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1.
PurposeSerious soil salinization, including excessive exchangeable sodium and high pH, significantly decreases land productivity. Reducing salinity and preventing alkalization in saline-sodic soils by comprehensive improvement practices are urgently required. The combinations of aluminum sulfate with different types of fertilizer at different rates were applied on rice paddy with saline-sodic soils of the Songnen Plain in Northeast China to improve soil quality and its future utilization. Materials and methodsExperiments were carried out in a completely randomized block design. Twelve treatments with aluminum sulfate at the rates of 0, 250, 500, and 750 kg hm?2 with inorganic, bio-organic, and organic-inorganic compound fertilizers were performed. Soil pH, electronic conductivity (EC), cation exchangeable capacity (CEC), exchangeable sodium percentage (ESP), total alkalinity, sodium adsorption ratio (SAR), soil organic carbon (SOC), available nutrients, soluble ions, rice growth, and yield in the saline-sodic soils were measured across all treatments. The relationships among the measured soil attributes were determined using one-way analysis of variance, correlation analysis, and systematic cluster analysis. Results and discussionThe pH, EC, ESP, total alkalinity, SAR, Na+, CO32?, and HCO3? in saline-sodic soil were significantly decreased, while CEC, SOC, available nitrogen (AN), available phosphorus (AP), available potassium (AK), K+, and SO42? were significantly increased due to the combined application of aluminum sulfate with fertilizer compared with the fertilizer alone. The most effective treatment in reducing salinity and preventing alkalization was aluminum sulfate at a rate of 500 kg hm?2 with organic-inorganic compound fertilizer. This treatment significantly decreased the soil pH, EC, ESP, total alkalinity, SAR, Na+, and HCO3? by 5.3%, 28.9%, 41.1%, 39.3%, 22.4%, 23.5%, and 35.9%, but increased CEC, SOC, AN, AP, AK, K+, SO42?, rice height, seed setting rate, 1000-grain weight, and yield by 77.5%, 115.5%, 106.3%, 47.1%, 43.3%, 200%, 40%, 6.2%, 43.9%, 20.3%, and 42.2%, respectively, compared with CK treatment in the leaching layer. ConclusionsThe combined application by aluminum sulfate at a rate of 500 kg hm?2 with organic-inorganic compound fertilizer is an effective amendment of saline-sodic soils in Songnen Plain, Northeast China. These results are likely related to the leaching of Na+ from the soil leaching layer to the salt accumulation layer and desalination in the surface soil, and the increase of SOC improved the colloidal properties and increased fertilizer retention in soil. In addition, the environmental impact of aluminum sulfate applied to soil needs to be further studied. 相似文献
2.
为了揭示钾肥对Cd污染土壤钝化修复效果的影响,为土壤钝化修复过程中合理施钾肥提供理论依据。本文选取不同剂量(含量以K2O计算,分别为0.1 g·kg~(-1)、0.2 g·kg~(-1)和0.3 g·kg~(-1))的KCl和K_2SO_4作为典型钾肥,以海泡石(10 g·kg~(-1))作为钝化材料,通过油菜盆栽试验,研究了两种钾肥在海泡石钝化条件下对Cd污染土壤修复效应的影响。结果表明:K_2SO_4显著增加了油菜的生物量,其增幅为6.06%~10.05%。与单施海泡石钝化相比,在海泡石钝化时施用KCl和K_2SO_4两种钾肥,油菜地上部茎叶Cd含量分别增加16.38%~60.73%和15.62%~25.19%;施用KCl和K_2SO_4对土壤p H未产生显著性影响,却显著地增加了土壤有效态Cd含量,其增幅分别为25.51%~34.65%和18.5%~24.96%。添加海泡石可使土壤的Zeta电位向负值方向移动,提高土壤对Cd的负载能力;但添加海泡石下施用KCl和K_2SO_4均能提高土壤的Zeta电位,降低土壤对Cd的负载能力。等温吸附试验同样表明,添加KCl和K_2SO_4均能降低海泡石对Cd的吸附量,在水溶液中海泡石对Cd的最大吸附量为5.30 mg·kg~(-1),添加KCl和K_2SO_4后吸附量分别降低至2.87 mg·g~(-1)和4.92 mg·g~(-1)。KCl和K_2SO_4显著改善了土壤中K、Mn、Cu和Zn等营养元素的有效态含量。从上述结果可以发现,在海泡石钝化修复Cd污染土壤过程中,施K_2SO_4对钝化效果的影响小于施KCl。 相似文献
3.
We investigated the potential effects of elevated water-column sulfate (SO 4) levels on heterotrophic microbial respiration and net phosphorus (P) release for soils collected from impacted and unimpacted Everglades wetlands in south Florida. Soils from three sites, ranging from low P and low SO 4 to high P and high SO 4 environments, were examined under controlled laboratory conditions. The soils were subjected to anaerobic incubations to evaluate net P release and organic matter decomposition in response to SO 4 amendments of 32 or 96 mg l −1 (0.33 and 1.0 mM).Three processes have been described in the literature to explain why SO 4 enrichment may lead to P release from soils under anaerobic conditions. First, alkalinization can lead to a more favorable pH environment for decomposition. For the soils examined here, alkalinization due to the hydrogen ion-consuming reaction of SO 4 reduction was not a prominent mechanism. We found that pH decreased in the incubation vessels, and that increases in alkalinity were more likely attributable to calcium carbonate dissolution than SO 4 reduction. Moreover, all the soils exhibited near circum-neutral pH levels, with moderate to high concentrations of native alkalinity.Second, formation of iron sulfide (FeS x) compounds has been shown to mobilize iron (Fe)-associated P. Soils from only one of the study sites had Fe concentrations that would be expected to be high enough to influence P mobility. Relatively high porewater Fe:soluble reactive P (SRP) ratios (>83:1) were observed at this site, which suggests that Fe could theoretically exert control over the release of P from the soil. However, soil P levels at this site were too low to measure any substantial influence of Fe on net P mobilization.Finally, availability of electron acceptors such as SO 4 is a major determinant of decomposition rate, and thus rate of organic P release. Amending the soils with SO 4 did not result in either more heterotrophic microbial respiration as measured by carbon dioxide (CO 2) and methane (CH 4) production, or increased net P mobilization. In two of the SO 4-amended soils where post-incubation total sulfide concentrations were as high as 23.4 mg l −1, SO 4 addition reduced production of respiratory carbon end products, suggesting hydrogen sulfide inhibition. Moreover, limitations imposed by substrate quality and low P contributed to the lack of meaningful enhanced decomposition of organic matter with the addition of 32 or 96 mg SO 4 l −1 to the oligotrophic wetland soils. Even though P release did occur under anaerobic conditions for the more enriched site, addition of SO 4 did not enhance P release. 相似文献
4.
Soluble organic N and C were extracted from soils under long-term kikuyu grass pasture, annual ryegrass pasture and annual maize production using water, 0.5 M K 2SO 4 and 2 M KCl. Quantities extracted with K 2SO 4 were more than double those extracted with water while those extracted with KCl exceeded those using K 2SO 4. Differences in soluble organic C and N between land uses were much more obvious when water rather than salt solutions were used. It was suggested that water extracts give more realistic values than salt solutions. Regardless of the extractant used, the proportion of total N present as soluble N was considerably greater than the equivalent proportion of organic C present as soluble C. While the percentage of soil organic C and total N present in the light fraction and microbial biomass was lower in the kikuyu than ryegrass and maize soils, the equivalent values for water soluble C and N were, in fact, greatest in the kikuyu soil.The leaching of organic C, N and NO 3− from these soils was also measured over a 6-month period in a greenhouse lysimeter study. The soils were either left undisturbed or were disturbed (broken into clods <50 mm diameter) to simulate tillage and stimulate microbial activity. Quantities of organic C and N leached were greater from the kikuyu than other treatments and tended to be greatest from the disturbed kikuyu soil. The percentage of total soil N leached as organic N was considerably greater than that of total organic C leached as soluble C. Leaching of NO 3− was greatest from the disturbed kikuyu soil and least from the undisturbed kikuyu soil. The mean percentage of total soluble N present in organic form in leachates ranged from 17 to 32% confirming the importance of this form of N to leaching losses of N from agricultural soils. 相似文献
5.
Accurate estimation of the available potassium (K +) supplied by calcareous soils in arid and semi‐arid regions is becoming more important. Exchangeable K +, determined by ammonium acetate (NH 4OAc), might not be the best predictor of the soil K + available to crops in soils containing micaceous minerals. The effectiveness of different extraction methods for the prediction of K‐supplying capacities and quantity–intensity relationships was studied in 10 calcareous soils in western Iran. Total K + uptake by wheat grown in the greenhouse was used to measure plant‐available soil K +. The following methods extracted increasingly higher average amounts of soil K +: 0.025 M H 2SO 4 (45 mg K + kg ?1), 1 M NaCl (92 mg K + kg ?1), 0.01 M CaCl 2 (104 mg K + kg ?1), 0.1 M BaCl 2 (126 mg K + kg ?1), and 1 M NH 4OAc (312 mg K + kg ?1). Potassium extracted by 0.01 M CaCl 2, 1 M NaCl, 0.1 M BaCl 2, and 0.025 M H 2SO 4 showed higher correlation with K + uptake by the crop (P < 0.01) than did NH 4OAc (P < 0.05), which is used to extract K + in the soils of the studied area. There were significant correlations among exchangeable K + adsorbed on the planar surfaces of soils (labile K +) and K + plant uptake and K + extracted by all extractants. It would appear that both 0.01 M CaCl 2 and 1 M NaCl extractants and labile K + may provide the most useful prediction of K + uptake by plants in these calcareous soils containing micaceous minerals. 相似文献
6.
To investigate the potential of synchrotron‐based X‐ray Absorption Near‐Edge Structure spectroscopy (XANES) at the sulphur (S) K‐edge for a discrimination of adsorbed and precipitated sulphate in soils and soil particles, XANES spectra of ionic sulphate compounds and Al/Fe hydroxy sulphate minerals were compared with spectra of SO 42? adsorbed to ferrihydrite, goethite, haematite, gibbsite or allophane. Ionic sulphate and hydroxy sulphate precipitates had broader white‐lines (WL) at 2482.5 eV (full width at half maximum (FWHM) of edge‐normalized spectra, 2.4–4.2 eV; Al hydroxy sulphates, 3.0 eV) than SO 42? adsorbed to Al/Fe oxyhydroxides or allophane (FWHM, 1.8–2.4 eV). The ratio of the white‐line (WL) height to the height of the post‐edge feature at 2499 eV (WL/PEF) was larger for SO 42? adsorbed to Al/Fe oxyhydroxides or allophane (8.1–11.9) than for Al/Fe hydroxy sulphates and ionic sulphates (3.9–5.7). The WL/PEF ratio of edge‐normalized S K‐edge XANES spectra can be used to distinguish adsorbed from precipitated SO 42? in soils and also at microsites of soil particles. The contribution of adsorbed and precipitated SO 42? to the total SO 42? pool can be roughly quantified. Adsorbed ester sulphate may result in overestimation of precipitated SO 42?. The spectra of most soils could be fitted by linear combination fitting (LCF), yielding a similar partitioning between adsorbed and precipitated SO 42? as an evaluation of the WL/PEF ratio. The SO 42? pool of German forest soils on silicate parent material in most cases was strongly dominated by adsorbed SO 42?; however, in three German forest soils subject to elevated atmospheric S deposition, a considerable portion of the SO 42? pool was precipitated SO 42?, most likely Al hydroxy sulphate. The same is true for Nicaraguan Eutric and Vitric Andosols subject to high volcanogenic S input. In the subsoil of the Vitric Andosol, adsorbed SO 42? and Al hydroxy sulphate coexist on a micron scale. 相似文献
7.
Net carbon dioxide (CO 2) emission from soils is controlled by the input rate of organic material and the rate of decomposition which in turn are affected by temperature, moisture and soil factors. While the relationships between CO 2 emission and soil factors are well-studied in non-salt-affected soils, little is known about soil properties controlling CO 2 emission from salt-affected soils. To close this knowledge gap, non-salt-affected and salt-affected soils (0-0.30 m) were collected from two agricultural regions: in India (irrigation induced salinity) and in Australia (salinity associated with ground water or non-ground water associated salinity). A subset (50 Indian and 70 Australian soils) covering the range of electrical conductivity (EC) and sodium adsorption ratio (SAR) in each region was used in a laboratory incubation experiment. The soils were left unamended or amended with mature wheat residues (2% w/w) and CO 2 release was measured over 120 days at constant temperature and soil water content. Residues were added to overcome carbon limitation for soil respiration. For the unamended soils, separation in multidimensional scaling plots was a function of differences in soil texture (clay, sand), SOC pools (particulate organic carbon (POC) and humus-C) and also EC. Cumulative CO 2-C emission from unamended and amended soils was related to soil properties by stepwise regression models. Cumulative CO 2-C emission was negatively correlated with EC in saline soils ( R2 = 0.50, p < 0.05) from both regions. In the unamended non-salt-affected soils, cumulative CO 2-C emission was significantly positively related to the content of POC for the Indian soils and negatively related to clay content for the Australian soils. In the wheat residue amended soils, cumulative CO 2-C emission had positive relationship with POC and humus-C but a negative correlation with EC for both Indian and Australian soils. SAR was negatively related ( β = −0.66, p < 0.05) with cumulative CO 2-C emission only for the unamended saline-sodic soils of Australia. Cumulative CO 2-C emission was significantly negatively correlated with bulk density in amended soils from both regions. The study showed that in salt-affected soils, EC was the main factor influencing for soil respiration but the content of POC, humus-C and clay were also influential with the magnitude of influence depending on whether the soils were salt affected or not. 相似文献
8.
The individual effects of salinity and sodicity on organic matter dynamics are well known but less is known about their interactive effects. We conducted a laboratory incubation experiment to assess soil respiration and dissolved organic matter (DOM) dynamics in response to salinity and sodicity in two soils of different texture. Two non-saline non-sodic soils (a sand and a sandy clay loam) were leached 3–4 times with solutions containing different concentrations of NaCl and CaCl 2 to reach almost identical electrical conductivity (EC 1:5) in both soils (EC 1:5 0.5, 1.3, 2.5 and 4.0 dS m ?1 in the sand and EC 1:5 0.7, 1.4, 2.5 and 4.0 dS m ?1 in the sandy clay loam) combined with two sodium absorption ratios: SAR < 3 and 20. Finely ground wheat straw residue was added (20 g kg ?1) as substrate to stimulate microbial activity. Cumulative respiration was more strongly affected by EC than by SAR. It decreased by 8% at EC 1.3 and by 60% at EC 4.0 in the sand, whereas EC had no effect on respiration in the sandy clay loam. The apparent differential sensitivity to EC in the two soils can be explained by their different water content and therefore, different osmotic potential at the same EC. At almost similar osmotic potential: ?2.92 MPa in sand (at EC 1.3) and ?2.76 MPa in the sandy clay loam (at EC 4.0) the relative decrease in respiration was similar (8–9%). Sodicity had little effect on cumulative respiration in the soils, but DOC, DON and specific ultra-violet absorbance (SUVA) were significantly higher at SAR 20 than at SAR < 3 in combination with low EC in both soils (EC 0.5 in the sand and EC 0.7 and 1.4 in the sandy clay loam). Therefore, high SAR in combination with low EC is likely to increase the risk of DOC and DON leaching in the salt-affected soils, which may lead to further soil degradation. 相似文献
9.
In soil incubation experiments we examined if there are differences in the kinetic parameters of atmospheric methane (CH 4) oxidation in soils of upland forests and forested peatlands. All soils showed net uptake of atmospheric CH 4. One of the upland forests included also managed (clear-cut with or without previous liming or N-fertilization) study plots. The CH 4 oxidation in the forested peat soil had a higher Km (510 μl l −1) and Vmax (6.2 nmol CH 4 cm −3 h −1) than the upland forest soils ( Km from 5 to 18 μl l −1 and Vmax from 0.15 to 1.7 nmol CH 4 cm −3 h −1). The forest managements did not affect the Km-values. At atmospheric CH 4 concentration, the upland forest soils had a higher CH 4 oxidation activity than the forested peat soil; at high CH 4 concentrations the reverse was true. Most of the soils oxidised CH 4 in the studied pH range from 3 to 7.5. The pH optimum for CH 4 oxidation varied from 4 to 7.5. Some of the soils had a pH optimum for CH 4 oxidation that was above their natural pH. The CH 4 oxidation in the upland forest soils and in the peat soil did not differ in their sensitivities to (NH 4) 2SO 4 or K 2SO 4 (used as a non-ammonium salt control). Inhibition of CH 4 oxidation by (NH 4) 2SO 4 resulted mainly from a general salt effect (osmotic stress) though NH 4+ did have some additional inhibitory properties. Both salts were better inhibitors of CH 4 oxidation than respiration. The differences in the CH 4 oxidation kinetics in the forested peat soil and in the upland forest soils reveal that there are differences in the physiologies of the CH 4 oxidisers in these soils. 相似文献
10.
Studies were conducted to determine the efficacy of K salts in alleviating lime‐induced chlorosis. Greenhouse studies using a Gibbon silt loam [fine‐silty, mixed (calcareous), mesic Typic Haplaquoll] and a 1: 1 mixture of Gibbon soil and washed sand were conducted with KCl, KNO 3, K 2SO 4, K 2HPO 4, or KHCO 3 applied at rates of 0, 250, and 500 mg K/kg soil. An FeEDDHA treatment was included for comparison. Similar studies were conducted at two field sites known to produce lime‐induced chlorosis. Potassium salts were applied at 0, 20, and 40 g K/m of row. In the greenhouse, plants treated with KCl, KNO 3, and K 2SO 4 on Gibbon soil were less chlorotic than controls or plants treated with K 2HPO 4, or KHCO 3. No K treatment totally alleviated chlorosis except FeEDDHA. Chlorophyll correlated positively with chlorosis rating. No relationship was found between leaf Fe uptake and chlorosis. Plants grown in soil/sand exhibited no chlorosis and had lower Fe uptake than plants grown in Gibbon soil. Thus chlorosis was not due strictly to low soil‐Fe availability or inadequate Fe uptake. Bicarbonate in the soil solutions of both growth media treated with KCl was lower than controls which may explain the reduced chlorosis associated with this treatment. One field site showed positive effects of K treatments on chlorosis rating, chlorophyll concentration, and seed yield. No treatment was as effective as FeEDDHA in influencing plant growth or yield. Total leaf Fe concentration was unrelated to leaf chlorophyll concentration. Inorganic cation/anion ratios in the plant were from 4.4–8.4 which could cause net H + efflux by the plant and alkalinization of plant tissues. One possibility is that H + efflux solubilizes P in the rhizosphere, which after uptake could immobilize Fe in the plant. Application of KCl, KNO 3, and K 2SO 4 generally lowered HCO 3 content of the upper 15 cm of both soils. High bicarbonate could increase rhizosphere P availability and increase immobilization of Fe in the plant. 相似文献
11.
Abstract The main objective of this study was to determine the efficacy of cement kiln flue dust as a substitute for potassium sulfate fertilizer. Chemical and X‐ray diffraction analyses revealed that the flue dust contained about 20.7% K of which 9.1% was present as aphthitalite (K 3Na(SO 4) 2) , 4.4% as sylvite (KCl) and the remaining 7.2% as arcanite (K 2SO 4) . Accordingly, about 80% of the potassium in the dust was present as sulfates, though it contained 30% total sulfate and 15% Ca. The effects of flue dust were compared to some or all of the following fertilizers: KCl, K 2SO 4 and a synthetic fertilizer, on 11 soils ranging in texture from sand to clay in three greenhouse experiments. The synthetic fertilizer was made from K 2SO 4 and CaSO 4.2H 2O which were applied at the same rate of K and Ca as contained in the flue dust. The experimental results show that flue dust is as effective a K source as any of the fertilizers tested as it increased potato, barley and alfalfa yields and tissue and soil K concentrations to the same level. Furthermore, the flue dust increased the tissue sulfur concentration and the quantities of available sulfate in soils to the same level as potassium sulfate. Finally, the Ca contained in flue dust increased the concentration of this element in potato tops and soils when grown on eight coarse textured soils. The flue dust had, however, no effect on soil pH on any of the soils tested. 相似文献
12.
In view of growing concern about sulfur (S) deficiency, we attempted to study the effect of soil characteristics on the adsorption and translocation of S in soils. Laboratory experiments were conducted with five surface soils collected from three regions in the state of Orissa (Eastern India). In an adsorption study, all the soils were equilibrated with graded doses of potassium sulfate (K 2SO 4). Freundlich adsorption isotherms provided good fit to S adsorption data. Free Fe 2O 3 and Al 2O 3 in the soils were primarily responsible for retaining added S in soils. Further, studies on the movement of sulfate‐S in 30‐cm plexiglass columns, where radio‐labeled S along with water (5 cm) was applied as gypsum and K 2SO 4, showed that K 2SO 4‐S migrated deeper than gypsum‐S. Sulfur moved deeper in case of initially water‐saturated soils than in initially air‐dry soils. 相似文献
14.
Determination of the labile soil carbon (C) and nitrogen (N) fractions and measurement of their isotopic signatures (δ 13C and δ 15N) has been used widely for characterizing soil C and N transformations. However, methodological questions and comparison of results of different authors have not been fully solved. We studied concentrations and δ 13C and δ 15N of salt‐extractable organic carbon (SEOC), inorganic (N–NH 4+ and N–NO 3?) and organic nitrogen (SEON) and salt‐extractable microbial C (SEMC) and N (SEMN) in 0.05 and 0.5 m K 2SO 4 extracts from a range of soils in Russia. Despite differences in acidity, organic matter and N content and C and N availability in the studied soils, we found consistent patterns of effects of K 2SO 4 concentration on C and N extractability. Organic C and N were extracted 1.6–5.5 times more effectively with 0.5 m K 2SO 4 than with 0.05 m K 2SO 4. Extra SEOC extractability with greater K 2SO 4 concentrations did not depend on soil properties within a wide range of pH and organic matter concentrations, but the effect was more pronounced in the most acidic and organic‐rich mountain Umbrisols. Extractable microbial C was not affected by K 2SO 4 concentrations, while SEMN was greater when extracted with 0.5 m K 2SO 4. We demonstrate that the δ 13C and δ 15N values of extractable non‐microbial and microbial C and N are not affected by K 2SO 4 concentrations, but use of a small concentration of extract (0.05 m K 2SO 4) gives more consistent isotopic results than a larger concentration (0.5 m ). 相似文献
15.
Salinity and sodicity are prime threats to land resources resulting in huge economic and associated social consequences in several countries. Nutrient deficiencies reduce crop productivity in salt‐affected regions. Soil fertility has not been sustainably managed in salt‐affected arid regions. Few researchers investigated the crop responses to phosphorus and potassium interactions especially in saline–sodic soils. A research study was carried out to explore the effect of diammonium phosphorus (DAP) and potassium sulphate (K 2SO 4) on sugar beet ( Beta vulgaris L.) grown in a saline–sodic field located in Kohat district of Pakistan. The crop was irrigated with ground water with EC iw value of 2.17–3.0 dS/m. Three levels each of K 2O (0, 75 and 150 kg/ha) as K 2SO 4 and P 2O 5 (0, 60 and 120 kg/ha) as DAP were applied. The application of P significantly affected fresh beet and shoot yield while K fertilizers had significant effect on fresh beet yield and ratio of beet:shoot, while non‐significant effects on the fresh shoot were observed. The application of K 1 and K 2 promoted sugar beet shoot yield by 49.2 and 49.2% at P 1 and 64.4 and 59.7% at P 2, respectively over controls. In comparison with controls, fresh beet yield was increased (%) by 15 and 51, 45 and 84, and 50 and 58 for corresponding K 1 and K 2 at P 0, P 1 and P 2, respectively. Addition of P 1 and P 2 increased beet yield by 37 and 47% over control. The shoot [P] (mmol/kg) were achieved as 55.2, 73.6 and 84.3 at P 0, P 1 and P 2, respectively. The shoot [Mg] and [SO 4] tended to decrease with increasing P levels, while [SO 4] was markedly reduced at P 2. The effect of P on leaf [Na] was non‐significant, but increasing levels of K decreased [Na] substantially at P 0 and P 1, but there was no difference in the effect of K level on [Na] at P 2. Consequently, K application reduced leaf Na:K ratios. Fresh shoot yield was weakly associated with leaf [P] ( R2 = 0.53). The leaf Na:K ratio showed a negative relationship ( R2 = 0.90) with leaf [K]. A strongly positive relationship ( R2 = 0.75) was observed between leaf [K] and fresh beet yield. The addition of K 2SO 4 also enhanced [SO 4] and SO 4:P ratios in leaf tissues. The ratio of Na:K in the shoot decreased with increasing K application. These results demonstrated that interactions of K and P could mitigate the adverse effects of salinity and sodicity in soils. This would contribute to the efficient management of soil fertility system in arid‐climate agriculture. 相似文献
16.
The efficiency of the fumigation extraction method on the determination of soil microbial biomass carbon and ninhydrin-N was tested in three different soils (UK grassland, UK arable, Chinese arable) amended with black carbon (biochar or activated charcoal). Addition of activated charcoal to soil resulted in a significant decrease in K 2SO 4 extractable carbon and ninhydrin-N in all three soils, whereas the addition of biochar generally did not. A lower concentration of the extraction reagent (0.05 M vs. 0.5 M K 2SO 4) resulted in a significantly lower extraction efficiency in the grassland soil. The extraction efficiency of organic carbon was more affected by black carbon than that of ninhydrin-N, which resulted in a decreased biomass C/ninhydrin-N ratio. The impact of black carbon on the extraction efficiency of soil microbial biomass depended on the type of black carbon, on the concentration of the extraction medium and on soil type. 相似文献
17.
Potassium is an essential macronutrient for plants; it is characterized by increased photosynthetic activity by ensuring a better utilization of light energy, also acts as a regulator of cell osmotic pressure, decreasing transpiration and helping to maintain cell turgidity. However, the sodium is not an essential element for plants, although it is beneficial to certain crops, in some instances can replace the potassium and osmotic regulation making and turgidity of the cells, this effect is greatest when the supply of potassium is deficient (Wild, 1992). Both elements, in periods of aridity, delayed the wilting of plants to maintain cellular osmotic potential and in cold periods, they lower the freezing point of sap (Navarro and Navarro, 2000).This is an experiment to study the influence of soil management techniques on the monovalent cations in soil solutions at different depths. The cropping systems studied are conventional tillage, minimum tillage and direct drilling.Conventional tillage releases more Na + and K + to the soil solution than the conservative techniques. In the case of Na +, the conventional tillage soil solution has an average concentration of 0.563 meq/L compared to 0.303 meq/L of minimum tillage and 0.340 meq/L of direct drilling. As for the K +, the soil solution concentration of conventional tillage is 0.097 meq/L, compared to 0.079 meq/L of the solution of minimum tillage and 0.056 meq/L of direct drilling.The behavior for the two cations studied is distinct at different depths. The Na + is more abundant in water samples of soil taken in depth. Therefore, the salinization risk may take place in the subsoil, especially in conventional tillage where the Bw 1 horizon values are three times higher than in the Ap horizon, while the K + is more abundant in the surface horizon. Conventional tillage and minimum tillage techniques, in the Ap horizon have a similar pattern with a K + concentration average of 0.15 meq/L and 0.14 meq/L, respectively, resulting in lower values for direct drilling.Studies on clay soils have not been performed previously because of the difficulty presented by these soils when soil solution extracted for analysis. We analyzed the monovalent cations (sodium and potassium) from soil solution; because the soil solution is the immediate source of sodium and potassium for plants. 相似文献
19.
Soil organic carbon (SOC) plays a key role in the structural stability of soils and in their resistance against erosion. However, and as far as andic soils are concerned, these mechanisms and processes, as well as the influence of the different types of SOC on aggregate stability, are not fully understood. The targets of this paper are: (i) to determine the content and forms of SOC in Andosols under evergreen forest vegetation [laurel ( Laurus) and heather ( Erica) forest] and (ii) to find out the role of soil organic matter (SOM) in the aggregate stability and in the resistance of Andosols to water erosion. Soil samples have been collected in 80 sites in a 40 km 2 area under udic soil moisture regime. In them, fulvic and humic acids, Walkley–Black SOC, pyrophosphate-extractable SOC, Fe and Al, potassium sulphate extractable SOC, dissolved SOC, acid oxalate-extractable Fe, Al and Si, USLE K-factor and aggregate stability have been determined. The Andosols over volcanic ash are Aluandic Andosols (non-allophanic Andosols), whereas over basaltic lava flows are Silandic Andosols (allophanic Andosols). The surface (0–30 cm) samples analyzed contain 9.5–30 kg C m − 2 being significantly higher in allophanic Andosols ( p < 0.5). Organic carbon adsorbed onto the mineral fraction (extractable pyrophosphate, C p) accounts for 35–55% of the total SOC. All samples show a high stability to slaking and raindrop impact, being the first one highly correlated (r = 0.6) with pyrophosphate extractable C (C p), Fe (Fe p), and Al (Al p) in allophanic Andosols, unlike non-allophanic ones. The stability to raindrop impact correlates with pyrophosphate extractable C (C p) and Fe (Fe p) in both types of soils (r = 0.3–0.6, p < 0.05). These findings suggest that the high stability to both slaking and water-drop impact is due to the occurrence of allophane–Fe–OC complexes, rather than to the total OC, and the active Fe and Al forms, generated by the weathering of volcanic materials, constitute an essential constituent responsible for C sequestration and resistance to degradation in these soils. 相似文献
20.
Abstract A modified selenium (Se) fractionation procedure was used to study Se distribution in three soils (two silt loams and one silty clay). This sequential procedure consisted of: i) 0.2 M potassium sulfate (K 2SO 4)‐soluble fraction, ii) 0.1 M potassium dihydrogen phosphate (KH 2PO 4)‐exchangeable fraction, iii) 0.5 M ammonium hydroxide (NH 3H 2O)‐soluble fraction, iv) 6 M hydrochloric acid (HCl)‐extractable fraction, and v) residual fraction digested with perchloric (HClO 4) and sulfuric (H 2SO 4) acids. The fractionation procedure had high recovery rates (92.5 to 106%). The Se distribution in soil was controlled by soil properties, such as pH, oxide, clay, and calcium carbonate (CaCO 3) contents. In the untreated soil samples, residual Se fraction was dominant. In the Se‐enriched soils, the silty clay had significantly more Se in the NH 3H 2O and residual fractions while in the two silt loams the largest were KH 2PO 4 and residual fractions. The Se availability in the two silt loams was higher than in the silty clay. The Se availability pattern in the untreated soils was: unavailable (HCl + residual fractions) >> potentially available (KH 2PO 4 + NH 3H 2O fractions) > available (K 2SO 4 fraction), while in the Se‐enriched soils it was potentially available > unavailable > available. 相似文献
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