Extractability of previously‐applied zinc as influenced by properties of calcareous soils

Abstract

The recovery of applied zinc (Zn) by plants is relatively small. Coupled with lack of leaching, this leads to accumulation of Zn in topsoil which may result in unfavorable growth conditions for the subsequent plants. Different extractants may be used for assessing the Zn status of soils previously treated with Zn sources. The extractability of retained Zn is influenced by soil properties. This experiment was conducted to study the influence of selected properties of calcareous soils on extractability of Zn by three popular Zn soil tests. Twenty samples from surface horizons (0–20 cm) of highly calcareous soils of southern Iran (pH 7.9 to 8.5; calcium carbonate equivalent 16 to 58%) previously treated with three levels of Zn (0, 10, and 20 mg Zn kg^‐1 soil as ZnSO₄#lb7H₂O) in triplicate and under one crop of corn (Zea mays L.) were extracted with DTPA, EDTA‐(NH₄)₂CO₃ and Na₂‐EDTA. Extractability (EXT) in a particular extractant was defined as the slope of the regression line, relating extractable Zn of each soil to the rate of applied Zn, multiplied by 100. The EXT values of soils ranged from 24.9 to 73.0% for DTPA, 47.2 to 84.4% for EDTA‐(NH₄)₂CO₃, and 28.2 to 56.7% for Na₂‐EDTA. Stepwise regression equations showed that cation exchange capacity (CEC) and calcium carbonate equivalent (CCE) followed by clay content were the most influential soil properties in EXT of retained Zn of highly calcareous soils. The EXT values decreased with increase in CEC, and CCE but increased with increase in clay.     

Growth and nutrition of pansy as influenced by N‐form ratio and temperature

Abstract

Pansy (Viola xwittrockiana Gams.) producers often observe nutrient disorders among plants grown during warm periods (>18°C) of the growing season. These disorders typically are not seen when production temperatures are optimal (≥18°C) even though fertility regimes may remain the same. Our objectives were to assess the effects of temperature and nitrogen (N) fertility on growth and nutrition of pansy. Pansies cultivar ‘Crown White’ were grown until lateral branches had open flowers. Treatments consisted of two temperatures (12 and 22°C) and three NO₃ ^?:NH₄ ⁺ molar % ratios (100:0, 62:38, and 25:75) with a total concentration of 100 mg N L^?1. A modified Hoagland's solution was used with NO₃ ^?‐N supplied as Ca(NO₃)₂ and KNO₃ and with NH₄ ⁺‐N as (NH₄)₂SO₄. Cumulative nutrient absorption and foliar nutrient content were determined when plant lateral branches flowered. Root and shoot growth were limited when NH₄ ⁺ was present in solutions at high ambient air temperature (22°C), but not at low temperature (12°C). Individual absorption and accumulation of plant nutrients varied with N regimes and temperatures. Overall, pansies absorbed more total N, NH₄ ⁺, NO₃ ^?, calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), zinc (Zn), and less iron (Fe) and manganese (Mn) at 12°C than at 22°C. In addition, absorption of NO₃ ^? by pansy was negligible if any NH₄ ⁺ was present in solutions at 22°C. Results suggest that pansy growers should adjust fertility programs according to production temperatures to avoid possible nutritional disorders and maximize plant growth. If maximum growth is to be obtained in warm temperatures, the use of NH₄ ⁺‐containing fertilizers should be reduced or eliminated. However, the choice of NO₃ ^?:NH₄ ⁺ ratio for nutrition may be less important under cool growing conditions.     

Soil phosphorus pools in the detritusphere of plant residues with different C/P ratio—influence of drying and rewetting

Little is known about the effect of drying and rewetting (DRW) on phosphorus (P) pools in the detritusphere, the soil adjacent to plant residues. Two plant residues differing in their potential to release P during decomposition were used: mature barley straw, C/P 255 or young faba bean, C/P 38. Residues were placed between two PVC caps filled with soil at 50% water-holding capacity with open ends covered by fine mesh onto which the residues were placed. The open ends of the two PVC caps were pressed together with residues in between. For the unamended controls, no residues were placed between the meshes. After 2 weeks incubation, the soil was separated from the residues and then either dried and kept dry for 2 weeks followed by rapid rewetting to 50% water-holding capacity (WHC) rewetting (RW) or maintained at 50% of WHC constantly moist (CM). Bioavailable P pools (readily available P pools: CaCl₂- and anion exchange-P; P bound to soil particles: citrate- and HCl-P; acid phosphomonoesterase- and microbial-P) were measured in dry soil and 1, 7, and 14 days after rewetting. Rewetting of dry soils induced a respiration flush on the first day after which respiration rates declined to those in CM. Compared to the unamended soil, the flush was about 75% higher with barley and more than twofold higher with faba bean. P pools were 3–20-fold higher with faba bean than with barley or in the control. At the end of the dry period, most P pools were higher in dry soil compared to CM. Rewetting had little effect on P pools 1, 7, and 14 days after rewetting compared to CM. To investigate if rewetting induced a short pulse of available P, a second experiment was carried out. As in the first experiment, faba bean detritusphere soil and control were generated and then dried or kept at 50% WHC for 2 weeks. Before rewetting, anion exchange membranes (AEM) were placed in the soil which were removed one, 2 or 4 days after rewetting. The P concentration on the AEM was more than threefold higher with faba bean than the control. One day after rewetting, the P concentration on the AEM with faba bean was about threefold higher in RW than in CM, but did not differ between RW and CM in the control. Four days after rewetting, nearly all P pools with faba bean were 10–30% lower in RW than in CM, except citrate-P which was about 5% higher in RW. We conclude that rewetting induces a short pulse of available P if the P pool concentration is high as in the detritusphere of faba bean. If P is removed from the soil (by binding to AEM or uptake by plants), rewetting can induce depletion of P pools compared to CM.     

The effects of biocidal treatments on metabolism in soil—III. The relationship between soil biovolume,measured by optical microscopy,and the flush of decomposition caused by fumigation

The hypothesis that the flush of decomposition following fumigation is a measure of the amount of biomass in a soil was tested by comparing the biomass thus found, and as calculated from direct microscopic measurement of the soil biovolume. Eight soils developed under contrasting systems of management and climate were used, six from England and two from Nigeria. The biovolume was measured by a modification of the Jones and Mollison procedure, in which agar films prepared from known amounts of soil were stained with phenolic aniline blue. Fluorescent stains were less satisfactory in that they did not stain as wide a range of organisms as phenolic aniline blue. Spherical organisms were divided into 13 size classes, with diameters ranging from 0·3 to 19 μm, and the numbers in each size class counted. Hyphae were divided into seven diameter classes, with dia. ranging from 1 to 11 μm, and the lengths in each class measured. For seven of the soils there was close agreement between the two different methods of measuring biomass C. With an acid woodland soil (pH 3·9). the biomass C, as calculated by direct microscopy, was seven times that calculated from the size of the flush; it is suggested that this discrepancy arose because stainable cell walls from dead organisms persist for much longer in the strongly acid soil than in the other, more nearly neutral, soils.Both methods were used to follow the effects of fumigation on the soil biomass. A near-neutral soil was fumigated with CHCl₃, the fumigant removed and the soil incubated for 53 days at 25° C. The decrease in biomass caused by fumigation was less as measured by direct microscopy than as measured from the size of the flush, suggesting that stainable cell walls of killed organisms can persist for a considerable time after fumigation.Data on the relationship between the size of soil organisms and their contribution to soil biovolume are presented graphically. The biovolume in hyphae and in ‘spherical’ organisms was roughly equal in all soils. There was a linear relationship between the cumulative biovolume and the logarithm of organism volume lor ‘spherical’ organisms over the volume range 0·05 μm³ to 100 μm³. If, for a given soil, the volume range is divided into equal volume classes on a logarithmic basis, each class contains the same biovolume. Thus, comparing equal logarithmic volume classes, a class of rare large organisms contains as much biovolume as a class of numerous small organisms.     

Seasonal sucrose,drymatter, and cation concentrations of sugarbeet as influenced by variety and N‐fertilization

Abstract

This study evaluated the effect of variety and nitrogen (N) fertilization on sucrose, dry‐matter, and cation concentrations in sugarbeet (Beta vulgaris L.) root tissue. A field experiment was conducted on a non‐saline, calcareous Nunn clay loam soil (Aridic argiustoll) using a factorial experimental design with three N‐rates, two varieties, and four replications. Beets were harvested nine times during the growing season. The first and final harvests were on June 25 and October 11, respectively. In addition to the above measurements, purity and extractable sucrose also were measured at the final harvest. Dry‐matter content, sucrose, sums of monovalent and divalent cations, and the monovalent:divalent cation ratios all were influenced significantly by variety, N‐fertilization, and date of harvest. Sucrose concentration was negatively correlated to the sum of monovalent and divalent cations. Root drymatter content was negatively correlated to the monovalent:divalent cation ratio. A relationship of cation concentration to the organic‐ and inorganic‐ anions that influence purity is discussed.     

Yield and nutritional evaluation of the banana hybrid ‘FHIA-18’ as influenced by phosphate fertilization

Abstract

The ‘FHIA-18’ hybrid banana is an alternative for producers as it is resistant to Black Sigatoka and Panama disease. However, few studies report the nutritional requirement of this hybrid, especially phosphorus. It is known that the efficiency of phosphorus use can be improved, reducing the need for application, depending on the genotype cultivated. Therefore, this study aimed to evaluate the yield and mineral nutrition of ‘FHIA-18’ hybrid banana on phosphate fertilization. A banana orchard with the cultivar ‘FHIA-18’ was conducted on a Typical Red Latosol. Then, triple superphosphate fertilizer was applied on plants at 0, 20, 30, 40, 50, and 60?kg ha^?1?year^?1, over three productive seasons. At the time of flowering the macro and micronutrient contents of the leaves were evaluated. Subsequently, the nutrient contents of the fruits were evaluated. For this, fruit pulp samples from the third and fourth hands were collected. In addition, yield was estimated considering cluster mass and plant density. The following dose 36?kg ha^?1 of P₂O₅ year^?1 increased the content of phosphorus in the leaf, despite that banana hybrid cultivar FHIA 18 demanded 50% of the recommended fertilizer to achieve its maximum yield (29.4 t ha^?1?year^?1). Phosphate fertilization promoted significant changes in P, Ca, Cu, and Zn contents of leaves and fruits. Therefore, it is concluded that the mineral nutrition of banana ‘FHIA-18’ is affected by phosphate fertilization, as well as requiring less P than recommended to achieve higher yield.     

Availability of phosphorus in a Brazilian Oxisol cultivated with eucalyptus after nine years as influenced by phosphorus‐fertilizer source,rate, and placement

Abstract

This work evaluated the effect of different placement and rates of two phosphorus (P) fertilizers on P‐availability by three methods of extraction, nine years after application to a Brazilian Oxisol cultivated with Eucalyptus camaldulensis. The treatments were applied to 24x18 m plots and 96 seedlings of E. camaldulensis were planted (3.0x1.5 m) in each plot. Single superphosphate (SSP) and rock phosphate (RP) were tested in three rates (100, 200, and 400 kg ha^‐1 of P₂O₅). Each fertilizer was either (1) surface‐applied in bands (0.6 m either side of the rows of trees) and incorporated before planting or (2) incorporated into furrows (0.2 m deep in the tree rows) before planting. As additional treatments, the combination of RP (96 kg ha^‐1 of P₂O₅ applied in broadcast, or bands, or in furrows) + SSP (54 kg ha^‐1 of P₂O₅ localized in the planting hole before planting) were tested. Twelve soil subsamples from two layers (0–15 and 25–40 cm) were taken from each plot (from the planting rows or between the planting rows) and were analyzed for pH in water (1:2.5), available P by Mehlich‐1, Bray‐1 and anionic resin, exchangeable Ca, and Al by 1 mol L^‐1 Kcl. For both methods of fertilizers placement, the highest values of available P were observed in the surface soil and in the planting row, and were strongly related to fertilizer rate. Samples taken between the planting rows did not exhibit treatment effects on available P. The higher values of available P obtained with Mehlich‐1 and the lower eucalyptus plant uptake efficiency of fertilizer‐P from banded RP confirms the fact that this extractant can overestimate the availability of P in soils receiving RP. The use of anion exchange resin in this situation to estimate available P is supported. The results obtained with the localized application of RP indicate root system activity (P and Ca uptake and acidification of rhizosphere) as a factor in increasing fertilizer dissolution rates.     

Nutritional (Fe-Mn) interactions in ‘Big Top’ peach plants as influenced by the rootstock and by the soil CaCO3 concentration

Manganese (Mn) toxicity in plants is often not a clearly identifiable disorder and it can interfere with the absorption, translocation, and utilization of other elements such as Ca, Mg, Fe, and P. Soil conditions, management factors, and the use of different genotypes of rootstock can determine the degree of Mn toxicity and of interaction with other elements in the orchard. Five plants of the cultivar ‘Big Top’® grafted onto itself, onto plum rootstock ‘Mr.S.2/5’ and onto hybrid peach x almond rootstock ‘GF677’ were grown in 25-L containers under three treatments, 0, 20, 30% concentration of total lime, obtained by mixing powdered CaCO₃ to a sandy soil. Plants were fertilized with manure and a solid fertilizer early in April and irrigated in summer periodically with water rich in manganese. After just 28 d, active lime caused a decrease of chlorophyll SPAD index especially in plants grafted on itself, while those grafted on the tolerant ‘GF677’ rootstock behaved better than those grafted on ‘Mr.S.2/5.’ From June to September, irrigation caused increases in soil Mn concentration and Mn concentration in control plants. This caused first a serious defoliation in Big Top / Big Top plants and then a re-greening of cultivar grafted onto ‘Mr.S.2/5’ and ‘GF677,’ probably due to the interaction between iron and manganese at high pH. In particular the 20% CaCO₃ addition to the soil preserved the plants of cultivar grafted onto ‘Mr.S.2/5’ from Mn toxicity, as shown by their high chlorophyll content and growth and lower Mn leaf concentrations. Plants grafted onto ‘GF677’ rootstock showed the best behaviour under 30% CaCO₃ treatment associated to higher Fe(III)-reducing capacity and photosynthetic activity. Rootstocks and soil conditions (lime and waterlogging) influenced mineral status and growth of the peach cultivar ‘Big Top,’ particularly by interacting together and modifying Fe-Mn availability.     

Changes in nutrient pools,microbial biomass and microbial activity in soils after transit through the gut of three endogeic earthworm species of the genus Postandrilus Qui and Bouché, 1998

Purpose

Endogeic earthworms play a significant role in biogeochemical cycles due to the large amount of soil they ingest, and because after transit through their guts, casts usually show differences in nutrient contents and microbial populations with bulk soil. Here, we studied how three endogeic earthworm species, Postandrilus majorcanus, Postandrilus sapkarevi and Postandrilus palmensis, inhabiting soils in Majorca island (Balearic Islands, W Mediterranean), modify nutrient pools and microbial communities of soil.

Materials and methods

To do this, we analysed C, N and P pools, microbial biomass (phospholipid fatty acids, PLFA) and microbial activity (fluorescein diacetate hydrolysis, FDA) in paired samples of bulk soil and fresh casts.

Results and discussion

The mineral and organic N contents were generally enhanced in casts produced by all three earthworm species. However, inorganic P and organic C contents were only higher in P. sapkarevi (32 %, only P) and P. majorcanus casts (100 % for both soil nutrient pools) than in bulk soil. Bacterial and fungal biomass were only higher than in bulk soil in P. majorcanus casts (65 and 100 %, respectively), but without effects on microbial activity, that was lower in P. palmensis casts (26 %). Earthworm gut transit strongly influenced the soil microbial community structure, resulting in differences between casts and soils.

Conclusions

The increased nutrient mineralization (6-, 1.3- and 1.4-fold for N, C and P, respectively) in casts produced by these earthworm species is of particular importance because of the amount of casts released and the seasonal variations in earthworm activity, which may favour plant growth.     

Stimulation of N2‐fixation in chickpea by gamma irradiation as affected by different levels of ammonium sulfate fertilizer

Abstract

A pot experiment was conducted under natural climatic conditions to study the effect of low doses of gamma irradiation (0, 5, 10, and 20 Gy) on the performance of winter chickpea (Cicer arietinum L.) in the presence of increased supply of ¹⁵N labeled ammonium sulfate (0, 20, 50, and 100 kg N ha^‐1). Presowing seed irradiation produced a significant increase in dry matter production (up to 3 6%) and total nitrogen yield (up to 45%). The stimulative effect of irradiation was more pronounced with the application of NH₄ ⁺‐N fertilizer. Seed irradiation increased the amount of N₂‐fixation by 8–61% depending on the dose and level of NH₄ ⁺‐N fertilizer rate. A 10 Gy was found to be the optimal irradiation dose for enhancing N₂‐fixation. High levels of NH₄ ⁺‐N decreased the percentage and the amount of N₂‐fixation, but did not affect nodule formation. However, the presowing 10 Gy irradiation dose reduced the negative effect of ammonia‐N fertilizer on N₂‐fixation. Therefore, we recommend irradiating chickpea seeds with a 10 Gy dose before planting in soil containing high levels of mineral nitrogen to reduce its negative effect on N₂‐fixation.     

Variation in the amounts of selected volatiles in a model population of fragaria × ananassa Duch. As influenced by harvest year

Volatile metabolites are a basis for sensory and resistance traits of Fragaria × ananassa . Stability of expression is important for the selection of cultivars. For the first time, the stability of volatiles in a strawberry population after cross-combination of two distinct cultivars ('Mieze Schindler' × 'Elsanta') has been investigated. In this work, environmentally caused variations in the synthesis of 18 volatiles were studied over two years using a model population of 158 clones. The stability varied throughout the F1 seedling population between the two years, defining stable and unstable genotypes with respect to volatile synthesis. Most of the stable genotypes exhibited low values in relative volatile concentration. Merely 6 stable volatiles were detected in the parental cultivars, whereas about 40% of the F1 progeny had up to 11 stable volatiles. Consequently, a higher stability in volatile synthesis can be achieved by breeding.     

Mineralization of native soil organic matter is not regulated by the size,activity or composition of the soil microbial biomass—a new perspective

Soil organic matter is extensively humified; some fractions existing for more than 1000 years. The soil microbial biomass is surrounded by about 50 times its mass of soil organic matter, but can only metabolize it very slowly. Paradoxically, even if more than 90% of the soil microbial biomass is killed, the mineralization of soil organic matter proceeds at the same rate as in an unperturbed soil. Here we show that soil organic matter mineralization is independent of microbial biomass size, community structure or specific activity. We suggest that the rate limiting step is governed by abiological processes (which we term the Regulatory Gate hypothesis), which convert non-bioavailable soil organic matter into bioavailable soil organic matter, and cannot be affected by the microbial population. This work challenges one of the long held theories in soil microbiology proposed by Winogradsky, of the existence of autochthonous and zymogenous microbial populations. This has significant implications for our understanding of carbon mineralization in soils and the role of soil micro-organisms in the global carbon cycle. Here we describe experiments designed to determine if the Regulatory Gate operates. We conclude that there is sufficient experimental evidence for it to be offered as a working hypothesis.     

Soil microbial biomass as affected by groundcover management in a Fraser fir (Abies fraseri [Pursh] Poir) plantation after 1?year

We investigated soil microbial biomass response to incorporating a non-leguminous [perennial ryegrass (Lolium perenne)] and two leguminous [Dutch white clover (Trifolium repens) and alfalfa (Medicago sativa)] cover crops into a newly established Fraser fir (Abies fraseri) plantation. Groundcover treatments consisted of growing each cover crop in the interspaces of the plantation, mowing the aboveground biomass every 3?weeks, and leaving the plant residues on the ground to decompose. Conventionally managed plots were used as a control. Soil total C, total N, and microbial biomass carbon (SMB-C) and nitrogen (SMB-N) were assessed at the 0–15-, 15–30-, and 30–35-cm soil depths. Soil total C was unaffected by groundcovers at any depths, whereas soil total N was significantly (P?=?0.031) higher in the cover crop treatments than in the conventional system at the top soil layer. Groundcovers increased SMB-C and SMB-N by 20–50% and 35–80%, respectively, in the top soil layer relative to the control. These results suggest that groundcovers could potentially improve soil fertility and be a good strategy for sustainable fir tree production.     

Pore-scale view of microbial turnover: Combining 14C imaging, μCT and zymography after adding soluble carbon to soil pores of specific sizes

The location of microorganisms and substrates within soil pore networks plays a crucial role in organic carbon (C) processing, and its microbial utilization and turnover, and has direct consequences for C and nutrient cycling. An optimal approach to quantify responses to new C inputs from microorganisms residing in specific pores is the addition of new C to pores of target sizes in undisturbed soil cores. We used the matric potential approach to add ¹⁴C-labelled glucose to small (< 40 μm, root free) or large (60–180 μm, potentially inhabited by roots) pores of undisturbed soil cores. Localization of glucose-derived C via ¹⁴C imaging was related to pore size distributions and connectivity, characterized via X-ray computed microtomography (μCT), and to β-glucosidase activity, characterized via zymography. After 2-week incubations, 1.3 times more glucose was mineralized (¹⁴CO₂) when it was added to the large pores; however, more ¹⁴C remained in microbial biomass when glucose was added to the small pores. Consequently, although utilizing the same amounts of easily available C, the microorganisms localized in the large pores had faster turnover compared to microorganisms in small pores. Stronger associations between β-glucosidase activity and glucose-derived C were observed when glucose was added to the large pores. We conclude that (a) the matric potential approach allows placing, albeit not exactly, of soluble substrates into pores of target diameter range, and (b) microorganisms localized in large pores respond to new C inputs with faster turnover, greater growth and more intensive enzyme production compared to those inhabiting the small pores.     

Distribution of Polycyclic Aromatic Hydrocarbons in the Soil–Plant System as Affected by Motor Vehicles in Urban Environment

Eurasian Soil Science - The paper focuses on the interactions among the components of urban natural complex (surface soil layer, rhizosphere, and aboveground phytomass of herbaceous plants)...     

Wood-decaying fungi in boreal forest: are species richness and abundances influenced by small-scale spatiotemporal distribution of dead wood?

We tested whether the spatiotemporal distribution of Norway spruce (Picea abies) logs influenced species richness and abundances of wood-decaying fungi in two 2-km² boreal forest study sites in southeastern Norway. According to the random sample null-hypothesis equally large subsamples of logs should be equally efficient in sampling fungi from a regional species pool. Based on 0.25-ha plots at 1-ha grid resolution, we compared plots with high and low densities of ‘new logs’ (decay stages 1-5) and plots with ‘old logs’ (decay stages 5-8) present or absent. Based on visible sporocarps, 45 fungus species, including 15 redlisted, were identified among 4151 logs. When rarefying species accumulation curves to the same number of logs, we found no difference in species richness between old forest plots having high and low densities of new logs, or between plots where old logs were present or absent. Curves from young forest revealed fewer species than in old forest. Multiple regression analysis of six redlisted and six common species corroborated the rarefaction analysis in showing that the probability of occurrence was independent of the spatiotemporal distribution of logs for all but two common species. Aside from the fact that more dead wood harboured more wood-decaying fungi, we conclude that the spatiotemporal distribution of dead wood was of minor importance in determining species richness and abundances at the scales of <1 ha and <100 years. This suggests that wood-decaying fungi are not dispersal-limited at these scales, and it offers an optional element in forest management.     

Microdistribution of aluminum and manganese in the tea leaf tissues as revealed by X‐ray microanalyzer

Abstract

Tea plants (Thea sinensis L.) were found to accumulate large amount of Al (4457 ppm, D.W.) in their old leaves. The results showed that Mn stimulated the Al uptake and increased the Al content in the leaves. High concentrations of Ca and Mg in the soils decreased the Al and Mn and increased the Ca and Mg contents in the leaves. No phosphorus and aluminum interaction was found in the leaves of tea plants.

Microdistribution patterns of Al and Mn in the tea leaf tissues were also studied by means of a wavelength dispersive type X‐ray microanalyzer in conjunction with cryostage. The results of X‐ray micrographs showed that Al was densely deposited on the cell walls of the adaxial epidermis and palisade parenchyma cells of the old leaf tissues, and this distribution pattern of Al was different than that of Mn which was found mostly concentrated in the epidermal cells.     

Responses of phosphorus flux in the sediment–water interface to C:N:P stoichiometry of different sediment components following temperature warming in steppe wetland,China

Journal of Soils and Sediments - The objectives of this study were to (i) determine the ecological stoichiometry of sediment resources, sediment microbial biomass, and sediment enzyme following...     

Variations in the soil microbial community composition of a tropical montane forest ecosystem: Does tree species matter?

We investigated tree species effects on the soil microbial community in the tropical montane forest on Mt. Kinabalu, in Malaysian Borneo. We investigated microbial composition (lipid profile) and soil physicochemical parameters (pH, moisture, total C, N and phenolics concentration) in top 5-cm soils underneath two conifers (Dacrycarpus imbricatus and Dacrydium gracilis) and three broad-leaves (Lithocarpus clementianus, Palaquium rioence and Tristaniopsis clementis). We found that the primary difference in microbial composition was between conifer versus broad-leaves. The abundance of specific microbial biomarker lipids correlated with soil pH, total C and N. We conclude that tree species have significant impacts on the soil microbial community through their effects on soil pH, total C and N.     

Availability of cobalt‐60 to corn and bean seedlings as influenced by soil type,lime, and DTPA

Abstract

Uptake of Co by corn (Zea mays) and bush beans (Phaseolus vulgaris) seedlings was affected by plant species, soil type and soil amendment. Bean leaves preferentially accumulated ⁶⁰Co in comparison with corn leaves. Both the DTPA and (lime and DTPA) treatments enhanced ⁶⁰Co uptake by both plant species, notably in the Troup soil which had lower cation exchange capacity (CEC) and lower soil fertility in comparison with Dothan soil. Conversely, soils with lime but without the chelating agent suppressed ⁶⁰Co uptake. This dictates that farming practices should be closely evaluated if crops for livestock and human consumption are to be raised in fields contaminated by radionuclides.