Potential effect of land-leveling on soil fertility in a Brazilian rice soil

Land-leveling to improve water management in lowland rice (Oryza sativa L.) production is becoming common in many countries. This technique exposes subsoil by removal and deposition of surface soil from high- to low-lying areas. The potential effect of land-leveling on soil fertility was studied in samples from an alluvial soil at depths of 0- to 5-, 5- to 15-, and 15- to 25-cm. Levels of soil cation exchange capacity; dilute acid-fluoride extractable P; DTPA extractable Cu, Mn, and Zn; exchangeable K; hot-water soluble B; and organic matter decreased with soil depth; whereas, soil pH increased with depth. Relatively low amounts of dilute acid-fluoride extractable P, exchangeable K, and DTPA extractable Zn occurred in the 15- to 25-cm layer of the soil. These data indicate the high likelihood that K, P, and Zn deficiencies would occur in rice grown on the subsoil that was exposed by land-leveling.     

Aluminum stimulates the proliferation and differentiation of osteoblasts in vitro by a mechanism that is different from fluoride

Summary Micromolar concentrations of aluminum sulfate consistently stimulated [³H]thymidine incorporation into DNA and increased cellular alkaline phosphatase activity (an osteoblastic differentiation marker) in osteoblast-line cells of chicken and human. The stimulations were highly reproducible, and were biphasic and dose-dependent with the maximal stimulatory dose varied from experiment to experiment. The mitogenic doses of aluminum ion also stimulated collagen synthesis in cultured human osteosarcoma TE-85 cells, suggesting that aluminum ion might stimulate bone formation in vitro. The effects of mitogenic doses of aluminum ion on basal osteocalcin secretion by normal human osteoblasts could not be determined since there was little, if any, basal secretion of osteocalcin by these cells. 1,25 Dihydroxyvitamin D₃ significantly stimulated the secretion of osteocalcin and the specific activity of cellular alkaline phosphatase in the human osteoblasts. Although mitogenic concentrations of aluminum ion potentiated the 1,25 dihydroxyvitamin D₃-dependent stimulation of osteocalcin secretion, they significantly inhibited the hormone-mediated activation of cellular alkaline phosphatase activity. Mitogenic concentrations of aluminum ion did not stimulate cAMP production in human osteosarcoma TE85 cells, indicating that the mechanism of aluminum ion does not involve cAMP. The mitogenic activity of aluminum ion is different from that of fluoride because (a) unlike fluoride, its mitogenic activity was unaffected by culture medium changes; (b) unlike fluoride, its mitogenic activity was nonspecific for bone cells; and (c) aluminum ion interacted with fluoride on the stimulation of the proliferation of osteoblastic-line cells, and did not share the same rate-limiting step(s) as that of fluoride. PTH interacted with and potentiated the bone cell mitogenic activity of aluminum ion, and thereby is consistent with the possibility that the in vivo osteogenic actions of aluminum ion might depend on PTH. In summary, low concentrations of aluminum ion could act directly on osteoblasts to stimulate their proliferation and differentiation by a mechanism that is different from fluoride.     

菌根真菌对酸铝胁迫的响应

酸性环境中活性铝浓度升高可能抑制菌根真菌生长,为探讨酸性条件下菌根真菌对活性铝的响应机制,以拟青霉(Simplicillium sp.,Si)、细长孢霉(Mortierella elongate,Me)、木霉菌(Trichoderma spp.,Tr)、瓶头霉(Phialocephala,Ph)和葡萄状穗霉(Stachybotrys chartarum,Sc)5种菌根真菌为供试材料,采用PDA液体培养基单种纯培养以pH值为5.5设定3个Al3+浓度梯度,分别为对照(0 mmol·L^-1)、低铝(0.2 mmol·L^-1)和高铝(1.0 mmol·L^-1),研究酸性条件下不同活性铝浓度对菌根真菌的生物量、有机酸分泌以及N、P、K含量等的影响。结果表明:(1)除拟青霉(Si)外,其他菌株均不同程度受活性铝浓度影响,Si生物量随活性铝浓度增加而增加,低铝时比对照增加了238%(P<0.05),而细长孢霉(Me)、木霉菌(Tr)、瓶头霉(Ph)和葡萄状穗霉(Sc)生物量均降低,其中,Ph和Sc分别比对照降低了38.1%和72.5%(P<0.05)。(2)5种菌根真菌分泌有机酸存在显著性差异,Si、Me、Tr和Sc的H+分泌量在高铝浓度时均低于对照,对Si产生显著性差异(P<0.05);仅Me分泌草酸,对照的分泌量是高铝时的1.12倍。(3)5种菌根真菌N、P、K含量随不同活性铝浓度胁迫存在显著性差异,Si和Sc的P、K含量随活性铝浓度增加而显著增加(P<0.05);Me和Ph的N含量随活性铝浓度增加而显著降低(P<0.05),Me的P、K含量分别在低铝和高铝时达到峰值,Tr和Ph的N、P、K含量在低铝时达到峰值而在高铝时受到抑制。(4)Si、Me和Tr受酸铝影响不显著,属耐酸铝型菌株,Ph和Sc属酸铝敏感型菌株。本工作可为天山雪岭云杉森林更新与幼苗存活问题研究的深入开展提供基础依据。     

Shifting Trade Patterns as a Means of Reducing Global Carbon Dioxide Emissions

This article extends and applies the world trade model with bilateral trade (WTMBT), a linear program with any number of goods, factors, and regional trade partners that determines regional production, bilateral trade patterns, and region-specific prices on the basis of comparative advantage by minimizing factor use. The model provides a consistent analysis of the global production system, representing geographical location at a regional level, region-specific technologies at a sector level, emissions from production, and resource constraints and costs. An illustrative analysis investigates how changes in the geographic distribution of production could contribute to reducing global carbon dioxide (CO₂) emissions and at what cost. The model provides a bridge between global objectives and their determinants and consequences in specific sectors in individual regions. Multi-objective analysis is used to construct a trade-off curve between global factor costs and CO₂ emissions. The relevance of both primal and dual solution variables is demonstrated. In particular, changes in goods prices and emissions are investigated. We conclude that the main impact of tightening carbon constraints is a substantial reduction in international trade accompanied by a shift away from regions most reliant on the combustion of coal. In addition to the analysis of the overall global trends, including the impact on prices, the implications of the global carbon constraint for one specific industry are investigated.     

Role of some trace metal ions in placental membrane lipid peroxidation

The antioxidative and/or pro-oxidative potential of three trace metal ions, namely aluminum (Al), manganese (Mn), and selenium (Se), has been studied. The effect of Al and Mn was found to be anion independent. The pro-oxidative potential of Al was more prominent than its antioxidative potential. This may be due to its redox inert nature. The increase in lipid peroxidation rates in placental syncytiotroblast membranes may contribute to the etiology of aluminum toxicity. Selenium had an antioxidative potential only in the whole-cell homogenate. This appears to be mediated by glutathione peroxidase of which Se is a cofactor. Manganese proved to be the trace metal ion of choice. It decreased the production of thiobarbituric acid reactive substances (TBARS). This may be due to its capacity to quench the superoxide anion and hydroxyl radicals and also due to its chain-breaking capacity. During the present course, ferrous-ascorbate mediated lipid peroxidation has been studied using various combinations of FeSO₄ and ascorbic acid. Extrapolating the combined ratio of the individual combination as substrate concentration ([S]) and treating the observed amount of malondialdehyde (MDA) produced equivalent to initial velocity (v _i ), as in the case of enzymatic studies, the data were treated according to Michaelis-Menten kinetics and the values of k _c and C _max have been calculated.     

Aluminum chelation by 3-hydroxypyridin-4-ones in the rat demonstrated by microdialysis

The ability and site of the metal-chelating 3-hydroxypyridin-4-ones (HPs) to mobilize aluminum (Al) was assessed in Al-loaded rats using microdialysis. Four HPs with greatly varying lipophilicity were studied. One week after Al loading, microdialysis probes were implanted in the liver, a jugular vein, and the frontal cortex. An HP was given iv followed by continuous microdialysis for 5 h. Al concentrations in dialysates from the liver increased rapidly and were consistently greater than from blood, suggesting that liver was a primary site of Al chelation. Brain dialysate Al concentrations remained low, suggesting little Al chelation in the brain and little distribution of the Al HP complex into the brain. Al concentrations were determined in the main organs/tissues of a separate group of Al-loaded rats, and the percentage of the total Al body burden in each organ/tissue was calculated. The skeletal system and liver had 57 and 28% of the Al body burden, consistent with the liver as a primary site of Al chelation. The HPs chelate extravascular Al and have been shown by others to be orally active. They warrant further investigation as Al chelators.     

Effect of aluminum sulfate on litter composition and ammonia emission in a single flock of broilers up to 42 days of age

New alternatives are necessary if the environmental impact linked to intensive poultry production is to be reduced, and different litter handling methods should be explored. Among these, acidifying amendments added to poultry litters has been suggested as a management practice to help reduce the potential environmental effect involved in multiple flock cycles. There have been several studies on the use of aluminum sulfate (alum) and its benefits, but almost no data are available under farm conditions in Europe. An experiment with Ross 308 broilers from 1 to 42 days of age was conducted to evaluate the effect of alum on litter composition, the solubility of some mineral elements and NH₃ emission during a single flock-rearing period in commercial houses located in southeast Spain. Broilers were placed on clean wood shavings in four commercial houses, containing 20 000 broilers each. Before filling, alum was applied at a rate of 0.25 kg/m² to the wood shavings of two poultry houses, whereas the remaining two were used as control. Litter from each poultry house was sampled every 3 to 5 days. Ammonia emissions from the poultry houses were monitored from 37 to 42 days of age. In comparison with the control group, alum treatment significantly reduced the pH level of the litter (P < 0.001) with an average difference of 1.32 ± 0.24 units. Alum-treated litter showed, on average, a higher electrical conductivity than the control litter (5.52 v. 3.63 dS/m). The dry matter (DM) and total N and P contents did not show differences between the treatments (P > 0.05). Regarding the NH₄⁺-N content, alum-treated litter showed a higher value than the untreated litter, with an average difference of 0.16 ± 0.07% (on a DM basis). On average, alum-treated litter had lower water-soluble P, Zn and Cu contents than the untreated litter. Alum noticeably reduced the in-house ammonia concentration (P < 0.001), with an average of 4.8 ppm at 42 days of age (62.9% lower than the control), and ammonia emissions from 37 to 42 days of age were significantly reduced by the alum treatment (P < 0.001), representing a reduction of 73.3%. The lower pH values might have reduced ammonia volatilization from the litter, with a corresponding positive effect on the building environment and poultry health. For these reasons, litter amendment with alum could be recommended as a way of reducing the pollution potential of European broiler facilities during a single flock cycle.     

Effects of soil physics,chemistry, and microbiology on soil carbon sequestration in infertile red soils after long-term cultivation of perennial grasses

Determining the effect of perennial energy crop (PEC) cultivation on soil organic carbon (SOC) in marginal land soil is vital for carbon neutrality and bioeconomy development. However, a comprehensive and systematic evaluation of the response of SOC content to different PECs and its underlying drivers is still lacking. We used soil data collected from infertile red topsoil (0–20 cm) after 10 years of cultivation with Miscanthus (MS), Panicum virgatum (SG), and Saccharum arundinaceum (SA) to explore the changes in SOC stock induced by PEC. The roles of physical, chemical, and microbiological factors driving the increase in the SOC stock were investigated. Results revealed that SA and MS enhanced SOC stock by 87.97% and 27.52% relative to the uncultivated control. Conversely, PEC increased the percentage of soil mega-aggregates, geometric mean diameters, soil chelate iron (Fe), and aluminum (Al) oxides, and reduced soil acidity for the infertile red soils. In addition, fungal richness and diversity for PEC soils were enhanced compared to the unplanted soil. It is possible that PEC cultivation reduced the relative abundance of copiotrophic fungi but increased the relative abundance of oligotrophic fungi. Furthermore, variance partitioning analysis revealed that chemical and microbiological factors accounted for 80.54% of the total variation for the SOC stock. The partial least squares path model showed that PEC cultivation enhanced soil carbon (C) stock via soil deacidification and increased soil bacterial function. In conclusion, this study confirms the SOC sequestration potential of PEC cultivation in marginal land and the underlying mechanism driving SOC stock. The main positive factors controlling soil C sequestration included “pH,” while the negative factors were “bacterial community,” “fungal community,” and “bacterial function.” Our research may help encourage and support decision-makers of wasted marginal land conversion to PEC cultivation.     

A comparison of microbially and chemically reducible iron in three soils

Microbially reducible iron (water-soluble plus exchangeable forms) in three soils represented about 20% of the chemically reducible iron. The amount of iron reduced by microorganisms increased for about ten days to two weeks following flooding and thereafter remained constant. A similar trend was observed for the release of added Fe-59 in the soils following flooding, except that the reduction of labelled iron began earlier. In the more weathered soil, a higher proportion of the total iron was reduced by citrate-dithionite than in the relatively unweathered alluvial soils. Of labelled iron added, sequential reduction showed approximately 70% in the three soils was microbially reducible, an additional 20% was reduced by citrate-dithionite, and 10% of the labelled iron had moved into the residual form.