Higher Soil pH Values Research Articles

Diversity of soil mites (Acari: Mesostigmata) in streamside mountain forests

AbstractHabitat loss and fragmentation are among the most influential factors responsible for recent biodiversity decline. The key to understanding the changes in ecosystem functioning is the analysis of the relationship between species diversity and environmental gradients such as those found near streamside forests. We used soil mites (Mesostigmata) as model species as they are predators in soil ecosystems, they occur in high relative abundance, their communities are species‐rich and are robust toward sampling and extraction methods. The main goals of this study were to (1) check how the plant community and associated environmental variables (light conditions, litter accumulation, and soil acidity) along mountain streams affect soil Mesostigmata abundance and diversity, and (2) to analyze the distance from mountain streams to which the ecosystem functions (Mesostigmata diversity) are affected, based on a distance gradient. We systematically established 31 study plots (500 m2) every 200 m along the watercourses, representing three habitat types along the stand composition gradient (ash‐sycamore [Fraxinus excelsior–Acer pseudoplatanus], European beech [Fagus sylvatica], and Norway spruce [Picea abies] forests) for measurements of soil litter thickness, soil acidity, and light conditions. We extracted soil Mesostigmata mites from samples in Tullgren funnels and identified them to the species level. We found that Mesostigmata abundance in forests decreased in the following order: Norway spruce forest > European beech forest > ash‐sycamore forest. Additionally, changes in Shannon diversity were associated with light conditions. In conclusion, streamside mountain forests maintained abundant, diverse and species‐rich Mesostigmata communities, which were associated with a plant community‐light condition gradient. Additionally, more abundant mite communities occurred in forests with higher soil pH values, and under higher light conditions.

Effects of Soil pH on the Growth and Cadmium Accumulation in Polygonum hydropiper (L.) in Low and Moderately Cadmium-Contaminated Paddy Soil

Wetland macrophytes have advantages when used in the remediation of cadmium (Cd)-contaminated paddy fields because they can adapt to overly wet soil environments; however, only a few studies have tested the efficiency of macrophytes in Cd phytoremediation. In this study, we investigated the effect of soil pH (pHs of 5, 6, and 7) on the accumulation and translocation of Cd by Polygonum hydropiper (L.) in low and moderately Cd-contaminated paddy soil (0.56 and 0.92 mg/kg, respectively). Our results indicated that Cd accumulation in stems and roots, as well as subcellular distribution in P. hydropiper, was affected by soil pH, with significant interactions between the soil pH and Cd level. At low soil Cd levels, stem and root Cd contents were higher at a soil pH value of 6. In addition, with higher soil pH values, the proportion of Cd distributed in the cell wall increased, whereas that distributed in the organelles decreased. The Cd content in the roots and stems of P. hydropiper significantly decreased with the increase in soil pH in the moderate Cd-contaminated soil. In addition, with higher soil pH values, the proportion of Cd distributed in the cell wall decreased, whereas that distributed in the organelles increased. The translocation factor (TF) of P. hydropiper was higher than one in all treatments, indicating that it can effectively transport root-absorbed Cd to the aboveground shoots. Based on the relatively high bioconcentration factor and TF, P. hydropiper has the potential to remediate Cd-polluted paddy soil. Furthermore, the remediation efficiency of P. hydropiper can be enhanced by adjusting the pH as per the soil-Cd pollution.

Habitat preferences rather than morphological traits affect the recovery process of Collembola (Arthropoda, Hexapoda) on a bare saline-alkaline land.

The Songnen Plain of China was once an important grassland used for sheep grazing, but it has largely been degraded to bare saline-alkaline land (BSAL). BSAL consists of plant-free areas characterized by high soil pH values (up to 10) and salt and alkali (e.g., Na+ and Ca2+) contents, as well as low soil organic matter and water contents; thus, very few soil faunal species can survive on BSAL. The recovery of degraded ecosystems provides a great opportunity to investigate the reconstruction of belowground soil faunal communities. Collembola are a class of widespread and abundant soil fauna that can colonize this harsh environment. Habitat changes on BSAL promote aboveground revegetation, which greatly facilitates the recovery of Collembola. A soil transfer experiment on the BSAL of the Songnen Plain was conducted to study the effects of habitat and Collembola morphological traits on the recovery process of Collembola. Defaunated and with-fauna soil blocks were transferred among three habitats: BSAL, reclaimed arable land, and naturally revegetated grassland. The recovered Collembola in the transferred soil blocks were compared two, seven, and 12 weeks after the start of the experiment. The results showed that (1) the majority of the Collembola, regardless of their morphological traits, recovered in the defaunated soil blocks within 2 weeks; (2) generalists and habitat-preferring species recovered faster than specialists; (3) the average total abundance, species richness, and community composition of Collembola recovered to the natural levels in 2 weeks; and (4) 12 weeks after replacement, the highest average total abundance and species richness of Collembola were found in the arable land. Our results indicate that the majority of Collembola in this study, regardless of their dispersal type, which is related to their morphological traits, are fast dispersers, and their recovery speeds are mainly affected by habitat preferences. We suggest that the reclamation of BSAL to arable land rather than its natural recovery to grassland aids in the recovery of Collembola in degraded grassland systems.

Resistance of flax gene pool samples to edaphic stress caused by low acidity

In conditions of vegetative trial carried out against selective backgrounds in 2017-2019 the response of 27 flax samples to a decrease in soil acidity to neutral pHKCl was studied. The scheme of the experiment was as follows: variant I (control) − pHKCl 5.3-5.5, P2O5 − 320-340 mg/kg, K2O − 81-92 mg/kg; variant II − pHKCl 6.2, P2O5 − 312-345 mg/kg, K2O − 84-98 mg/kg. It has been shown that during the «herringbone» phase in the majority of studied flax genotypes against the background of pH 6.2, the symptoms of “physiological oppression” of flax were observed: small spots developed on the upper leaves, the plants stopped growing, the stems thickened, and the tops of severely affected plants died off. As a result, at the beginning of the growing season at plant height of 7-10 cm, most of the samples were severely affected (from 69 to 100 %). The exceptions were varieties of fibre-flax Hermes (France), Vega 2 (Lithuania), Atlant (Russia) and linseed genotypes No. 3896 (Russia) and Norlin (Canada), which had a weak and medium degree of affection (8.3-45.5 %). Moreover, these genotypes showed a high level of both biological (75-90 %) and agronomic (77.3-85.6 %) resistance in the phase of "early yellow ripeness". The identified flax collection samples can be used as sources of resistance to flax «physiological oppression» caused by stressful edaphic factors in a neutral environment. On the basis of the analysis of the main elements of fiber productivity in studied flax genotypes, it has been established that against the background of pH 6.2 the reduce in plant height was from 11.4 to 52.1 % relative to the control, weight of the technical part of the stem − from 7.2 to 83.4 % , fiber mass − from 9.6 to 85.1 %. For the first time, on the basis of hybridological analysis, an assumption was done as to the pres-ence of a strong dominant gene, controlling the resistance to high soil pH values in the Hermes (France) flax variety and the linseed line No. 3896 (Russia).

Changes of oxygen isotope values of soil P pools associated with changes in soil pH

Field data about the effect of soil pH on phosphorus (P) cycling is limited. A promising tool to study P cycling under field conditions is the 18O:16O ratio of phosphate (δ18OP). In this study we investigate whether the δ18OP can be used to elucidate the effect of soil pH on P cycling in grasslands. Soils and plants were sampled from different fertilisation and lime treatments of the Park Grass long term experiment at Rothamsted Research, UK. The soils were sequentially extracted to isolate different soil P pools, including available P and corresponding δ18OP values were determined. We did not observe changes in plant δ18OP value, but soil P δ18OP values changed, and lower δ18OP values were associated with higher soil pH values. At sites where P was not limiting, available P δ18OP increased by up to 3‰ when lime was applied. We show that the δ18OP method is a useful tool to investigate the effect of pH on soil P cycling under field conditions as it highlights that different soil processes must govern P availability as pH shifts. The next challenge is now to identify these underlying processes, enabling better management of soil P at different pH.

Thoughts on acidification of soils by nitrogen and sulfur fertilizers

AbstractSome crops, like blueberries, require a pH of 4 to 5. Irrigation of acid‐loving crops with alkaline water can raise pH and cause micronutrient deficiencies. Diseases like citrus greening (Huanglongbing) are more severe at higher soil pH values. Application of acidifying fertilizers to lower soil pH may therefore benefit crop growth in such instances and release calcium from calcareous soils to remove sodium. Therefore, a good understanding of the processes involved and the amount of acidification from various fertilizer materials is needed. We show with an anion–cation balance of recent plant uptake data that the alkalinity released from plant uptake of nutrients alone gave a value of 2 kg CaCO3 equivalents of alkalinity per kilogram of N uptake, in close agreement with Association of Official Analytical Chemists values of 1.8. We also provide equations and calculations and a summary table that allows a user to compare the acidifying capacity of commonly available N and S fertilizers.

Impacts of earthworm species on soil acidification, Al fractions, and base cation release in a subtropical soil from China.

Soil-exchangeable aluminum (Al) has toxic effects on living organisms in acidic soils. Earthworm presence and activity can alter soil pH, which has a significant influence on Al toxicity. However, the effects of earthworms on soil Al toxicity and fractions are still largely unknown. This laboratory study focused on the effects of three earthworm species (endogeics Pontoscolex corethrurus and Amynthas robustus, anecis Amynthas aspergillum) on soil acidification, Al fraction distribution, and base cation release. Three native earthworm species and a soil (latosolic red soil) collected from a botanical garden in South China were incubated under laboratory conditions. After 40days of incubation, six Al fractions in soil, namely exchangeable (AlEx), weakly organically bound (AlOrw), organically bound (AlOr), amorphous (AlAmo), Al occluded in crystalline iron oxides (AlOxi), and amorphous aluminosilicate and gibbsite (AlAag) fractions, were extracted using a sequential procedure. Soil pH; organic carbon; total nitrogen; total Al (AlTotal); exchangeable K, Na, Ca, Mg contents; and CEC were determined as well. Compared to control soil, pH values increased by 0.79, 0.41, and 0.57units in casts in the presence of P. corethrurus, A. robustus, and A. aspergillum, and 0.70, 0.32, and 0.50units in non-ingested soil, respectively. Compared to control soil, the 61.7%, 30.7%, and 36.1% of AlEx contents in casts and 68.5%, 25.9%, and 39.0% of AlEx in non-ingested soil significantly decreased with the addition of P. corethrurus, A. robustus, and A. aspergillum, respectively. Moreover, compared to control soil, the 78.7%, 37.7%, and 40.1% of exchangeable Ca2+ and 12.3%, 24.7%, and 26.8% of exchangeable Mg2+ contents in casts significantly increased with the presence of P. corethrurus, A. robustus, and A. aspergillum, respectively. Soil treated with P. corethrurus had higher soil pH values, exchangeable Ca2+ contents, and lower AlEx than those with A. robustus and A. aspergillum. Results of principal component analyses showed that P. corethrurus, A. robustus, and A. aspergillum casts and non-ingested soil differ for soil pH, Al fractions, and exchangeable base cations release. These results indicate that earthworms, especially P. corethrurus, can reduce soil Al toxicity, increase soil pH, and affect the release of exchangeable base cations.

Emissions of nitrous oxide (N2O) affected by pH-related nitrite accumulation during nitrification of N fertilizers

The potential of nitrogen (N) fertilizer forms to mitigate N2O emissions from agricultural fields is not very well understood. It is known that both reduced and oxidized N forms can be beneficial, depending on site-specific edaphic and climatic conditions. In the present study four laboratory incubation experiments were conducted under conditions that should minimize denitrification to investigate N2O emissions during the nitrification of solid N fertilizers.It was found that on two loamy sand soils with pH values slightly above pH5, urea caused 2.7–3.8 fold higher cumulative N2O emissions than ammonium sulphate (AS). N2O emission rates from urea were accompanied by elevated soil nitrite levels, while those of AS were not. The direct addition of a NaNO2 solution revealed an exponential relationship between soil nitrite levels and cumulative N2O emissions, indicating that soil nitrite induces N2O emissions, probably by nitrite reduction via nitrifier denitrification. When the soil pH was increased to 6.3 (soil from a long-term liming experiment) nitrite accumulation during nitrification was observed for both N forms. Cumulative N2O emissions did not differ between N forms on the latter soil, but N2O emission kinetics were faster for urea. Cumulative N2O emissions from AS at soil pH6.3 were significantly higher than those of AS at pH values around 5.It was concluded that i) nitrite accumulation during nitrification of reduced N fertilizer forms can significantly contribute to N2O emissions under non-denitrifying conditions, ii) the risk of nitrite accumulation increases with higher soil pH values, and iii) that the alkalizing hydrolysis of urea increases the risk of nitrite accumulation and thus higher N2O emissions as well. This mechanism would explain why urea causes higher N2O emissions than fertilizers in the form of ammonium salts.

Effects of municipal waste compost and nitrogen fertilizer on growth and mineral composition of tomato

Since simultaneous use of organic and mineral fertilizers on the basis of their chemical compositions can lead to better plant growth and soil fertility, the roles of municipal waste compost (MWC) and nitrogen (N) fertilizer on growth and mineral composition of tomato and some soil properties were evaluated under greenhouse condition. Treatments involved four MWC rates (0, 1, 2, and 4% on the basis of soil dry weight) and four N levels (0, 50, 100, and 200 mg kg−1 soil). Red cloud variety of tomato was sown in treated soils and 9 weeks later dried plant shoots and soil sub-samples were subjected to analysis. Combined use of MWC and N led to better growth of tomato than sole application of either MWC or N fertilizer. Plant concentration and/or uptake of nitrogen, phosphorus, zinc, copper, iron, and manganese were increased by both MWC and N. The beneficial effect of MWC on nutrients uptake was more pronounced with N addition. Plant and soil concentrations of cadmium and lead were under the detection limit of atomic absorption spectrophotometer. Soluble salts, organic matter, sodium, chloride and DTPA-extractable zinc, copper, iron, and manganese in the soil were effectively increased with addition of MWC. Due to high soil pH and calcium carbonate equivalent (CCE) values of the calcareous soil, MWC heavy metals had no hazardous effect on tomato and even played a nutritional role. The most important problem raised from MWC application was the accumulation of soluble salts in the soil which must be monitored when making repeated application of MWC over an extended period of time.

Denitrification potential of marsh soils in two natural saline-alkaline wetlands

Little information is available on denitrification potential of marsh soils in natural saline-alkaline wetlands. The denitrification potentials of an open wetland in the floodplain (Erbaifangzi wetland) and a closed wetland (Fulaowenpao wetland) in backwater areas in Jilin Province of Northeast China were monitored by an anaerobic incubation at 30°C for 25 days. Our results showed that the relative denitrification index (RDI) increased gradually with incubation time, and showed a rapid increase in the first 5 days of incubation. The RDI values declined quickly from surface soils to subsurface soils and then kept a small change in deeper soils along soil profiles over the incubation time. Denitrification proceeded much faster in the top 20 cm soils of open wetland than in the closed wetland, whereas no significant differences in RDI values were observed in deeper soils between both wetlands. The RDIs were significantly negatively correlated with bulk density and sand content, while a significantly positive correlation with clay content, soil organic matter, total nitrogen and phosphorous. The maximum net NO3 −-N loss through denitrification in 1 m depth were higher in the open wetland than the closed wetland with higher soil pH values. Future research should be focused on understanding the influencing mechanisms of soil alkalinity.

Predicting the solubility and lability of Zn, Cd, and Pb in soils from a minespoil-contaminated catchment by stable isotopic exchange

The Rookhope catchment of Weardale, England, has a diverse legacy of contaminated soils due to extensive lead mining activity over four centuries. We measured the isotopically exchangeable content of Pb, Cd and Zn (E-values) in a large representative subset of the catchment soils (n=246) using stable isotope dilution. All three metals displayed a wide range of %E-values (c. 1–100%) but relative lability followed the sequence Cd>Pb>Zn. A refinement of the stable isotope dilution approach also enabled detection of non-reactive metal contained within suspended sub-micron (<0.22μm) colloidal particles (SCP-metal). For most soils, the presence of non-labile SCP-metal caused only minor over-estimation of E-values (<2%) but the effect was greater for soils with particularly large humus or carbonate contents. Approximately 80%, 53% and 66% of the variability in Zn, Cd and Pb %E-values (respectively) could be explained by pH, loss on ignition and total metal content. E-values were affected by the presence of ore minerals at high metal contents leading to an inconsistent trend in the relationship between %E-value and soil metal concentration. Metal solubility, in the soil suspensions used to measure E-values, was predicted using the WHAM geochemical speciation model (versions VI and VII). The use of total and isotopically exchangeable metal as alternative input variables was compared; the latter provided significantly better predictions of solubility, especially in the case of Zn. Lead solubility was less well predicted by either version of WHAM, with over-prediction at low pH and under-prediction at high soil pH values.

Assessing the potential soil acidification risk under dryland agriculture in the Mlondozi district in the Mpumalanga Province of South Africa

The farming community in the Mlondozi district in the Mpumalanga Province of South Africa has been part of a government liming intervention with the objective to ameliorate the serious soil acidity problem in the district. The current study was undertaken in order to evaluate the impact of the liming intervention and the risk of re-acidification of the soil due to natural and agricultural activities. Acid production in the 0-250 mm depth varied from a measured 0.21 to 10.31 (mean 3.70 kmol H+ ha- 1 year- 1) in crop production sites. Approximately 190 kg lime ha- 1 yr- 1 is required to maintain current soil pH levels under crop production. The rate of pH decline for the top 0-250 mm depth was between 0.051 and 0.918 (mean 0.237) pH units year- 1. In the absence of remedial lime applications, pH(H2O) values in most of the area are projected to decrease to the critical value of 5.68 or lower within 4 years. The upper and lower critical pH(H2O) were found to be between ca. 5.73 and 5.68. Below the lower critical value a reduction in crop production can be expected and above the upper critical value, accelerated acidification takes place. Soils with an extractable Al and acidity of <0.180 and <0.253 cmol (+) kg−1 soil, respectively, a clay content of 26%, and an ECEC value of 3.29 cmol (+) kg soil−1, or high initial soil pH values, are more at risk to accelerated acidification than soils with lower extractable Al and acidity, higher clay contents and higher ECEC values.

Evaluation of the ecological restoration potential of plant communities in Norway spruce plantations using a life‐trait based approach

Summary In Europe, intensively managed coniferous plantations rarely achieve similar nature conservation functions as deciduous woodlands. The ability to identify coniferous plantations that might be successfully converted to deciduous woodland is a key goal in forest management. The herbaceous plant community composition of mature plantations may be an accurate selection criterion for stands that are most suitable for initiating the conversion process to deciduous forest. The herbaceous plant communities in Norway spruce plantations were analysed using a functional group approach. The analysis was conducted in three steps: (i) identification of emergent groups (EG) by multivariate classification; (ii) comparison of EG abundance between coniferous and deciduous stands (i.e. the target communities); (iii) partitioning the variation in EG abundance in coniferous plantations between forest management, local environmental and regional variables. Seven EG were identified: two core forest groups (short geophytes and zoochoreous perennials), two groups from open habitats (annuals and helophytes) and three mixed groups (anemochoreous perennials, graminoids and short perennials). Among the core forest groups, short geophytes were severely under‐represented in plantations (because of their low dispersal abilities and specific habitat requirements) while zoochoreous perennials were slightly more abundant (because of their good dispersal and competitive abilities). Regional variables largely influenced the abundance of core‐forest EG. Restoration of communities rich in zoochoreous perennials is far easier than restoring short geophyte‐rich communities because of the different colonization abilities of these EG. Forest management variables were of secondary importance for the restoration potential of plantations. Because generalist EG were favoured by low stand densities, forest practitioners should avoid large thinning operations. Local environmental variables played a minor role in determining EG abundance. However, short geophytes preferred rather high soil pH values and were therefore negatively affected by acidification caused by coniferous litter. Synthesis and applications. The performance of short geophytes is the key to conversion success of Norway spruce plantations to deciduous forest. Stands located on base‐rich soils and in landscapes with high forest connectivity are the most appropriate candidates for initiating the conversion process. For other types of stands, future work should explore the possibility of restoring other land‐use types, such as annually mown meadows.

Spatial Variability of Radial Growth in the Forest-Tundra Ecotone of Rocky Mountain National Park, Colorado

HESSL, A. E., P. J. WEISBERG3 AND W L. BAKER (Department of Geography and Recreation, University of Wyoming, Laramie, WY 82071). Spatial variability of radial growth in the forest-tundra ecotone of Rocky Mountain National Park, Colorado. Bull. Torrey ecotone of Rocky Mountain National Park, Colorado. Bull. Torrey Bot. Club 123: 206-212. 1996.-Radial growth in trees has often been used to measure the relationship between climate and tree growth. Variation in radial growth with respect to environmental variables may indicate how trees in diverse landscapes may respond to climate change. The purpose of this study is to determine whether radial growth is spatially heterogeneous throughout the forest-tundra ecotone of Rocky Mountain National Park and whether this spatial variability can be related to environmental variables. Increment cores were taken from 5-10 of the largest trees in 59 sampling locations distributed across the forest-tundra ecotone of Rocky Mountain National Park. Mean annual ring width for 1978-1987 was measured in the laboratory. Stepwise weighted least squares linear regression was used to relate mean annual growth to 25 environmental variables measured at each sampling location. Mean radial growth is higher at sampling locations with higher soil pH values and where there is small rock material but varies with zone and associated shrub species. When all statistically significant variables are considered, radial growth is slowest in the krummholz zone, intermediate in the patch forest zone, and fastest in the closed forest zone. Within each zone, the presence of Juniperus communis indicates slow radial growth, Vaccinium spp. indicate intermediate radial growth, and Salix spp. indicate rapid radial growth. These results differ from previous studies of vertical seedling leader growth in the FTE, which found higher rates of growth in the krummholz zone. Differing rates of radial and vertical growth may reflect different settings or different responses, though both may indicate tree success.

Effect of fertilizers on soil pH and performance of apple and pear trees. II. Grown in different soils in the orchard

Abstract In the apple orchard, trees fertilized with calcium nitrate resulted in the highest soil pH (6.4) whereas the lowest pH (4.7 and 4.6) occurred with ammonium nitrate and with mono‐ammonium phosphate (MAP) applications, respectively. Soil pH values were lowest with the high rates of nitrogen (N) fertilizers. Red skin color of ‘Delicious’ apples was generally improved with calcium nitrate fertilization, higher soil pH values, and with lower fruit manganese (Mn) concentrations or with lower N fertilizer rates. Incidence of bitter pit was lowest for trees fertilized with ammonium nitrate or calcium nitrate. In the pear orchard, the lowest soil pH (4.2) occurred when trees were fertilized with the high rate of MAP and the highest soil pH (4.8) occurred with the high rate of calcium nitrate applications. Fruit size was slightly smaller on trees fertilized with the high rate of MAP. Lowest incidence of superficial cork or green stain fruit disorders occurred on trees receiving the high rate of calcium ni...

Iron oxide minerals in soils of the Ha'apai group, Kingdom of Tonga

The iron oxide mineralogy of three soils from the Ha'apai Group (c. latitude 19�50�S., longitude 174�30' W.), Kingdom of Tonga, has been investigated. The Group consists mainly of an archipelago of low coral atolls. Soils are formed in the andesitic tephra which overlie the coral. Accessions of marine salts are high and give rise to high soil pH values (&gt;7) and high concentrations of exchangeable cations. The soils are dark reddish brown to reddish brown in colour, with limited colour differentiation with soil depth, and they are not hqdromorphic. The results of study of whole soils and size fractions by chemical extraction, X-ray diffraction, differential thermal analysis, Moessbauer spectroscopy, and by measurement of variation of magnetic attraction following heating to various temperatures, lead to the following conclusions: iron oxide minerals comprise 7-12% by weight of the soils; the predominant clay size iron oxide is very poorly crystalline aluminium-substituted lepidocrocite (�-Fe 0.8Al 0.2,OOH); ferrihydrite is probably also present in the clay fraction; lepidocrocite and ferrihydrite together account for 50-60% of the total iron in the soils studied; magnetite, probably partially oxidized towards maghemite, is present, particularly in sand and silt fractions, and accounts for about 10% of the total iron in the soils. The remainder of the total iron occurs in unweathered minerals in the silt and sand fractions and in the structure of halloysite in the clay fraction. The common soil iron oxides, goethite and hematite, have not been detected. Although the occurrence of lepidocrocite is usually linked with hydromorphic soil conditions, this report, along with others, suggest that it is also found under non-hydromorphic conditions.

Effects of liming on phosphate availability in acid soils

The critical factors involved in the plant-soil-phosphorus-lime interaction are outlined and discussed. Conflicting reports suggest that the prior liming of highly weathered acid soils can result in an increase, a decrease, or no change in the availability of applied phosphate. Adsorption of phosphate by amphoteric soil surfaces generally decreases slowly as the pH is raised from 4.0 to 7.0. However, in soils initially high in exchangeable Al3+, liming results in the formation of new, highly active, phosphate adsorbing surfaces as the Al3+ ions precipitate as insoluble polymeric hydroxy-Al cation species. Thus, if an acid soil is reacted with lime and then phosphate, without intervening air drying, liming can increase phosphate adsorption. If the same limed soil is air dried before reaction with phosphate (e.g. adsorption isotherm studies), liming decreases phosphate adsorption. Apparently, air drying alters the surface characteristics of recently limed soils, probably by promoting the crystallization of the hydroxy-Al cation polymers as gibbsite. An important phenomenon, which is often overlooked, is that liming can increase phosphate availability by stimulating mineralization of soil organic phosphorus. However, at high soil pH values, the precipitation of insoluble calcium phosphates can decrease phosphate availability. Since Al toxicity is characterised by the inhibition of the uptake, translocation and utilization of phosphate by plants, liming often increases the utilization of soil phosphate by plants through amelioration of Al toxicity. When making lime recommendations or interpreting the data collected from lime-phosphate experiments, it is important to consider all the complex interacting soil and plant factors involved.

Mineral nutrition associated with flower color in hydrangea

Abstract Analysis of blue and pink flowers of Hydrangea macrophylla DC growing in gardens in Los Angeles gave poor differentiation by concentration of Al in them in contrast to the effect reported in literature. Blue flowers usually associated with acid soils contained 510 μg Al/g dry weight while pink flowers usually associated with alkaline soils contained 481 μg/g. Pink flowers contained 322, 18, 1793, 42, 1.1, 0.6 and 4. 7 μg/g respectively of Fe, Mn, Si, Ti, Mo, Cr and Sn. Blue flowers simultaneously contained respectively of the same elements, 146, 27, 622, 22, 0.4, 0.3, and 2.8. Some of these differences may relate to flower color. Hydrangea cuttings grown in a glasshouse in soils of different pH values had blue flowers at soil pH 3.5 and these flowers were higher in Al, Mn, Mg and Si than flowers which were pink or pinkish blue on plants grown at higher soil pH values.

Effect of Trifluralin and Metribuzin Combinations on Soybean Tolerance to Metribuzin

In field trials, soybeans [Glycine max(L.) Merr.] treated with trifluralin [α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine] at 0.56 and 0.84 kg/ha were protected from injury by metribuzin [4-amino-6-tert-butyl-3-(methylthio-as-triazine-5(4H)one] at 0.28 to 1.12 kg/ha. Soybean injury from metribuzin at high soil pH values was reduced by applying it in combination with trifluralin. Trifluralin also protected soybeans from injury caused by low rates of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] greenhouse studies. The trifluralin treatment reduced root development and greatly reduced14C-atrazine and14C-metribuzin uptake and content within the soybean plant.

Uptake of lead by coen from roadside soil samples

Abstract The uptake of Pb by young, greenhouse grown corn plants from roadside soil samples was found to be not only dependent upon the total amount of Pb in the soil, but also upon the amount of Pb in the soil relative to the soils capacity to sorb Pb. This is in agreement with the uptake of Pb by corn grown on soils amended with PbCl2, although plant accumulation of Pb from roadside soils was much less than from PbCl2 amended soils at comparable Pb concentrations. The use of crushed limestone as a road building material which results in high soil pH values next to the roadside is probably responsible for the reduced plant availability of Pb in the roadside soils.