Release of exchangeable and non-exchangeable magnesium from nigerian soils on cropping with maize or chemical extraction

A greenhouse experiment with maize (Zea Mays L.) using 12 representative soils of Western Nigeria indicated that the rate of release of non-exchangeable Mg was too slow to meet crop requirements. Total Mg removed by four successive crops of maize (y) was well correlated with initial exchangeable Mg (x) (y = 6.34 + 1.06 x, r = 0.996***) suggesting that neutral N NH₄OA c-extractable Mg is the best measure of available Mg in these soils even under intensive cropping. The slow release of non-exchangeable-extractable Mg in the soils may be due to low percentages of silt and clay and their mineralogy. Total and non-exchangeable Mg extracted by acidified N NH₄OA c (pH 1.0) in 15 min at a soil extractant ratio of 1:5 correlated best with the total and non-exchangeable Mg removed by cropping (r = 0.944*** and 0.734*** respectively). The use of such an acid extractant on these soils is, however, open to question in view of the relatively large amounts of non-exchangeable Mg extracted by it compared with that extracted by cropping. Incipient Mg deficiency symptoms appeared in two-week-old plants when they contained 0.11–0.15% Mg. Persistent deficiency symptoms were associated with 0.1% Mg in the plants, 21–22 parts/10⁶ exchangeable Mg and 5% (or less) Mg saturation of CEC.     

Exogenous γ‐aminobutyric acid alleviates oxidative damage caused by aluminium and proton stresses on barley seedlings

BACKGROUND: Proton (H⁺) and aluminium (Al³⁺) toxicities are major factors limiting crop production on acid soils, while γ‐aminobutyric acid (GABA) is a non‐protein amino acid involved in various stress tolerances in plants. In this study, to determine whether exogenous GABA is functional in alleviating oxidative stress induced by H⁺ and Al³⁺ toxicities, the antioxidant defence response regulated by GABA was investigated in barley (Hordeum vulgare L.). RESULTS: After 24 h treatments of seedlings under H⁺, Al³⁺ and combined stresses with and without GABA, morphological and biochemical assays were conducted. It was observed that the inhibition of seedling root elongation caused by Al³⁺ and H⁺ toxicities was significantly mitigated by GABA. The amount of carbonylated proteins with molecular masses of 14.4–97 kDa was decreased. The activities of antioxidant enzymes were enhanced, the content of malondialdehyde was reduced and the accumulation of reactive oxygen species (ROS), as shown by staining roots with nitroblue tetrazolium, declined in GABA‐treated seedlings. CONCLUSION: GABA can alleviate oxidative damage caused by H⁺ and Al³⁺ toxicities in barley seedlings by activating antioxidant defence responses and reducing the elevated levels of carbonylated proteins caused by ROS. Copyright © 2010 Society of Chemical Industry     

Release of nitrogen,sulphur, phosphorus,calcium, magnesium,potassium and sodium from four tropical hays during their digestion in nylon bags in the rumen

The rate of release of N, S, P, Ca, Mg, K and Na from four milled tropical hays in nylon bags in the rumen of cattle over a 168 h period were measured. The hays were: Medicago sativa, Stylosanthes humilis, Chloris barbata and Heteropogon contortus. Three ways were used to express results: (a)element as % of element initially present; (b) element as % of dry matter initially present, and (c) element as its concentration in residual dry matter. The proportions of elements removed during digestion were positively related to initial concentration of the elements in the hays, with the exception of P in C. barbata hay. High proportions of Mg and K were released within 48 h in all hays. Only about 60% of N, P and Ca initially present was removed even after 168 h in the rumen. Amounts of elements remaining became constant for each element after 48 h and were for N, 6.0; Ca, 3.0; K, 1.0; P, 0.7; Na, 0.7; S, 0.5 and Mg, 0.3 g element kg^?1 DM initially present. Concentrations of elements in the residual dry matter after decreasing in the first 24 h, increased in the latter stages of digestion, even though cell wall digestion continued. The four hays released the seven elements differently. Generally, the elements in Medicago were most soluble and those in Heteropogon the least. However, the extent of solubilisation in Stylosanthes and in Chloris varied with the element concerned. In Heteropogon hay, which had low element concentrations initially, less than half of the N, S, P, Ca and Na were released even after 168 h digestion.     

Gastric H+, K+-ATPase Inhibition,and Antioxidant Properties of Selected Commonly Consumed Vegetable Sources

Oxidative stress and upregulation of gastric H⁺, K⁺-ATPase enzyme activity have been known to cause ulcer pathogenicity for which safer drugs are yet to be identified. Aqueous extracts of seven commonly consumed vegetable sources were screened for inhibition of H⁺, K⁺-ATPase and antioxidant activities. Results indicated that Z. officinale (Ginger) followed by M. arvensis (Pudina) are potent gastroprotective sources with inhibition of H⁺, K⁺-ATPase of IC₅₀ of 18.3 ± 0.7 and 25.2 ± 0.9 μg gallic acid equivalents/ml respectively, which is almost equivalent or better than the known inhibition of H⁺, K⁺-ATPase—Omeprazole (IC₅₀ ?27 μg/ml). Further, all these vegetable extracts showed multi-potent antioxidant activity, such as free radical scavenging, reducing power ability, and inhibition of lipid peroxidation, which are required to inhibit complex steps of ulcerations. On the basis of the absolute amounts and potency of inhibition of H⁺, K⁺-ATPase as well as antioxidant activity of individual phenolic acids, the relative percentage contribution of phenolic acids from different vegetable extracts to both inhibition of H⁺, K⁺-ATPase and antioxidant activity was calculated and data revealed that gentisic and protocatechuic acid contributes significantly to both inhibition of H⁺, K⁺-ATPase and antioxidant activity.     

Fertiliser requirements of potatoes in relation to kind of soil and soil analysis

Responses of maincrop potatoes to N, P and K fertilisers were measured in 119 experiments done by Soil Scientists of the National Agricultural Advisory Service in the years 1955-62. The experimental sites were spread over 13 soil groups, most of which corresponded to particular soil series. Average crop responses to P and K are given for each soil group. The amount of response was related to soil texture and to content of soluble P or K in the soil. For a given content of soluble P in the soil, crops on loamy sand and sandy loam soils gave a larger response to the first level of P fertiliser (0.5 cwt P₂O₅ per acre) than did those on silty loams, clay loams and clays; but the additional response to the second level of P fertiliser and, consequently to the optimum dressings of P, was greater for crops grown on the heavier-textured soils. P response was also related to depth of freely drained soil, sites with impeded drainage giving larger responses to P than freely drained sites. The proportion of soils poor in K, crop responses to K and optimum dressings of K fertiliser were all greater for the loamy sands and sandy loams than for the silty loam, clay loam and clay soils. The optimum dressings of N and K for almost all the soil groups were less than the average amounts currently used on maincrop potatoes in Great Britain; however, the seasons seem to have been relatively unfavourable to N and K responses. For P, the average amounts used were less than the optimum for most of the silty loam, clay loam and clay soils but more than the optimum for most soils of lighter texture.     

Estimation of non-exchangeable potassium in soils using a cation-exchange resin

Studies of a cation-exchange resin method for the estimation of non-exchangeable potassium in soils showed that the release of potassium was dependent on the quantity of resin in contact with the soil. Continuous shaking of the resin-soil mixture for 20 h at 80° formed the basis of a reliable method for the routine analysis of non-exchangeable potassium.     

Nitrogen release dynamics and transformation of slow release fertiliser products and their effects on tea yield and quality

BACKGROUND: Tea (Camellia sinensis (L.) O. Kuntze) is a perennial leaf harvested crop. It requires more nitrogen than most other crops and preferentially utilises NH₄⁺ to NO₃^? when both are available in the soil. It is expected that slow release fertilisers coupled with a nitrification inhibitor could improve the N use efficiency and simultaneously reduce environmental pollution. In this study, three slow release fertilisers were developed and tested: Ca? Mg phosphate coated urea with dicyandiamide (DCD) as a nitrification inhibitor and polyolefin coated urea with and without DCD. The main aim was to compare the nitrogen release dynamics and transformation of these fertilisers and their effects on tea yield and quality. RESULTS: The results showed that the coatings significantly slowed N release and kept mineral N in soils at a higher concentration for a longer time compared to uncoated urea. Polyolefin was a superior coating to Ca? Mg phosphate. DCD was an effective nitrification inhibitor and significantly reduced the ratio of nitrate to total mineral N in a highly acidic tea soil. The ¹⁵N use efficiency was 29% where uncoated fertiliser was applied and 46% where polyolefin coated fertiliser with DCD was applied. The application of slow release fertilisers increased the chlorophyll content in mature leaves and enhanced the uptake of mineral elements by tea plants. Bud sprouting, shoot growth and mature leaf longevity were significantly improved, resulting in higher biomass of tea plants. Slow release fertilisers increased the yield of shoots by 51–143% (mean, 106%) in a pot experiment and 4–14% (mean, 9%) in a field experiment compared to uncoated urea. Tea quality parameters, especially free amino acids, were also significantly increased. CONCLUSION: Slow release fertilisers, especially polyolefin coated urea with DCD could significantly increase the N use efficiency and improve tea growth. Their uses in tea fields not only improved the profit margin, but possibly reduced environmental pollution. Copyright © 2008 Society of Chemical Industry     

H+‐ATPase‐Defective Variants of Lactobacillus delbrueckii subsp. bulgaricus Contribute to Inhibition of Postacidification of Yogurt during Chilled Storage

Continued acid production by Lactobacillus delbrueckii subsp. bulgaricus during the chilled storage of yogurt is the major cause of postacidification, resulting in a short shelf life. Two H⁺‐ATPase defective variants of L. delbrueckii subsp. bulgaricus were successfully isolated and their H⁺‐ATPase activities were reduced by 51.3% and 34.3%, respectively. It was shown that growth and acid production of variants were remarkably inhibited. The variants were more sensitive to acidic condition and had a significant rate for inactivation of H⁺‐ATPase by N, N‐dicyclohexylcarbodiimide (DCCD), along with a low H⁺‐extrusion, suggesting that H⁺‐ATPase is direct response for H⁺‐extrusion. In addition, the variants were also more sensitive to NaCl, while H⁺‐ATPase activities of variants and parent strain were significantly enhanced by NaCl stress. Obviously, H⁺‐ATPase might be involved in Na⁺ transportation. Furthermore, variants were inoculated in fermented milk to ferment yogurt. There was no significant difference in flavor, whereas the postacidification of yogurt during chilled storage was remarkably inhibited. It is suggested that application of L. delbrueckii subsp. bulgaricus with reduced H⁺‐ATPase activity in yogurt fermentation is one of effect, economic and simple avenues of inhibiting postacidification of yogurt during refrigerated storage, giving a longer shelf life. Practical Application: During yogurt fermentation, continued acid production by Lactobacillus delbrueckii subsp. bulgaricus during the chilled storage of yogurt leads to milk fermentation with high postacidification, resulting in a short shelf life. In this work, 2 acid‐sensitive variant strains of L. delbrueckii subsp. bulgaricus were isolated. The characteristics related to H⁺‐ATPase were compared and it was observed that milk fermented by the variants had lower postacidification, giving a longer shelf life. Application of L. delbrueckii subsp. bulgaricus with reduced H⁺‐ATPase activity in yogurt fermentation might be one of effect, economic and simple avenues of inhibiting yogurt postacidification during chilled storage, giving a longer shelf life.     

Effect of beet vinasse on germination and seedling performance of ryegrass (Lolium multiflorum Lam cv Barwoltra)

The effect of a concentrated, depotassified beet vinasse (desugared beet molasses) on both germination (in vitro and in soil) and seedling development (in soil) of ryegrass Lolium multiflorum has been studied. Germination and root elongation of the ryegrass in vitro were more negatively affected by vinasse (concentration of 0.15 and 0.5% w) than those of cress (Lepidium sativum). Seedling emergence of ryegrass in pots sown in three different soils (a moderately acid, sandy loam soil, without CaCO₃; a red, sandy clay loam soil, 12% CaCO₃; and a light yellowish-brown sandy clay loam soil, 30% CaCO₃) was, in general, not affected by the application of a moderate dose of pure vinasse ( ～ 3 t ha^?1) at sowing or 30 days before. Only in the acid soil was seedling emergence significantly (P < 0.05) limited during the first week. The application of vinasse at sowing caused an initial significant shortening (P < 0.05) of the primary roots of ryegrass in the three soils studied (measured at the fourth day). However, plant fresh weights (measured at the thirtieth day) were not affected by this treatment, especially in the calcareous soils. In general, the vinasse application produced beneficial results for ryegrass seedling in the three soils.     

Optimization of Trace Metals Concentration on Citric Acid Production by Aspergillus niger NRRL 2001

Citric acid is nowadays produced by submerged fermentation of Aspergillus niger. The process yield depends on the composition of the medium, as well as on the microorganism strain. In this work, the effect of Fe⁺³, Zn⁺², and Mn⁺² on citric acid production by A. niger NRRL 2001 is presented. The culture medium composition was glucose (120 g/L) KH₂PO₄ (1.0 g/L); K₂HPO₄ (1.0 g/L), MgSO₄.7H₂O (0.5 g/L), (NH₄)₂SO₄ (3.0 g/L). The ions Fe⁺³, Zn⁺², and Mn⁺² had their concentrations changed according to an experimental design. The experiments were carried out in an orbital shaker at 200 rpm and 30°C. The strain produced an extracellular polysaccharide that was also quantified. The optimum experimental condition was found using 7.0 mg/L of Fe⁺³ and 6.5 mg/L of Zn⁺² in absence of Mn⁺². No oxalic acid formation was observed using this experimental condition. Metal contents were not significant for the production of the polysaccharide. The highest production rate (2.95 g L⁻¹ day⁻¹) was reached after 10 days of fermentation. After this period, the productivity decreased slightly. In 20 days, the citric acid production rate (2.44 g L⁻¹ day⁻¹) was 82% of the highest productivity. The conversion into citric acid increased continuously, yielding 45.8% in 20 days of fermentation.     

Potassium retention and release in rothamsted and saxmundham soils

The retention and release of K from ‘No K ’and K-treated soils from the Rothamsted Classical Experiments and Saxmundham Experiment were examined using K-Ca exchange equilibria and the kinetics of K release to Ca-saturated resin. Free energies and enthalpies of Ca→K exchange showed that Saxmundham soils had the greater preference for K, and that residual K from long-term manuring significantly decreased K binding strength and preference. K release kinetics showed that residual K increased the rate of K release chiefly from the ‘surface’ region, and the amount of K released from ‘surface’ and ‘peripheral’ regions of 2:1 layer silicates in soils. The increased K release from ‘peripheral’ regions of K fertilised soils, together with their decreased K preference, was associated with slowly reversible K fixation on the weathered periphery of 2:1 layer silicates.     

Temperature and pH affect copper release kinetics from copper metal foil and commercial copperware to food simulants

ABSTRACT

Copper (Cu) metal and alloys are used in cookware and other food contact surfaces due to their desirable properties for various applications. However, Cu metal can ionise and subsequently transfer to food and beverages under certain conditions. Here, we tested how pH and temperature affected Cu release kinetics using model systems utilising Cu metal foil and commercially available copperware. Cu foil and copperware were exposed to food simulants composed of 3% (w:w) aqueous solutions of citric acid, malic acid, acetic acid, or deionised (DI) water at temperatures ranging from 4°C to 60°C. An additional pilot experiment tested how simulated long-term cleaning affected subsequent Cu release from lined and unlined copperware to 3% citric acid. Food simulants were then analysed by ICP-MS for total Cu. After 180 min, incubation of Cu metal foil with acid-containing food simulants at 4°C resulted in Cu release ranging from 8.7 - 14.0 µg cm^?2, while 21.5–38.1 µg cm^?2 was released at 60°C. In contrast, Cu transfer from metal foil to DI water was relatively low, with <0.6 µg cm^?2 released after 180 min at 60°C. With citric acid food simulant, lined copperware released between 0.6 and 3.0 µg Cu cm^?2 over 180 min at the set temperatures, while unlined copperware released approximately 25–45 fold higher amounts of Cu (26.9–74.6 µg cm^?2) over this same time period. In contrast, use of DI water food simulant resulted in Cu release of <0.1 µg cm^?2 for the lined copperware and <2 µg cm^?2 for the unlined type. No significant effect of simulated long-term cleaning on Cu release from copperware was observed. These data indicate that Cu release is affected by temperature and pH, and that specific steps can be taken to limit Cu metal release from food contact surfaces to foods and beverages.     

Properties,Classification and Management Implications of Soils of Illela Sand Dunes,Northwestern Nigeria

Soils representative of the stabilised Illela sand dunes in northwestern Nigeria were examined in the field and additional properties of four pedons determined in the laboratory. The soils are deep, dark-brown and sandy throughout their profile. Organic carbon contents are very low, less than 2 g kg⁻¹, and with the siliceous parent material the consequence is low amounts of available nutrients, particularly Ca, K, Mg and N. However, P is moderate to high due to the occurrence of phosphatic nodules at depth. Available micronutrients, Cu, Zn, Mn and Fe, are generally above the critical limits and are adequate for most crops. The high bulk density and low porosity constituted largely of macroporosity impart low water-holding capacity to the soils. Quartz is the dominant mineral in the sand and silt fractions while kaolinite dominates the clay fraction of the soils. According to the USDA Soil Taxonomy and FAO/UNESCO systems of soil classification, all pedons are classified as Ustic Quartzipsamments or Ferralic Arenosols, except four pedon 2 which is classified as Arenic Haplustult or Haplic Acrisol. From the general characteristics of the soils, it is recommended that proper organic matter management via the incorporation of crop residues into the soil, the use of organic manure and crop rotation involving legumes, will greatly enhance the productivity of the soils.     

Comparative study of physiological adaptation to salt stress in the genome shuffled Candida versatilis and a wild-type salt-tolerant yeast strain

Candida versatilis is a yeast with a complex salt-tolerant system. It can maintain normal physiological activities and metabolic fermentation under a high-salt environment. The cellular mechanisms of adaptation to salt stress in strains of a wild type of C. versatilis (WT) and S3–5, genome shuffling strains of C. versatilis with improved tolerance to salt, were investigated. The content of intra- and extra-cellular glycerol, intra-cellular Na⁺, as well as membrane fluidity and permeability, were determined under salt-stressed yeast growth conditions. The results showed that Na⁺/H⁺-antiporter played a primary role in Na⁺ extrusion and H⁺-ATPase has been associated with yeast survival under salt stress. Considerable amounts of glycerol were produced and secreted by the yeast to outside the cell under this salt stress. Changes in the portion of membrane saturated and unsaturated fatty acid composition of C. versatilis in response to osmotic stress lead to membrane permeability and fluidity decreases. They could restrict the influx of Na⁺, enhance H⁺-ATPase activity, and prevent leakage of glycerol across the cell membrane under osmotic stress. The salt tolerance of genome shuffled strain S3–5 was higher than WT. It could be correlated with a higher level of intra-cellular accumulation of glycerol and sodium ions in cells of S3–5 than WT as well as a higher portion of oleic fatty acid (C18: 1) and a lower level of linoleic acid (C18: 2) in cell membranes of the studied yeast mutant. It can be concluded that S3–5 improved physiological regulatory mechanisms of response to salt stress, such as decreased membrane fluidity and a permeability that rapidly adjusted to osmotic stress.     

Effects of waterlogging at different stages of development on the growth and yield of winter wheat

The response of winter wheat to waterlogging at different stages of growth outdoors was studied for 3 years using lysimeters containing undisturbed monoliths of sandy loam and clay soils. The treatments were selected as the most extreme likely to occur in field conditions in Britain, i.e. waterlogging to the soil surface for up to 16 days in October, 42 days in January and February and 6 days in May. Waterlogging in midwinter was common to all experiments. Yield losses from mid-winter waterlogging ranged from 15% when yields were heavy (10 t ha^?1), to nil when yields were light (3-4 t ha^?1) after the plants had been affected by frost damage in late winter and by take-all. Winter wheat was most sensitive to waterlogging after germination but before emergence. At this stage, 16 days waterlogging killed all seedlings and 6 days waterlogging depressed plant populations to 12% (clay) and 38% (sandy loam) of the control. However, there was vigorous compensatory growth in the remainder of the growing season and yield was only depressed to about 82% of the control. When the crop was waterlogged at any stage after emergence plant populations were not affected; however, winter waterlogging treatments usually depressed shoot numbers and, to a lesser extent, ear numbers at harvest. Shoot survival under waterlogged conditions seemed related to nitrogen availability in the soil. The amount of ‘take-all’ (Gaeumannomyces graminis var. tritici) was increased by waterlogging.     

Antioxidative and Anti-Inflammatory Neuroprotective Effects of Astaxanthin and Canthaxanthin in Nerve Growth Factor Differentiated PC12 Cells

ABSTRACT: Nerve growth factor differentiated PC12 cells were used to examine the antioxidative and anti‐inflammatory effects of astaxanthin (AX) and canthaxanthin (CX). PC12 cells were pretreated with AX or CX at 10 or 20 μM, and followed by exposure of hydrogen peroxide (H₂O₂) or 1‐methyl‐4‐phenylpyridinium ion (MPP⁺) to induce cell injury. H₂O₂ or MPP⁺ treatment significantly decreased cell viability, increased lactate dehydrogenase (LDH) release, enhanced DNA fragmentation, and lowered mitochondrial membrane potential (MMP) (P < 0.05). The pretreatments from AX or CX concentration‐dependently alleviated H₂O₂ or MPP⁺‐induced cell death, LDH release, DNA fragmentation, and MMP reduction (P < 0.05). Either H₂O₂ or MPP⁺ treatment significantly increased malonyldialdehyde (MDA) and reactive oxygen species (ROS) formations, decreased glutathione content, and lowered glutathione peroxidase (GPX) and catalase activities (P < 0.05). The pretreatments from AX or CX significantly retained GPX and catalase activities, and decreased MDA and ROS formations (P < 0.05). H₂O₂ or MPP⁺ treatment significantly decreased Na⁺‐K⁺‐ATPase activity, elevated caspase‐3 activity and levels of interleukin (IL)‐1, IL‐6, and tumor necrosis factor (TNF)‐α (P < 0.05); and the pretreatments from these agents significantly restored Na⁺‐K⁺‐ATPase activity, suppressed caspase‐3 activity and release of IL‐1, IL‐6, and TNF‐α (P < 0.05). Based on the observed antioxidative and anti‐inflammatory protection from AX and CX, these 2 compounds were potent agents against neurodegenerative disorder.     

Effect of drought and irrigation on the fate of nitrogen applied to cut permanent grass swards in lysimeters: Nitrogen balance sheet and the effect of sward destruction and ploughing on nitrogen mineralisation

Fuor years after ¹⁵N labelled fertiliser nitrogen (as Ca(NO₃)₂ and equivalent to 400 kg N ha^?1) was applied to permanent grass swards growing in lysimeter monoliths, approximately one-quarter remained immobilised in soil organic matter. In the intervening years similar but non-labelled applications were made. Although differing rainfall regimes applied during the experiment had significantly affected nitrogen uptake by plants and nitrate loss in drainage, they caused no significant effect on the tracer nitrogen remaining in the soil, the ranges were 85–97 kg N ha^?1 and 79–94 kg N ha^?1 respectively for the 135 cm deep clay and silt loam soil monoliths. Labelled nitrogen unaccounted for in crop, drainage or soil was presumed to have been denitrified. These losses averaged 62 and 49 kg N ha^?1 on the clay and silt loam soils respectively; again the differing rainfall regimes caused no significant differences. The ratio between estimates of labelled nitrogen denitrified and of annual nitroux oxide loss was approximately 9:1 for both soils. The conversion from permanent grass to winter wheat in autumn 1981, involving killing and then burying the sward, resulted in no pronounced increase in net mineralisation of labelled nitrogen. However, the balance between crop uptake and the quantity leached did change. Labelled nitrogen assimilated was less for the wheat (growing without addition of fertiliser nitrogen) than for the grass in its last year, and the quantity leached was considerably greater than under grass swards that were supplied with an average rainfall distribution. Following the first wheat harvest total nitrogen leached averaged 51 and 44 kg N ha^?1 on the clay and silt loam soils respectively. Rates of nitrous oxide emissions during the autumn following sward destruction were greater than in earlier years, but this enhanced loss was of short duration. The crop clearly benefited from the succession of nitrogen applications made to grass, as grain yield and total nitrogen uptake exceeded 7 t ha^?1 and 120 kg N ha^?1 respectively on both soils. These quantities exceed the national averages for winter wheat and are also considerably greater than for crops from lysimeters which received no nitrogen fertiliser throughout the experiment.     

The removal of soluble organic carbon from synthetic winery wastewater by repeated application to soil

The removal of soluble organic carbon from synthetic winery wastewater containing uniformly ¹⁴Clabelled lactic acid and glycerol applied repeatedly to soils sampled at various depths from a brown earth and solod was determined from decreases in the solution concentration of ¹⁴C of soil extracts. A previously developed logistic model was used to quantify the adsorption and microbial metabolism of the ¹⁴C-compounds in the various soil layers. Adsorption of ¹⁴C-compounds to soil particles resulted in the removal of 10 to 50% of the added ¹⁴C within the first hour after wastewater application. It was greater in soils containing a higher percentage of clay and/or organic carbon. Repeating wastewater applications up to 17 times reduced initial adsorption by most of the soil layers of the brown earth, whereas little change occurred in the solod. Microbial uptake and metabolism were responsible for the removal of ¹⁴C-compounds remaining in solution to less than 5% of ¹⁴C input. In contrast with their effect on adsorption, repeated applications of wastewater decreased or eliminated the lag period before the onset of rapid metabolism and also increased the rates of metabolism of ¹⁴C-compounds in all soils. This led to significant reductions in the removal times of the soluble-¹⁴C. Acclimatisation of microbial populations in soils newly exposed to the wastewater was most rapid within the uppermost layers. Acclimatised soils were able to reduce the solution concentration of ¹⁴C to less than 5% of input levels within 1 d after application when the lag period lasted less than 2 h, and when the daily removal of solution-¹⁴C, due to microbial metabolism, exceeded the ¹⁴C input. Regular applications of wastewater were required to maintain rapid removal of the soluble-¹⁴C in acclimatised soils. Implications for managing the disposal of wastewaters rich in organic material on new and existing sites are discussed.     

Molecular hydrogen produced by elemental magnesium inhibits rumen fermentation and enhances methanogenesis in dairy cows

Hydrogen is a key metabolite that connects microbial fermentation and methanogenesis in the rumen. This study was to investigate the effects of elevated H₂ produced by elemental Mg on rumen fermentation and methanogenesis in dairy cows. Four nonlactating Chinese Holstein dairy cows were employed for this experiment in a replicated crossover design. The 2 dietary treatments included a basal diet supplemented with Mg(OH)₂ (14.5 g/kg of feed dry matter) or elemental Mg (6.00 g/kg of feed dry matter). When compared with Mg(OH)₂ treatment, cows fed diet with elemental Mg had similar rumen Mg²⁺ concentration, but higher rumen dissolved H₂ and methane concentrations at 2.5 h after morning feeding. Also, elemental Mg supplementation decreased feed digestibility, rumen volatile fatty acid concentration, and relative abundance of group Ruminococcaceae_UCG-014, genus Bifidobacterium, and group Mollicutes_RF9, increased acetate to propionate ratio, succinate concentration, and abundance of family Christensenellaceae. Elemental Mg supplementation increased enteric CH₄ emission, altered methanogen community with increased abundance of order Methanomassiliicoccales, 16S ribosomal RNA gene copies of methanogens, and order Methanobacteriales. In summary, the pulse of elevated dissolved H₂ after feeding produced by elemental Mg inhibited rumen fermentation and feed digestibility by decreasing the abundance of carbohydrate-degrading bacteria, promoted H₂ incorporation into succinate by increasing family Christensenellaceae and genus Bacteroidales_BS11, and increased H₂ utilization for methanogenesis by favoring growth of methanogens.     

Effect of Acid Pretreatment on the Stability of Ascorbic Acid Complexes with Various Iron Sources in a Wheat Flake Cereal

The effect of acid incubation of ascorbic acid with each of five iron sources (ferrous sulfate, ferric chloride, ferric orthophosphate, hydrogen and electrolytically reduced iron) on iron solubilization in a wheat flake cereal was evaluated. Incubation produced more soluble iron at pH 2 but not necessarily at the endogenous pH of the cereal nor at pH 6. At pH 2, Fe⁺² rather than Fe ⁺³ was produced, apparently by a reduction of bound Fe ⁺³ and subsequent release of Fe⁺². At pH 6, the soluble iron was mainly in a complexed form. This indicates that acid incubation with ascorbate might facilitate bioavailability of iron if it were incorporated by fortification techniques.