Impact of entomopathogenic nematodes on adults of Phyllotreta spp. (Coleoptera: Chrysomelidae) under laboratory conditions

Abstract

In 2005, preparations of four species of the entomopathogenic nematodes Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora, and H. megidis, were tested under laboratory conditions for their ability to kill adult flea beetles, Phyllotreta spp. (Coleoptera: Chrysomelidae). The nematode preparations were tested at doses of 200, 1000, and 2000 IJs per adult and at temperatures 15°C, 20°C, and 25°C. The numbers of beetles killed were recorded two, four, six, and eight days after treatment. The nematodes were more effective at 20°C and 25°C than at 15°C. At 20°C, the nematodes had killed between 44% (H. megidis at the lowest dose tested) and 77% (S. feltiae at the lowest dose tested) of the beetles eight days after treatment. At the two highest doses tested, the S. feltiae, S. carpocapsae, and H. bacteriophora preparations each killed at least 74% of the beetles at 25°C. Steinernema feltiae was the most effective nematode (LC₅₀=483–1467 IJs/adult) and, as an alternative to chemical insecticides, appears to have the highest potential for controlling overwintered flea beetles (May) under field conditions. The nematodes S. feltiae, S. carpocapsae and H. bacteriophora would all be suitable for controlling adult flea beetles during warm summer months, when flea beetles occur in high numbers in Slovenia.     

Differentiation of nitrogen and microbial community in the littoral and limnetic sediments of a large shallow eutrophic lake (Chaohu Lake,China)

Purpose

Nitrogen (N) is one of the major elements causing eutrophication in freshwater lakes, and the N cycle is mainly driven by microorganisms. Lake littoral zones are found to be “hotspots” for N removal from both the basin and receiving waters. However, the environmental factors that drive the distribution of microorganisms are diverse and unclear. Here, we examined the differentiation of nitrogen and microbial community between the littoral and limnetic sediments to explore their interactions.

Materials and methods

Sediment samples were collected in the littoral and limnetic zones of Chaohu Lake in winter (ca. 7 °C) and autumn (ca. 22 °C). Abundances of the bacterial and archaeal genes amoA (ammoxidation), nirS and nirK (denitrification), hzsB (anaerobic ammonium oxidation; anammox), and nrfA (dissimilatory nitrate reduction to ammonium; DNRA) were measured via quantitative real-time polymerase chain reaction (qPCR). Clone libraries were constructed for further phylogenetic analysis to study the community composition.

Results and discussion

We observed significant higher concentration values in terms of sedimentary NH₄⁺-N and NO₃^?-N in the limnetic zone than littoral zone (p?<?0.05; n?=?12). In general, abundance values of the above six genes in the littoral zone were all higher than those in the limnetic zone, while higher in winter (7 °C) than in autumn (22 °C) (p?<?0.05; n?=?6). The spatial heterogeneity had the most significant effect on the distribution of ammonia-oxidizing archaea (AOA) and anammox bacteria abundance. Both temporal (temperature) and spatial heterogeneity affected the abundance of ammonia-oxidizing bacteria (AOB). The variation in the abundance of denitrifying bacteria and DNRA bacteria mainly reflected the temporal (temperature) heterogeneity.

Conclusions

The six N-cycle-related microorganisms were affected by different environmental factors and presented different distribution patterns. The lower nitrogen content and the higher microbial abundance and diversity showed that the littoral zone was the “hotspot” of N-cycling-related microorganisms in a large, eutrophic, and turbid lake. It is suggested that increasing the area and restoring the ecological function of the littoral zone was effective and significant in eutrophic lake management.

     

Amylose and Amylopectin Interact in Retrogradation of Dispersed High-Amylose Starches

Retrogradation of three high-amylose starches (HAS: ae du, ae V, and ae VII) and common corn starch (CCS) was examined by dynamic oscillatory rheometry (7.5% [w/w] starch in 20% [v/v] dimethyl sulfoxide [DMSO]), differential scanning calorimetry (DSC; 30% [w/w] starch in water), and turbidity (0.5% [w/w] starch in 20% [v/v] DMSO). Nongranular lipid-free starch and starch fractions (amylose [AM], amylopectin [AP], and intermediate material [IM]) were studied. Gels were prepared by dispersing starches or fractions in 90% DMSO and diluting with water, followed by storage for seven days at 4°C. For AM from each starch, the elastic modulus (G′) was similar when heated from 6 to 70°C. The G′ of HAS AP gels at 6°C was higher than for CCS AP gels. For nongranular CCS and ae du gels, G′ dropped dramatically (≈100×) when heated from 6 to 70°C, less (≈10×) for ae V gels, and least (≈5×) for ae VII gels. By DSC, each AM endotherm had a peak temperature of ≈140°C, whereas all AP endotherms were complete before 120°C. Endotherms >120°C were not observed for any nongranular starch despite the high AM content of some starches. After cooling starch suspensions from room temperature to 5°C and subsequent rewarming to room temperature, each AM and the ae VII nongranular starch remained highly turbid. Each AP and the remaining nongranular starches lost turbidity during rewarming. Our work suggests that branched molecules of CCS and HAS influence gel properties of nongranular starches by inhibiting or altering AM-AM interactions.     

Diversity of anammox bacteria and abundance of functional genes for nitrogen cycling in the rhizosphere of submerged macrophytes in a freshwater lake in summer

Purpose

Submerged plants make an important contribution to nitrogen cycling in lakes including in the rhizosphere microenvironment through microbial activities. The main objective of this study was to investigate the abundance of functional genes for nitrogen cycling and the ecological relationship between these genes in the rhizosphere sediment of a freshwater lake in summer.

Materials and methods

Sediment from the rhizosphere of four submerged macrophytes (Ceratophyllum demersum, Hydrilla verticillata, Potamogeton maackianus, and Vallisneria spiralis) was sampled in Lake Liangzi, China, in summer. The anammox bacteria community structure and abundance of five functional genes for nitrogen cycling, ammonia monooxygenase (amoA) of ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA), anammox 16S rRNA, and nitrite reductase genes (nirK and nirS) in the sampled sediment, were determined.

Results and discussion

A total of 100 anammox gene sequences were grouped into eight operational taxonomic units (OTUs) and genus Ca. Kuenenia was the dominant species in Lake Liangzi in summer. Quantitative polymerase chain reaction (qPCR) revealed that gene copies of AOA amoA (2.42?×?10⁶ copies g^?1) were more than one order of magnitude higher than those of AOB amoA (1.98?×?10⁵ copies g^?1). The nirS gene (4.13?×?10⁸ copies g^?1) was more abundant than the nirK gene (7.28?×?10⁷ copies g^?1). There was no significant difference in the abundance of the AOB amoA gene among the rhizosphere of the four macrophytes. Redundancy analysis (RDA) showed a positive correlation between the abundance of the anammox 16S rRNA gene, AOA amoA and AOB amoA, which suggested two of these microbes may have provided a substrate for anammox bacteria in summer.

Conclusions

The diversity of anammox in the rhizosphere of submerged macrophytes of the freshwater lake in summer was very low, but the plant species could affect the abundance of most nitrogen circulating bacteria, especially for anammox bacteria. Anammox 16S rRNA gene was positively correlated with four other functional genes, indicating that all four genes had significant effects on anammox bacteria.

     

An Enhanced Direct Process Temperature Validation Framework in Composting: Case Study of a Full-Scale Covered Aerated Static Pile

ABSTRACT

To ensure the safety of compost products, the Canadian Council of Ministers of the Environment's compost guidelines specify upper limits for certain pathogenic and indicator microbes, which are presumably achieved by exposing every particle of compost to temperatures ≥55°C for at least three consecutive days. A rugged temperature probe that behaves like a random compost particle was used to investigate whether every compost particle meets the time temperature criterion and to measure sanitation efficacy. An inoculum consisting of Salmonella enterica var. Meleagridis, Escherichia coli K12, and phi-S1 bacteriophage (all at levels of ～1 × 10⁶ CFU/PFU mL^?1) was added into 17 probes. The probes were randomly introduced into a covered, aerated static pile along with 17 probes that only monitored the temperature. After 56 days of composting, with one pile turn the probes were recovered. Organism levels were determined via culture-based methods. Before turning, 80% of the randomly introduced probes satisfied the time-temperature criterion. After turning, this number increased to 87%, demonstrating that turning is somewhat useful for sanitation. The cool zones largely remained mesophilic with the pile turning having minimal impact, which could potentially be an indication that the pile was not turned thoroughly. One of the 17 probes with cryovials reached only 40.2°C, and survival of S. meleagridis (2.5 × 10⁶ CFU ml^?1) was observed. The remaining probes with cryovials exceeded 55°C and were pathogen free. It appears that the specified time-temperature conditions are likely adequate. However, more observations are needed before a firm conclusion can be made.     

Ryegrass Response to Mineral Fertilization and Organic Amendment with Municipal Solid Waste Compost in Two Tropical Agricultural Soils of Mali

Abstract

A pot experiment was conducted to assess the effect of mineral fertilization and compost on the growth and chemical composition of ryegrass (Lolium perenne L.) grown on two Malian agricultural soils coming from Baguinéda, abbreviated as Bgda, (12°23′ S, 7°45′ W) and Gao (16°18′ N, 0°). Treatments included non‐fertilized control, NPK alone, NPK + C₂₅, NPK + C₅₀, NPK + C₁₀₀, PK + C₅₀, NK + C₅₀, NP + C₅₀, K + C₅₀, P + C₅₀, N + C₅₀, and C₅₀ alone, where NPK represents the non modified Hoagland's solution and C₂₅, C₅₀, and C₁₀₀ represent the different rates (25, 50, and 100 T/ha) of compost. Compost and mineral fertilization significantly increased dry matter production. The application of 50 T/ha of compost alone increased the dry matter yield by 10 and 17.5% while mineral nitrogen–phosphorus–potassium (NPK) increased yield by 69.7 and 65% for Gao and Bgda, respectively. The combination of compost and mineral NPK (NPK + C₂₅ for Gao and NPK + C₅₀ for Bgda) affected the highest dry matter yield. For both soils, N concentrations in plants increased significantly with compost rate. Phosphorus and K concentrations in plants varied according to the soil. The application of compost increased the uptake of iron (Fe), manganese (Mn), zinc (Zn), copper (Cu), and potassium (K from both soils). Increases in soil organic carbon, available P, calcium (Ca), magnesium (Mg), Fe, Mn, Zn, Cu, K, and pH were observed in treatments receiving compost. Therefore, compost appeared to be a good supplier of nutrients for tropical soils.     

Turbulent mixing accelerates PAH desorption due to fragmentation of sediment particle aggregates

Purpose

Stripping contaminants from sediments with granular activated carbon (GAC) is a promising remediation technique in which the effectiveness depends on the rate of contaminant extraction from the sediment by the GAC. The purpose of the present study was to investigate the effect of mixing intensity on the short-term extraction rate of polycyclic aromatic hydrocarbons (PAHs) from contaminated sediment.

Materials and methods

PAH desorption from sediment at a wide range of rotational speeds (min^?1; rotations per minute (rpm)) was monitored by uptake in Tenax polymeric resins using a completely mixed batch reactor. Desorption data were interpreted using a radial diffusion model. Desorption parameters obtained with the radial diffusion model were correlated with particle size measurements and interpreted mechanistically.

Results and discussion

Fast desorption rate constants, D _e /r ², with D _e the effective diffusion coefficient and r the particle radius, ranged from 3.7 × 10^?3 to 1.1 × 10^?1 day^?1 (PHE) and 6 × 10^?6 to 1.9 × 10^?4 day^?1 (CHR), respectively, and increased with the intensity of mixing. The D _e /r ² values would correspond to D _e ranges of 1.8 × 10^?14–1.2 × 10^?16 m² × day^?1 and 1.8 × 10^?12–3.7 × 10^?15 m² × day^?1, assuming fast desorption from the measured smallest particle size (9 μm) classes at 200 and 600 rpm, respectively.

Conclusions

Desorption of PAHs was significantly accelerated by a reduction of particle aggregate size caused by shear forces that were induced by mixing. The effective intra-particle diffusion coefficients, D _e , were larger at higher mixing rates.

     

The effect of preplant nitrogen and soil temperature on yield and nitrogen accumulation of alfalfa 1

Abstract

Recommendations for the use of preplant N in alfalfa establishment are controversial. Growth chamber experiments were conducted to examine the effect of preplant N and soil temperature on yield and N accumulation of alfalfa (Medicago sativa L.). Alfalfa was grown in river sand at three day/night soil temperatures (18/12°C, 24/16°C, and 27/21°C), and at five levels of preplant N (0, 10, 20, 40, 80 kg ha^?1). At 18/12°C, 40 kg ha^?1 preplant N resulted in a 69% increase in shoot dry matter yield. Dry matter and N accumulation rates were greatest at 40 and 80 kg ha^?1. Preplant N effects on dry matter and N accumulation at 18/12°C were expressed primarily between the early bud and early flowering stages. Assessment of soil temperature and soil N availability is necessary to determine the potential for a yield response of alfalfa to preplant N.     

Transformation of clay minerals in nanoparticles of several zonal soils in China

Purpose

Clay minerals significantly affect the physical, chemical, and biological processes of soils. They undergo spontaneous modification and transformation depending to the climatic conditions. Information concerning the compositions and transformation of clay minerals in nanoparticle colloids (NPs) (25–100 nm) is severely lacking. Studying clay mineral transformation is important approach to understand soil formation. This study was conducted to determine the transformation sequence of clay minerals in several zonal soil NPs.

Materials and methods

Four soils (Haplustalf, Alf-1; Hapludalf, Alf-2; Hapludults, Ult-1 and Ult-2) were collected from B horizons developed under three different climatic zones of China. Alf-1 (36° 05′ N and 117° 24′ E) was located under a warm temperate zone and Alf-2 (30° 38′ N and 115° 26′ E), Ult-1 (29° 13′ N and 113° 46′ E), and Ult-2 (19° 27′ N and 109° 17′ E) under a subtropical zone. The clay particles (<?2000 nm) (CPs) and nanoparticles (25–100 nm) (NPs) of tested soils were separated. The element composition of CPs and NPs was identified by microwave digestion method. The mineralogy and chemical bonding of clay minerals were studied by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR).

Results and discussion

With decreasing latitude, NPs and CPs showed that the molar ratio of SiO₂ to Al₂O₃ trends to diminish, indicating the phenomenon of desilication and allitization in the tested soils. XRD analysis revealed that the main clay mineral of Alf-1 NPs was illite, followed by vermiculite, kaolinite, and kaolinite interstratified minerals (KIMs). The clay minerals of Alf-2, Ult-1, and Ult-2 NPs were dominated by kaolinite (and KIMs), followed by illite, with a little content of hydroxyl-interlayered vermiculite (HIV) in Ult-1 NPs and trace content of gibbsite in Ult-2 NPs. With decreasing latitude, vermiculite and HIV decreased in NPs. When compared to CPs, smectite as well as illite-vermiculite mix-layer mineral (I-V) and illite-HIV mix-layer mineral (I-HIV) were not detected in NPs. The analysis of d060 region by XRD showed that with decreasing latitude, the main clay minerals in NPs were dioctahedral minerals (e.g., illite or kaolinite). These clay minerals resulted from the transformation of trioctahedral minerals in CPs. The disappearance of 2:1 swelling minerals and trioctahedral minerals showed that the NPs were more susceptible to weathering than CPs.

Conclusions

With decreasing latitude, the transformation of clay minerals followed the sequence of illite?→?HIV?→?kaolinite?→?gibbsite in tested NPs.

     

Changes in phosphorus fractions in three tropical soils amended with corn cob and rice husk biochars

ABSTRACT

The formation of phosphorus (P) compounds including iron-P, aluminum-P and calcium-P in highly weathered tropical soils can be altered upon biochar addition. We investigated the effect of corn cob biochar (CC) and rice husk biochar (RH) pyrolyzed at three temperatures (300°C, 450°C and 650°C) on phosphorus (P) fractions of three contrasting soils. A 90d incubation study was conducted by mixing biochar with soil at a rate of 1% w/w and at 70% field capacity. Sequential P fraction was performed on biochar, soil and soil-biochar mixtures. Increase in most labile P (resin-P_i, NaHCO₃-P_i) and organic P fraction (NaHCO₃-P_o + NaOH-P_o) in CC and RH biochars were inversely related to increasing temperature. HCl-P_i and residual P increased with increasing temperature. Interaction of CC and RH with soils resulted in an increase in most labile P as well as moderately labile P (NaOH-P_i) fractions in the soils. CC increased most labile P in the soils more than RH. The increase in most labile P fraction in soils was more significant at relatively lower temperatures (300°C and 450°C) than 650°C. However, the increase in HCl-P_i and residual P of the soils was more predominant at high temperature (650°C). The study suggested that biochar pyrolyzed at 300–450°C could be used to increase P bioavailability in tropical soils.     

Mineralization and microbial biomass formation in upland soil amended with some tropical plant residues at different temperatures

A model experiment was carried out at 15, 25, and 35°C to investigate the changes in microbial biomass and the pattern of mineralization in upland soil during 8 weeks following the addition of 8 organic materials including 6 tropical plant residues, ipil ipil (Leucaena leucocephala), azolla (Azolla pinnata), water hyacinth (Eichhornia crassipes), dhaincha (Sesbania rostrata), cowpea (Vigna unguiculata), and sunhemp (Crotalaria juncea). The amounts of CO₂-C evolved and inorganic N produced at 35°C were about 2 times larger than those at 15°C. At any temperature, the flush decomposition of C was observed within the first week and thereafter the rate of mineralization became relatively slow. A negative correlation was observed between inorganic N and C/N ratios of the added organic materials. The relationships between the amounts of cellulose or cellulose plus hemicellulose and the amount of mineralized N of the added organic materials were also negative.

The changes in the microbial biomass were affected by temperatures. The amount of biomass C and N was maximum after 42 d of incubation at 15°C, and after 7 d at 25 and 35°C, and thereafter decreased. The rate of biomass decline was slower at 15°C and faster at 35°C than at 25°C. Regardless of the temperatures, the addition of organic materials enhanced microbial biomass formation throughout the incubation periods.     

Influence of temperature on the growth of bermudagrass selections from the Appalachian region

Abstract

The hilly terrain of the Appalachian region creates an environment in which large differences in soil temperature occur over a very short distance on the landscape. The ability of a grass to display adequate growth over a range of temperatures would greatly enhance its adaptability and use as a forage or for soil conservation. A growth chamber experiment was conducted to evaluate the influence of temperature on the growth of six bermudagrass [Cynodon dactylon (L.) Pers.] selections from the Appalachian region. Midland, a cold tolerant bermudagrass, was included in the study for comparison purposes. The grasses were grown under a 14 hour day length with three day/night temperature regimes: 18°C/13°C, 27°C/21°C, and 35^OC/29°C. Two of the selections had significantly higher dry matter production than Midland over the range of temperatures.

This effect was especially pronounced at 35°C where the top growth of Quicksand common and Selection 13 exceeded that of Midland by 206% and 158%, respectively. The higher yielding selections were comparable to the other bermudagrasses when mineral concentrations, neutral detergent fiber, acid detergent fiber and acid detergent lignin levels were considered. Both Quicksand common and Selection 13 seem to have the potential to be particularily useful on south facing slopes where elevated soil temperatures are encountered.     

Rheological and Thermal Properties of Aged Starch Pastes from Three Waxy Maize Genotypes

The rheological and thermal properties of aged starch gels (15:85 starch-water) from three waxy maize genotypes (wx, wx sh1, and du wx) during storage (4°C for up to 25 days) were studied. After storage, changes of storage modulus (G′) and phase angle (δ) of the gels as a function of temperature were measured using oscillatory rheometry. For the du wx samples, G′ at 25°C increased rapidly during the first four days of storage at 4°C, compared to the gradual increases over the 25-day storage period for the wx and wx sh1 samples. A peak in G′ at 45°C was observed during heating for the du wx samples after 10 days of storage and for the wx sample stored for 25 days. The G′ peak may have been due to syneresis in the gels. Retrogradation of amylopectin of the aged starch samples was examined using differential scanning calorimetry. The du wx starch had greater retrogradation enthalpies than the other two samples (which showed similar retrogradation behavior) throughout the storage. The retrogradation enthalpy of the du wx samples increased rapidly during the first seven days, followed by a slower increase through the rest of storage. For the wx and wx sh1 samples, no endotherm was observed during the first four days of storage, after which the enthalpy increased steadily as a function of storage time. Addition of sucrose delayed the formation of gel networks for all three starches. The greater tendency for gelling and retrogradation of the du wx starch might be attributed to the greater proportion of DP20–30 chains of the amylopectin.     

β-Glucanase Activity and Molecular Weight of β-Glucans in Barley After Various Treatments

β-Glucanase activity interferes with molecular characterization of mixed-linkage (1→3)(1→4)-β-d -glucans (β-glucans). Reductions in β-glucanase activity were determined after barley cvs. Azhul, Waxbar, and Baronesse were treated with autoclaving (120°C, 45 min), calcium chloride (0.05M, 1 hr), 70% ethanol (80°C, 4 hr), hydrochloric acid (0.1N, 1 hr), oven heating (120 and 140°C, 40 min), sodium hydroxide (0.0025M, 1 hr), and 5% trichloroacetic acid (TCA) (40°C, 1 hr). High-performance size-exclusion chromatography (HPSEC) of α-amylase-treated aqueous extracts was used to demonstrate the effects of treatments on the molecular weights of β-glucans. The HPSEC system included multiple-angle, laser light scattering, refractive index, and fluorescence detectors. β-Glucanase activities, ranging from 52 to 65 U/kg of barley, were reduced by autoclaving (50–75%), hot alcohol (67–76%), oven heating (40–96%), CaCl₂ (75–95%), NaOH (76–89%), and TCA (92–96%). Some malt β-glucanase activity remained after most treatments. HCl and TCA treatments reduced extraction and molecular weights of β-glucans. Weight-average molecular weights (M_w) for β-glucans extracted with water at 23°C were low (most <8 × 10⁵). Base treatment (pH 9) and extraction at 100°C for 2.5 hr resulted in the greatest extraction of β-glucans and highest M_w. As a result, the conditions seem appropriate for measurement of physical characteristics of β-glucans in cereal products.     

Effects of soil texture and gravel content on the infiltration and soil loss of spoil heaps under simulated rainfall

Purpose

Large spoil heaps formed during construction projects have caused serious soil erosion and threatened ecological security. The recent researches on soil erosion of spoil heaps are based on one or several soil types, which can only represent the soil texture category within the limited area, but cannot be used in other larger scale areas. Soil texture and gravel are the main factors affecting infiltration and erosion processes of spoil heaps.

Materials and methods

The runoff plot dimensions were 5.0 m?×?1.0 m?×?0.5 m (length × width × depth). A series of rainfall experiments with a constant rainfall intensity of 1.0 mm min^?1 and a slope gradient of 25° were conducted to investigate the effects of soil texture (sandy, loam, and clay) and gravel mass content (GC, 0%, 10%, 20%, and 30%) on the infiltration and erosion processes. The gravels are divided into 3 classes according to particle size 2–14 mm (small), 14–25 mm (medium), 25–50 mm (large), and the mass ratios were 30%, 50%, and 20%. The duration of each rainfall event was 45 min after runoff out of the plot.

Results and discussion

Results showed that there was a critical GC (10%) improving or controlling infiltration and soil loss. Infiltration rate of sandy spoil heap (SSH) decreased within 45 min, but it decreased first and then stabilized for loam spoil heap (LSH) and clay spoil heap (CSH). Soil loss rate (SLR) of SSH stabilized first and then increased, while it decreased and then stabilized for LSH and CSH. SLR at early stage (0–18 min) was 0.08–0.23 times than it was at later stage (18–45 min) for SSH, but it was 2.06–5.06 times and 1.46–1.95 times for LSH and CSH, respectively. The soil texture had a more significant effect on SLR (P?< 0.05) than GC did. The effects of gravel on SLRs were dependent on soil texture.

Conclusions

The greater the GC was, the lower the SLR was for the spoil heaps. Special attention should be paid to the later stage during rainfall events for SSHs and the early stage for LSHs and CSHs when considering erosion protection measures.

     

Response of mango tree nutritional status and biochemical constituents to boron and nitrogen fertilization

Abstract

A field experiment was conducted at Al Malak Valley Farm, El-Sharkeya Governorate-Egypt (30°–51° N; 32°–53° E) using 15 years old productive mango (Mangifera indica L.) trees cv. Zebda. The experiment was repeated for two successive seasons (2014/2015) and (2015/2016). The trees were planted 8×8 meters apart in sandy soil under drip irrigation system using the Nile water. Treatments included three concentrations of boron (0.0, 250, 500?mg L^?1) and three concentrations of nitrogen (1000, 1250, 1500?g nitrogen/tree/year). Boron was applied as foliar spray of boric acid and nitrogen was applied to the soil as ammonium sulfate. Treatments were arranged in a factorial Completely Randomized Block Design with three replicates for each treatment. Results show that boron application has improved mango tree nutritional status. Leaf nitrogen, phosphorus, potassium and boron concentrations significantly increased as the boron application rate increased. In addition, boron application resulted in significant increase in leaf total chlorophyll, total carbohydrates, total sugars, carbon/nitrogen (C/N) ratio and decrease in total phenol content. Boron showed higher impact than nitrogen on all tested parameters. The interaction treatment of 250?mg L^?1 boron and 1500?g/tree nitrogen proved to be the best treatment.     

Estimation of imogolite in soils and clays by DTA

Abstract

DTA (differential thermal analysis) was used on mixtures of allophane and imogolite, and a calibration curve for estimating imogolite was obtained using the height of the endothermic peak near 400°C. This peak occurs between 390°C to 430°C, is distinctive and can be used to estimate imogolite in clay fractions and soils. An endothermic peak near 470°C observed in some Andisols probably arises from dehydroxylation of hydrated glass.     

Organic matter determination in arid region soils: loss-on-ignition versus wet oxidation

ABSTRACT

The precise assessment of soil organic matter (SOM) is required when studying soil pedology, chemistry, physics, and fertility. Besides, it is a key for evaluating soil quality, plant growth, and sustainable land management. This research aims to correlate the SOM resulted from loss-on-ignition (LOI) with those from wet combustion (Walkley–Black, WB). A total of 130 soil samples were collected from Egypt and analyzed using WB and LOI. In LOI, samples exposed to the combustion temperatures of 300, 375, 430, and 550°C for 2 and 4 hours. Using RStudio, simple linear regressions were conducted to estimate the most suitable temperature/time combinations. The results showed that applying lower temperatures (300 and 375°C) for 2 hours provided a strong correlation between LOI and WB with R² of 93 and 94% for all dataset and sandy soils, respectively. For clay soils the respective R² values at 300 and 375°C were 83 and 85%. The proposed combinations were valid to estimate SOM content for different soils with correlation up to 0.99 for sandy soils.     

Foliar Injuries Caused by Ozone in Betula pubescens Ehrh. and Phleum pratense L. as Influenced by Climatic Conditions Before and During O3 Exposure

Seedlings of Betula pubescens Ehrh. (mountain birch) and Phleum pratense L. (timothy) were grown for 42 days under full light or 50% shade in the field at 12°C, and at comparable photosynthetic active radiation (PAR) levels in a greenhouse at 18°C. Plants from the four pretreatments were exposed to 78 nmol mol^-1 (ppb) O₃ (8 h day^-1) under two temperatures (15 and 25°C), two relative air humidities (50 and 80% RH) or two CO₂     

Digestion of plant tissue for analysis by ICP emission spectroscopy

Abstract

A method of digesting plant tissue samples for multi‐element analysis by inductively‐coupled plasma (ICP) emission spectroscopy was developed which does not require the use of HclO₄. A substitute oxidant, H₂O₂, eliminated the hazards associated with hot, concentrated HClO₄. Optimal conditions for pre‐digestion and digestion were investigated.

The procedure adopted consists of a pre‐digestion in concentrated HNO₃ from room temperature to 60°C in 30 min followed by digestion at 90°C for 90 min with the addition of 30% H₂O₂ Analysis of NBS standard tissue samples by the proposed method gave results in good agreement with analysis following digestion in HNO₃,‐HClO₄ and with certified values, except for Fe.