Assimilation of ammonia by the azolla‐anabaena symbiosis

¹⁵N‐labeled ammonia was rapidly assimilated by Azolla caroliniana and incorporated into plant material even though sustained growth of the fern‐algae symbiosis cannot be maintained with ammonia as nitrogen source. During ammonia uptake, the nitrogenous pool of the fern rapidly increases and contains large amounts of free ammonia and glutamine. N₂ fixation activity of the algal symbiont declines during assimilation of ammonia, but it is restored to a high level upon transfer of plants to nitrogen‐free media, as the pool ammonia content decreases. During growth of the fern on N₂, the algal symbiont supplies ammonia in a manner permitting sustained growth of the plant. Exogenous ammonia, therefore, appears to interrupt regulation of inorganic nitrogen metabolism of the plant‐algal symbiosis.     

Removal of 17α-Ethinylestradiol by Biogenic Manganese Oxides Produced by the Pseudomonas putida strain MnB1

Synthetic and persistent endocrine disrupting chemicals (EDCs) such as 17α-ethinylestradiol (EE2) have been frequently detected in the effluent of wastewater treatment plants and induce hazards to humans and wildlife. In this study, biogenic Mn oxides were tested for the removal of EE2, and factors affecting the reaction were also investigated. The biogenic Mn oxides produced by Pseudomonas putida strain MnB1 were nano-sized and poorly crystallized particles. A concentration of 7.9 mg l⁻¹ biogenic Mn oxides showed 87% EE2 (1 mg l⁻¹) removal efficiency in 2 h, which confirms the excellent potential of biogenic Mn oxides for removal of estrogens. EE2 removal was enhanced at high Mn oxide doses and at low pH. Co-existing heavy metals significantly inhibit EE2 removal, due to their competition for the reactive sites of biogenic Mn oxides. Humic acid (HA) also obstructed EE2 removal, but the adverse effect was alleviated as HA concentration increased, possibly due to the formation of soluble complexes with the released Mn²⁺, of which adsorption onto Mn oxides reduces surface reactive sites.     

Estimation of soil pollution by the main ecotoxicants in the Vorob’evy Gory nature park

Soils of the Vorob’evy Gory nature park (Moscow) are characterized by a high content of technogenic ecotoxicants. Dangerous levels of pollution are fixed on ∼60% of soil cover for benzopyrene, ∼40% of soil cover for heavy metals, and ∼6% of soil cover for mineral oils. Besides the total high aerogenic load, the local sources of soil pollution in cities are highways; increased concentrations of heavy metals are also registered near unauthorized dumps. Benzopyrene and mineral oils are characterized by high migratory ability in soils and can form secondary auras of pollution in accumulative landscape facies.     

Is invasion of deforested Amazonia by the earthworm Pontoscolex corethrurus driven by soil texture and chemical properties?

Pontoscolex corethurus (Müller, 1857) is the most common invasive earthworm in disturbed lands in the tropics. Conditions required for its successful colonization of new plots are still not understood since some areas can be invaded while others, sometimes in the vicinity, are not. We kept newly hatched P. corethrurus in a wide range of Amazonian soils where population densities had been previously evaluated. We identified soil conditions that best sustain survival, soil ingestion and growth of P. corethrurus in controlled laboratory conditions and checked if presence/absence in the field was consistent with laboratory observations. While pH and Ca influenced survival; Mg and C content were the greatest determinants for growth and C:P, Mg and clay contents determined soil ingestion rates. Soil ingestion and growth rate were correlated. There were no differences in earthworm soil ingestion rates between invaded and non-invaded soils. However, growth rate and survival were higher in soils from invaded sites than in soils from non invaded sites, indicating that soil quality may play a role in the invasion process. We identified two cases where P. corethrurus did not occur: (1) unfavourable soil texture and chemical properties, but also some areas with and (2) favourable soil texture and chemical properties but no invasion. Other parameters, like vegetation cover (grass or trees), soil structure and compaction, soil hydrologic processes or biotic resistance of native earthworm communities could potentially also be key elements for understanding why P. corethrurus populations occur in some sites and not in others.     

Extreme pollution of soils by emissions of the copper–nickel industrial complex in the Kola Peninsula

The distribution of the total Ni, Cu, Co, Cd, Pb, and Zn contents was studied in the soil profiles of six catenas in the zone subjected to emissions of the copper-nickel industrial complex, which is the largest source of SO₂ and heavy metals in northern Europe. The results show that, at present, the concentrations of Ni and Cu in the upper organic soil horizons in the impact zone reach extreme levels of 9000 and 6000 mg/kg, respectively. Under conditions of the long-term intense multi-element industrial emissions, the modern levels of the accumulation of polluting substances in soils greatly depend on the indirect factors, such as the degree of the technogenic degradation of soils with the loss of a significant part of soil organic matter, the reaching of threshold saturation of the topsoil with polluting metals, and competitive relationships between chemical elements. The state of the ecosystems in the impact zone varied greatly and did not always agree with the contents of the main metals-pollutants in the soils. The moisture conditions determined by the landscape position affected significantly the resistance of the ecosystems to emissions.     

Is earthworms' dispersal facilitated by the ecosystem engineering activities of conspecifics?

In this work, we documented the influence of earthworm's galleries on their speed of movements during dispersal events in the soil. We quantified, by using X-rays, the dispersal behaviour of earthworms in the soil. The observations were conducted in mesocosms in controlled conditions for 12?h. Our experiments revealed that during a dispersal sequence of a batch of individuals of the species Aporrectodea terrestris (Savigny 1826): (a) individuals used preferentially existing conspecifics' galleries, (b) individual velocity increased after each dispersal event and (c) the lag time before each dispersal event did not seem to be influenced by previous dispersers. Therefore, dispersal seems to be facilitated by conspecifics' activity, which strongly supports the hypothesis of a feedback between ecosystem engineers' activity and their dispersal speed.     

Are the rates of photosynthesis stimulated by the carbon sink strength of rhizobial and arbuscular mycorrhizal symbioses?

Rhizobial and arbuscular mycorrhizal (AM) symbioses each may consume 4-16% of recently photosynthetically-fixed carbon to maintain their growth, activity and reserves. Rhizobia and AM fungi improve plant photosynthesis through N and P acquisition, but increased nutrient uptake by these symbionts does not fully explain observed increases in the rate of photosynthesis of symbiotic plants. In this paper, we test the hypothesis that carbon sink strength of rhizobial and AM symbioses stimulates the rates of photosynthesis. Nutrient-independent effects of rhizobial and AM symbioses result in direct compensation of C costs at the source. We calculated the response ratios of photosynthesis and nutrient mass fraction in the leaves of legumes inoculated with rhizobial and/or AM fungi relative to non-inoculated plants in a number of published studies. On average, photosynthetic rates were significantly increased by 28 and 14% due to rhizobial and AM symbioses, respectively, and 51% due to dual symbiosis. The leaf P mass fraction was increased significantly by 13% due to rhizobial symbioses. Although the increases were not significant, AM symbioses increased leaf P mass fraction by 6% and dual symbioses by 41%. The leaf N mass fraction was not significantly affected by any of the rhizobial, AM and dual symbioses. The rate of photosynthesis increased substantially more than the C costs of the rhizobial and AM symbioses. The inoculation of legumes with rhizobia and/or AM fungi, which resulted in sink stimulation of photosynthesis, improved the photosynthetic nutrient use efficiency and the proportion of seed yield in relation to the total plant biomass (harvest index). Sink stimulation represent an adaptation mechanism that allows legumes to take advantage of nutrient supply from their microsymbionts without compromising the total amount of photosynthates available for plant growth.     

Availability and diffusion kinetic process of phosphorus in the water–sediment interface assessed by the high-resolution DGT technique

Journal of Soils and Sediments - Desorption of phosphorus (P) bound to iron-containing minerals (Fe-P) is a crucial component of the eutrophication process in lakes. However, the main process and...     

Factors affecting the adsorption of micro‐amounts of tagged phosphorus by soils

Abstract

Adsorption of a small amount of P by soil from a solution, which delivers concentrations approximating the composition of soil solution systems, was measured for a heterogeneous group of 343 soils using ³²P‐labelled KH₂PO₄ solution. The method allowed accurate determination of small quantities of P and identified the P under consideration as that added from solution. Simple correlations and stepvise linear regression analyses indicated that soil pH, Ca, P, Al, Fe, organic matter and particle size significantly influenced the amount of P adsorbed by the soils.     

Oxidative Degradation of EDTA in Aqueous Solution by the Bimetallic Fe–Cu

Water, Air, &; Soil Pollution - The sorption behaviors of brilliant blue FCF dye by natural clay and modified with iron chloride were determined. The materials were characterized by X-ray...     

Effect of the Extraction Period on the Routine Assessment of Soil P Status by Ion‐Exchange Resin Membranes

The cation–anion exchange resin membrane (CAERM) system is one of the most promising alternative methodologies for the assessment of soil phosphorus (P) availability. Nevertheless, the CAERM method has a recommended period of extraction (16 h) that limits its applicability. With the aim to improve the use of CAERM in routine laboratory work, seven extraction times were studied and compared for repeatability and biological accuracy, using 150 samples of soils and covering a wide range of properties. The results showed dissimilar quantities of extractable P, according to the nature of soils and the period of extraction time. On average of all soils, values of extractable P ranged from a 2.4 mg kg^?1 and 26.7 mg kg^?1 in 0.25‐h and 16‐h extraction times, respectively. Relative to the repeatability aspects, the results reveal a tendency of increasing results with the decrease of the period of extraction, showing coefficient variation (CV) values ranging from 5% (16 h) to 14% (0.25 h). All the extraction periods tested for the CAERM presented highly significant values of r (0.824–0.943) between extractable P and each of the three biological parameters: relative yield of ryegrass, P content, and P uptake. Considering the three biological parameters simultaneously, the best results were obtained for extraction periods of 8 h, 2 h, and 4 h. Based on the results, and considering both practical and accuracy aspects, it is conclude that 2 h of extraction is a valid alternative to the 16‐h standard extraction period for the CAERM methodology.     

Evaluation of the growth and quality of the “Ife Plum” tomato as affected by boron and calcium fertilization

A local variety of tomato (Lycopersicon esculentum, Ife plum cv. 51691) was grown in soil culture for 5 months and treated with B at concentrations of 0, 1, 2, 4, 8, and 16 ppm as H₃BO₃, and Ca at 0, 40, 80, and 160 ppm as Ca(OH)₂. A significantly positive correlation was established between organic matter and water ‐ soluble B (r = 0.970), while the relationship between pH and B was negative (r = ‐0.490). Application of B at 2 ppm improved all growth parameters studied. Boron application higher than 2 ppm, induced leaf chlorosis and later necrosis of nodes and roots. Fruit yield correlated positively with soil ‐ B, stem diameter and floral number (r = 0.597, r = 0.650 and r = 0.812, respectively). Soil‐ and plant‐B were positively correlated (r = 0.790). Calcium when applied singly at higher levels increased total chlorophyll content of the leaf. Tomato fruit yield was optimum at B:Ca treatment concentration of 2 ppm B (4.48 kg/ha B) and 160 ppm Ca (358.4 kg/ha Ca), corresponding to a B:Ca fertilizer ratio of 1.80.     

Corn Growth as Affected by Plastic Cover Under Drip Irrigation Condition in the Desert

Plastic cover,as a method to minimize soil water evaporation and improve water use efficiency,was used for corn during the whole growing period in a desert area.Field Studies were conducted to determine the effect of plastic covering nmanagement on corn growth and rooting pattern and its relationship with changes in climate.Four treatments.0) bared soil without cover,1) covering one side of the crop,2) covering both sides of the crop,and 3) covering the surface totally,were established on a sandy loam soil.Results showed that treatment 0 was significantly different from others and revealed that plastic covering was not always good to corn growht.Improper usage of plastic cover might weaken root development and thereafter lower the total yield of the crop.Suitable practices cvombining different methods discussed could not only improve water use efficiency but also increase the crop yield.     

Metabolites of the fungistatic agent 2β-methoxyclovan-9α-ol by Macrophomina phaseolina

Biotransformation of 2β-methoxyclovan-9α-ol (1), a fungistatic agent against Botrytis cinerea, was investigated with Macrophomina phaseolina. Demethoxylation, regioselective oxidation at C-9 and C-13, and inversion of the configuration at C-9 of compound 1 afforded six oxidative metabolites, 2β-methoxyclovan-9-one (2), clovan-2β,9β-diol (3), clovan-2β,9α-diol (4), clovan-2β,13-diol-9-one (5), 2β-methoxyclovan-9α,13-diol (6), and clovan-2β,9β,13-triol (7). Compounds 5-7 are described here for the first time, and their structures were deduced by different spectroscopic techniques. The antifungal activity of new metabolites 5-7 was also evaluated against B. cinerea.     

Long-Term Organic Nutrient Management Fosters the Eubacterial Community Diversity in the Indian Semi-arid Alfisol as Revealed by Length Heterogeneity–PCR

Agricultural practices influence the community structure and functional diversity of soil microorganisms. In the present study, the impact of nutrient-management systems on the changes in the biological properties of Indian semi-arid Alfisol was assessed. The long-term organically managed (OGF) and inorganically fertilized (IGF) soils from century-old experimental plots were compared for eubacterial diversity using amplicon length heterogeneity PCR (LH-PCR) targeting three hypervariable domains (V1, V1_V2, and V3) of 16S rRNA gene. Of these domains, V1_V2 could discriminate the bacterial communities between the soil types. The relative ratios of amplicons differed between OGF and ICF soils, and eubacterial diversity was decreased substantially because of the inorganic chemical fertilizers, as compared to organic amendments. The Bray–Curtis similarity index and diversity indices of amplicons were greater in OGF soil than in ICF soil. This polyphasic approach revealed that the diversity and functionality of the soil eubacterial community were encouraged by long-term organic manures more than inorganic chemical fertilizers.     

An Oxidative Mechanism for the Inhibition of Iodothyronine 5′-Monodeiodinase Activity by Lead Nitrate in the Fish,Heteropneustes fossilis

An oxidative mechanism in the lead-induced inhibition of thyroid function with special reference to iodothyronine 5′- monodeiodinase (5′-ID) activity has been identified in the fish, Heteropneustes fossilis. Lead treatment (2.5, 5.0 and 10.0 ppm of lead nitrate/day for 30 days) enhanced tissue lipid peroxidation (LPO) and decreased the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). In addition, serum triiodothyronine (T3) concentration and hepatic 5'-ID activity were markedly decreased by 10 ppm of lead nitrate. These findings support the view that higher concentrations of lead nitrate inhibit the extrathyroidal conversion of thyroxine (T4) to T3. Moreover, oxidative stress from lead intoxication could be responsible for inhibiting 5′-ID activity.     

Estimating the Demand for Organic Foods by Consumers at Farmers’ Markets in Northwest Arkansas

To answer the question, “How interested in buying organic foods are the majority of the current shoppers at our farmers’ market?,” more than 300 consumers at three diverse farmers’ market locations were surveyed for their organic food purchasing habits. Comparisons were made between purchasers who were new to purchasing organic foods and purchasers who had been buying organic foods for many years. Analysis showed that a majority of respondents (74%) were frequent purchasers of organic foods, buying once or twice a month and a significant percentage (44%) of those had been purchasing organic foods for 7 years or more. Opportunities exist to expand organic sales at these farmers’ markets in Arkansas, where only 42% purchased most of their organic foods and 80% surveyed answered “yes” that they would buy more organic if its price was similar to that of conventional foods.     

The measurement of low concentrations of ammonia in the atmosphere by flow‐injection analysis

Abstract

A flow injection procedure, based on the reaction between ammonia, salicylate, nitroprusside and alkaline dichlorisocyanurate, was developed which enabled changes in the concentration of ammonia in the atmosphere to be monitored at 15 minute intervals. The detection limit was 10 ppb NH₃‐N in solution for a working range of 0 ‐ 1000 ppb, corresponding to a concentration in the air of 4 μg NH₃‐N/m³. Regression analysis revealed a complex inter‐relationship between the concentrations of the reagents. The method was validated by the close correlation obtained between the results with a cross‐check analysis by ion chromatography and its use demonstrated by following the volatilization of ammonia from a soil core treated with urine.     

Is Nitrous Oxide Reduction Primarily Regulated by the Fungi-to-Bacteria Abundance Ratio in Fertilized Soils?

The production of nitrous oxide (N₂O) is a widespread trait in fungi and is of interest because denitrifying fungi lack the N₂O reductase gene (nosZ) that regulates N₂O reduction to nitrogen gas (N₂). The adaptive ability of soil fungi is better than that of bacteria in acidic soils. We investigated the N₂O reduction potential, described by the N₂O product ratio (R_N2O), N₂O/(N₂O+N₂), in soils of different types of fields under crop cultivation with different fertilizer inputs and a bare fallow field with no fertilization as a control. The fungi-to-bacteria abundance ratio (R_F/B) was negatively correlated (P < 0.01) with the natural pH of the soil; however, the high value of R_F/B measured in vineyards was due to the large inputs of manure. When the denitrification potential was measured at natural pH values of soils, R_N2O was negatively correlated (P < 0.01) with soil pH. When the denitrification potential was measured after short-term modifications of soil pH, however, no significant correlation was found between R_N2O and the modified pH. Based on stepwise multiple regression analysis, soil pH and residual nitrate (NO₃^-) were the key factors regulating N₂O reduction in soils at natural pH values (R²=0.88, P < 0.001), whereas the key factor was the soil residual NO₃^- alone (R²=0.83, P < 0.001) when the soil pH was modified. When the effect of the soil chemical properties was weakened, a high R_F/B value had the potential (P < 0.01) to affect N₂O reduction; however, the role of fungi was offset by the presence of denitrifying bacteria. These results provide evidence that compared to the indirect effects of R_F/B, the direct effects of the soil chemical properties have a greater effect on N₂O reduction in fertilized soils.     

Shortcut Approach Alternative to the Step‐by‐Step Conventional Soil Phosphorus Fractionation Method

Abstract

In an attempt to characterize the phosphorus (P)–supplying capacity of a soil and to understand the dynamics of soil P, a procedure was followed whereby consecutive extraction procedures were carried out on a soil sample, first by dialysis membrane tubes filled with hydrous ferric oxide (DMT‐HFO), followed by subsequent P fractionation procedure. However, this combined method is lengthy and time‐consuming, and an approach to shorten these P desorption studies in soils was important. The major objective of this article, therefore, was to present a shortcut method as an alternative approach to the combined fractionation method. Comparison of the sum of DMT‐HFO‐P_i, sodium bicarbonate (NaHCO₃)‐P_i, sodium hydroxide (NaOH)‐P_i, D/hydrochloric acid (HCl)‐P_i, and C/HCl‐P_i extracted by a conventional step‐by‐step method with the sum of DMT‐HFO‐P_i and a single D/HCl‐P_i extraction as a shortcut approach for all extraction periods resulted in a very strong and significant correlations. Both these methods were correlated with maize grain yield, and it was found to be highly significant. This study revealed that this shortcut approach could be a simplified and economically viable option to study the P dynamics of soils especially for soils where the P pool acting as a source in replenishing the labile portion of P is already identified.