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1.
A sequential extraction procedure was used to fractionate Cu, Cd, Pb and Zn in 4 soil profiles into the designated forms of water soluble + exchangeable, organically bound, carbonate and Mn oxides bound. Soil profiles were obtained from the Rural Development District 063, State of Hidalgo, which have been irrigated with wastewater coming out of the basin of Mexico. The total heavy metal contents range as follows: Cu, 8.9 to 86.5 mg kg-1 Cd, 0.86 to 5.07 mg kg-1 Pb, 18.1 to 131.7 mg kg-1 and Zn, 101 to 235.5 mg kg-1. The highest concentrations of total heavy metals were found in the surface layers at all soil profiles. Sequential chemical fractionation indicated that the four metals were predominantly associated with the organic fraction at most soil samples. The contents in all fractions of the four metals showed a decrease with depth which has been explained by the variations in the organic matter and CaCO3 contents in the different layers of soils. These soil properties were also the most important variables in the biological availability of the metals in these soils. 相似文献
2.
通过土柱淋洗试验的方法,研究了脱硫副产物在改良碱性土壤过程中对碱性土壤化学指标(代换性钠、ESP、SAR、pH值)的影响。本研究采用两种碱性土壤(强度碱化土和碱土),两种土壤各分两个脱硫副产物施用水平(强度碱化土为3 g kg-1和3 6 g kg-1;碱土为7 g kg-1和8 4 g kg-1)。结果表明,经过施加烟气脱硫副产物和淋洗各种试验处理的代换性钠、ESP、SAR和pH值都有了明显的降低,碱性土壤得到了改良;同时,高烟气脱硫副产物施加水平的碱性土壤改良效果要优于低施加水平的碱性土壤;强度碱化土和碱土分别施加3 6 g kg-1、8 4 g kg-1烟气脱硫副产物后,在强度碱化土表层(0~40 cm)和碱土表层(0~20 cm)ESP<15、SAR<13和pH<8 5,已经降至中度碱化土水平,改良效果显著。 相似文献
3.
采用连续化学提取法对粤东凤凰山茶区12个大型茶园共60份土壤样品中Cu和Cr的5种化学形态分布和茶叶有效性进行研究。结果发现,土壤中Cu的5种化学形态的分布规律为残渣态〉有机束缚态〉铁锰氧化态〉碳酸盐态〉交换态,而Cr的化学形态分布为残渣态〉有机束缚态〉交换态〉碳酸盐态〉铁锰氧化态。可交换态Cu和有机束缚态Cu含量与土壤有机质呈显著正相关,而土壤pH值与土壤可交换态Cu呈极显著负相关,与碳酸盐态Cu呈极显著正相关,与有机束缚态Cu和铁锰氧化态Cu呈显著正相关。可交换态Cr含量与土壤有机质呈显著正相关,而土壤pH值与土壤可交换态Cr呈极显著负相关,与碳酸盐态Cr呈极显著正相关。凤凰山茶叶Cu含量的范围在41.20～118.93mg·kg^-1之间,平均为52.92mg·kg^-1。茶叶中Cu含量与土壤可交换态Cu、有机束缚态Cu、有机质都有显著的正相关性,而与土壤pH值有显著的负相关性。茶叶Cr含量的范围在2.73～6.29mg·kg^-1之间,平均为4.13mg·kg^-1。茶叶Cr含量与土壤有机质和pH值分布呈显著正相关和显著负相关。 相似文献
4.
5.
Cosmas Parwada Johan Van Tol 《Acta Agriculturae Scandinavica, Section B - Plant Soil Science》2017,67(1):67-76
Soil erosion has serious off-site impacts caused by increased mobilization of sediment and delivery to water bodies causing siltation and pollution. To evaluate factors influencing soil erodibility at a proposed dam site, 21 soil samples collected were characterized. The soils were analyzed for soil organic carbon (SOC), exchangeable bases, exchangeable acidity, pH, electrical conductivities, mean weight diameter and soil particles’ size distribution. Cation exchange capacity, exchangeable sodium percentage, sodium adsorption ratio, dispersion ratio (DR), clay flocculation index (CFI), clay dispersion ratio (CDR) and Ca:Mg ratio were then calculated. Soil erodibility (K-factor) estimates were determined using SOC content and surface soil properties. Soil loss rates by splashing were determined under rainfall simulations at 360?mmh?1 rainfall intensity. Soil loss was correlated to the measured chemical and physical soil properties. There were variations in soil form properties and erodibility indices showing influence on soil loss. The average soil erodibility and SOC values were 0.0734?t?MJ?1?mm?1 and 0.81%, respectively. SOC decreased with depth and soil loss increased with a decrease in SOC content. SOC significantly influenced soil loss, CDR, CFI and DR (P??1. Addition of organic matter stabilize the soils against erosion. 相似文献
6.
Effects of organic material amendment and water content on NO, N2O, and N2 emissions in a nitrate-rich vegetable soil 总被引：1，自引：0，他引：1
Amending vegetable soils with organic materials is increasingly recommended as an agroecosystems management option to improve soil quality. However, the amounts of NO, N2O, and N2 emissions from vegetable soils treated with organic materials and frequent irrigation are not known. In laboratory-based experiments, soil from a NO 3 ? -rich (340 mg N?kg?1) vegetable field was incubated at 30°C for 30 days, with and without 10 % C2H2, at 50, 70, or 90 % water-holding capacity (WHC) and was amended at 1.19 g?C kg?1 (equivalent to 2.5 t?C ha?1) as Chinese milk vetch (CMV), ryegrass (RG), or wheat straw (WS); a soil not amended with organic material was used as a control (CK). At 50 % WHC, cumulative N2 production (398–524 μg N?kg?1) was significantly higher than N2O (84.6–190 μg N?kg?1) and NO (196–224 μg N?kg?1) production, suggesting the occurrence of denitrification under unsaturated conditions. Organic materials and soil water content significantly influenced NO emissions, but the effect was relatively weak since the cumulative NO production ranged from 124 to 261 μg N?kg?1. At 50–90 % WHC, the added organic materials did not affect the accumulated NO 3 ? in vegetable soil but enhanced N2O emissions, and the effect was greater by increasing soil water content. At 90 % WHC, N2O production reached 13,645–45,224 μg N?kg?1 from soil and could be ranked as RG?>?CMV?>?WS?>?CK. These results suggest the importance of preventing excess water in soil while simultaneously taking into account the quality of organic materials applied to vegetable soils. 相似文献
7.
Yoshinori WATANABE Tsugiyuki MASUNAGA Oluwarotimi Omotola FASHOLA Adeniyi AGBOOLA Peter K. OVIASUYI Toshiyuki WAKATSUKI 《Soil Science and Plant Nutrition》2009,55(1):132-141
The present study described the relationship between growth and soil physico-chemical properties in Eucalyptus camaldulensis (Myrtaceae) and Pinus caribaea (Pinaceae), two important species in Nigerian forest recovery programs. The study sites were located in a 17-year-old plantation in a Northern Nigeria forest reserve. The soils at the study sites were nutrient poor compared with other plantations. Growth of E. camaldulensis was positively correlated with exchangeable K content in soils 0–20 cm deep, and negatively correlated with total N and exchangeable Na in soils 20–150 cm deep. Growth of P. caribaea was positively correlated with available P in soils 0–20 cm deep, and volumetric water content in soils 20–150 cm deep. Soils in the top layers were very hard and plinthite layers were well developed at shallow soil depths at most sites. E. camaldulensis exhibited a comparatively high survival rate, and its growth was comparable to that in other plantations. However, the survival rates of P. caribaea were low and its growth was lower than that in other plantations. The survival rate of E. camaldulensis was lower at sites where plinthite layers were found within 50.8 cm of the surface. These results indicated that E. camaldulensis is suitable for afforestation in Northern Nigeria. However, it is not recommended for sites where the plinthite layer occurs at shallow soil depths. 相似文献
8.
玉米秸秆应用和腐化对钙质苏打土改良的影响: 实验室试验研究 总被引：7，自引：0，他引：7
A laboratory lysimeter experiment was conducted to investigate the effects of forage corn (Zea mays L.) stalk application on the CO2 concentration in soil air and calcareous sodic soil reclamation. The experimental treatments tested were soil exchangeable sodium percentage (ESP) levels of 1, 11, and 19, added corn stalk contents of 0 to 36 g kg-1, and incubation durations of 30 and 60 days. The experimental results indicated that corn stalk application and incubation significantly increased CO2 partial pressure in soil profile and lowered pH value in soil solution, subsequently increased native CaCO3 mineral dissolution and electrolyte concentration of soil solution, and finally significantly contributed to reduction on soil sodicity level. The reclamation effciency of calcareous sodic soils increased with the added corn stalk. When corn stalks were added at the rates of 22 and 34 g kg-1 into the soil with initial ESP of 19, its ESP value was decreased by 56% and 78%, respectively, after incubation of 60 days and the leaching of 6.5 pore volumes (about 48 L of percolation water) with distilled water. Therefore, crop stalk application and incubation could be used as a choice to reclaim moderate calcareous sodic soils or as a supplement of phytoremediation to improve reclamation effciency. 相似文献
9.
《Communications in Soil Science and Plant Analysis》2012,43(5-6):337-349
Abstract A study of soil chemical properties of eleven soils present in different geographycal locations where palm trees (Copernicia tectorum) grow in Venezuela gave the following relevant results: 1) ten soils have at least one layer with exchangeable Mg higher than exchangeable Ca (Mg/Ca>1.00; magnesic layer); 2) eight soils have at least one layer with more than 15% exchangeable Na (sodic layer); 3) ten soils have layers with predominance of Na+Mg in the exchangeable complex (Na + Mg >50%, sodic‐magnesic layers); 4) very acid soil pH values (3.75 to 5.00) on the soil surface layers increasing markedly (even to alkaline values) with depth; and 5) all profiles have very low available P values. The common occurrence of these rather unusual chemical properties, especially the first three ones on most of these soils were considered as evidence of their role as fundamental edaphic factors on palm tree adaptation and distribution. These results also indicate that, besides the already described soil physical (high clay content, slow permeability) and environmental conditions (seasonal flooding and drought, and yearly burning), unusual soil chemical properties seem to be also involved with the ecological conditions associated with the presence of palm trees. 相似文献
10.
Sota Tanaka Shinya Funakawa Thammanoon Kaewkhongkha Tomoo Hattori Koyo Yonebayashi 《Soil Science and Plant Nutrition》2013,59(3):695-708
Abstract Soil degradation caused by excessive land use is presently one of the major constraints on sustainable agriculture in the mountainous area of northern Thailand. In order to obtain basic information about soil fertility problems involved in the transition from traditional shifting cultivation to more intensive upland farming, the dynamics of K, Mg, and Ca, and soil acidity in the farming systems of both Karen and Hmong/Thai peoples were investigated. In the fields that lay fallow for more than 5 y, the soils were highly acidic and poor in exchangeable bases, mainly due to the fact that the fallow vegetation rapidly absorbed inorganic bases (K, Mg, and Ca) in the soils. In the fields both under fallow and cropping within 3 y after the slash and burn practice, the high acidity observed in the soils at the fallow stage seemed to be alleviated by ash input with high alkalinity. The aboveground biomass ranged from 9 to 10 t ha?1 in the 8 y fallow field and the sum of inorganic bases and alkalinity, which were expected to be added to the soils with ash input, ranged from 3 to 4 kmol( + ) ha?1 or kmol(-) ha?1 , respectively. In the fields under continuous cultivation for more than 4 y after the slash and burn practice, the subsoils showed a more acidic nature than in the fields immediately after burning. Judging from the high concentrations of inorganic bases in the soil solution from the subsoils, the decrease of the content of exchangeable bases and resulting soil acidification might have proceeded through leaching loss of these bases. Among the exchangeable bases in the soils, Ca and Mg were generally predominant and K occurred as trace. Comparison of the total contents of the bases with the contents of exchangeable ones showed that most of Ca occurred in an exchangeable form while most of K and Mg occurred in the nonexchangeable forms in the soils. Therefore, Ca was likely to be readily depleted along with soil acidification in continuous cultivation. 相似文献
11.
黄土高原生物结皮对土壤养分的表层聚集与吸附固持效应 总被引：2，自引：0，他引：2
12.
《Communications in Soil Science and Plant Analysis》2012,43(3-4):347-361
Abstract The accumulation of heavy metals in plants is related to concentrations andchemical fractions of the metals in soils. Understanding chemical fractions and availabilities of the metals in soils is necessary for management of the soils. In this study, the concentrations of copper (Cu), cadmium (Cd), lead (Pb), and zinc (Zn) in tea leaves were compared with the total and extractable contents of these heavy metals in 32 surface soil samples collected from different tea plantations in Zhejiang province, China. The five chemical fractions (exchangeable, carbonate‐bound, organic matter‐bound, oxides‐bound, and residual forms) of the metals in the soils were characterized. Five different extraction methods were also used to extract soil labile metals. Total heavy metal contents of the soils ranged from 17.0 to 84.0 mgCukg?1, 0.03 to 1.09 mg Cd kg?1, 3.43 to 31.2 mg Pb kg?1, and 31.0 to 132.0 mg Zn kg?1. The concentrations of exchangeable and carbonate‐bound fractions of the metals depended mainly on the pH, and those of organic matter‐bound, oxides‐bound, and residual forms of the metals were clearly controlled by their total concentrations in the soils. Extractable fractions may be preferable to total metal content as a predictor of bioconcentrations of the metals in both old and mature tea leaves. The metals in the tea leaves appeared to be mostly from the exchangeable fractions. The amount of available metals extracted by 0.01 mol L?1 CaCl2, NH4OAc, and DTPA‐TEA is appropriate extractants for the prediction of metals uptake into tea plants. The results indicate that long‐term plantation of tea can cause sol acidification and elevated concentrations of bioavailable heavy metals in the soil and, hence, aggravate the risk of heavy metals to tea plants. 相似文献
13.
Ammonium fixation by clay minerals in different layers of two paddy soils after flooding 总被引：5，自引：0，他引：5
The influence of flooding and cellulose addition on the fixation of NH4
+ in different soil layers of two paddy soils from China (an entisol and an ultisol) was investigated. In both soils the content
of total reducing substances (TRS) sharply increased during the first days after flooding and was highest in the anoxic layers.
This increase, which was more pronounced in the entisol with the higher total C content, was accompanied by an increase in
the concentration of non-exchangeable NH4
+ in both soils. The increase in mineralization after flooding, resulting in higher concentrations of exchangeable NH4
+, favoured the fixation of NH4
+. Although the application of cellulose resulted in higher TRS contents, the fixation of NH4
+ ions decreased, which may have been the result of microbiological N immobilization.
Received: 29 April 1998 相似文献
14.
Hailegnaw Niguss Solomon Mercl Filip Pračke Kateřina Száková Jiřina Tlustoš Pavel 《Journal of Soils and Sediments》2019,19(5):2405-2416
Purpose
The majority of biochar studies use soils with only a narrow range of properties making generalizations about the effects of biochar on soils difficult. In this study, we aimed to identify soil properties that determine the performance of biochar produced at high temperature (700 °C) on soil pH, cation exchange capacity (CEC), and exchangeable base cation (Ca2+, K+, and Mg2+) content across a wide range of soil physicochemical properties.
Materials and methodsTen distinct soils with varying physicochemical properties were incubated for 12 weeks with four rates of biochar application (0.5, 2, 4, and 8% w/w). Soil pH, CEC, and exchangeable base cations (Ca2+, K+, and Mg2+) were determined on the 7th and 84th day of incubation.
Results and discussionOur results indicate that the highest biochar application rate (8%) was more effective at altering soil properties than lower biochar rates. Application of 8% biochar increased pH significantly in all incubated soils, with the increment ranging up to 1.17 pH unit. Biochar induced both an increment and a decline in soil CEC ranging up to 35.4 and 7.9%, respectively, at a biochar application rate of 8%. Similarly, biochar induced increments in exchangeable Ca2+ up to 38.6% and declines up to 11.4%, at an 8% biochar application rate. The increment in CEC and exchangeable Ca2+ content was found in soils with lower starting exchangeable Ca2+ contents than the biochar added, while decreases were observed in soils with higher exchangeable Ca2+ contents than the biochar. The original pH, CEC, exchangeable Ca2+, and texture of the soils represented the most crucial factors for determining the amount of change in soil pH, CEC, and exchangeable Ca2+ content.
ConclusionsOur findings clearly demonstrate that application of a uniform biochar to a range of soils under equivalent environmental conditions induced two contradicting effects on soil properties including soil CEC and exchangeable Ca2+ content. Therefore, knowledge of both biochar and soil properties will substantially improve prediction of biochar application efficiency to improve soil properties. Among important soil properties, soil exchangeable Ca2+ content is the primary factor controlling the direction of biochar-induced change in soil CEC and exchangeable Ca2+ content. Generally, biochar can induce changes in soil pH, CEC, and exchangeable Ca2+, K+, and Mg2+ with the effectiveness and magnitude of change closely related to the soil’s original properties.
相似文献15.
Sota Tanaka Joseph Jawa Kendawang Jun Ishihara Kenji Shibata Akiko Kou Augustine Jee 《Soil Science and Plant Nutrition》2013,59(5):689-699
Experimental shifting cultivation was conducted at the Balai Ringin (B. Ringin) and Sabal sites in Sarawak, Malaysia. At the sites, plots (10 x 10 m2) were burned with the fuel of aboveground biomass amounting to 0 (control), 100, 200, and 300 Mg ha-1. At the B. Ringin site, the soils were clayey and strongly weathered with a strongly acidic characteristic. Ash addition enabled to alleviate the soil acidity and to increase the amounts of nutrients of the soils, especially the surface soils. It was indicated that 1) N addition from ash to the soils was negligible, 2) the losses of nutrients by runoff water were not substantial compared with the amounts of nutrients contained in ash, 3) ash alkalinity seemed to be consumed for inactivating exchangeable AI mainly in the surface soils, and 4) development of variable negative charges could contribute to the retention of inorganic bases derived from ash. After harvest of upland rice, the soil chemical properties in the plots treated with 100 and 200 Mg ha-1 fuel returned to the levels before burning, indicating the rapid loss of nutrients due to leaching and erosion as well as the uptake by plants. However, the soils treated with 300 Mg ha-1 fuel still showed high contents of exchangeable bases and a low content of exchangeable AI. On the other hand, the soils at the Sabal site were sandy and were characterized by a very low nutrient status. The changes in the amounts of nutrients by ash addition were similar to those at the B. Ringin site. However, the changes in the level of exchangeable AI which were not appreciable were probably due to the low AI content. It was postulated that because of the sandy texture and low CEC of the soils, inorganic bases contained in ash were only suspended in the soil solution. Taking into account the low yield of rice and low level of secondary biomass, it appeared that most of the nutrients were lost downward in soils by leaching. 相似文献
16.
通过在天津滨海新区的野外灌水脱盐试验,对比分析了灌溉淡水、中水和微咸水的中壤质、重壤质土和粘土土壤含盐量及pH的动态变化。结果表明,粘质滨海盐土经灌淡水后的土壤全盐量降低是逐渐的;重壤质滨海盐土的土壤全盐变化趋势与粘质土相似,最初4次灌水使各层土壤全盐累积降幅较大;中壤质滨海盐土则第一次灌水后土壤含盐量降低较多,表层（0～20cm）由1.75%降到0.511%,以后灌溉土壤全盐量降低得较缓慢,20～40cm土层的含盐量始终降低得较缓慢。灌溉淡水、中水、微咸水均能使土壤全盐量降低,灌溉中水、微咸水后表层和土体下层土壤的含盐量均逐渐降低,而灌溉淡水的表层土壤全盐量以初次降低明显,土体下层的土壤全盐量始终变化幅度较小。同灌淡水的情况下,中壤质滨海盐土的土壤pH较为稳定,在7.5～8.5范围,而重壤质和粘土在最初表现下降,至约7.5后上升到8.5～9.0范围,质地越粘土壤pH越高。灌溉淡水、中水、微咸水均使土壤pH有升高的趋势,灌溉淡水后表层土壤pH能够上升到9.0,灌溉微咸水、中水后土壤pH能够升高至8.5左右。 相似文献
17.
Jana Wäldchen Ingo Schöning Martina Mund Marion Schrumpf Susanne Bock Nadine Herold Kai Uwe Totsche Ernst Detlef Schulze 《植物养料与土壤学杂志》2012,175(3):367-376
Soil texture is one of the main factors controlling soil organic carbon (SOC) storage. Accurate soil‐texture analysis is costly and time‐consuming. Therefore, the clay content is frequently not determined within the scope of regional and plot‐scale studies with high sample numbers. Yet it is well known that the clay content strongly affects soil water content. The objective of our study was to evaluate if the clay content can be estimated by a simple and fast measure like the water content of air‐dried soil. The soil samples used for this study originated from four different European regions (Hainich‐Dün, Germany; Schwäbische Alb, Germany; Hesse, France; Bugac, Hungary) and were collected from topsoils and subsoils in forests, grasslands, and croplands. Clay content, water content of air‐dried soil, and SOC content were measured. Clay content was determined either by the Pipette method or by the Sedigraph method. The water content of air‐dried soil samples ranged from 2.8 g kg–1 to 63.3 g kg–1 and the corresponding clay contents from 60.0 g kg–1 to 815.7 g kg–1. A significant linear relationship was found between clay content and water content. The scaled mean absolute error (SMAE) of the clay estimation from the water content of air‐dried soil was 20% for the dataset using the Pipette method and 28% for the Sedigraph method. The estimation of the clay content was more accurate in fine‐textured than in coarse‐textured soils. In this study, organic‐C content played a subordinate role next to the clay content in explaining the variance of the water content. The water retention of coarse‐textured soils was more sensitive to the amount of organic C than that of fine‐textured soils. The results indicate that in our study the water content of air‐dried soil samples was a good quantitative proxy of clay contents, especially useful for fine‐textured soils. 相似文献
18.
咸水结冰融水入渗对土壤水盐运移和玉米苗期生长的影响 总被引：2，自引：0，他引：2
依据咸水冰盐水融离原理,利用土柱模拟试验,设置4个灌溉方式,分别为对照处理(淡水)、咸水灌溉、咸水结冰灌溉和咸水结冰灌溉+秸秆覆盖,研究咸水结冰灌溉条件下土壤水盐的独特运移机制。结果表明,与淡水灌溉相比,咸水灌溉处理表层0~40 cm土壤水分含量偏低,而深层土含水量则较高;咸水结冰灌溉下这一规律更为明显。但配合秸秆覆盖措施能在一定程度提高咸水结冰灌溉后各土层土壤含水量。咸水直接浇灌使各土层土壤盐度EC1:5偏高,盐分累积量增大,且盐分具有明显表层聚集特性,表层0~40 cm盐分累积量占0~80 cm土体的62.2%;而咸水结冰后灌溉则显著降低表层0~40 cm土层的盐分累积,仅占18.6%;咸水结冰后灌溉配合秸秆覆盖则进一步促进表层的脱盐率提高,特别在0~10 cm土层,土壤盐度仅为0.15 dS·m -1,盐分累积67.8 g·m-2,与淡水处理间差异未达显著水平(P>0.05)。咸水结冰灌溉配合秸秆覆盖可促进表层土壤的脱盐,使土壤根系分布密集层保持较低盐分水平,缓解或消除盐分对作物生长的危害,使玉米的生长状况达到淡水灌溉处理的效果。 相似文献
19.
采煤塌陷裂缝对降雨后坡面土壤水分的影响 总被引：4，自引：0，他引：4
为探究采煤塌陷裂缝对坡面储蓄降水的影响,本文对降雨后不同坡向上裂缝两侧的不同土层水分动态变化特征进行了研究。结果表明:降雨主要补充坡面地表0~20 cm土层土壤水分,且在雨后0~20 cm土层土壤水分散失也较为严重;雨后阴坡土壤含水率最高,0~10cm、10~20cm和20~40 cm土层土壤水分差异显著(p0.05)。降雨结束8 d后,裂缝附近的土壤水分变化幅度较大,尤以坡面裂缝上部边缘处最为明显,裂缝处与远离裂缝的土壤水分之间差异显著(p0.05);阳坡土壤水分损失最高,阳坡裂缝周边土壤水分平均损失量高达3.31%。可见,裂缝的出现会在一定程度上打破坡面储蓄降水的格局,加剧坡面局部土壤水分散失,这一点在植被恢复与建设过程中不容忽视。 相似文献
20.
《Communications in Soil Science and Plant Analysis》2012,43(5):601-614
Abstract Potassium is an essential element for plant growth and its importance in agriculture has been well recognized. With continuous cropping of a soil, exchangeable ? levels decrease to a minimum, steady‐state level if no ? is added. This minimum level is important to both modeling soil ? cycling and fertilizer ? recommendations, and it has been determined by field studies lasting from 2 to 10 years. Consequently, there is a need for estimation of minimum exchangeable ? levels for a wide range of soil types from soil physical and chemical properties. A literature survey provided 19 studies where minimum exchangeable ? had been measured and regression analysis was conducted on this data to determine predictive relationships. Minimum exchangeable ? is closely related to soil clay content (r2 from 0.66 to 0.99), however, regression constants varied from study to study. Improved correlations were obtained between minimum exchangeable ? and clay content when all the soils (22A, r2=0.69) were divided into 3 groups according to the Fertility Capability Soil Classification (FCC) System and Soil Taxonomy (r2 of 0.86, 0.82, and 0.68). Differences in regression constants between groups were consistent with changes in soil properties associated with ? levels and exchangeability. This analysis provided relationships to estimate minimium exchangeable ? level from soil clay content for a wide range of soil types, which should aid soil ? modeling and fertilizer ? recommendations. 相似文献