Acid deposition: Effects of sulphuric acid at pH 3 on chemical and biochemical properties of bracken litter

The effects of increased acid deposition on some biochemical and chemical properties of bracken litter overlying a podzolic soil contained in monolith lysimeters were investigated. Pairs of lysimeters each received 1500 mm yr^?1 of “rain” consisting either of distilled water or pH 3.0 sulphuric acid applied evenly over a 5-yr period. The acid-treatment resulted in a marked acidification of the litter, associated with accelerated leaching of Ca²⁺, Mg²⁺, K⁺ and Mn²⁺. Acid treatment also increased the concentration of extractable Al³⁺ in the litter. The biochemical changes observed in the litter as a consequence of acidification included decreases of 33% in ATP content and 54% in respiration rate. Significant reductions in the mineralization rates of urea, glucose and acetate, and in the activities of 4-nitrophenylphosphatase, $\text{β-N-}\text{acetyl-}\text{d}\text{-glucosaminidase}$, exo-1,4,β-d-xylosidase and peroxidase were also observed in the acid-treated litter. The acid-treated litter also contained slightly less total N, ammonium-N and total P, and slightly more residual hexose carbohydrate than the control litter. The effects observed were consistent with a decrease in microbial activity associated with litter acidification and were reflected in a small (5.5%) but significant (P < 0.05) decrease in litter decomposition. Acid treatment decreased the ATP content of the mineral soil by about 13% in the 3 cm immediately beneath the litter, but below this depth no significant difference was observed.     

Phosphorus availability and grass growth in biochar-modified acid soil: A study excluding the effects of soil pH

The low efficiency of phosphorus fertilization in weathered soils can limit plant development. The application of biochars in these areas has been seen as an important way to increase the efficiency of phosphorus fertilization and to promote better plant growth. However, biochars are alkaline materials that can increase soil pH and thus change the nutrient dynamics, which has been often ignored in studies of this nature. Here, all treatments had their pH standardized at 6.1 to eliminate the influence of pH on biochar application responses. The main goal of this study was to evaluate the real potential of coffee straw and eucalyptus bark biochars, produced under different pyrolysis temperatures, in the optimization of phosphorus fertilization and the development of Brachiaria brizantha. A greenhouse experiment was set up in a 2 × 2 × 5 factorial scheme, conducted for 120 days. The biochars, prepared from coffee straw and eucalyptus bark at 350 and 600°C, were applied at five rates in a Red-Yellow Oxisol. The application of biochars may reduce the demand for nutrients and correctives, optimize phosphorus fertilization and improve the development of Brachiaria brizantha, but this ability depends on the raw material and the pyrolysis temperature used in its production. All analysed biochars can contribute to higher tillering and dry matter production, but only coffee straw biochars and eucalyptus bark biochar produced at 350°C were efficient in the optimization of phosphorus fertilization until 120 days of cultivation of Brachiaria brizantha.     

Use of agricultural by-products to study the pH effects in an acid tea garden soil

The amelioration of an acid Alfisol from a tea garden was studied by incorporating various plant materials: canola straw, wheat straw, rice straw, corn straw, soybean straw, peanut straw, faba bean straw, Chinese milk vetch shoot and pea straw prior to incubation for a maximum of 65 days. Soil pH increased after incubation with all the incorporated materials with the legumes causing the largest increases. The final soil pH was correlated with ash alkalinity ( r ² = 0.73), base cations ( r ² = 0.74) and N content ( r ² = 0.93) of the applied materials. It was assumed that the incubation released the base cations in plant materials as they decomposed which ultimately increased the base cation saturation of the soil. Similarly, soil exchangeable Al was also decreased with the incorporation of the legume plant materials and corn straw and rice straw. Our investigation demonstrated that legumes are the preferred choice for controlling the soil acidity and also for reducing the toxicity of Al in acid soils.     

Temperature and pH effects on biodegradation of hexachlorocyclohexane isomers in water and a soil slurry

This study was conducted to monitor the biodegradation of alpha-, beta-, gamma-, and delta-hexachlorocyclohexane (HCH) isomers in liquid culture by a Pandoraea species and determine the influence of pH and temperature on the biodegradation of alpha- and gamma-HCH in liquid as well as in soil slurry cultures. The Pandoraea species degraded 79.4% delta-HCH and 34.3% gamma-HCH in liquid culture at 4 weeks of incubation. alpha- and beta-HCH exhibited almost identical rates (41.6 and 42.4%, respectively) of degradation. The highest degradation of alpha- and gamma-HCH (67.1 and 60.2%, respectively) was observed at an initial pH of 8.0 in liquid; 58.4 and 51.7% rates of degradation of alpha- and gamma-HCH, respectively, at an initial pH of 9.0 were found in soil slurry cultures. An incubation temperature of 30 degrees C was optimum for effective degradation of alpha- and gamma-HCH isomers (62.5 and 57.7%, respectively) in liquid culture, and 54.3 and 51.9% rates of degradation of alpha- and gamma-HCH isomers, respectively, were found in a soil slurry. Increasing the soil/water ratio decreased the extent of degradation of both HCH isomers. Degradation of HCH isomers occurred concomitant with bacterial growth. Byproducts of growth from Pandoraea species significantly decreased the pH of the liquid and the soil slurry during the growth on HCH isomers. The results of this study suggest that this bacterial strain may effectively be used for remediating polluted sites and water contaminated with different HCH isomers over a range of environmental conditions.     

磷酸对石灰性土壤pH及微量元素有效性的影响

通过室内培养试验 ,以硫酸为对照研究了磷酸对石灰性土壤的酸化效果及微量元素有效性的影响。培养 1周结果表明 ,随酸浓度增加 ,土壤 pH降低 ,低浓度时磷酸对石灰性土壤的酸化效果强于对照硫酸 ,高浓度时硫酸酸化效果强于磷酸 ,有效Fe、Mn的含量随着酸浓度的增加先增加后降低 ,有效Zn的含量随着酸浓度的增加而增加 ,有效Cu的含量随着磷酸浓度的增加而增加 ,但随着对照硫酸浓度的增加有效Cu含量先增加后降低     

Cultivation effects on the dynamics of a Johnson grass seed population in the soil profile

The effect of maize and wheat cultivation on a Johnson grass (Sorghum halepense (L.) Pers.) seed population, and its vertical distribution in a 20-cm soil profile was evaluated from autumn to early spring. The experiment was carried out in plots with 2 different types of seed-banks:

1. (A) with 1 generation of seeds distributed on the surface of the soil;

2. (B) with 2 generations of seeds, 1 buried and the other distributed on the surface of the soil.

The wheat system had one tilling operation in April with a mouldboard plough and rotary cultivator and another one in August, before sowing, with the rotary cultivator only. The maize system had 2 tilling-operations with a mouldboard plough and rotary cultivator; the first one in April and the second one in October, before sowing.

Treatments were a combination of cultivation systems and seed-bank types.

A significant seed loss was detected only in those plots under the maize cultivation system with 2 generations of Johnson grass seeds.

Tilling with the mouldboard plough and rotary cultivator significantly changed the vertical pattern of seed distribution. No appreciable modification was observed after cultivation with the rotary cultivator alone.

The mouldboard plough appeared to be more efficient at burying seeds (ca. 80%) than at bringing them to the surface (ca. 38%).

In the maize crop system, after sowing, there was a significantly greater number of full florets (25%) in the 0–4-cm layer, in relation to the total in the soil profile, than in the wheat crop system (7%).

Ecological implications of these cultivation methods on Johnson grass seed dynamics are discussed.     

Testing a mechanistic model. III. The effects of pH on fluoride retention by a soil

The pH of a soil was altered by incubating it with either lime or acid at 60°C for 1 day. Subsamples were then mixed with fluoride solutions in order to measure the effects of pH on fluoride retention. The results were compared with those previously obtained with phosphate on the same soil. At equal concentration of total fluorine in solution, fluoride retention was greatest at about pH 5.5 and decreased at both lower and higher pH. The decrease at low pH appeared to be caused by the formation of complexes between fluoride and aluminium in solution. As a result, only a small proportion of the total fluorine in solution was present as fluoride ions. At equal concentrations of fluoride ions, fluoride retention decreased with increasing pH. It was shown that this decrease could be explained by decreases in the electrostatic potential of the variable charge materials. The decrease in potential was steeper than that required to describe phosphate retention. This is consistent with the plane of adsorption of fluoride ions being closer to the plane of adsorption of H⁺ and OH^? ions.     

Fulvic acid studies: evidence for a polycarboxylate co-ordination mode at soil pH

The reactions of two fulvic acid samples with Cu²⁺ and Cd²⁺ have been studied by potentiometric titration (pH and ion selective electrode). The metal-uptake curves for samples initially rendered ‘metal-free’ by a precipitation-solvent extraction technique resemble those for citric and malic acids at soil pH (4–6.5). The presence of aliphatic and aromatic components was established by ¹³C nmr spectroscopy; the presence of phenolic components was inferred from pH titrations. It is shown that a polycarboxylate component (simulated by citrate) would mask reactions of phenolic components with metals in weakly acidic and neutral media. The mode of coordination between fulvic acid and metals will vary with pH and with the metal: fulvic acid ratio.     

Acid precipitation effects on soil pH and base saturation of exchange sites

The typical values and probable ranges of acid-precipitation are evaluated in terms of their theoretical effects on pH and cation exchange equilibrium of soils characteristic of the humid temperature region. The extent of probable change in soil pH and the time required to cause such a change are calculated for a range of common soils. Hydrogen ion input by acid precipitation is compared to cation inputs from nutrient cycling and other sources. For example it can be calculated that 100 yr of acid precipitation (10000 cm at pH 4.0) could be expected to shift the percentage base saturation in the top 20 cm of a typical midwestern forest soil location exchange capacity of 20 meq 100 g^?1 downward 20%, thus lowering the pH of the Al horizon by approximately 0.6 units, if there are no countering inputs of basic materials.     

Effect of different amounts of acid application in fertigation on calcareous soil pH

This study was carried out during 3 different periods and in 24 various greenhouses. Average pH values of the irrigation water (7.61, 7.55, 7.29) and average soil pH values before fertigation (7.61, 7.57, 7.55) were measured. Average fertigation pH values were measured to be 6.80, 6.61 and 6.44. Depending on fertigation pH values, average soil pH values decreased at the rate of 0.52, 0.65 and 0.60 compared to those before fertigation. Although average soil pH decreased depending on acid doses used by growers in the greenhouse, this decrease was not sufficient. In conclusion, if growers fertilize with lower fertigation pH doses, availability of plant nutrients can be increased. Additionally, this may lead to less fertilizer use by increasing availability of fertilizers used in fertigation in soils that have calcareous and high pH values. It is clear that further studies should be done with this approach.     

The effects of pH and chloride concentration on mercury sorption. II. By a soil

The pH of a soil was altered by incubation with either acid or lime, and the sorption of mercury was measured in the absence of chloride and at three chloride concentrations. In the absence of chloride there were only small effects of pH on sorption between pH 4 and 6; sorption decreased at higher pH. Addition of chloride decreased sorption at low pH but had little effect on sorption at high pH. Consequently, in the presence of chloride, sorption increased with increasing pH between pH 4 and 6 and then decreased. Many of the mercury sorption curves were sigmoid. This was explained by assuming that a small amount of complexing material was present in the solution after mixing with the soil. Calculation of the mercury species present in solution was made difficult by uncertainties about the postulated complexing material. Nevertheless, between pH 4 and pH 5.8, it was possible to explain the effects of pH and of chloride concentration on sorption as entirely due to changes in the HgOH⁺ concentration.     

不同pH条件下腐植酸对土壤中砷形态转化的影响

为了探索在不同pH条件下腐植酸对土壤中砷形态转化及生物毒性的影响,应用油菜盆栽试验,检测砷加入土壤后15 d、45 d、90d土壤中AE-As(水溶态、可交换态和碳酸盐结合态)Fe,Mn-As(铁/锰氧化物结合态),O,S-As(有机物及硫化物结合态),Res-As(残渣态)的含量及油菜生物量.结果表明,外源水溶态砷加入土壤后均迅速向相对稳定的形态转化,15 d时A3H1(pH9.5,腐殖酸用量为0g/kg)和A3H4(pH9.5,腐殖酸用量20 g/kg)处理的AE-As含量分别为13.40 mg/kg、9.23 mg/kg,转化率分别为78.7％、82.51％;在90 d时,A3H4处理的AE-As、Fe,Mn-As含量分别为6.28 mg/kg、1.23 mg/kg,仅为处理A3H1处理的53.9％和10.7％,O,S-As、Res-As含量分别为20.24 mg/kg、41.21 mg/kg,是处理A3H1的165％和127％.说明腐植酸更有利于土壤中AE-As向其他相对稳定的形态转化,主要体现在O,S-As的增加,腐植酸对碱性土壤中砷向较稳定形态转化的促进作用更加显著,而且与腐植酸的施用量呈正相关.外源砷在碱性条件下对植物的毒害更大,腐植酸用量在10 g/kg土时就可以有效降低砷的毒害.     

pH 升高对红壤硝化过程产生 N2O 的影响

对红壤添加NaOH培养获得不同pH系列的土壤.通过室内培养试验.研究了3种pH条件下土壤的N_2O排放和无机N的变化情况.结果表明:硝化活性随土壤pH升高而增强:pH升高增加了土壤N_2O的释放;纯化学过程对N_2O散发的贡献随pH的升高而降低;Nitrapyrin在pH 4.8和pH 6.0时表现山硝化抑制作用,在pH 8.5时抑制效果不明显,且提高了培养期间pH8.5土壤N_2O的释放量.     

Response of Ammophila breviligulata to acid rain and low soil pH

The effects of simulated acid rain and low soil pH on the growth of Ammophila breviligulata (Cape Strain), American beach grass, were studied in greenhouse experiments. Plants treated with acid rain were shorter, but shoot density, live shoot biomass, and rhizome biomass were not adversely affected by the acid rain treatments. Root biomass was greatest in the acid rain treatments. A manipulated soil pH of 4.0, typical of that found in field sites of dying beach grass, resulted in significantly reduced plant height, shoot density, shoot biomass, and rhizome biomass. Root biomass was greater in the low pH treatment and was six times greater than rhizome biomass in that treatment while the root to rhizome ratio was approximately 1∶1 in the control — likely a reflection of the plant's response to decreased nutrient availability in the low pH soil. Acid rain treatment of dune sand resulted in the leaching of Al, a potentially phytotoxic element.     

砂姜黑土钙质结核剖面分布特征及其对土壤持水性的影响

钙质结核是砂姜黑土重要的成土特征,直接影响土壤结构和水分运移,但目前关于钙质结核对土壤持水性作用机制的研究主要集中在实验室尺度,而且报道较少.基于此,该研究在田间尺度上研究了钙质结核剖面垂直分布特征及其对土壤持水性的影响.结果表明:钙质结核主要分布在20 cm以下的土层,其含量和粒径均随土层深度的增加呈现增大趋势,>8...     

Beryllium effects on potatoes and oats in acid soil

The most likely means of Be entry into the food chain would appear to be via root, tuber, and forage crops grown on acid soils. Potatoes (Solanum tuberosum) and oats (Avena sativa) were grown in greenhouse pots of a strongly acid soil treated with 0 to 300 ppm Be and 0 to 1000 ppm CaC0₃. Germination and yield decreased, and plant Be content increased, with increasing soil Be content. The Be content of the potato tubers appeared to be low and unaffected by the soil Be content. Liming the soil and increasing the time between Be contamination and crop planting lessened the effect of Be.     

Influence of electrolyte composition and pH on cadmium sorption by an acid sandy soil

Extraction of soil with CaCl₂, has been recommended as a measure of bioavailability of heavy metals. Interpretation of soil extraction data in terms of plant uptake potential may improve when the chemical behaviour of heavy metals in these extracts is ascertained. The effect of pH, Cd complexation by Cl, and competition between Cd and Ca on Cd sorption was studied at an ionic strength of 0.03 m . Sorption of cadmium was measured in 0.01 m CaCl₂, in 0.01 m Ca(NO₃)₂, in a mixture of 0.02 m NaCl and 0.01 m NaNO₃, and in 0.03 m NaNO₃, at different values of pH ranging from 3.8 to 4.9. Adsorption isotherms were all linear, with a negative intercept on the y-axis. This intercept indicated (linear) desorption of only part of the initial soil Cd content. About 50% of the Cd in solution was complexed in the presence of 0.02 m Cl at ionic strength of 0.03. Due to competition between Cd and Ca, sorption of Cd was reduced by 80% in the Ca-electrolytes as compared with the Na-electrolytes. Sorption was highly sensitive to pH as each 0.5 unit increase in pH resulted in twice as much sorption of Cd. An empirical factor in the sorption equation that accounts for this effect of pH showed a similar response to changes in pH as a mechanistic factor. This mechanistic factor was developed by assuming that Cd and protons sorb onto the same sites and that a two-site Langmuir sorption isotherm for protons was able to describe the titration curve of the soil. This similarity may explain the successful application of the empirical factor in this and previous studies.     

硅钙钾镁肥及引入柠檬酸对红壤和潮土pH值及养分含量的影响

通过土壤培养试验研究了硅钙钾镁肥(SCPM)及引入柠檬酸的复混肥(CA-SCPM)在酸性红壤和石灰性潮土上的养分供给和酸碱度调节能力.硅钙钾镁肥添加量设置为6 g/kg,硅钙钾镁肥与柠檬酸(CA)的比例为88％:12％.与对照处理相比,培养至150 d时,SCPM肥及CA-SCPM肥提高红壤pH值约1.16个单位,提高...