Distribution of exchangeable cations in a soil catena in the area of Baer mounds

The soil cover of the Baer mounds in Astrakhan oblast consists of brown solonetzes on the tops of the mounds, solonetzic brown and meadow brown soils on the slopes, and solonchaks at the footslopes. The exchangeable sodium percentage in the brown soils on the tops and slopes varies from 7 to 42%. However, the morphological features of the solonetzic process are weakly pronounced in these soils, except for some cementation of the soil mass and the poorly developed columnar structure in the B horizon. This is probably related to the coarse soil texture and the relatively low exchange capacity (<10 meq/100 g of soil). The portion of exchangeable sodium reaches 2–9%. A direct correlation between the sodium concentrations in the water extracts and in the soil exchange complex is clearly seen.     

Effects of salt stress on distribution of Na+ and some other cations in two soybean varieties differing in salt tolerance

In the course of investigations on the impact of salinity on mineral ion transport in differentially salt susceptible soybeans (“Lee” and “Jackson”) short-term experiments were conducted to elucidate the distribution pattern of Na⁺ and some other cations. The results showed that low salinity (7.5 mM NaCl) did not induce varietal differences in Na⁺ content during a 30 hrs uptake period. At 66.5 mM NaCl, however, the Na⁺ contents increased more in the leaves of the salt sensitive variety “Jackson” than in “Lee”. Both soybean varieties retained Na⁺ in the proximal root and stem. Furthermore, they extruded considerable amounts of Na⁺ from the roots to the medium. Increasing the level of salinity in the solution substantially reduced the Ca²⁺ uptake of both soybean varieties. In an experiment with the salt sensitive variety under constant salinity but increasing Ca²⁺ concentration in the medium, the plants showed a reduction in Na⁺ uptake and translocation to stem and leaves and an enhanced Ca²⁺ uptake and translocation to the shoots. It is suggested that the injury observed in “Jackson” after salt treatment is not only related to the insufficient control of Cl^? transport. At higher salinity levels the increasing accumulation of Na⁺ in the leaves and the varietally independant depression of Ca²⁺ uptake and translocation may enhance the development of leaf necrosis.     

Effect of mono- and divalent cations on sorption of water-extractable organic carbon and microbial activity

Biology and Fertility of Soils - Sorption is an important process for retention of organic carbon (C) in soils. The effect of Na+ and Ca2+ on sorption of organic C has been studied in salt-affected...     

铝(氢)氧化物对有机酸和磷酸根的竞争吸附研究

研究了磷 /草酸浓度比 (Cp/Cox)、草酸 (OX)与磷 (P)加入顺序、多种有机酸共存等条件下铝 (氢 )氧化物 (Al(OH)x)对有机酸和磷的吸附量变化。结果表明 :磷浓度一定时 ,随Cp/Cox减小 ,Al(OH)x吸附磷量降低 ,吸附OX量增高 ,吸附阴离子总量一般随浓度升高而增加 ;Cp/Cox相同时 ,5种加入方式吸P顺序为P/OX P -OX OX +P OX -P OX/P ;Cp/Cox不同时 ,Al (OH)x吸附配位体的总量也相应变化 ;几种有机酸共存时 ,Al(OH)x对体系中的各种阴离子均有吸附 ,且相互影响和制约 ,总吸附量取决于离子种类和浓度 ,3种有机酸影响P吸附量的顺序为柠檬酸 (CA) 草酸 (OX) 酒石酸 (Tar) ;Al (OH)x加磷后随平衡时间延长 ,先吸附的OX和CA对吸附P量的影响逐渐减弱 ,它们的相对亲合力越来越成为主导因素。     

Nitrogenase activity in relation to season,carbohydrates and organic acids in a temperate zone root association

Nitrogenase activity associated with grasses is commonly reported to be maximal during reproductive growth. For Spartina alterniflora, a perennial grass growing in salt marshes, seasonal changes in potential (excised root) N₂ase activity followed, by about 2 weeks, seasonal changes in ethanol soluble carbohydrate concentrations in roots and rhizomes. Both varied by about 3-fold during the year, declined rapidly with the onset of vegetative growth, and increased to previous levels during reproductive growth. N₂-ase activity measured on intact systems in situ was also maximal during reproductive growth, but the absolute rates were much lower than the potential N₂ase activities.     

Quantitation of volatiles and nonvolatile acids in an extract from coffee beverages: correlation with antioxidant activity

The antioxidant activities of a commercial brewed coffee were investigated by measuring malonaldehyde (MA) formation from oxidized cod liver oil using a gas chromatographic method (MA-GC assay) and a thiobarbituric acid method (TBA assay). The highest antioxidant activity obtained by the MA-GC assay was from regular whole brewed coffee (97.8%) at a level of 20%, and the highest antioxidant activity obtained by the TBA assay was from decaffeinated whole brewed coffee (96.6%) at a level of 5%. Among 31 chemicals identified in a dichloromethane extract, guaiacol, ethylguaiacol, and vinylguaiacol exhibited antioxidant activities, which were comparable to that of alpha-tocopherol. Among nine chlorogenic acids (three caffeoylquinic acids, three feruloylquinic acids, and three dicaffeoylquinic acids) identified, 5-caffeoylquinic acid contained the greatest amount both in regular (883.5 microg/mL) and in decaffeinated (1032.6 microg/mL) coffees; it exhibited 24.5% activity by the MA-GC assay and 45.3% activity by the TBA assay at a level of 10 microg/mL. Caffeic and ferulic acids showed moderate antioxidant activities in both assays.     

Formation constants of cu2+ complexes with humic and fulvic acids

Formation constants for Cu²⁺ complexes with humic and fulvic acids were determined by a modification of the well-known Bjerrum potentiometric titration method. Highly stable complexes were formed with formation constants of the order of those observed for synthetic polycarboxylic acids. Overall formation constants for a two-step process (B₂) ranged from 2.5 · 10^?4 to 7.9 · 10^?3.     

The in vivo and in vitro effects of Ca2+ and Al3+ upon ATPases from barley roots

Experiments were performed to test the effect of Ca²⁺ and Mg²⁺ upon ATPases (E.C. 3.6.1.3) from barley roots (Hordeum distichon L. cv. MULTUM) that had or had not taken up Al³⁺. Furthermore, the effect of the uptake period was examined. With longer duration of the Al³⁺ uptake, the activity of the ATPases dropped, independently of whether they were activated by Ca²⁺ or by Mg²⁺. Mg²⁺ stimulated the activity of the ATPases if no Al³⁺ had been taken up with lacking Ca²⁺ in the assay. If Al³⁺ had been taken up no additional activation by Mg²⁺ to the Ca²⁺ stimulation could be observed, and in some cases Mg²⁺ decreased the Ca²⁺ stimulation.     

Retention of added copper by two soils as affected by organic matter,CaCO3, and exchangeable ions

The effects of addition and removal of organic matter and CaCO₃ and of saturating a loam and a loamy sand soil with hydrogen (HCl treated), with calcium and with sodium on the retention of added copper were studied. Removal of organic matter reduced the copper-retaining capacity in soils, while addition of 1 to 4% humic acid to H₂O₂-treated soils increased the retention. Soil organic matter had higher specific copper retaining as well as fixing capacity than the added humic acid. Humic acid fixed about 62 and 49% of the copper it retained, while soil organic matter fixed about 65 and 61% in the loam and loamy sand respectively, which could not be extracted with 0.1 N HCl. About 30% extra copper retained by the added humic acid was exchangeable. Saturating the soils with hydrogen (HCl treatment) decreased the retention of added copper considerably but addition of CaCO₃ up to 8% increased the retention by increasing the pH of the soil system. The CaCO₃ induced retention was lower than caused by humic acid additions. The specific copper retention by native CaCO₃ was slightly higher than that of added CaCO₃. However, other changes associated with the pre-treatment of the soil may have caused those differences in specif is copper retention. Although CaCO₃ had as high a copper fixing capacity as organic matter its contribution towards exchangeable copper was negligible.     

Fe2+与胡敏酸的络合特征及其抗氧化性和生物有效性研究

在研究不同来源胡敏酸性质的基础上,研究了Fe2+与胡敏酸的络合特征以及络合态Fe2+的抗氧化性和生物有效性。结果表明,来源于土的胡敏酸属于A型,而来源于腐解秸秆、粪肥的胡敏酸属于RP型。A型胡敏酸与Fe2+络合能力大于RP型。HA-Fe2+络合物的络合稳定常数越大,络合物中Fe2+抗氧化性越强,玉米叶片中全铁含量也越高,但存在活性铁含量和全铁含量不一致现象。     

Mycorrhizal activity and diversity in a long-term organic Mediterranean agroecosystem

In organic agriculture, soil fertility and productivity rely on biological processes carried out by soil microbes, which represent the key elements of agroecosystem functioning. Arbuscular mycorrhizal fungi (AMF), fundamental microorganisms for soil fertility, plant nutrition and health, may play an important role in organic agriculture by compensating for the reduced use of fertilizers and pesticides. Though, AMF activity and diversity following conversion from conventional to organic farming are poorly investigated. Here we studied AMF abundance, diversity and activity in short- and long-term organically and conventionally managed Mediterranean arable agroecosystems. Our results show that both AMF population activity, as assessed by the mycorrhizal inoculum potential (MIP) assay, the percentage of colonized root length of the field crop (maize) and glomalin-related soil protein (GRSP) content were higher in organically managed fields and increased with time since transition to organic farming. Here, we showed an increase of GRSP content in arable organic systems and a strong correlation with soil MIP values. The analysis of AMF spores showed differences among communities of the three microagroecosystems in terms of species richness and composition as suggested by a multivariate analysis. All our data indicate that AMF respond positively to the transition to organic farming by a progressive enhancement of their activity that seems independent from the species richness of the AMF communities. Our study contributes to the understanding of the effects of agricultural managements on AMF, which represent a promising tool for the implementation of sustainable agriculture.     

Relationship between extractable Al and organic C in volcanic soils of Chile

In previous studies, Al extracted by acid ammonium acetate (Al_a) or Na-pyrophosphate (Al_p), rather than silt or clay content and climate conditions, was the most important factor that controls organic matter (OM) levels in volcanic soils. Here, the hypothesis was tested that Al_a is a comparable method (as much as CuCl₂) to quantify the proportion of Al bound to OM in allophanic soils. As far as we know, there are no previous antecedents in which selective dissolution method has been compared with this extractant. Secondly, we examine the effects of (a) Al, (b) silt plus clay content (particles size 0-53 µm) and (c) clay mineralogy on the control of organic carbon (OC) level in Chilean volcanic soils. This was achieved by sampling 16 soils series (11 Andisols, one Alfisol and four Ultisols, USDA classification) including 48 soil pedons up to 0.4 m depth. Soils were analyzed for Al_a, Al_p, oxalate (Al_o, Si_o and Fe_o), cold NaOH (Al_n) and un-buffered salts, CuCl₂ (Al_Cu), LaCl₃ (Al_La) and KCl (Al_k). We also measured the Al-humus as soluble C fraction after pyrophosphate extraction and the C associated to the silt plus clay fraction after sonication and gravity decantation. The statistical package (S)MATR was used to examine bivariate linear regressions among soil properties by computing the standardized major axis (SMA). Our results indicate that Al_a had a good correspondence with Al_p (R² = 0.76) in the top soil with Al_a/Al_p ratio of 0.19 and both extractans presented significant and positively relationship with soil OC (R² > 0.62). Acid ammonium acetate was as effective as Al_Cu to determine the Al-OM in allophanic soils. It is cheaper than Al_Cu and Al_p and 0.5 h shaking is required compared to 2 h of Al_Cu and 16 h of Al_p. The efficiency of the extraction was: Al_n ≥ Al_o > Al_p > Al_Cu ≥ Al_a > Al_La > Al_k. We also found that allophane content (estimated by Al/Si ratio) was strongly correlated (R² = 0.82) with the OC in the fine silt plus clay and that Al-humus together with C in the finest particles explained (R² > 0.60) the largest proportion of variation of soil OC across studied soils.     

Hydrochemical modelling of a stream dominated by organic acids and organically bound aluminium

An existing hydrogeochemical model, the Birkenes model (BIM), has been extended to include production of dissolved organic carbon (DOC) in the soil/water system and its chemical interactions with H⁺ and A1³⁺. The model has been calibrated and verified using precipitation and runoff data from the Svartberget catchment in northern Sweden. The catchment is impacted by moderate amounts of sulphur deposition (6 kg S ha^?1 a^?1; the stream is high in DOC (7–35 mg L^?1) and experiences episodically low pH-values (～4.0). The refined BIM is able to simulate the main variations in major chemical components of the stream water (H⁺, Ca²⁺, Mg²⁺, Al_i, Al₀, Cl^?, SO₄ ^?2 and DOC), as well as stream discharge and ¹⁸O, while Na⁺ is not well reproduced. Although very simplified relationships are used for the chemical interactions between DOC and H⁺ and aluminium, the model shows that these interactions are essential to stream acidity and aluminiumspecies content. Some of the model parameters are poorly determined by calibration with runoff data only. Soil and soil water investigations may contribute to the evaluation and development of the model structure and the representation of chemical processes. Further improvements of the model should emphasize DOC-production/absorption, detailed studies on DOC chemical behaviour and hydrological structure.     

Changes in organic matter,nitrogen, phosphorus and cations in soil as a result of fire and water erosion in a Mediterranean landscape

Fire affects large parts of the dry Mediterranean shrubland, resulting in erosion and losses of plant nutrients. We have attempted to measure these effects experimentally on a calcareous hillside representative of such shrubland. Experimental fires were made on plots (4 m × 20 m) in which the fuel was controlled to obtain two different fire intensities giving means of soil surface temperature of 439°C and 232°C with temperatures exceeding 100°C lasting for 36 min and 17 min. The immediate and subsequent changes induced by fire on the soil's organic matter content and other soil chemical properties were evaluated, together with the impact of water erosion. Seven erosive rain events, which occurred after the experimental fires (from August 1995 to December 1996), were selected, and on them runoff and sediment produced from each plot were measured. The sediments collected were weighed and analysed. Taking into account the variations induced by fire on the soil properties and their losses by water erosion, estimates of the net inputs and outputs of the soil system were made. Results show that the greatest losses of both soil and nutrients took place in the 4 months immediately after the fire. Plots affected by the most intense fire showed greater losses of soil (4077 kg ha^?1) than those with moderate fire intensity (3280 kg ha^?1). The unburned plots produced the least sediment (72.8 kg ha^?1). Organic matter and nutrient losses by water erosion were related to the degree of fire intensity. However, the largest losses of N‐NH₄⁺ and N‐NO₃^– by water erosion corresponded to the moderate fire (8.1 and 7.5 mg N m^?2, respectively).     

在铝胁迫下离子通道抑制剂和钙螯合剂对黑麦根系分泌有机酸的影响

以药理学的方法研究了铝对根系分泌有机酸的诱导作用及钙离子的调控作用。50μm o l/L A l处理24 h后的黑麦根系分泌物的高效液相色谱(HPLC)分析结果表明,铝诱导黑麦根系分泌柠檬酸(C it)与苹果酸(M a l)。在铝溶液中加入阴离子通道抑制剂尼氟灭酸(NA,1~2μm o l/L)、苯甲酰甲醛(PG,10μm o l/L),有机酸的分泌受到极显著的抑制。C a2 通道抑制剂L a(NO3)3(25μm o l/L)、异搏定(VP,25、50、100μm o l/L)显著或者极显著抑制铝诱导的有机酸分泌,而且在50μm o l/L A l溶液中加入的C a2 专一性螯合剂乙二醇-双-(2-氨基乙基)四乙酸(EGTA,250、500μm o l/L)能显著抑制柠檬酸的分泌。这些结果表明,阴离子通道是铝胁迫下黑麦根系分泌有机酸的重要通道,C a2 可能介导此分泌过程。     

Effects of biotechnology byproducts and organic acids on nitrification in soils

Summary Recent developments in biotechnology industries produce increasing amounts of byproducts with potential uses in agriculture. The present research focused on the nitrification of NH _inf4 ^sup+ -N in biotechnology byproducts added to soils, and on the effects of 29 naturally occurring organic acids (19 aliphatic and 10 aromatic) on nitrification in soils. A 10-g soil sample was incubated for 10 days at 30°C with 2.0 mg NH _inf4 ^sup+ -N in a byproduct or with 10 or 50 mol organic acid and 2.0 mg reagent-grade NH _inf4 ^sup+ -N. In condensed molasses-fermentation solubles, produced during the microbial fermentation of sugar derived from corn (Zea mays L.) and molasses derived from beets (Beta sp.), in the production of lysine as a supplement in animal food, the nitrification of NH _inf4 ^sup+ -N was similar to that of byproduct or reagent-grade (NH₄)₂SO₄. Nitrite accumulated when either of these materials was added to a calcareous Canisteo soil. The NH _inf4 ^sup+ -N in slops (produced during microbial fermentation processes occurring in the production of citric acid) was not nitrified in soils. Some organic acids inhibited, whereas others activated, nitrification in soils. Formic, acetic, and fumaric acids enhanced the production of NO _inf2 ^sup- -N in a calcareous Canisteo soil, whereas all other aliphatic and aromatic acids studied decreased the accumulation of NO _inf2 ^sup- -N. It is concluded that the addition or production of organic acids in soils affects the microbial dynamics, leading to significant changes in rates of nitrification and possibly in other N-transformation processes in soils.     

蓼科、禾本科植物细胞膜对铝胁迫反应的比较研究

以4种蓼科植物(荞麦、金荞麦、虎杖、无辣蓼)和2种禾本科植物(水稻、小麦)为材料,比较研究不同科属植物的细胞膜对铝胁迫反应的差异。结果表明:(1)6种植物叶片的游离脯氨酸含量、MDA含量和根系质膜透性均随着Al3 胁迫浓度增加而增大,禾本科植物的游离脯氨酸含量高于4种蓼科植物,荞麦、金荞麦的质膜透性、MDA含量高于虎杖、无辣蓼、水稻、小麦。(2)荞麦、小麦叶片的SOD和POD活性随Al3 胁迫浓度持续增长,虎杖和水稻持续下降,金荞麦和无辣蓼在25 mg/L Al3 处理时最高,100 mg/L Al3 胁迫明显降低。综合细胞膜对铝胁迫反应的各种特征,可以说明蓼科植物细胞膜透性变化是Al3 引发氧化胁迫的一种受损表现,而禾本科植物细胞膜透性变化是对A3 胁迫的一种适应性反应。     

The role of organic acids in the soil solution chemistry of a podzolized soil

The soil solution chemistry of a podzolized soil in the north of Sweden was monitored for four years using percolation lysimeters. Weak organic acids were a major constituent of the soil solution and are important because of their ability to form complexes with aluminium. Dissolved organics leached from the mor layer enhance the weathering rate in the eluvial horizon by forming complexes with aluminium, especially during the autumn when the leaching of dissolved organics was greatest. The weak organic acids were titrated and their pK_a values were evaluated. Aluminium was speciated with an ion-exchange method and by applying equilibrium calculations. Formation constants for the organic aluminium complexes were calculated to be log K_Along=5.42±0.32 m ^?1 (n=13) in spring and summer and log K_Alorg=4.87±0.14 m ^?1 (n=6) in autumn. Equilibria of Al³⁺ with solid phases were also examined using solubility constants. Percolation lysimeters below undisturbed and cut-off mor layers were compared.     

Antioxidant activity of a flavonoid-rich extract of Hypericum perforatum L. in vitro

A flavonoid-rich extract of Hypericum perforatum L. (FEHP) was prepared by adsorption on macroporous resin and desorption by ethanol. Total flavonoid content of FEHP was determined by a colorimetric method. The major constituents of FEHP, including rutin, hyperoside, isoquercitrin, avicularin, quercitrin, and quercetin, were determined by HPLC analysis and confirmed by LC-MS. Different antioxidant assays were utilized to evaluate free radical scavenging activity and antioxidant activity of FEHP. FEHP was an effective scavenger in quenching DPPH and superoxide radical with IC50 of 10.63 microg/mL and 54.3 microg/mL, respectively. A linear correlation between concentration of FEHP and reducing power was observed with a coefficient of r2 = 0.9991. Addition of 150 microg of FEHP obviously decreased the peroxidation of linoleic acid during 84 h incubation, but the amount of FEHP over 150 microg did not show statistically significant inhibitory effect of peroxidation of linoliec acid (p > 0.05). FEHP exhibited inhibitory effect of peroxidation of liposome induced both by hydroxyl radical generated with iron-ascorbic acid system and peroxyl radical and showed prominent inhibitory effect of deoxyribose degradation in a concentration-dependent manner in site-specific assay but poor effect in non-site-specific assay, which suggested that chelation of metal ion was the main antioxidant action. According to the results obtained in the present study, the antioxidant mechanism of FEHP might be attributed to its free radical scavenging activity, metal-chelation activity, and reactive oxygen quenching activity.