (HCl), and 0.1 M sodium pyrophosphate. By comparing amounts extracted by 0.05 M HCl and 0.1 M sodium pyrophosphate relative to that dissolved by hot 14 M HNO₃, some conclusions were drawn concerning the chemical forms of the metals in the extractable pool. The amount released by 0.05 M HCl was generally less than 10% of the HNO₃‐extractable fraction but showed considerable variation among the elements studied. The relative amount extracted by pyrophosphate increased with organic‐matter content of the soils for Cu, Zn, Pb, Al, Fe, and Cr; stayed more or less constant for Mn, K, and Mg; and decreased for Ca. These findings are discussed with respect to the different binding forms of the metals in the soil and the processes affecting their mobility. From the present results, the metals were ranked as follows with respect to their ability to form organic complexes in natural soils: Cu>Cr, Pb>Ca>Al>Fe, Zn, Mn, K>Mg. However, the use of cold dilute HCl as a fractionation step may be questionable in cases of soils with a high content of substances possessing large neutralization capacity for protons.     

大小兴安岭林区不同林型土壤养分综合评价

基于大小兴安岭地区主要林型野外采样数据,利用统计学方法分析了红松林、针阔混交林、白桦林、樟子松林和蒙古栎林土壤有机质、全氮、速效磷和速效钾的垂直分布特征,并对土壤养分状况进行了综合评价.结果表明,不同林型土壤(0-40 cm)有机质、全氮、速效磷、速效钾养分含量差异显著.有机质、全氮、速效磷3种土壤养分的总体分布是白桦林、针阔混交林比较高,针叶林次之,蒙古栎林比较低;而速效钾含量以蒙古栎林、白桦林为最高,针阔混交林却比较低.用改进的内梅罗综合指数法进行综合评价,结果显示,大小兴安岭林区土壤有机质和全氮含量特别丰富,速效磷含量为中等至较丰富,不同林型土壤养分总体处于良偏优水平,但速效钾比较缺乏,成为该林区土壤质量的主要限制因素.     

鼎湖山不同森林类型土壤纤毛虫群落比较研究

为了丰富对鼎湖山自然保护区生物多样性的研究,了解不同植被类型下土壤原生动物群落的特征,本文对采自鼎湖山自然保护区7种不同植被下的土壤样品进行了土壤纤毛虫定性和定量分析。结果显示:在全部土壤样品中,共检出44属70种土壤纤毛虫。在全部纤毛虫种类中,仅有4种出现在全部土壤样中,它们分别是Bresslaua vorax、Colpoda cucullus、Cyclidium elogatum和Cyrtolophosis elongata。依据物种出现频率高低,鼎湖山自然保护区土壤纤毛虫中,广布种和特有种较少,而常见种较多。不同植被类型下土壤纤毛虫群落丰度介于1 730~29 200 ind./g,表现为针叶林-马尾松林山顶灌草丛针阔叶混交林河岸常绿阔叶林沟谷常绿阔叶林温带季风常绿阔叶林山地常绿阔叶林的特点。纤毛虫群落相似性分析显示:各样点土壤纤毛虫群落间处于中等不相似(0.25~0.5)到中等相似(0.5~0.75)的水平。从本研究结果看,土壤纤毛虫的分布更符合Foissner的"生物地理模型"。相关性分析显示:土壤含水量与土壤纤毛虫丰度之间有极显著的相关性(P0.01),而土壤NO–3-N含量与纤毛虫丰度也有显著的相关性(P0.05)。而多元相关分析表明鼎湖山土壤纤毛虫丰度变化与多个土壤理化因子组合共同作用间存在相关性,其中土壤含水量均作为一个重要组合元素出现。CCA分析显示不同的土壤理化因子对一具体纤毛虫种类的作用存有差异。     

岭南稀土矿区土壤侵蚀状况分析

以我国南方岭南丘陵地区风化壳离子型稀土矿区为研究对象,利用多时相卫星遥感影像数据对研究区土壤侵蚀状况进行了动态分析,得到不同强度土壤侵蚀面积变化的总体趋势,并依据土地覆盖类型对导致不同强度侵蚀区面积变化的因素进行了分析,揭示了稀土矿开采对土壤侵蚀的影响。     

Distribution of Radioactive and Rare-Earth Elements in Soils of the Guangdong Province,China

Eurasian Soil Science - The mineral and geochemical features of soils with increased natural radioactivity in the southern China province of Guangdong have been studied. The distribution patterns...     

科尔沁沙地不同土地利用类型土壤入渗特征比较研究

[目的] 探究科尔沁沙地不同土地利用类型土壤入渗特征的差异,为干旱—半干旱区包气带水分与物质运移等相关研究提供科学参考。[方法] 利用双环入渗仪野外实测和室内土壤物理性质分析相结合的方法,研究了科尔沁沙地具有代表性的8种土地利用类型(樟子松林地、小叶锦鸡儿林地、白柠条林地、撂荒草地、草甸草地、疏林草地、玉米农田以及裸沙地)土壤入渗特征及其影响因素,同时采用Kastiakov模型、Horton模型、Philip模型和G-P综合模型对其水分入渗过程进行了拟合,比较其拟合优度。[结果] ①不同土地利用类型土壤入渗特征存在显著差异,初始入渗率变化范围为1.595～12.020 mm/min,由大到小依次为：裸沙地>白柠条林地>玉米农田>樟子松林地>小叶锦鸡儿林地>草甸草地>撂荒草地>疏林草地;15 min入渗率变化范围为0.617～3.690 mm/min,由大到小依次为：裸沙地>白柠条林地>樟子松林地>小叶锦鸡儿林地>玉米农田>撂荒草地>草甸草地>疏林草地;土壤稳定入渗率变化范围为0.576～3.495 mm/min,由大到小依次为：裸沙地>白柠条林地>玉米农田>小叶锦鸡儿林地>樟子松林地>撂荒草地>草甸草地>疏林草地; ②不同土地利用类型入渗率与土壤容重、细砂含量呈极显著负相关,与中砂含量呈极显著正相关;稳定入渗率与非毛管孔隙度呈显著正相关; ③各模型对科尔沁沙地土壤入渗过程的拟合优度依次为：Horton模型>G-P综合模型>Kastiakov模型>Philip模型,其中Horton模型决定系数最高且相对误差最小,能更准确地模拟科尔沁沙地土壤入渗的实际情况。[结论] 科尔沁沙地不同土地利用类型土壤入渗特征存在差异,土壤性质对其入渗特征影响显著;Horton模型在科尔沁沙地拟合度较高,可应用此模型来估算水分入渗过程。     

浙江安吉主要植被类型土壤抗蚀性指标筛选及评价模型构建

在野外调查基础上,应用主分量分析方法得到衡量森林土壤抗蚀性的3个最佳指标:>0.25mm水稳性团聚体、>0.5mm水稳性团聚体和土壤水稳性指数,并以此为变量分析比较不同植被类型及不同土层的土壤抗蚀性变化规律。进一步经DIDCRIM过程判别分析,构建了安吉地区主要植被类型土壤抗蚀性强、较强、差3个等级的判别函数,模型平均误判概率仅为0.0704,具有较高的可信度。     

Effect of Calcium on the Soil Adsorption of Cadmium and Zinc in Some Spanish Sandy Soils

Castellón Plain is a natural area with an extension of 464 km², situated in Castellón (eastern coast of Spain), with an important number of ceramic industries which generate waste waters containing cadmium and zinc. In this paper, equilibrium adsorption isotherms have been obtained to examine the behaviour of cadmium and zinc in three selected soils of Castellón Plain (Spain) by means of batch experiments. Both metals exhibit non-linear adsorption isotherms with adsorption maximum beyond the dissolved concentration range considered in this study. Statistical analysis showed that data fit slighty better to Freundlich linearization than that of Langmuir. Adsorption coefficients obtained from Freundlich approximation were calculated to evaluate the relative cadmium and zinc distribution between solution and studied soils obtaining coefficients ranging from 5200 to 5900 μg kg^-1μg l^{-1 -n} for cadmium and from 3500 to 43200 μg kg^-1μg l^{-1 -n} for zinc. The effects of salt concentration and calcium competition for adsorption sites were investigated providing different concentrations of CaCl₂ in background solutions. Adsorption capacities of cadmium and zinc in the studied soils decreased when the salt concentration increased. A tenfold increase in calcium concentration reduced the cadmium adsorption capacity approximately by one third whereas the Ca²⁺ ion does not seem a significant competitor with Zn²⁺ for adsorption sites in soils with high organic matter content, where precipitation of zinc can be expected.     

北京山区不同植被恢复类型土壤质量综合评价

[目的] 综合评价北京山区不同植被恢复类型土壤质量,并进一步确定影响土壤质量的关键因素,为该地区植被恢复与重建提供数据支撑。[方法] 以立地条件相近的侧柏纯林、油松纯林、侧柏油松混交林、侧柏针阔混交林、油松针阔混交林、落叶阔叶混交林和无林地(对照)为研究对象,测定14个土壤理化指标作为土壤质量评价的总数据集(TDS),采用主成分分析法(PCA)和Pearson相关性分析建立土壤质量最小数据集(MDS),利用线性(L)和非线性(NL)2种评分方法计算土壤质量指数(SQI)和一般线性模型(GLM)确定影响土壤质量的关键因素。[结果] 植被恢复后相较于无林地,土壤容重、砂粒含量下降,而有机质、全氮、全钾、速效氮、速效钾等土壤养分含量增加。筛选出的研究区土壤质量评价MDS指标为全氮、砂粒、全钾、pH、有效含水量。4种方法(SQI-LT、SQI-NLT、SQI-LM、SQI-NLM)下,不同植被恢复类型的SQI值排序均为落叶阔叶混交林＞侧柏针阔混交林＞油松纯林＞油松针阔混交林＞侧柏油松混交林＞侧柏纯林＞无林地,植被恢复后土壤质量显著提升。SQI-NLM的土壤质量评价方法在北京山区具有更好的适用性。相较于无林地,其他植被恢复类型的SQI-NLM分别提高64%,48%,45%,36%,33%,27%。GLM模型解释了土壤质量指数总变异的85.24%,植被类型对土壤质量指数的解释比例最大(45.09%)。[结论] 选择适宜的植被恢复类型是改善区域土壤质量的关键。未来实施植被恢复时,树种选择上优先考虑阔叶树种。造林配置方式的选择应取决于树种而定,如侧柏纯林中引入本土阔叶树种形成侧柏针阔混交林或选择油松纯林是最佳造林模式。     

不同土壤类型对硫酸钾镁肥中钾、镁、硫吸附特性研究

在水稻土、红壤、潮土中分别加入不同浓度的硫酸钾镁肥溶液,研究3种土壤在不同浓度硫酸钾镁肥下pH值的变化及对K、Mg、S吸附的能力。结果表明:在3种土壤中加入硫酸钾镁肥都使土壤pH值下降,下降速度是红壤>水稻土>潮土。3种土壤对K的吸附能力较强,可用一元线性方程拟合,在0~354 mg kg-1的K加入量范围内,吸附率在50.4%~74.1%;对S的相对吸附率居中,可用一元二次方程拟合,在0~311 mg kg-1的S加入量范围内,吸附率在35.6%~88.1%;对Mg的吸附能力极弱。3种土壤对K、S吸附能力大小顺序为:潮土>红壤>水稻,对镁吸附能力大小顺序为:潮土>水稻土>红壤。土壤田间施用硫酸钾镁肥量应根据不同土壤对养分的吸附能力大小进行相应的调整。     

Soil Adsorption of Urea II

Soils have generally been considered to adsorb little amounts of urea because it scarcely dissociates in water solution. A few works^1-3) have been reported on this problem. But it should be noticed that an electrostatic adsorption might not be the sole mechanism of soil adsorption of urea. In the previous paper⁴⁾ a correlation between equilibrium concentrations of urea in soil solutions and the amount of adsorbed urea was worked out, using Tanashi paddy soil of volcanic ash origin. An adsorption coefficient of Urea on the soil was calculated from the correlation and it was suggested that the soil possibly adsorbed considerable amounts of urea by a force which was weaker than the electrostatic force. together with experiments⁴⁾ using urea derivatives such as thiourea, methylurea or dimethylurea, it was concluded that the soil adsorption of Urea was possibly due to the formation of hydrogen bondings, principally arising from amino hydrogens and partly from carbonyl oxygen in a urea molecule.     

Evaluation of Universal Extractants for Determination of Some Macronutrients from Soil

Evaluation of nutrient status in soil is important for nutritional, environmental, and economical aspects. The objective of this work was to find out the most suitable universal extractant for determination of available phosphorus (P) and nitrate (NO₃-) and exchangeable potassium (K), calcium (Ca), and magnesium (Mg) from soils using 0.01 M calcium chloride (CaCl₂), 0.01 M barium chloride (BaCl₂), 0.1 M BaCl₂, 0.02 M strontium chloride (SrCl₂), Mehlich 3, and ammonium bicarbonate diethylene triamine penta acetic acid (AB-DTPA) extractants. Composite surface soil samples (0–20 cm) were collected from the Eastern Harage Zone (Babile and Haramaya Districts), Wolaita Zone (Damot Sore, Boloso Bombe, Damot Pulasa, and Humbo Districts), and Dire Dawa Administrative Council by purposive sampling. The experiment was carried out in a completely randomized design (CRD) with three replications. Results indicated that the greatest correlations were found between Mehlich 3 and Olsen method and also between 0.02 M SrCl₂ and Olsen method for available P. The amount of NO₃^– extracted by 0.02 M SrCl₂ was significantly correlated to the amount determined by 0.5 M potassium sulfate (K₂SO₄). The amounts of exchangeable K, Ca, and Mg determined by ammonium acetate (NH₄OAc) method were significantly correlated to the amount determined by universal extractants tested. In general, both 0.02 M SrCl₂ and Mehlich 3 can serve as universal extractants for the macronutrients considered in this study with the former being more economical when NO₃^– is included.