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1.
Abstract

Arsenic (As) is a deadly poison at high concentrations. It is mysterious in the sense that people are exposed to it most of the time through drinking groundwater, fortunately at much lower concentrations than the deadly levels, and usually without knowing it. Arsenic content in alluvial aquifers of Punjab varied from 3.5 to 688 µg L?1. Arsenic status of groundwater is classified into low (<10 µg L?1), moderate (≥10 to <25 µg L?1), high (≥25 to <50 µg L?1), and very high (>50 µg L?1). In zone I, the concentration of As in groundwater varied from 3.5 to 42 µg L?1 with a mean value of 23.4 µg L?1. On the basis of these limits, only 8% of samples were low, whereas 51 and 41% of the total samples collected from this region fall in the moderate and high As categories. The concentration of As in groundwater of zone II varied from 9.8 to 42.5 µg L?1 with a mean value of 24.1 µg L?1. Arsenic concentration in the alluvial aquifers of the central plain of zone II is 2 and 52% in the low and moderate limits. In this region, 46% of groundwater sites contain high As concentrations. Arsenic concentrations in the aridic southwestern parts are significantly different from other two provinces. The As concentration ranged from 11.4 to 688 µg L?1 with average value of 76.8 µg L?1. Eleven percent of the aquifers of the southwestern region of zone III are in the moderate category, 54% in the high, and 35% in the very high. According to safe As limits (<10 µg L?1), only 3 and 1% of the groundwater samples collected from zones I and II were fit for dinking purposes with respect to As content. In the aridic southwest, zone III, all water samples contained As concentrations greater than the safe limits and thus are not suitable for drinking purposes. The presence of elevated As concentrations in groundwater are generally due to the results of natural occurrences of As in the aquifer materials. The concentration of other competitive oxyanions in waters such as phosphate, sulfate, and borate also depressed the adsorption of As on the sorption sites of aquifer materials and thereby eventually elevate the As concentration in groundwaters. In groundwater of alluvial aquifers of Punjab, released from sulfide oxidation and oxyhydroxide of iron, elevated (>10 µg L?1) concentrations of As were widespread because of high pH (>8.0) and higher concentrations of phosphate, borate, sulfate, and hydroxyl anions. It is conclusively evident that geochemical conditions, such as pH, oxidation–reduction, associated or competing ions, and evaporative environments have significant effects on As concentration in groundwater. These conditions influence how much As is dissolved or precipitated into the water and how much is bound to the aquifer materials or the solid particles in water.  相似文献   

2.

Purpose

Transformation and transport of soil phosphorus (P) from chemical fertilizer or manure are affected by agronomic practices (i.e., fertilization, irrigation, and tillage) and numerous abiotic factors (i.e., temperature, drought, and rainfall). Previous studies on the effects of manure application on P loss were mostly conducted during cultivation and often using the laboratory column approach. Validated field observations by integrating P availability with the risk of P loss are few. This study aimed to evaluate the effects of rainfall and manure application on P leaching during fallow season.

Materials and methods

An in situ field lysimeter experiment was performed. Leachate was collected and analyzed for total P (TP) and dissolved reactive P (DRP). At the end of the lysimeter trial, soils were sampled incrementally to a depth of 40 cm with the following depth intervals: 0–4, 4–10, 10–20, 20–30, and 30–40 cm. Soil water extractable P (Pw) was analyzed and degree of P saturation (DPS) was calculated after oxalate and Mehlich-3 (M3) extractions.

Results and discussion

Phosphorus loading was found below 40 cm in all treatments and P was most concentrated in the 4–10 cm soil layer. High rainfall enhanced P leaching and consequently led to lower Pw and higher leachate DRP and TP than low rainfall. Furthermore, P leaching was observed regardless of manure application, with the highest leachate DRP (1.83 mg L?1) and TP (7.46 mg L?1) concentrations found at the end of experiment (day 53). Observed P leaching loads during fallow season (53 days) varied between 0.08 and 1.21 kg ha?1. The thresholds of DPS indicating P leaching were identified at 18.9% DPSM3(Ca) and 12.9% DPSM3(Ca+Mg), respectively. In this study, the DPSM3(Ca) and DPSM3(Ca+Mg) values exceeded the corresponding thresholds in the upper 30-cm soil layer but did not reach the thresholds at 30–40 cm. Nevertheless, the leachate DRP and TP indicated soil P leaching.

Conclusions

The results showed that intensive rainfall could significantly increase P leaching from manure application. Moreover, P leaching could occur in fallow season even in the absence of manure input, which should be assessed by not only soil P sorption capacities, but also soil fertilization history and hydrologic conditions. Implementation of soil P level evaluation is critical before spreading manure on land to avoid P pollution. Cost-effective and applicable soil test methods are required to generate environmental indicators to classify agricultural lands for risk of P loss, providing basis to safe manure disposal.  相似文献   

3.
ABSTRACT

Contamination of ground water as a consequence of soil leaching processes is an issue of major concern. In this context, a simulation of the soil leaching process was designed. A sequential injection (SI) method to monitor the soil leaching of iron complexes with in-line rain simulation for leachate production is described. The developed methodology comprises the SI determination of both iron(III) and 3-hydroxy-4-pyridinones iron(III) complexes, coupled to a mini soil column (mSC) for displaying in-line rain simulations. The described SI method enabled iron(III) determination within the range 2.0–35 µmol L?1, with a detection limit of 0.42 µmol L?1, and determination of iron(III) complexes in the range 1.0–45 µmol L?1. It was successfully applied to leachates from laboratory scale soil columns (LSSC), with good precision for both iron(III) and iron complexes determinations: calculated relative standard deviation (RSD) of 5% and 6%, respectively. A step further in automation and miniaturization was attained with the incorporation of a mini soil column for the in-line leachate production. The system enabled the soil leachate production and assessment in less than 5 min, including determinations in triplicate.  相似文献   

4.

Purpose

A total of 58 dewatered sludge samples were collected from 58 sewage treatment plants (STPs) geographically located in 31 provincial cities of China; the concentrations of heavy metals and antibiotics were determined to monitor the pollutant levels on a large scale, and the pollutant concentrations in sludge samples from different sources of sewage sludge and different geographical regions were compared.

Materials and methods

All the samples were divided into two portions, one of which was air-dried for determination of heavy metals. The other portion was placed in a brown glass bottle and frozen at ?20 °C for antibiotics analysis. Total heavy metals were digested with aqua regia and determined by atomic absorption spectrophotometry (Varian SpectrAA 220FS and Varian SpectrAA 220Z). The antibiotics were extracted with EDTA-sodium phosphate buffer with acetonitrile/Mg(NO3)2-NH3?H2O, v/v, 3:1 and analysed by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) and quantified by the isotope-labelled internal standard method.

Results and discussion

In all the sludge samples, zinc was the most abundant metal followed by copper, with relatively low concentrations of chromium, lead, nickel and cadmium. Only 20 % of samples exceeded the Chinese class A values of heavy metal standards for agricultural use (GJ/T309-2009). Sixteen different antibiotics were detected in all the sludge samples, and fluoroquinolones (FQs) and tetracyclines (TCs) were more abundant than sulfonamides (SAs). Concentrations of ∑FQs, ∑TCs and ∑SAs ranged from 1,569 to 23,825 μg kg?1 (mean 8,274 μg kg?1, dry weight), from 592 to 37,895 μg kg?1 (mean 8,326 μg kg?1, dry weight) and from 20.1 to 117 μg kg?1 (mean 55.4 μg kg?1, dry weight), respectively. Tetracyclines (except chlortetracycline) were significantly correlated with zinc and lead. No significant regional trends were observed in the concentrations of heavy metals and antibiotics in sludges.

Conclusions

Heavy metal concentrations are not the major factor restricting domestic and mixed flow sludge application, but the antibiotic concentrations in sludges are problematic; regulation of antibiotic use and establishment of standards to ensure safe handling of sludges are needed.  相似文献   

5.
Engineered plant growth media must support plant growth while minimizing environmental impact. The objective of this research was to determine how different growth media influence nutrient leaching. Plant growth media contained varied amounts of soil, sand, compost that did or did not contain manure, and possible sorbents for phosphorus. If the plant growth media included compost derived partly from manure, leaching losses of nutrients were excessive due to the high nutrient load in the compost. Layering compost over the plant media mix resulted in lower nitrate concentrations in effluent (87 mg L?1) compared with mixing compost into the media (343 mg L?1); however, growth of prairie grasses was reduced because of dense media below the compost blanket (0.09 versus 0.31 g). Using lower amounts of compost that did not contain manure resulted in lower mean nitrate concentrations in effluent (101 versus 468 mg L?1). Media that had no soil (13.3 mg L?1) had greater loss of phosphorus after harvest for unsaturated drainage than media with soil (1.8 mg L?1). To reduce nitrate leaching, only small amounts of low-nutrient compost (higher C:N ratio) should be incorporated into the media. If compost is applied as a surface blanket without incorporation, then soil should be added to the sand to reduce density of the media and increase plant growth.  相似文献   

6.
The rate at which dried soils are rewetted can affect the quantities and forms of nutrients in leachates. Both dried and moist replicated (n?=?3) samples of two contrasting grassland soil types (clayey vs brown earth) were irrigated during laboratory experiments with identical total amounts of water, but at different rates, ranging from 0 h, increasing by 30-min increments up to 4 h, and additionally a 24-h rewetting rate. Total P concentrations in leachates from dried samples of both soils generally decreased as rewetting rate increased, ranging from 2,923?±?589 μg P L?1 (0.5 h rewetting rate) to 731?±?46.0 μg P L?1 (24 h, clayey soil) and 1,588?±?45.1 μg P L?1 (0.5 h) to 439?±?25.5 μg P L?1 (24 h brown earth). Similar patterns in concentrations occurred for molybdate reactive P (MRP), although concentrations were generally an order of magnitude lower, indicating that the majority of the leached P was probably organic. The moist brown earth leached relatively high concentrations of MRP (maximum 232?±?10.6 μg P L?1, 0.5 h), unlike the moist clayey soil (maximum 20.4?±?10.0 μg P L?1, 0 h). The total oxidised N concentrations in leachates were less affected by rewetting rate, although longer rewetting rates resulted in decreased concentrations in leachates from the dried samples of both soils. The difference in responses to rewetting rates of the two soils is probably due to differences in the fate of the microbial biomass and adsorption properties in the soils. Results show that soil moisture could be an important factor in regulating nutrient losses and availability, especially under changing patterns of rainfall predicted by future climate change scenarios.  相似文献   

7.
A flow injection analysis (FIA) method capable of automation for molybdate reactive phosphorus (P) determination in soil extracts is described. Results obtained using this method in three soil extracts [calcium chloride (CaCl2), Olsen, and Mehlich I] were the same as those provided by the manual molybdate blue colorimetric method. Linear range extending to 2 mg P L?1, detection limits ranging from 6 to 26 µg L?1 depending on the soil extract, and accurate recoveries from P‐spiked samples were achieved. The sensitivity of the system was around 0.3 absorbance units per mg P L?1, and the sampling frequency was 72 samples h?1, higher than those described for most of the flow injection methods.  相似文献   

8.
Abstract

The effect of zinc–phosphorus (Zn‐P) interaction on Zn efficiency of six wheat cultivars was studied. The higher dry matter yields were observed when Zn was applied at 5 µg g?1 soil than with no Zn application. Phosphorus applications also increased dry matter yield up to the application of 25 µg P g?1 soil. The dry matter yield was significantly lower at the P rate of 250 µg g?1 soil. At the Zn‐deficient level, the Zn‐efficient cultivars had higher Zn concentrations in the shoots. Zinc concentrations in all cultivars increased when the P level in the soil was increased from 0 to 25 µg P g?1 soil except for the cv. Durati, in which Zn concentrations decreased with increases in P levels. However, when Zn×P interactions were investigated, it was observed that at a Zn‐deficient level, Zn concentrations in the plant shoot decreased with each higher level of P, and more severe Zn deficiency was observed at P level of 250 µg g?1 soil.  相似文献   

9.
Response of the integrated use of mycorrhiza, inorganic and organic manures on microbial variables and yield performance of colocasia (Colocasia esculenta L.) was studied in an acid Alfisol. Significantly highest mean cormel yield (14.13 t ha?1) was recorded due to application of super optimal doses of nitrogen, phosphorus, and potassium (NPK). Integrated application of lime + farmyard manure (FYM) + ½ NPK + zinc sulfate (ZnSO4) has recorded the highest dehydrogenase activity (2.048 µg TPF hr?1 g?1) and Fluorescein Diacetate Hydrolysis assay (1.855 µg g?1 hr?1). The highest acid and alkaline phosphatase activities (77.67 and 51.18 µg PNP g?1 h?1, respectively) were observed due to Vesicular Arbuscular Mycorrhiza (VAM) inoculation in combination with lime + FYM + ½ NPK. Dehydrogenase and phosphatase activities had a highly significant relationship with cormel yield and the biochemical constituents of colocasia. The study emphasized the conjunctive use of balanced inorganic fertilizers and organic manures to enhance the enzymatic activities and to realize higher crop yields of colocasia in acid Alfisols.  相似文献   

10.

Purpose

A simple and highly efficient economic method for the analysis of 11 antibacterial drugs including two tetracyclines, three quinolones, four sulfonamides, chloramphenicol and tylosin, in livestock manure, was developed using solid-phase extraction (SPE) and high-performance liquid chromatography (HPLC).

Materials and methods

The analytes were successively extracted by EDTA-McIlvaine solution and organic solvent mixture. The extracts were degreased with n-hexane and cleaned through SPE on a hydrophile-lipophile balance (HLB) cartridge. All compounds were determined on a C18 reverse phase column with gradient elution.

Results and discussion

Recoveries calculated from spiked samples of animal manures ranged from 62.65 to 99.16 % for 11 antibiotics with relative standard deviations of less than 10.0 %. Limits of detection ranged from 0.1 to 1.9 μg kg?1, and limits of quantification ranged from 0.3 to 5.9 μg kg?1.

Conclusions

The results show that SPE-HPLC is an inexpensive and practical method for rapid detection of multiple antibiotics in animal manure.
  相似文献   

11.
Inceptisols and Vertisols are two dominant soil orders that support major agricultural production in India. These soils often exist in semi-arid and arid regions. Low precipitation and high evaporation demand leads to salt accumulation in these areas. The problem of salt accumulation is further compounded by the presence of saline/alkaline groundwaters. We evaluated the effect of modified Ca/Mg waters on ionic composition, dispersion, and clay flocculation of sodic Inceptisols, saline-sodic Inceptisols, and normal Vertisols from different parts of India. A completely randomized factorial design with three replications of individual soils were sequentially leached with five pore volumes of deionized, saline water of 60 and 120 me L?1 total electrolyte concentration (TEC) at a fixed SAR of 5.0 mmol1/2 L?1/2 and Ca:Mg ratio of 2:1, 1:1 and 1:2. Application of saline waters decreased pH and increased EC of the soil leachates after leaching five pore volumes of three Ca/Mg ratios of 60 and 120 me L?1 solutions in sodic Inceptisols and normal Vertisols. In saline-sodic Inceptisols, application of saline waters decreased both pH and electrical conductivity (EC) of the soil leachates. Preferential Ca2+ holding in soil was only noticed in sodic Inceptisols when leaching process was performed with independent saline waters, but Mg2+ has a tendency to hold in soil upon application of independent saline waters for all soils except sodic Inceptisols. Periodic application of deionized water could increase soil dispersion and decreased flocculation of clay particles. Mg2+ ion had less flocculating vis-à-vis high-dispersion effect on soil clays than the Ca2+ ion.  相似文献   

12.
Three hydroponic experiments were set up to study the rhizofiltration of cadmium (Cd) or nickel (Ni) from artificially contaminated nutrient solution with sunflower, squash, or Indian mustard. After 48 h of exposure with 2 mg L?1 Cd‐contaminated water, 460, 415, or 1092 µg Cd g?1 (dry weight) was detected in roots of 33‐day‐old sunflower and squash or in 50‐day‐old Indian mustard, respectively. As calculated, 1 g of root dry matter of the tested crop species removed 5.7–12.4% of total Cd content present in the nutrient solution. It was supposed that pseudomonads (soil rhizoplane bacteria) and the plant growth hormone ethylene can enhance the specific surface of roots and hence roots' metal adsorption capacity. As a trend, pretreatment of Indian mustard with Pseudomonas fluorescens bacteria enhanced slightly the Cd (from 1793 to 2346 µg g?1) or Ni (from 1088 to 1192 µg g?1) concentration of roots. Cadmium concentration in roots was also enhanced from 2694 to 3273 µg g?1 when the roots of Indian mustard were pretreated with Cd‐tolerant rather than Cd‐sensitive Pseudomonas cepacia. In spite of the occurrence of new root hairs, the pretreatment of roots with ethylene proved to be ineffective in enhancement of the Cd rhizofiltration capacity of Indian mustard.  相似文献   

13.
A method for simultaneous analysis of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) in water supply was developed using solid-phase extraction and high-performance liquid chromatography with fluorescence detection. The linearity was evaluated between 2.5 and 200 μg L?1 (r> for the analytes. The limits of quantification were 1.5 and 2.1 ng L?1 for BPA and EE2, respectively. The extraction was made with C18 cartridges, and recoveries obtained varied between 70 and 102 % for the strengthening of 5 μg L?1. After the validation, the method was applied in the determination of pollutants in surface water and water supply of Sao Luis, Brazil, where BPA was found in two of the eight samples analyzed, with concentrations of 1.11 and 3.61 μg L?1.  相似文献   

14.
Abstract

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry‐season) rice (Oryza sativa) and their residual effects on the following Aman (wet‐season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L?1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L?1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L?1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 µg g?1 and its concentration in rice straw varied from 2.4 to 9.6 µg g?1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus.  相似文献   

15.
Abstract

Soils under the main mangrove (Rhizophora racemosa and Avicennia germinans) forest in the Niger Delta, Nigeria, were characterized, and their capacities to retain heavy metals were examined by using soil column leaching experiments, using 20 mg L?1 Cu, 50 mg L?1 Zn, 20 mg L?1 Cd, and 100 mg L?1 Mn solutions. At the end of the leaching experiments, soil samples from each column were divided into two layers (0–5 cm and 5–10 cm) and analyzed for total metal retained. The fractionation of heavy metals in the surface soil samples (0–5 cm) was investigated by the sequential extraction technique. The study showed that the soils were influenced by tidal flow and characterized by the presence of very fine textured, thin (0–5 cm) to moderately thick (10–15 cm) layer of alluvium (mud) on the surface. The fibric soil material beneath the surface mud varies in thickness from about 70 to 100 cm, and beyond the histic layer is the plastic, very sticky, massive clay. In situ, the soils were neutral in reaction (pH 7.0–7.2), but became strongly acid (pH 3.3–4.8) upon drying. They are saline, high in soluble salts, highly reduced, with CEC that is low in the fibric layer, but high in the mineral, clayey subsoil horizon. The soils are saturated with water for much more than 30 days in a year and have fiber content that is more than 40 cm thick, with the fibric sphagnum constituting more than three‐fourths by volume to a depth greater than 90 cm. The soils, classified as Typic Sphagnofibrists, sequestered considerable amounts of copper (Cu), zinc (Zn), cadmium (Cd), and manganese (Mn) with most of the metals retained in the surface soils. The anthropogenic heavy metals were mostly adsorbed probably to the negatively charged sites of organics and clay. These loosely bound metals may be desorbed and reenter the aqueous phase, thus becoming a secondary source of metal pollution.  相似文献   

16.
Water loss as deep percolation is considerable in furrow irrigation in light soils due to the high infiltration rate. Application of soil conditioners such as bentonite reduces the infiltration rate and improves irrigation application efficiency (Ea) in these soils. The effects of bentonite application rates (BAR) of 0, 2, 4 and 6 g L?1 on infiltration of a loamy sand soil were determined in a soil column in the laboratory. The exponent of the Kostiakov infiltration equation was not influenced by BAR. Maximum reduction in infiltration equation coefficient and final infiltration rate (i f) occurred with 2 g bentonite L?1 and this reduction was lower on increasing BAR from 2 to 4 and 4 to 6 g L?1 compared with control. The effect of 2 g L?1 BAR on infiltration and its effect on the design of furrow irrigation in a field with a loamy sand soil indicated that in the first irrigation after field ploughing and seed planting, longer furrow length, lower deep percolation and higher Ea are obtained.  相似文献   

17.
《Journal of plant nutrition》2013,36(12):2067-2083
Abstract

Information is desired on plant species that have a great potential in phytoremediation of copper (Cu) contaminated soils. Two contrasting ecotypes of Elsholtzia argyi were comparatively studied using nutrient solution culture for their growth response and uptake, distribution, and translocation of Cu. The results show that the ecotype from an old mined area (Sanmen-ecotype) had greater tolerance to Cu than that from the nonmined area (Jiuxi-ecotype) based on dry matter yield at different Cu supply levels. Inhibited root and leaf growth was noted at the external Cu levels > 50 µmol L?1 for the Sanmen-ecotype, and at the Cu supply levels > 5 µmol L?1 for the Jiuxi-ecotype. Stem growth was most sensitive to Cu toxicity in E. argyi, and was inhibited at the Cu levels ≥ 2.5 µmol L?1 for Jiuxi-ecotype and ≥ 25 µmol L?1 for Sanmen-ecotype. Root Cu concentrations were higher in Sanmen-ecotype than in Jiuxi-ecotype, but leaf, especially stem Cu concentrations were much lower in the former than in the latter. Furthermore, Jiuxi-ecotype was much more efficient than Sanmen-ecotype in the translocation of Cu from root to the shoot, and it had higher ratios of stem/root and leaf/root Cu concentration. At the Cu supply levels higher than 10 µmol L?1, root concentrations of potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) considerably decreased in Jiuxi-ecotype, but were not affected or even increased in Sanmen-ecotype. Zinc concentrations in the stems, particularly in the leaves of Sanmen-ecotype increased by 3 folds, but were hardly changed in Juixi-ecotype when grown at the Cu levels higher than 10 µmol L?1. These results indicate that the Sanmen-ecotype of E. argyi is a Cu-tolerant ecotype, and its tolerance to high Cu levels was mainly related to its extraordinary capability to restrict Cu uptake, especially Cu translocation from root to the shoot, probably by competitive uptake and translocation of Zn.  相似文献   

18.
An estimated 97 percent of the soils in Laos are characterized by low phosphorus (P). This characteristic, together with high acidity, constrains food crop production. The P status, sorption, and associated properties were evaluated for fifteen important agricultural soils from the uplands. Soil pH values ranged from 4.5 to 5.9. Soil organic carbon (C) varied from 7.0 to 22.9 g kg?1. Soil clay varied from 179 to 709 g kg?1. The cation exchange capacity (CEC) also varied from 4.30 to 32.1 cmolc kg?1. Extractable P levels of thirteen of the fifteen soils were P deficient with medium to very high P sorption, indicating substantial fertilizer P requirements. Dithionite and oxalate aluminum and iron predicted P sorbed at 0.2 mg P L?1. The extractable P increase per unit added P, P buffer coefficient (PBC), was low, also indicating high P sorption. Field studies are needed to confirm predictions of P requirements.  相似文献   

19.
Silicon has the potential to improve drought tolerance in crops. Seeds primed with silicon were used in the present study to explore its potential benefit to withstand water stress. Seeds of two wheat varieties, NARC-2009 and Chakwal-50, were sown in pots after priming with distilled water and different concentrations (0.5%, 1.0% and 1.5%) of silicon sources (silicic acid, sodium silicate and silica gel) at PMAS, Arid Agriculture University, Rawalpindi. Maximum silicon uptake at three-leaf stage (0.028 µg g?1 dry weight (DW)), anthesis (0.072 µg g?1 DW) and maturity (0.103 µg g?1 DW) was recorded for silica gel. Silicon uptake increased significantly in response to increase in Si concentration from 0.5% to 1.5%. Leaf membrane stability index, epicuticular wax, relative water content and proline remained maximum – 78.90%, 2.6 mg g?1 DW, 83.88% and 54.90 µg g?1 – for silica gel treatments compared with others. Silica gel with 1.5% silicon concentration resulted in maximum spike length (14.3 cm), biological yield (7.63 g pot?1), hundred-grain weight (3.97 g pot?1) and grain yield (2.46 g pot?1). Based on the study outcomes, it is concluded that silica gel might be a good priming option with 1.5% silicon concentration to establish plant under drought stress.  相似文献   

20.

Purpose

Crop straws and animal manure have the potential to ameliorate acidic soils, but their effectiveness and the mechanisms involved are not fully understood. The aim of this study was to evaluate the effectiveness of two crop (maize and soybean) straws, swine manure, and their application rates on acidity changes in acidic red soils (Ferralic Cambisol) differing in initial pH.

Materials and methods

Two red soils were collected after 21 years of the (1) no fertilization history (CK soil, pH 5.46) and (2) receiving annual chemical nitrogen (N) fertilization (N soil, pH 4.18). The soils were incubated for 105 days at 25 °C after amending the crop straws or manure at 0, 5, 10, 20, and 40 g kg?1 (w/w), and examined for changes in pH, exchangeable acidity, N mineralization, and speciation in 2 M KCl extract as ammonium (NH4+) and nitrate plus nitrite (NO3??+?NO2?).

Results and discussion

All three organic materials significantly decreased soil acidity (dominated by aluminum) as the application rate increased. Soybean straw was as effective (sometimes more effective) as swine manure in raising pH in both soils. Soybean straw and swine manure both significantly reduced exchangeable acidity at amendment rate as low as 10 g kg?1 in the highly acidic N soil, but swine manure was more effective in reducing the total acidity especially exchangeable aluminum (e.g., in the N soil from initial 5.79 to 0.50 cmol(+) kg?1 compared to 2.82 and 4.19 cmol(+) kg?1 by soybean straw and maize straw, respectively). Maize straw was less effective than soybean straw in affecting soil pH and the acidity. The exchangeable aluminum decreased at a rate of 4.48 cmol(+) kg?1 per pH unit increase for both straws compared to 6.25 cmol(+) kg?1 per pH unit from the manure. The NO3??+?NO2? concentration in soil increased significantly for swine manure amendment, but decreased markedly for straw treatments. The high C/N ratio in the straws led to N immobilization and pH increase.

Conclusions

While swine manure continues to be effective for ameliorating soil acidity, crop straw amendment has also shown a good potential to ameliorate the acidity of the red soil. Thus, after harvest, straws should preferably not be removed from the field, but mixed with the soil to decelerate acidification. The long-term effect of straw return on soil acidity management warrants further determination under field conditions.
  相似文献   

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