Reduced Soil pH Research Articles

Effect of different amendments on rice (Oryza sativa L.) growth, yield, nutrient uptake and grain quality in Ni-contaminated soil.

Rice ( Oryza sativa L.) is one of the main staple food crops which is inherently low in micronutrients, especially iron (Fe), and can lead to severe Fe deficiency in populations having higher consumption of rice. Soils polluted with nickel (Ni) can cause toxicity to rice and decreased Fe uptake by rice plants. We investigated the potential role of biochar (BC) and gravel sludge (GS), alone and in combination, forin situ immobilization of Ni in an industrially Ni-contaminated soil at original and sulfur-amended altered soil pH. Our further aim was to increase Fe bioavailability to rice plants by the exogenous application of ferrous sulfate to the Ni-immobilized soil. Application of the mixture of both amendments reduced grain Ni concentration, phytate, Phytate/Fe, Phyt/Zn molar ratios, and soil DTPA-extractable Ni. In addition,the amendment mixture increased 70% Fe and 229% ferritin concentrations in rice grains grown in the soil at original pH. The Fe and ferritin concentrations in S-treated soil was increased up to 113 and 383% relative to controlrespectively. This enhanced Fe concentration and corresponding ferritin in rice grains can be attributed to Ni/Fe antagonism where Ni has been immobilized by GS and BC mixture. This proposed technique can be used to enhancegrowth, yield, and Fe biofortification in rice by reducing soil pH while in parallel in situ immobilizing Ni in polluted soil.

Effects of magnetized water application on soil and maize growth indices under different amounts of salt in the water

Application of low quality water for irrigation is compulsive in facing water scarcity. Use of a magnetic field is an approach to overcome this challenge. This study examined the impact of magnetic field technology on improving germination under water of different salinity levels. An experiment was conducted to determine the effects of saline water levels, i.e. (S1):0.5, (S2):2, (S3):4 and (S4):6 dS/m combined with magnetized technology (with or without) on maize growth. Thus, magnetic treatment was applied by passing the irrigation water through a 1,500 mT magnetic field at 3 litres per minute (lpm) flow rate. Some emergence indices, such as emergence index, emergence rate index (ERI) and mean emergence time, were used to evaluate the germination of maize seed. As for soil properties after plant harvest, the use of magnetically treated irrigation water reduced soil pH but increased soil electrical conductivity and available N and P. ERI increased from 7.6 to 10.2, 9.1 to 11.1, 10.3 to 13.3, and 11.8 to 13.3 when applying the magnetized field for S1, S2, S3 and S4, respectively. Overall, the growth parameters of maize were improved by using magnetic technology with saline water, while the opposite trend was shown for increasing salinity without magnetic treatment.

Fast-growing Acer rubrum differs from slow-growing Quercus alba in leaf, xylem and hydraulic trait coordination responses to simulated acid rain.

We investigated the effects of historic soil chemistry changes associated with acid rain, i.e., reduced soil pH and a shift from nitrogen (N)- to phosphorus (P)-limitation, on the coordination of leaf water demand and xylem hydraulic supply traits in two co-occurring temperate tree species differing in growth rate. Using a full-factorial design (N × P × pH), we measured leaf nutrient content, water relations, leaf-level and canopy-level gas exchange, total biomass and allocation, as well as stem xylem anatomy and hydraulic function for greenhouse-grown saplings of fast-growing Acer rubrum (L.) and slow-growing Quercus alba (L.). We used principle component analysis to characterize trait coordination. We found that N-limitation, but not P-limitation, had a significant impact on plant water relations and hydraulic coordination of both species. Fast-growing A. rubrum made hydraulic adjustments in response to N-limitation, but trait coordination was variable within treatments and did not fully compensate for changing allocation across N-availability. For slow-growing Q. alba, N-limitation engendered more strict coordination of leaf and xylem traits, resulting in similar leaf water content and hydraulic function across all treatments. Finally, low pH reduced the propensity of both species to adjust leaf water relations and xylem anatomical traits in response to nutrient manipulations. Our data suggest that a shift from N- to P-limitation has had a negative impact on the water relations and hydraulic function of A. rubrum to a greater extent than for Q. alba We suggest that current expansion of A. rubrum populations could be tempered by acidic N-deposition, which may restrict it to more mesic microsites. The disruption of hydraulic acclimation and coordination at low pH is emphasized as an interesting area of future study.

Lowering Soil pH to Optimize Nutrient Management and Crop Production

Because temperatures are relatively high and it rains a lot in the region, mineral soils in the southeastern United States tend to be naturally acidic. Managing soils for both pH and nutrients helps maintain soil fertility levels and ensure economic agricultural production. If they are not maintained in the 6.0 to 6.5 pH range, which is best for most crops, most mineral soils in the Southeast will gradually return to their natural acidic state and their fertility levels will drop. In order to keep the soil in the right range, farmers have been encouraged to make routine applications of lime. Calibrated lime requirement tests are part of standard soil tests in this region, but getting the balance right can be tricky. This 4-page fact sheet explains the factors that contribute to increased soil pH and describes methods for reducing soil pH that will reduce the chances of either under- or over-liming the soil. Written by Rao Mylavarapu, George Hochmuth, Cheryl Mackowiak, Alan Wright, and Maria Silevira and published by the Soil and Water Science Department, January 2016. SL437/SS651: Lowering Soil pH to Optimize Nutrient Management and Crop Production (ufl.edu)

Optimizing Gypsum Levels for Amelioration of Sodic Soils to Enhance Grain Yield and Quality of Rice (Oryza sativaL.)

Field experiment was conducted on a fine loamy, mixed, hyperthermic, highly sodic soil having pH (10.5), electrical conductivity (EC) (2.42 dS m−1), exchangeable sodium percentage (ESP) (89.0), organic carbon (OC) (0.80 g kg−1) and available nitrogen (94 kg ha−1) to determine the response of two rice (Oryza sativa L.) varieties (CSR 13 and Pant 4) to gypsum levels [(control, 15, 25 and 50% gypsum requirement (GR)]. The study revealed that all the growth parameters (plant height, number of tillers, dry matter accumulation, number of leaves/hill, leaf weight/hill and leaf area index), yield attributes (length of panicle, number of grains/panicle, test weight) and yields (biological yield, straw yield and grain yield) significantly increased with increasing doses of gypsum. Application of gypsum at 50% GR (15.4 t ha−1) was significantly superior over the control and 15% GR doses but at par with that of 25% GR. Significant reduction in soil pH (10.50 to 8.91), EC (1.43 to 0.48 dS m−1) and ESP (89 to 28.5) and increment in OC (0.8 to 1.2 g kg−1) and available N (94 to 190 kg ha−1) were recorded after three years of study with 50% GR level. Grain quality of rice in terms of N content in grain, grain length, length: breadth ratio, brown rice recovery, milled rice recovery, head rice recovery and gel consistency were higher with 50% GR as compared to control but statistically at par with that of 25% GR. There were significant varieties × gypsum interactions on number of effective tillers, dry matter accumulation, number of leaves/hill, leaf weight, number of panicles m−2, length of panicle, number of grains/panicle, test weight and grain yield indicating that the varieties responded to gypsum differently. Variety ‘CSR 13’ showed significant increase over ‘Pant 4’ in all the growth parameters and yield attributes except length of panicle.

Assessment of Nitrogen Source, Sulfur, and Fall Fungicide Applications on the Management of Spring Dead Spot of Bermudagrass.

Spring dead spot, caused by species of Ophiosphaerella, is the most serious disease of bermudagrass (Cynodon spp.) in regions where cold temperatures induce winter dormancy. Previous research indicates that soil pH reduction may reduce spring dead spot severity. Of the 165 isolates collected from 16 sites in Missouri and surrounding regions, Ophiosphaerella herpotricha was the most prominent spring dead spot pathogen found, with 154 confirmed isolates. Ten isolates were identified as O. korrae, being detected at a low incidence at 6 of 16 sites. In in vitro assays, most mycelial growth of both species occurred from pH 5 to 6, with more growth on calcium-nitrate-amended media than ammonium sulfate. In a naturally infested field study, nitrogen source alone did not affect spring dead spot severity. Less spring dead spot severity (P < 0.05) was observed in plots receiving tebuconazole but no treatment provided more than 38% control after 1 year. Three sulfur applications (each at 98 kg ha-1) provided as much control as a single fall tebuconazole application (0.28 kg a.i. ha-1) in the second year; however, significant phytotoxicity was observed in sulfur-treated plots thereafter. The suppression obtained from one fall tebuconazole treatment was as effective as two.

Assessment of tomato and wine processing solid wastes as soil amendments for biosolarization

Pomaces from tomato paste and wine production are the most abundant fruit processing residues in California. These residues were examined as soil amendments for solarization to promote conditions conducive to soil disinfestation (biosolarization). Simulated biosolarization studies were performed in both aerobic and anaerobic soil environments and soil temperature elevation, pH, and evolution of CO2, H2 and CH4 gases were measured as metrics of soil microbial activity. Tomato pomace amendment induced conditions associated with soil pest inactivation, including elevation of soil temperature by up to 2°C for a duration of 4days under aerobic conditions and a reduction of soil pH from 6.5 to 4.68 under anaerobic conditions. White wine grape pomace amendment showed similar trends but to a lesser extent. Red wine grape pomace was generally less suitable for biosolarization due to significantly lower soil temperature elevations, reduced acidification relative to the other pomaces and induction of methanogenesis in the soil.

Response of soil microorganisms after converting a saline desert to arable land in central Asia

Uncultivated saline lands are reserve resources for arable land without environmental degradation. A field experiment was conducted in a continuously cultivated farm station in Xinjiang province, northwest China, including a saline-desert land. The objective was to investigate the effects of different cotton cultivation periods from 1 to 16 years on soil chemical and soil biological properties. Cultivation led to a decrease in soil electrical conductivity and reduced soil pH from 8.9 in uncultivated land to 7.9. Soil organic C showed a small and variable increase after cultivation. After year 1 of cultivation, the contents of muramic acid, galactosamine and glucosamine were all roughly 30% lower, similarly to those of PLFA in comparison with the uncultivated soil. Further cultivation led to a continuous non-linear 40% increase until year 16 in comparison with the uncultivated soil, which mainly occurred within five years of cultivation. The ratio of fungal C to bacterial C, based on fungal glucosamine and bacterial muramic acid, varied around 0.7 in the uncultivated soil and around 1.4 from the second year on after cultivation. Microbial biomass C showed a 100% increase to contents around 300μgg−1 soil from year 4 to 16 in comparison with the initial values. The microbial biomass C to SOC ratio ranged from 2 to 6% without clear cultivation effects. The ergosterol to microbial biomass C ratio increased from values around 0.04% during the first 3 years to values around 0.2% from year 4 on. Also, the Gram-negative to Gram-positive bacterial PLFA ratio increased with increasing cultivation time, whereas the microbial biomass C to total PLFA ratio varied in a relatively small range around 8.9μgnmol−1.

Comparative Studies on the Use of Binary and Ternary Combinations of Various Acidifying Agents for the Reduction of Soil pH

ABSTRACTThe present study deals with the effects of addition of sulfur along with other acidifying agents for their ability to lower and maintain the pH in a given range for a longer period of time. The chemicals were subjected to batch test individually and in combinations. Treatments were applied to three soils of different textures: sandy clay loam, clay loam, and silt loam. A 1:1 soil/water paste along with the added amendment was maintained at room temperature for 2 months. Most of the chemical treatments lowered the pH significantly. Combinations containing S/Al2(SO4)3/H2SO4, S/Al2(SO4)3/H2O2, and S/H2O2/H2SO4 were found to be very effective in lowering the pH. The soil pH remained acidic for 2 months, indicating the suitability of chemically amended soil for the plantations requiring acidic soil pH.

Influence of phosphorus and soil amendments on black seed (Nigella sativa L.) oil yield and nutrient uptake

In order to investigate the effects of sulfur (S) oxidation and vermicompost (V) application on black seed (Nigella sativa L.) oil yield and its nitrogen and phosphorus uptake, a two-year field experiment was conducted at Faculty of Agriculture, Ferdowsi University of Mashhad, Iran in a calcareous soil during 2013 and 2014. A randomized complete block design arranged in factorial with four replications was used to analyze 12 treatments. The calcareous soil amendments (control, V+Thiobacillus thiooxidans (T), S+T and V+S+T) and three levels of P (0, 30 and 60kgha−1) were considered as the first and the second experimental factors, respectively. All calcareous soil amendments (V+T, S+T and V+S+T) caused a significant reduction in soil pH, and a significant increase in electrical conductivity (EC). In addition, calcareous soil amendments showed a considerable effect on soil available P content. The highest grain, oil and essential oil yields were obtained from V+S+T treatment. The soil amendments significantly increased N and P concentration in plants and improved P harvest index. Although a positive correlation was observed between P and N concentration, there was a negative correlation between grain yield and P use efficiency. It seems that any approach that would allocate more P to seeds, during seed development on the mother plants, would increase final yield in black seed.

English

The experiment was conducted in a protected cultivation in the Marechal C&acirc;ndido Rondon, PR, Brazil. The experimental design was constituted of randomized blocks with six piggery wastewater doses (0, 25, 50, 100, 200 and 400 m&sup3; ha-1) in four repetitions. The variables evaluated were: number of tillers, plant height, dry matter, leaf area, leaf number, potassium content, phosphorus content and crude protein in the culture, leachate and soil analysis. The number of tillers increased linearly with the addition of SRW doses. At the beginning of the development of millet culture, swine raising wastewater (SRW) application causes a decrease in plant height; however, over the course of time, this management increases those values. There was an increase in the number of leaves at the beginning, and leaf area at the end of the development of millet crop. The SRW doses applied did not cause increase in phosphorus and potassium contents in plants, raising only the crude protein. The dry mass is highly influenced by the increase in SRW doses, with their highest levels in a dose of 319.75 m&sup3; ha-1. The SRW doses cause reduction in soil pH and its constituents are not leached. &nbsp; Key words: Fertilization, swine dejects, nutrient leaching.

Effects of applying hyperaccumulator straw in soil on growth and cadmium accumulation of Galinsoga parviflora

The effects of application of the straw of cadmium accumulating species (Youngia erythrocarpa (cadmium hyperaccumulator), Bidens pilosa (cadmium hyperaccumulator), Solanum photeinocarpum (potential cadmium hyperaccumulator), and Siegesbeckia orientalis (cadmium accumulator)) in cadmium contaminated soil on the growth and cadmium accumulation of Galinsoga parviflora were studied. The root biomass, stem biomass, shoot biomass, total biomass, and the antioxidant enzyme activity of G. parviflora were increased by application of the straw of Y. erythrocarpa. The straw of Y. erythrocarpa, S. orientalis, and B. pilosa reduced soil pH, increased the soil exchangeable Cd concentration, and increased the Cd contents in stems, leaves, and shoots of G. parviflora compared with the control. The straw of Y. erythrocarpa and B. pilosa increased the Cd extraction amount in stems, leaves, shoots and the whole plant of G. parviflora compared with the control, with the effect of Y. erythrocarpa higher than that of B. pilosa. Therefore, the straw of Y. erythrocarpa and B. pilosa improved the Cd extraction ability of G. parviflora from cadmium‐contaminated soil, and the straw of Y. erythrocarpa demonstrated to be the best material. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 618–623, 2016

The Use of Soil Parameters in Predicting Weed Infestation in Maize (&lt;i&gt;Zea mays&lt;/i&gt; L.)

A field work was carried out to investigate the extent to which selected soil chemical properties can influence weed species distribution. There were sixteen treatments of two factors (Fertilizer type and weeding regimes) laid out in RCBD. The treatments included four fertilizer types; no fertilizer (F1), inorganic fertilizer – NPK 15:15:15 applied at 100 kg NPK/ha (F2), organic fertilizer – phosphocompost applied at 2.5 t/ha and organomineral – 50% NPK 15:15:15 plus 50% phosphocompost. Four weeding regimes: weedy treatment (W1), weeding once (W2), weeding twice (W3) and weed free (W4). Weed free and weed once significantly improved maize growth and yield parameter under inorganic and organomineral fertilizer types. Increasing soil pH, organic carbon and available phosphorus significantly reduced total weed biomass with plot that received no fertilizer been responsible for highest weed population. In organic fertilizer treatment significantly reduced soil pH from the initial 6.5 to 6.0 though, it combination with weed once or weed twice gave highest grain yield. Better nutrition (in terms of improved soil nutrient especially macro nutrient and organic carbon) when combined with weeding once can ascertain proper weed management and sustainable maize production.

Dryland soil chemical properties and crop yields affected by long-term tillage and cropping sequence.

Information on the effect of long-term management on soil nutrients and chemical properties is scanty. We examined the 30-year effect of tillage frequency and cropping sequence combination on dryland soil Olsen-P, K, Ca, Mg, Na, SO4–S, and Zn concentrations, pH, electrical conductivity (EC), and cation exchange capacity (CEC) at the 0–120 cm depth and annualized crop yield in the northern Great Plains, USA. Treatments were no-till continuous spring wheat (Triticum aestivum L.) (NTCW), spring till continuous spring wheat (STCW), fall and spring till continuous spring wheat (FSTCW), fall and spring till spring wheat–barley (Hordeum vulgare L., 1984–1999) followed by spring wheat–pea (Pisum sativum L., 2000–2013) (FSTW-B/P), and spring till spring wheat-fallow (STW-F, traditional system). At 0–7.5 cm, P, K, Zn, Na, and CEC were 23–60% were greater, but pH, buffer pH, and Ca were 6–31% lower in NTCW, STCW, and FSTW–B/P than STW-F. At 7.5–15 cm, K was 23–52% greater, but pH, buffer pH, and Mg were 3–21% lower in NTCW, STCW, FSTCW, FSTW–B/P than STW-F. At 60–120 cm, soil chemical properties varied with treatments. Annualized crop yield was 23–30% lower in STW-F than the other treatments. Continuous N fertilization probably reduced soil pH, Ca, and Mg, but greater crop residue returned to the soil increased P, K, Na, Zn, and CEC in NTCW and STCW compared to STW-F. Reduced tillage with continuous cropping may be adopted for maintaining long-term soil fertility and crop yields compared with the traditional system.

The Use of Soil Parameters in Predicting Weed Infestation in Maize (&lt;i&gt;Zea mays&lt;/i&gt; L.)

A field work was carried out to investigate the extent to which selected soil chemical properties can influence weed species distribution. There were sixteen treatments of two factors (Fertilizer type and weeding regimes) laid out in RCBD. The treatments included four fertilizer types; no fertilizer (F1), inorganic fertilizer – NPK 15:15:15 applied at 100 kg NPK/ha (F2), organic fertilizer – phosphocompost applied at 2.5 t/ha and organomineral – 50% NPK 15:15:15 plus 50% phosphocompost. Four weeding regimes: weedy treatment (W1), weeding once (W2), weeding twice (W3) and weed free (W4). Weed free and weed once significantly improved maize growth and yield parameter under inorganic and organomineral fertilizer types. Increasing soil pH, organic carbon and available phosphorus significantly reduced total weed biomass with plot that received no fertilizer been responsible for highest weed population. In organic fertilizer treatment significantly reduced soil pH from the initial 6.5 to 6.0 though, it combination with weed once or weed twice gave highest grain yield. Better nutrition (in terms of improved soil nutrient especially macro nutrient and organic carbon) when combined with weeding once can ascertain proper weed management and sustainable maize production.

Effect of gypsum and sulfur with Acidithiobacillus on soil salinity alleviation and on cowpea biomass and nutrient status as affected by PK rock biofertilizer

The reclamation of saline soils requires the application of amendments such as gypsum and organic matter. The effects of gypsum and sulfur inoculated with Acidithiobacillus applied individually for the alleviation of saline soils is recognized, but the effects of mixed proportions of these products, especially on plant parameters, have not been studied. The aim of this study was to evaluate the effects of gypsum (G) and sulfur inoculated with Acidithiobacillus (S*) at various rates and mixing proportions, S*:G, on the alleviation of soil salinity. A control treatment that did not receive amendment was included, but the seeds did not germinate in this treatment. The effect of PK rock biofertilizer in interaction with the amendment treatments was also observed in cowpeas. The seeds were inoculated with effective Bradyrhizobium strains. At 45 days of growth, the cowpea shoot dry weight (DW) and the nutrient uptake in the shoots (total N, Na, P and K) were determined in the plants, and the soil was analyzed for pH, exchangeable Na, and available P and K. The results indicate that sulfur inoculated with Acidithiobacillus reduced soil pH, especially when applied without gypsum. The biofertilizer effectively increased the shoot biomass and nutrient uptake and increased the available P and K in the amended soil, and the best results were observed when the biofertilizer was used in interaction with S* and G in a mixing proportion equivalent to 50:50. In saline soil with high pH, PK rock biofertilizer seems to be an important factor for improving soil quality and may be an alternative to P and K fertilization.

English

An experiment was conducted on an alkaline clay loam soil of Golagamdi, India during 2005-2006 to study the effect of Farm Yard Manure and pressmud on fertility status of alkali soil under maize-wheat cropping sequence. The treatment consist of three levels of organic manure M0- no manure; M1- FYM at the rate of 10 tha-1; M2- Pressmud at the rate of 5 tha-1 and six fertilizer levels; F0- no fertilizer; F1- 75% of recommended N and P; F2-100% of recommended N and P; F3- 75% of recommended N and P+S+Zn+Fe; F4-100% of recommended N and P+S+Zn+Fe; F5- 100% of recommended N and P+foliar spray of 1% multi-micronutrient. The direct effect of FYM (M1) and pressmud (M2) reduced pH of soil. The maximum pH (8.26) was recorded from control after the harvest of wheat and the lowest (8.17) from F5. The highest EC (0.38 dS m-1) was recorded from F5 followed by F4 (0.37 dS m-1) and the lowest from control (0.27 dS m-1). The pressmud was more effective in reducing soil pH and increasing the EC than by FYM. The application of FYM (M1) and pressmud (M2) increased the available N, P, S, Fe, Zn, Cu and Mn in soil. The available N, S, Fe and Zn content under pressmud application was more than the FYM. However, the residual effect of FYM (M1) maintained higher available P (71.49 kg ha-1), K, Zn than PM (M2). Residual effect of the pressmud (M2) showed maximum available S (27.99 mg kg-1) as compared to FYM (M1) (15.86 mg kg-1). M2F3 and M2F4 treatment combinations performed better than other combinations regarding the S and Zn content of soil. The direct effect of pressmud was higher in case of Fe content than FYM. The residual effect of both FYM (1.02 mg kg-1) and pressmud (1.01 mg kg-1) significantly increased DTPA extractable Mn content in soil over control (3.27 mg kg-1) after wheat harvest. Direct effect of FYM on maize was found slightly depressed DTPA extractable Cu contents as compared to pressmud. However, the Cu content was increased again after the harvest of wheat. &nbsp; Key words: Farm yard manure (FYM), pressmud, residual effect, electrical conductivity (EC), maize-wheat cropping.

Disruption of metal ion homeostasis in soils is associated with nitrogen deposition-induced species loss in an Inner Mongolia steppe

Abstract. Enhanced deposition of atmospheric nitrogen (N) resulting from anthropogenic activities has negative impacts on plant diversity in ecosystems. Several mechanisms have been proposed to explain the species loss. Ion toxicity due to N deposition-induced soil acidification has been suggested to be responsible for species loss in acidic grasslands, while few studies have evaluated the role of soil-mediated homeostasis of ions in species loss under elevated N deposition in grasslands with neutral or alkaline soils. To determine whether soil-mediated processes are involved in changes in biodiversity induced by N deposition, the effects of 9-year N addition on soil properties, aboveground biomass (AGB) and species richness were investigated in an Inner Mongolia steppe. Low to moderate N addition rate (2, 4, 8 g N m−2 yr−1) significantly enhanced AGB of graminoids, while high N addition rate (≥ 16 g N m−2 yr−1) reduced AGB of forbs, leading to an overall increase in AGB of the community under low to moderate N addition rates. Forb richness was significantly reduced by N addition at rates greater than 8 g N m−2 yr−1, while no effect of N addition on graminoid richness was observed, resulting in decline in total species richness. N addition reduced soil pH, depleted base cations (Ca2+, Mg2+ and K+) and mobilized Mn2+, Fe3+, Cu2+ and Al3+ ions in soils. Soil inorganic-N concentration was negatively correlated with forb richness and biomass, explaining 23.59% variation of forb biomass. The concentrations of base cations (Ca2+ and Mg2+) and metal ions (Mn2+, Cu2+ and, Fe3+) showed positively and negatively linear correlation with forb richness, respectively. Changes in the metal ion concentrations accounted for 42.77% variation of forb richness, while reduction of base cations was not associated with the reduction in forb richness. These results reveal that patterns of plant biodiversity in the temperate steppe of Inner Mongolia are primarily driven by increases in metal ion availability, particularly enhanced release of soil Mn2+.

Ecological impacts of long-term application of biosolids to a radiata pine plantation

Assessment of the ecological impact of applying biosolids is important for determining both the risks and benefits. This study investigated the impact on soil physical, chemical and biological properties, tree nutrition and growth of long-term biosolids applications to a radiata pine (Pinus radiata D. Don) plantation growing on a Sandy Raw Soil in New Zealand. Biosolids were applied to the trial site every 3years from tree age 6 to 19years at three application rates: 0 (Control), 300 (Standard) and 600 (High) kg nitrogen (N) ha−1, equivalent to 0, 3 and 6Mg ha−1 of dry biosolids, respectively. Tree nutrition status and growth have been monitored annually. Soil samples were collected 13years after the first biosolids application to assess the soil properties and functioning. Both the Standard and High biosolids treatments significantly increased soil (0–50cm depth) total carbon (C), N, and phosphorus (P), Olsen P and cation exchange capacity (CEC), reduced soil pH, but had no significant effects on soil (0–20cm depth) physical properties including bulk density, total porosity and unsaturated hydraulic conductivity. The High biosolids treatment also increased concentrations of soil total cadmium (Cd), chromium (Cr), copper (Cu) and lead (Pb) at 25–50cm depth, but these concentrations were still considered very low for a soil. Ecotoxicological assessment showed no significant adverse effects of biosolids application on either the reproduction of springtails (Folsomia candida) or substrate utilisation ability of the soil microbial community, indicating no negative ecological impact of bisolids-derived heavy metals or triclosan. This study demonstrated that repeated application of biosolids to a plantation forest on a poor sandy soil could significantly improve soil fertility, tree nutrition and pine productivity. However, the long-term fate of biosolids-derived N, P and litter-retained heavy metals needs to be further monitored in the receiving environment.

Leaching of copper and nickel in soil-water systems contaminated by bauxite residue (red mud) from Ajka, Hungary: the importance of soil organic matter.

Red mud is a highly alkaline (pH >12) waste product from bauxite ore processing. The red mud spill at Ajka, Hungary, in 2010 released 1 million m3 of caustic red mud into the surrounding area with devastating results. Aerobic and anaerobic batch experiments and solid phase extraction techniques were used to assess the impact of red mud addition on the mobility of Cu and Ni in soils from near the Ajka spill site. Red mud addition increases aqueous dissolved organic carbon (DOC) concentrations due to soil alkalisation, and this led to increased mobility of Cu and Ni complexed to organic matter. With Ajka soils, more Cu was mobilised by contact with red mud than Ni, despite a higher overall Ni concentration in the solid phase. This is most probably because Cu has a higher affinity to form complexes with organic matter than Ni. In aerobic experiments, contact with the atmosphere reduced soil pH via carbonation reactions, and this reduced organic matter dissolution and thereby lowered Cu/Ni mobility. These data show that the mixing of red mud into organic rich soils is an area of concern, as there is a potential to mobilise Cu and Ni as organically bound complexes, via soil alkalisation. This could be especially problematic in locations where anaerobic conditions can prevail, such as wetland areas contaminated by the spill.Electronic supplementary materialThe online version of this article (doi:10.1007/s11356-015-4282-4) contains supplementary material, which is available to authorized users.