Raised Soil pH Research Articles

Calculation of spatially explicit amounts and intervals of agricultural lime applications at county-level in China

Liming is a long-established and widely used agricultural practice to ameliorate soil acidity and improve crop production. Sustainable liming strategies for regional applications require information on both lime requirements and liming intervals given land use and soil dependent acidification rates. We developed a method to optimize lime requirements and liming intervals at regional level. Lime requirements were based on soil pH buffering capacity and liming intervals were estimated by ongoing soil acidity production, derived from major cations and anions balances in cropland systems. About 66% of croplands in Qiyang required liming to raise soil pH to 6.5, with a total lime requirement of 2.4 × 105 t CaCO3, with an average rate of 2.4 t ha−1 for paddy soils and 2.6 t ha−1 for upland soils. The remaining 34% were mainly calcareous soils. Nutrient management practices and crop rotations, affecting N transformation and crop removal, were the main drivers controlling the spatial variation in total acid production in non-calcareous soils, on average contributing 73% and 25%, respectively. Under current soil acidification rates, 33% of Qiyang's croplands would need liming within 30 years after raising the soil pH to 6.5. Averaged liming interval was 20 years, and 6.8 t ha−1 would be required to maintain soil pH ranges between 5.5 and 6.5. Areas with high soil acidification risk were mostly located in the southeast of Qiyang.

Changes in Soil Phosphorus Pools and Chemical Properties under Liming in Nitisols of Farawocha, South Ethiopia

Understanding the nutrient dynamics in acid soil is fundamental to carry out proper management. The study was conducted to investigate phosphorus (P) pools and selected properties under different rates of lime for acid nitisols of Farawocha, Southern Ethiopia. Four lime rates incubated for a month in three replications were tested. The lime rates were 0 t/ha (0%), 5.25 t/ha (50%), 10.5 t/ha (100%), and 15.75 t/ha (150%). Lime requirement (LR) for 100% was calculated targeting soil pH of 6.5. Data on the P pools such as soluble P (P-sol) and bounded forms of P with iron (Fe-P), aluminum (Al-P), calcium (Ca-P), organic part (Org-P), residual P (Res-P), and total of P fractions were measured. In addition, changes in soil chemical properties such as pH, exchangeable acidity, calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), boron (B), zinc (Zn), and manganese (Mn) were analyzed. The result showed that total P was 357.5 mg/kg. Compared to nontreated soil, liming at a rate of 15.75 t/ha significantly improved P-sol (34.2%, r2 = 0.88), Ca-P (61.6%, r2 = 0.92), and Res-P (195%, r2 = 0.94); however, it reduced Fe-P (58.5%, r2 = −0.83), Al-P (71%, r2 = −0.97), and Org-P (19.1%, r2 = 0.93). Overall, the P-associated fractions in the soil, regardless of the lime rates, were in the order of Org_P > Res_P > Fe_P > Ca_P > Al_P > P-sol. Liming raised soil pH by 2.1 units (4.5 to 6.6) over nonlimed soil, whereas it reduced exchangeable acidity from 4.18 to 0.23 meq/100 g soil. Available P, Ca, Mg, S, Cu, Zn, and B contents were significantly improved with lime application. However, liming reduced Fe and Mn contents. In conclusion, these findings showed that liming facilitated the release of P from various pools, modified pH and exchangeable acidity, and resulted in beneficial changes for most of the soil chemical properties.

Sewage sludge biochars effects on corn response and nutrition and on soil properties in a 5-yr field experiment

Sewage sludge biochar (SSB) is the solid product obtained after the pyrolysis of sludge. In the last ten years, hundreds of studies have evaluated the effects of SSB as a soil amendment over a short period of time. Thus, doubts remain about the temporal behavior of SSB under field conditions. The objective of this study was to evaluate, under field conditions, the effects of SSB on the fertility indicators (pH, potential acidity, Mehlich1-P and -K, CEC and KCl-exchangeable Ca, Mg and Al) and corn yield in an Oxisol over five years. For this purpose, soils receiving biochar produced at 300 and 500°C (SSB300 and SSB500, respectively) and biochar in combination with mineral fertilization (SSB300 + NPK and SSB500 + NPK) were evaluated. Grain yield, soil pH, soil H + Al, and macronutrient contents (N, P, K, Ca, Mg and S) in soil and corn leaves were determined. Over five years, SSB increased total N and Mehlich1-P in the soil. Nevertheless, biochars were unable to raise soil pH and provide satisfactory amounts of K. The combination of SSB with mineral NPK fertilizer provided all the macronutrients required for corn and increased the leaf contents, especially for P, leading to an average 16% increase in grain yield in soils that received the treatment SSB300 + NPK. In general, pyrolysis temperature did not alter the parameters evaluated. SSB has the potential to provide nutrients to the soil, with a residual effect of at least three years, which can be enhanced by combined application with mineral NPK fertilizer.

Review on role of lime on soil acidity and soil chemical properties

One of the chemical soil degradation difficulties which affect soil production in the Ethiopian highlands is due to soil acidity. These review efforts to put together soil acidity concept, causes extent and management practices. Soil acidity is the problem of agricultural activities in Ethiopian highlands or cultivated lands and is getting an increase. To adjust acid soils and increase yields of crops of their choices farmers need simple and supportable methods, such as liming. An important role for raising soil pH and enhancing crop productivity liming has play an important role. In Ethiopia, because of soil acidity and associated toxic nutrient availability the gap between probable and actual yield is very varied .The application of mineral fertilizers without adjustments is simply wastage of resources, because acidic soils are not reactive those mineral fertilizer. Improving yield production and there by satisfying yield gains effective and efficient acid soil management practices is important .This review emphases on the role of liming on soil chemical properties and also causes and managements of soil acidity and its successive effect on soil fertility and crop yield, in addition to this Integrated acid soil management improves the permanence of yields and maximizes nutrient use efficiency

Calcite in combination with olive pulp biochar reduces Ni mobility in soil and its distribution in chili plant

The presence of Ni above the permissible limit in agriculture soils poses negative effects on soil health, crop quality, and crop productivity. Surprisingly, the usage of various organic and inorganic amendments can reduce Ni mobility in the soil and its distribution in the crops. A pot experiment was conducted to elucidate the effects of olive pulp biochar (BR), calcite (CAL), and wheat straw (WS), as sole amendments and their mixtures of 50:50 ratio, added to Ni polluted soil on Ni mobility in the soil, Ni immobilization index (Ni − IMi), soil enzymatic activities, Ni distribution in parts of chili plant, Ni translocation factor and bioaccumulation factor in fruit, plant growth parameters and oxidative stress encountered by the plants. Outcomes of this pot experiment revealed that amendments raised soil pH, improved soil enzymatic activities, values of Ni − IMi, while significantly reduced bioavailable Ni fraction in the post-harvest soil. However, the highest activities of acid phosphatase, urease, catalase, and dehydrogenase by 50, 70, 239, and 111%, respectively, improvement in Ni − IMi up to 60% while 60% reduction in the bioavailable Ni fraction was observed in BR + CAL treatment, compared to control was noted. Among all amendments, the top most reduction in Ni concentrations in shoots, roots, fruit, Translocation Factor (TF), and Bioaccumulation Factor (BAF) values of fruit by 72%, 36%, 86%, 72%, and 86%, in BR + CAL treatment, compared to control. Moreover, the plants growing on BR + CAL amended Ni contaminated soil showed the topmost improvement in plant phonological parameters while encountered the least oxidative stress. Such findings refer to the prospective usage of BR + CAL at 50:50 ratio than BR, CAL, WS alone, and BR + WS as well as WS + CAL for reducing Ni mobility in the soil, improving Ni − IMi, soil enzymatic activities, plant phonological and oxidative stress while reducing Ni distribution in plant parts. Novelty statement In this experiment, it was hypothesized that amending Ni polluted soil with olive pulp biochar (BR), CAL, and WS as alone soil amendments and their combinations at 50:50 ratios can reduce Ni bioavailability in soil, Ni distribution in chili plant and oxidative stress encountered by the plants. Moreover, these amendments may improve, soil enzymatic activities, Ni immobilization index, plant phenological traits. Therefore, it was aimed to undertake useful scientific planning and research, to restore and rehabilitate the dwellings, biological resources and to minimize the sufferings of the peoples in nutrient-poor Ni contaminated soils, by improving soil health and chili productivity.

Response of N2O emissions to biochar amendment on a tea field soil in subtropical central China: A three-year field experiment

High inputs of fertilizer nitrogen (N) in tea fields lead to declining soil pH and high emissions of N2O. Amending the soil with biochar can potentially reduce N2O emissions and alleviate soil acidification. To assess the multi-year effects of wheat straw-derived biochar on N2O emissions and tea yield in tea fields, a three-year (2014–2016) field trial following the wheat straw-derived biochar addition was conducted in a tea plantation in southern China under three treatments, namely, conventional treatment (CON, application of conventional organic-chemical fertilizer without biochar), and treatments with conventional organic-chemical fertilizer + straw-derived biochar addition at 10 t ha−1 (BC10) and 40 t ha−1 (BC40) applied once at the beginning of the experiment. Compared to BC10 treatment, the annual total N2O emissions of BC40 were increased by 32.0–46.2% in 2015 and 2016 (p ＜ 0.05) while no significant difference was found between BC10 and CON (p = 0.32–0.97), and N2O emissions of BC10 showed a declined trend during the three years. An increase in tea yield of 24.2–26.0% (p ＜ 0.05) was also observed in BC10 treatment in 2015 and 2016 relative to CON. Differences between treatments in NH4+-N were mostly significant (p ＜ 0.05) but not in NO3--N and DOC (p = 0.16–0.81). The BC40 treatment significantly raised soil pH relative to the CON (p < 0.05). Our collective data indicated that N2O fluxes were positively correlated with the abundance of nirK-denitrification gene during the tea-growing season (p ＜0.05). Long-term impact of straw-derived biochar amendment on N2O was inconsistent with previous short-term biochar studies in tea field soil. Our results indicated that wheat straw-derived biochar amendment at a low rate (BC10) into tea field soil is more feasible for reducing yield-scale N2O emissions in the studied tea field system.

Multi-year soil microbial and extracellular phosphorus enzyme response to lime and phosphate addition in temperate hardwood forests

While reported short-term microbial responses to nutrient enrichment experiments are common, we provide results from a six-year data set in response to field manipulations of soil phosphorus (P) availability. We hypothesized that long-term shifts in P economics should result in the persistent suppression of P-acquiring extracellular enzymes when compared with ambient soils, as opposed to acclimation by the microbial community. P availability was experimentally increased, either directly by addition of phosphate fertilizer or indirectly by raising soil pH with lime in relatively P rich (i.e., glaciated) and P poor (i.e., unglaciated) forest soils. Soil chemistry, phosphatase enzymes (phosphomonoesterase, PM and phosphodiesterase, PD), and microbial structure (PLFA analysis) were measured annually for six years. Since the start of the experiment, the microbial communities have become more distinct across treatments. PD enzyme activity was more responsive to the treatments than PM, especially in the glaciated elevated P treatment where ambient P availability was greatest. The treatments dramatically suppressed P-acquiring enzyme activity with no indication of acclimation. These results suggest that the initial conditions and ambient nutrient supply of an ecosystem will have a strong influence on its response sensitivity to continuous nutrient enrichment.

Review on the Work Done For the Last Decade on Acid Soil Management for Better Yields in Southwestern Ethiopia

Population is increasing exponentially over time but resources are limited. To support this population, increasing productivity of the resources is importantly inevitable. One of the resources, the base of production, is soil. Its fertility is declining due to expansion of soil acidity and its low inherent fertility status. Soil fertility management is therefore, a key for sustainable crop production for food security. Last10-15 years of research and its achievement in soil acidity management in annual crops by Jimma Agricultural research center have been reviewed. To fulfill the increasing demand for food and raw materials, soil health and fertility has remained as the major factor to increase and sustain crop yields. This calls for proper use of knowledge of soil acidity and its amelioration to maximize agricultural productivity. Farmers require simple and sustainable techniques to amend acid soils and improve yields of crops of their choices. Recommendations on reclamation of acid soils need to change with new developments, such as liming, use of acid-tolerant crop varieties and integrated soil fertility management. Liming has played an important role in raising soil pH and enhancing crop productivity. In Ethiopia, southwestern area the gap between potential and actual yield is very wide because of soil acidity and associated nutrient availability. Acidic soils are not responsive to the application of inorganic fertilizers without amendments-it is simply wastage of resources. Thus, developing effective and efficient acid soil management practices is indispensable for enhancing crop productivity and thereby sustaining yield gains. Natural Resources Management Research process, acid soil management research program of the Jimma Agricultural Research center has been conducting different research activities on soil acidity management to enhance, and sustain agricultural productivity in the country. Using amendments such as lime and organic fertilizer for acid soil management showed good result in maize and soybean productivity in acidic soils in Jimma and Illubabor. This review finding provides important information on management options to amend soil acidity and improve the entire fertility of soils, and other organic amendments that can be applied to remedy soil acidity to the desired pH level and improve soil quality. Integrated acid soil management enhances the stability of yields and maximizes nutrient use efficiency. The information contained in this finding serves the interests of policymakers, researchers, students, agronomists and users associated with acid soils management.

Effect of sugarcane bagasse ash and manure amendments on selected soil properties in Western Kenya

This research determined the effects of incorporating sugarcane bagasse ash and cattle manure on soil pH, available P, and cation exchange capacity (CEC) during a 2 seasons’ field experiment in Kakamega County of Western Kenya. The experiment used a Randomized Complete Block Design, 3 replications, and a 3 × 3 factorial arrangement of treatments. Sugarcane bagasse ash and cattle manure application showed highly significant effects on soil properties at P≤0.01. The combined application of 5 t ha-1 sugarcane bagasse ash with 5 t ha-1 cattle manure raised soil pH by 0.18, and with 10 t ha-1 manure by 0.17. These increments were higher than the positive control (2 t ha-1 lime alone), that raised soil pH by 0.03, while negative control (no amendment) decreased soil pH by 0.01 at the end of the 2nd season. Soil available P increased by 6 ppm due to 5 t ha-1 cattle manure and by 4 ppm due to 5 t ha-1 sugarcane bagasse ash. Soil CEC increased due to high application rates of cattle manure at the end of the second season. This study concluded that, the incorporation of sugarcane bagasse ash and cattle manure increased soil pH, available P and CEC. Key words: Available P, bagasse ash, cation exchange capacity (CEC), cattle manure, soil pH, Western Kenya.

Study on safe usage of agricultural land in karst and non-karst areas based on soil Cd and prediction of Cd in rice: A case study of Heng County, Guangxi

It is well-known that Cd concentration in the soil, Cd bioavailability, and Cd bioaccumulation in rice (Oryza sativa L.) grains vary greatly in different soil parent materials. Therefore, the classification of agricultural land environmental quality and agricultural land safe usage based on the Cd content in the soil has a wide deviation. By the application of systematic sampling and analysis of soil and rice samples, and in comparison with the different soil parent materials in Heng County, it was found that soil derived from carbonate rocks has higher total Cd and lower mobile Cd proportion than soil from the non-karst areas. This result indicated that soil carbonates raised soil pH and the adsorption of Fe/Mn oxide/hydroxide on Cd significantly reduced the bioavailability of Cd in karst areas. In contrast, acidic soils with relatively lower CaO, TFe2O3, Mn and total Cd contents, the grown rice plants accumulated higher Cd in their grains. Further research confirmed significant differences in Cd bioaccumulation abilities in the soil between karst and non-karst areas. On this basis, the bioaccumulation factor prediction models of Cd in rice grains were developed in karst and non-karst areas. According to the total concentration of Cd in topsoil samples obtained from the area survey and the predicted Cd content in rice grains, an agricultural land safe usage scheme was put forward. The results showed that the agricultural land classification method based on Cd concentration in the soil and rice grains was more accurate and scientific than that based on the Cd contents in the soil alone.

Dose-dependent Effect of Biochar as Soil Amendment on Reducing Copper Phytotoxicity and Mobility

Using biochar to remediate metal-contaminated agricultural soil has attracted increasing attention due to it is relatively low cost and high efficiency. In this study chemical speciation, greenhouse experiments, and column leaching study were conducted to understand the mechanisms of copper (Cu) immobilization by pine needle biochar (PNB) and sweet potato residue biochar (SPRB) to evaluate the effect of biochar amendment rate for remediation Cu contaminated soils. The results showed that both PNB and SPRB amendment effectively raised soil pH and converted Cu into more stable chemical forms. 1% (W/W) SPRB was adequate for reducing exchangeable Cu fractions from 43.3 to 9.9 mg kg−1 in the contaminated soils. 1% (W/W) SPRB and 5% (W/W) PNB treatments show the best result to promote sweet potato growth. Over liming caused by 5% (W/W) SPRB resulted in inhibition of plant growth. 5% (W/W) PNB treatment also shows the best result for reducing Cu mobility: the cumulative amount of Cu in the leachate after 9 leaching events was reduced from 7.0 to 1.0 mg kg−1. However, 5% (W/W) SPRB amendment is a little effective for reducing Cu mobility. Although the biochar amendment can provide additional sorption sites for metal pollution remediation, soil pH after an amendment is also a critical factor to estimate optimal biochar application dosage for promoting plant growth and reduce metal leachability.

Phosphorus in an arable coarse sandy soil profile after 74 years with different lime and P fertilizer applications

The distribution of fertilizer phosphorus (P) in the soil profile affects its plant availability and the risk of P loss. We examined the P distribution and sorption in soil profiles of a field experiment initiated in 1942 on coarse sandy soil with four rates of lime (0, 4, 8 or 12 t ha−1 every 5–9 years) and two rates of P (no P or 15.6 kg P ha−1 annually). In 2016, intact soil cores were retrieved to 100 cm depth and divided into five depth intervals (0–20, 20–30, 30–50, 50–70 and 70–100 cm). Soil samples were analyzed for total P, P extracted with sodium bicarbonate (Olsen P) and water (Pw), oxalate-extractable P (Pox), iron (Feox) and aluminum (Alox), pH, carbon (C), and single point sorption index (PSI). Liming raised soil pH significantly at all depths. Addition of P increased total P, Olsen P, Pw and Pox in the upper 30 cm only. In the topsoil the extractability of P in bicarbonate (Olsen P to total P ratio) and water (Pw to total P ratio) declined with liming. Below 30 cm, soil P pools were unaffected by lime and P application. PSI increased with depth until 50–70 cm and related strongly to content of Alox, but not to Feox, Olsen P, soil C and pH. We conclude that Alox plays a dominating role for retention of P in this sandy soil profile, formed by melt-water during the Weichsel glaciation period. The retention of P in soil below 30 cm depth was strong and unaffected by addition of lime.

New methods for estimating lime requirement to attain desirable pH values in Brazilian soils

In Brazil, empirical models are traditionally used to determine lime requirement (LR), but their reliability is doubtful in most cases, since they can lead to under- or overestimation of LR for different soil types. In this study, the most critical characteristics influencing LR were selected to develop reliable models for predicting LR that raise soil pH to optimum values for crop production in Brazil. Soil samples (n = 22) with varying proportions of clay (5-88 %) and organic matter [...]

Mitigation of Cd accumulation in rice with water management and calcium-magnesium phosphate fertilizer in field environment.

Pollution of Cd has seriously threatened environmental safety and human health. The field experiment was conducted to investigate the effects of calcium-magnesium phosphate fertilizer and water management on bioavailability of Cd in soils and its accumulation in rice. The results revealed that continuous flooding has enhanced soil pH from 5.10 to 5.72 and reduced soil redox potential (Eh) from 164 to - 60mV. Application of calcium-magnesium phosphate fertilizer has significantly raised soil pH from 5.10 to 6.45 (P < 0.05). The treatment of calcium-magnesium phosphate fertilizer and continuous flooding has reduced available content of Cd in soils by 28.57%. The content of Cd in brown rice was significantly diminished by 51.36% (P < 0.05). The continuous flooding has promoted formation of residual Cd in soil with application of calcium-magnesium phosphate fertilizer. The biomass and grain production of rice was not significantly decreased compared with control.

Contrasting effects of different pH‐raising materials on N2O emissions in acidic upland soils

AbstractAcidic soils, occupying ca. 40% of the world's arable soils, often need to be managed (e.g., to raise their pH and to improve crop productivity); however, the environmental impact of raising soil pH is often difficult to assess. Increasing soil pH stimulates the reduction of N2O to N2, thus lowering N2O emissions associated with denitrification, but can also increase autotrophic nitrification rates and related N2O emission. Using a 15N tracing technique, we provide process‐based insights into the effects of two acid‐neutralizing materials (quicklime [CaO] vs. pig manure) on N2O emissions in an acidified upland soil that had experienced excessive N application. Without pH adjustments we found that N2O emissions, stimulated by supply of reactive N, were related to denitrification‐ and heterotrophic nitrification‐derived N2O emissions, whereas autotrophic nitrification‐derived N2O emissions declined with decreasing soil pH. These effects were reversed by increasing soil pH via liming. However, increasing the soil pH via application of pig manure significantly increased soil N2O emissions from both nitrification and denitrification. Our study highlights that pH‐amelioration practices may enhance N2O emissions depending on the type of material applied to the soil. Therefore, both pH remediation and greenhouse gas mitigation options need to be considered together to avoid adverse environmental effects. The effect of different acid‐neutralizing materials on soil N2O emissions should be incorporated into ecosystem models to better estimate global N2O emissions when pH amelioration is practised.Highlights Enhanced N2O emission by N input was from denitrification and heterotrophic nitrification. Chemical N input and liming have reversible effects on N2O emission. Soil N2O emission was decreased by liming but increased by animal manure input. Careful consideration of pH raising substrates is needed to avoid adverse effects.

Exploring the Influence of Raising Soil pH on the Ecotoxicological Effects of Silver Nanoparticles and Micron Particles on Soil Microbial Communities

Silver contamination of soil systems has been shown to have significant negative effects on soil microbial communities and key functional processes. However, few studies to date have addressed the influence that soil physico-chemical characteristics may have on silver toxicity. In this study, the influence of soil pH soil was investigated on the toxicity of both silver nano-(NP) and micron-(MP) particles to microbial communities and community functioning in a pastureland soil. An acidic soil, pH 5.1, was harvested from an agricultural pastureland and divided into two batches, one of which was adjusted with calcium carbonate to a neutral pH of 7. The effect of 50 mg kg−1 of AgNP and AgMP amendment on the acidic soil and the neutral soil microbial communities was then examined in a microcosm-based experiment. Our results found dehydrogenase activity, which was used as a proxy measure for microbial activity, to be far more susceptible to both AgNP and AgMP contamination in the acidic soil than in the neutral soil. Additionally, both AgNPs and AgMPs significantly affected bacterial and fungal community structures in the acidic soil; however, community structures in the pH-neutral soil amended with AgNPs and AgMPs remained similar to those in the unamended control. The results from this study indicate that soil pH was an influential factor affecting AgNP toxicity in our soil system with the acidic soils far more susceptible to silver contamination than the neutral soil.

No-tillage and liming increase the root mycorrhizal colonization, plant biomass and N content of a mixed oat and vetch crop

The combination of no-tillage (NT) and liming has been proposed as feasible means to restore degraded acid soils. However, the synergistic effect of both practices on nutrient acquisition by crops has not been addressed. Similarly, the simultaneous impact on arbuscular mycorrhizal fungi (AMF) is under-investigated despite its essential role in plant growth and nutrient uptake, especially under stress conditions. We evaluated the plant growth, nutrient acquisition and mycorrhizal root colonization at three stages during a growing season along with soil properties of a rainfed oat (Avena sativa L.) and vetch (Vicia sativa L.) mixture under Mediterranean condition. The experiment was located in south-west Spain where tillage type (no tillage: NT and traditional tillage: TT) and lime application were evaluated in a full factorial design. Liming raised soil pH, increased soil calcium and magnesium availability and stimulated the microbial activity while NT enhanced soil carbon content. Both practices improved oat biomass production (40 times at biomass harvest) and root colonization of both crops (80 % and 60 % higher respect to TT without liming in oat and vetch, respectively). Liming enhanced vetch biomass production (20 times at harvest) and foliar N content, while NT increased foliar N content of oat. Plant phosphorous (P) contents were unaffected by the treatments. The high N:P of both crops indicates P limitation despite of the high soil P content. The P limitation together with the increased N supply could lead to strengthening of mutualism between plants and AMF, where P acquisition through AMF is stimulated in order to take advantage of the “luxury” N supply provided by NT and liming. Thus, both practices together increase nutrient use efficiency by stimulating crop-microbe interactions.

Soil nitrification increases with elevated phosphorus or soil pH in an acidic mixed mesophytic deciduous forest

The role of phosphorus (P) mediating nitrogen (N) transformation processes is poorly understood which raises an important question: Does P, like soil pH, have a strong control in altering the cycling of soil N? From 2010 to 2018, pH and/or P availability was elevated with lime and P fertilizer in three mixed mesophytic deciduous forests on the unglaciated portion of the Allegheny Plateau, southeast Ohio, USA. We hypothesized that in addition to soil pH, P addition can influence the cycling of soil N because both can change N dynamics, which can alter nitrification rates. Increasing soil pH increased nitrification and nitrate pools by 30 and 4 times, respectively during the growing season. Furthermore, elevating P also stimulated nitrification and increased soil nitrate pools by 10 and 2 times, respectively. However, the influence of raising soil pH on nitrification was diminished when combined with P addition. Results suggest that N biogeochemical processes are sensitive to P availability, but the mechanistic nature of this relationship appears complex with unclear feedback systems regulating nitrification rates from these deciduous forests.

Fly-ash from a pulp and paper mill: A potential liming material for agricultural soils in Western Newfoundland.

Most agricultural soils in Western Newfoundland are acidic and need lime to raise soil pH to be productive. Corner Brook Pulp and Paper Ltd produces a substantial amount of fly-ash, disposed of at a local landfill. This study was conducted to assess the potential for using fly-ash as a liming material for agricultural soil (pH 5.5) in Western Newfoundland. Heavy metal concentration in the soil and fly-ash were analysed and compared with soil and compost guidelines. As per quality guidelines, only part of the lime requirement can be substituted by fly-ash. The percentage may vary depending on initial soil pH and the desired pH for the crop to be grown. The total lime requirement can be met when fly-ash is applied combined with other soil amendments low in trace element concentration.

Performances and mechanisms of sludge dewatering by a biopolymer from piggery wastewater and application of the dewatered sludge in remediation of Cr(VI)-contaminated soil

In this study, a biopolymer was harvested from piggery wastewater to treat biological sludge. Effectiveness of the combination of polyaluminum chloride (PAC) and this biopolymer in sludge dewatering was investigated and the dewatering mechanism was discussed. Results showed that as high as 3.11 g of biopolymer can be harvested from 1 L of piggery wastewater by cultivating Bacillus megaterium. After treated by PAC with a dosage of 1.5 g/L at pH point of 7.5, specific resistance to filtration (SRF), moisture content (MC), settled volume after 30 min (SV30) and capillary suction time (CST) of the sludge were decreased to 3.4 × 1012 m/kg, 84.5%, 79.8% and 65 s, respectively, and dry solid (DS) was increased to 21.4%, indicated that sludge dewatering was obviously enhanced by PAC. After further treated by 2 g/L of the biopolymer, SRF, MC, SV30 and CST were further decreased to 2.1 × 1012 m/kg, 59.8%, 55.6% and 39 s, respectively, and DS was increased to 28.6%, indicated that sludge dewatering was further enhanced by the biopolymer. For the enhancing mechanism, on the one hand, the extracellular polymeric substances (EPS) was significantly disintegrated to release binding bound water, which was facilitating sludge dewatering; on the other hand, the synergistic effect of PAC coagulation and biopolymer flocculation, including charge neutralization and bridge-aggregation, were favorable to sludge dewatering. Additionally, we found that the dewatered sludge was helpful for remediation of chromium (Cr)(VI)-contaminated soil by raising soil pH and decreasing bioavailability of Cr(VI) in the soil, after remediated by 75 g/kg of the dewatered sludge for 60 days, the soil pH was increased from its initial value of 4.32–8.52, and the residue Cr(VI) in the soil extract was appeared as 2.2 mg/L.