Some impacts of urban waste landfills on Mediterranean soils

Seventy soil samples around and under urban waste landfills in central Spain were studied for 28 physical and chemical properties. In the unaffected surroundings of landfills there is always a higher proportion of coarse and fine gravel. Chlorides, sulphates and nitrates increase noticeably in all the soils affected by landfills as do Na⁺, B³⁺ and Zn²⁺. Multivariate analyses show that higher or lower water retention in the surface layer plays a main role in the organization of both acid and sandier soils as well as of basic soils and those with a higher proportion of silt and clay. Depending on the acidity or basicity, however, the other main factors reveal different hierarchical levels in the soil variables with regard to the organization of these systems. Thus, in acid soils, Zn²⁺ and B³⁺ contribute most noticeably to the second hierarchical level in the edaphic organization. In basic soil without gypsum, the second important gradient of variation is the stoniness (gravel)–fine sand (<2 mm fraction) while the importance of the K⁺, B³⁺ and SO₄⁼ is relegated to the third factor. In the basic soils with gypsum, not only sulphate, but also Na⁺, Cl⁻ and Zn²⁺ plays an essential role in the first factor and the coarse surface elements are also important. The principal components analysis made it possible to establish the main factors involved in the degradation caused by leachates from landfills. Consequently, greater attention could be given to these factors with a view to rehabilitation of degraded soils. © 1998 John Wiley & Sons, Ltd.     

Browsing by red deer negatively impacts on soil nitrogen availability in regenerating native forest

Herbivores can have important indirect effects on belowground properties and processes that govern ecosystem form and productivity. A major way that herbivores affect ecosystem productivity is by modifying feedbacks that occur between dominant plants and belowground properties, and especially by changing the rates of nutrient mineralisation. In this study, we examine the effects of browsing by red deer, relative to landscape factors such as variations in microclimate and topography, on soil biological properties and N cycling in regenerating forest in an upland region of the Scottish Highlands. The site at Creag Meagaidh in the Scottish Highlands was sampled three times over the growing season of 2001 and soil cores were taken from four exclosures. Measures of soil biological properties and nitrogen availability were made. The results presented here suggest that although spatial and temporal variation were the dominant factors affecting soil biological properties and nitrogen dynamics in this ecosystem, herbivory also had consistent and significant effects on these measures. Browsing significantly reduced measures of DOC (27%), NO₃⁻ (48%), NH₄⁺ (49%) and N-mineralisation (53%). The microbial C:N ratio was also significantly greater (89%) in browsed than un-browsed areas, suggesting that the removal of deer reduced the extent that the microbial community was N-limited. These significant negative effects of browsing on soil nitrogen cycling have the potential to reduce ecosystem productivity. We conclude that removal of browsing over 14 years has accelerated native woodland regeneration, leading to subsequent increases in soil C- and N-mineralisation, further increasing plant N supply and tree growth in this ecosystem.     

生物质能技术的发展、经济和环境影响及展望

该文概述了生物质在整个能源供应中的重大贡献，以及国际上对生物质能的利用情况。对现代生物质能转换技术做了系统的介绍，分析了主要的生物质能转换途径的技术特点。根据生物质的生产成本和发电成本分析了生物质能的经济效益，从水土保持、农业生产、生物多样性等方面综合论述了生物质能开发利用对环境的影响。最后总结了生物质能发展的障碍并提出了相应的对策。     

Interplay of omnivory, energy channels and C availability in a microbial-based soil food web

 To study the effects of omnivory on the structure and function of soil food webs and on the control of trophic-level biomasses in soil, two food webs were established in microcosms. The first one contained fungi, bacteria, a fungivorous nematode (Aphelenchoides saprophilus) and a bacterivorous nematode (Caenorhabditis elegans), and the second one fungi, bacteria, the fungivore and an omnivorous nematode (Mesodiplogaster sp.) feeding on both bacteria and the fungivore. Half of the replicates of each food web received additional glucose. The microcosms were sampled destructively at 5, 9, 13 and 19 weeks to estimate the biomass of microbes and nematodes and the soil NH₄ ⁺-N concentration. The evolution of CO₂ was measured to assess microbial respiration. Microbial respiration was increased and soil NH₄ ⁺-N concentration decreased by the addition of glucose, whereas neither was affected by the food-web structure. Supplementary energy increased the biomass of fungi and the fungivore, but decreased the biomass of bacteria, the bacterivore and the omnivore. The omnivore achieved greater biomass than the bacterivore and reduced the bacterial biomass less than the bacterivore. The biomass of the fungivore was smaller in the presence of the omnivore than in the presence of the bacterivore at three sampling occasions. Fungal biomass was not affected by food-web structure. The results show that the effects of the omnivore were restricted to its resources, whereas more remote organisms and soil processes were not substantially influenced. The results also indicate that the presence of an omnivore does not necessarily alter the control of populations as compared with a food web containing distinct trophic levels, and that the fungal and bacterial channels may respond differently to changes in energy supply. Received: 15 December 1997     

Relating the biological stability of soil organic matter to energy availability in deep tropical soil profiles

Tropical subsoils contain large reservoirs of carbon (C), most of which is stored in soil organic matter (SOM). Subsoil OM is thought to be particularly stable against microbial decomposition due to various mechanisms and its position in the soil profile, potentially representing a long-term C sink. However, few experiments have explicitly investigated SOM stability and microbial activity across several orders of magnitude of soil C concentrations as a function of soil depth. The objective of this study was to evaluate the biological stability of SOM in the upper 1.4 m of tropical forest soil profiles. We did so by measuring CO₂ evolution during a 90-day laboratory incubation experiment on a sample set that was previously characterized for C and nutrient concentrations and microbial biomass. We concurrently measured the energy content of SOM using differential scanning calorimetry (DSC) as an index of the energy available for microbial metabolism, with the hypothesis that the biological stability of SOM would be inversely related to the energy contained within it. Cumulative CO₂ evolution, mean respiration rates, and the energy density of SOM (energy released during combustion normalized to soil C) all declined with soil depth (P < 0.01). Biological indices of C stability were well correlated with measures of SOM energy. There was no change in the mean respiration rate as a function of depth when normalized to soil C, and a trend toward increased respiration per-unit microbial biomass (P = 0.07). While reduced microbial respiration in subsoils suggests an increase in the biological stability of SOM, we suggest this is driven principally by concurrent declines in energy availability as measured by DSC and the size of the microbial biomass pool. On a per-unit biomass basis, subsoil OM may be as prone to decomposition and destabilization as surface SOM.     

Distinct and combined impacts of climate and land use scenarios on water availability and sediment loads for a water supply reservoir in northern Morocco

The objective of this study was to examine the impacts of climate and land use changes on water availability and sediment loads for a water supply reservoir in northern Morocco using data-intensive simulation models in a data-scarce region. Impacts were assessed by comparing the simulated water and sediment entering the reservoir between the future period 2031–2050 and the 1983–2010 reference period. Three scenarios of land use change and two scenarios of climate change were developed in the Tleta watershed. Simulations under current and future conditions were performed using the Soil and Water Assessment Tool (SWAT) model. The simulations showed that climate change will lead to a significant decrease in the annual water supply to the reservoir (−16.9% and −27.5%) and in the annual volume of sediment entering the reservoir (−7.4% and −12.6%), depending on the climate change scenarios tested. The three scenarios of land use change will lead to a moderate change in annual water inflow into the reservoir (between −6.7% and +6.2%), while causing a significant decrease in sediment entering the reservoir (−37% to −24%). The combined impacts of climate and land use changes will cause a reduction in annual water availability (−9.9% to −33.3%) and sediment supplies (−28.7% to −45.8%). As a result, the lifetime of the reservoir will be extended, but at the same time, the risk of water shortages will increase, especially from July to March. Therefore, alternative water resources must be considered.     

中国北方地区牧草气候生产力及主要限制因子

计算了我国北方地区牧草的气候生产力，并分析了影响气候生产力的主要气候因子。结果表明，我国北方地区牧草气候生产力的分布趋势由东向西、由南向北逐渐降低，最低值＜2000kg/hm^2，而最高值＞3万kg/hm^2，最高值与最低值间相差15倍以上。指出影响牧草生长的主要气候因子是干旱，人工牧场有广阔的发展前景；在退耕还林过程中必须将退耕退出的水资源返还到牧业（林业）中去，以保证牧业（林业）生产的持续、高效、稳定发展。     

Increase of leaf tipburn in chervil and lettuce by restricting volume of growing medium

Abstract

The objective of this investigation was to examine the effect of restriction of growing medium volume on the level of tipburn in chervil and leaf lettuce. Chervil: The plants were grown in different sizes of rock wool cubes: a. 31 cm³, b. 64 cm³, c. 135 cm³. The incidence of tipburned leaves decreased by increasing the size of cubes. Leaf lettuce: Plants were grown in different sizes of pots: 12 cm pots with capacity of 0.6 L and 8 cm pots with capacity of 0.25 L. The incidence of tipburned leaves increased by decreasing pot size.     

农村可再生能源项目的社会影响评价——以“三位一体”模式项目为例

农村可再生能源项目是近年来在中国广大农村地区重点推广的发展项目之一,项目的社会评价是对经济评价和环境评价的补充,有利于全面衡量项目的实施效果,从而对项目的决策和推广起促进作用。本文以茶园村“三位一体”模式项目为例,对项目产生的社会影响进行了系统评价,全面衡量了项目的实施效果,并在一定程度上弥补了农村可再生能源项目社会评价领域的空白。同时,为研究其他模式的农村可再生能源项目的社会影响评价提供借鉴和研究思路,提出的评价成果可供有关专家、学者和政府工作者参考。     

Characterization of nicosulfuron availability in aged soils

Sorption-desorption interactions of pesticides with soil determine their availability for transport, plant uptake, and microbial degradation. These interactions are affected by the physical-chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. This research evaluated changes in sorption/availability of nicosulfuron (2-[[[[(4,6-dimethoxy-2-pyrimidinyl]amino]carbonyl]amino]sulfonyl]-N,N-dimethyl-3-pyridinecarboxamide) herbicide with aging in different soils, using a radiolabeled ((14)C) tracer. Aging significantly increased sorption. For instance, after the 41-day incubation, calculated K d,app increased by a factor of 2 to 3 in Mollisols from the Midwestern United States and by a factor of 5 to 9 in Oxisols from Brazil and Hawaii, as compared to freshly treated soils. In view of this outcome, potential transport of nicosulfuron would be overpredicted if freshly treated soil K d values were used to predict transport. The fact that the nicosulfuron solution concentration decreased faster than the soil concentration with time suggested that the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption of the neutral species from the soil particles. It may have also been due to nicosulfuron anion diffusion to less accessible sites with time, leaving the more strongly bound neutral molecules for the sorption characterization. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during the characterization of the sorption process for mathematical models of pesticide degradation and transport.     

Soil fixation and availability of phosphate fertilizer

Abstract

The addition of low quantity (up to 50 mg/kg) of phosphorus (P) to two calcareous soils in the Argentine semiarid‐subhumid pampean region increased the formation of DCPD (Brushite) and decreased the P (Paer) extractable by an anionic exchange resin. This latter effect was not observed when the quantities of added P were over 50 mg/kg. The pH decreased with P addition up to a point (50 mg/kg) after which it returned to its original value. The percentage in weight of peds smaller than 74 μm increased with the added P up to certain point which decreased to values nearing the original ones. To obtain a positive Availability Index (F₁) by incubating for six months the soil with additional P, it is suggested that there are at least two points where the increase of labile P (Paer) takes place.     

Estimations of daily energy and nutrient availability based on nationally representative household budget survey data. The Data Food Networking (DAFNE) project

OBJECTIVE: To describe a cost-efficient method for estimating energy and nutrient availability using household budget survey (HBS) data. DESIGN: Four different approaches were tested and the results were compared with published nutrient intake data. The selected method was exemplarily applied in German and Greek data. SETTING: Germany, 1998; Greece, 1998/99. MATERIAL: Nationally representative HBSs. RESULTS: Comparisons showed that HBS-based estimates were generally close to intake data when results were presented as contributions to daily energy intake. Daily energy and protein availabilities were similar in Germany and Greece. Differences were observed in the availability of carbohydrates (German households reported a 5 percentage points higher contribution to daily energy availability) and lipids (Greek households recorded higher values for total fat, but lower values for saturated fat). Meat, added lipids and potatoes were important energy suppliers in Germany, whereas in Greece the first three energy suppliers were added lipids, cereals and meat. In both countries, meat, cereals, milk and cheese were important protein sources and cereals, potatoes, fruits and nuts contributed more than 60% of the daily carbohydrate availability. Added lipids were the major source of fat in the daily diet of both countries, but their contribution amounted to less than one-third in Germany and two-thirds in Greece. CONCLUSIONS: National HBS data can be used for monitoring and comparing nutrient availability among representative population samples of different countries. The ground is set for the development of a harmonised food composition table to be applied to HBS food data at international level.     

Integral energy of conventional available water, least limiting water range and integral water capacity for better characterization of water availability and soil physical quality

Different approaches have been proposed for quantification of soil water availability for plants but mostly they do not fully describe how water is released from the soil to be absorbed by the plant roots. A new concept of integral energy (E_I) was suggested by Minasny and McBratney (Minasny, B., McBratney, A.B. 2003. Integral energy as a measure of soil-water availability. Plant and Soil 249, 253-262) to quantify the energy required for plants to take up a unit mass of soil water over a defined water content range. This study was conducted to explore the E_I concept in association with other new approaches for soil water availability including the least limiting water range (LLWR) and the integral water capacity (IWC) besides conventional plant available water (PAW). We also examined the relationship between E_I and Dexter's index of soil physical quality (S-value). Twelve agricultural soils were selected from different regions in Hamadan province, western Iran. Soil water retention and penetration resistance, Q, were measured on undisturbed samples taken from the 5-10 cm layer. The PAW, LLWR and IWC were calculated with two matric suctions (h) of 100 and 330 hPa for field capacity (FC), and then the E_I values were calculated for PAW, LLWR and IWC. There were significant differences (P < 0.01) between the E_I values calculated for PAW₁₀₀, PAW₃₃₀, LLWR₁₀₀, LLWR₃₃₀ and IWC. The highest (319.0 J kg⁻¹) and the lowest (160.7 J kg⁻¹) means of E_I were found for the E_I(IWC) and E_I(PAW330), respectively. The E_I values calculated for PAW₁₀₀, LLWR₁₀₀ and LLWR₃₃₀ were 225.6, 177.9 and 254.1 J kg⁻¹, respectively. The mean value of E_I(PAW330) was almost twice as large as the mean of E_I(IWC) showing that IWC is mostly located at lower h values when compared with PAW₃₃₀. Significant relationships were obtained between E_I(IWC) and h at Q = 1.5 MPa, and E_I(LLWR100) or E_I(LLWR330) and h at Q = 2 MPa indicating strong dependency of E_I on soil strength in the dry range. We did not find significant relationships between E_I(PAW100) or E_I(PAW330) and bulk density (ρ_b) or relative ρ_b (ρ_b-rel). However, E_I(LLWR100) or E_I(LLWR330) was negatively and significantly affected by ρ_b and ρ_b-rel. Both E_I(PAW100) and E_I(PAW330) increased with increasing clay content showing that a plant must use more energy to absorb a unit mass of PAW from a clay soil than from a sandy soil. High negative correlations were found between E_I(PAW100) or E_I(PAW330) and the shape parameter (n) of the van Genuchten function showing that soils with steep water retention curves (coarse-textured or well-structured) will have lower E_I(PAW). Negative and significant relations between E_I(PAW100) or E_I(PAW330) and S were obtained showing the possibility of using S to predict the energy that must be used by plants to take up a unit mass of water in the PAW range. Our findings show that E_I can be used as an index of soil physical quality in addition to the PAW, LLWR, IWC and S approaches.     

Carbon dioxide and energy flux partitioning between the understorey and the overstorey of a maritime pine forest during a year with reduced soil water availability

Carbon dioxide, water vapour and energy fluxes were measured above and within a maritime pine forest during an atypical year with long-lasting reduced soil water availability. Energy balance closure was adequately good at both levels. As compared with what is usually observed at this site the ecosystem dissipated less energy via latent heat flux and more via sensible heat flux. The understorey canopy was responsible for a variable, significant component of the whole canopy fluxes of water vapour and carbon dioxide. The annual contribution of the understorey was 38% (154 mm) of the overall evaporation (399 mm) and 32% (89 mm) of the overall sensible heat flux (274 mm). The participation of the understorey reached 45% of the overall evaporation and 30% of the daytime overall assimilation during significant soil water deficit periods in summertime. Even during winter, understorey photosynthesis was consistent as it compensated soil and understorey respiration. The ecosystem behaved as a sink of carbon, with a negative annual carbon budget (−57 g C m⁻²). However, due to high soil water deficit, the annual ecosystem GPP was 40% less than usually observed at this site. This budget resulted from a sink of −131 g C m⁻² for the overstorey and a source of +74 g C m⁻² for the understorey. Moreover, on an annual basis the overstorey layer contributed to almost two-thirds of the ecosystem respiration. Finally, the effect of long-lasting soil water deficit on the maritime pine forest was found more important than the effect of the heat wave and drought of summer 2003.     

Plant availability of p in commercial superphosphate fertilizers

Abstract

The quality of phosphate rock (PR) is declining and the use of lower quality PR results In lower water‐soluble and higher citrate‐soluble P in the fertilizer product. A greenhouse study was conducted to evaluate the plant availability of P in commercial superphosphate fertilizers having various levels of water‐soluble P. Seven commercial fertilizers, Including 6 granular concentrated superphosphates and one normal superphosphate, were evaluated. Reagent grade monocalcium phosphate served as a control. The fertilizers were manufactured from PR deposits located in the United States (Florida, Idaho and North Carolina) and Morocco. Water‐soluble P ranged from 77 to 92 X of the total fertilizer P. Citrate‐soluble, water‐insoluble P ranged from 7 to 20 % of the total fertilizer P. Four of the 5 American fertilizers had a lower percentage of water‐soluble P as compared to the concentrated superphosphate from Morocco. Fertilizers manufactured from U.S. phosphate deposits contained an average of 6 times more Fe and 4 times more Al than the Moroccan concentrated superphosphate.

Each source was added to a Mountvlew slit loam soil (pH = 6.5) at rates to supply 0, 10, 20, 30, 40 and 50 mg P kg^‐1soil (0, 22.9, 45.8, 68.7, 91.6, and 114.5 ppm P₂O₅, respectively). Sorghum‐sudangrass (Sorghum bicolor) was harvested at 28 and 56 days after planting in the treated soil. Herbage yields and the P concentration in harvested forage were not affected by the source of added P. The effect of the rate of added P on forage yield and P concentration was described by polynomial regression. The granular concentrated superphosphate fertilizers used in this study contained ≥ 80 % of their plant available P in a water‐soluble form and were as effective as reagent grade monocalcium phosphate. Thus the level of water‐soluble P that will be required to reduce the performance of a fertilizer is lower than the levels currently found in American commercial concentrated superphosphates     

Apparent availability of nitrogen in composted municipal refuse

The use of composted municipal refuse on agricultural land requires prior knowledge of the interactions among compost, soil, and plants. Research into the availability of N in highly matured municipal refuse compost is particularly important considering the current concern about groundwater contamination by NO _inf3 ^sup- -N. A greenhouse pot bioassay was conducted to determine the percentage of short-term apparent bioavailable N of a highly matured refuse compost and its relative efficiency in supplying inorganic N to the soil-plant system in comparison with NH₄NO₃. Municipal refuse (after 165 days of composting) was applied at rates equivalent to 10, 20, 30, 40, and 50 t ha^-1 to a ferrallitic soil from Tenerife Island (Andeptic Paludult). NH₄NO₃ was applied at rates equivalent to the total N content of the compost treatments. Perennial ryegrass (Lolium perenne L.) was grown in 3-kg pots and the tops were harvested at regular intervals after seedling emergence. The compost increased dry matter yield, soil mineral N, and plant N uptake proportional to the applied rate. These increases were significantly higher than the control at an application rate of 20 t ha^-1. After 6 months the apparent bioavailable N ranged from 16 to 21%. The relative efficiency was 43% after 30 days. This suggests that large inputs of inorganic N into soil can be obtained with high rates of this kind of compost, with a potential for NO _inf3 ^sup- -N contamination. However, applied at moderate rates in our bioassay (<50 t ha^-1), compost showed a low N-supplying capacity to ryegrass, i.e. a small fraction of the mineralized compost N was used by plants in the course of time. This was ascribed to a partial biological immobilization. This pattern of N availability in highly matured municipal refuse compost, positive net mineralization but partial immobilization, is similar to the pattern of N availability in biologically active soils and is therefore extremely interesting for the conservation of N in agro-ecosystems.     

Assessment of iron availability in soilless potting media

Abstract

Ferrous sulphate added to potting media based on wood wastes is rapidly rendered insoluble in water. The extractability by DTPA of the added Fe declines over about 7 days to a steady value which is maintained for at least 10 months whether plants are growing in the media or not. The sawdusts and barks tested all required at least 100 mg/L Fe, added as ferrous sulphate, to provide an optimum amount of available Fe; peats needed less Fe and were quite variable in their requirements. In several pot trials, excellent correlations (R² 0.80–0.86) were obtained between quality or growth of shoots and a combination of medium pH and the concentration of Fe in unbuffered DTPA extractants of concentrations in the range 0.001 to 0.005M, or a saturation extract containing DTPA. Fe concentrations in DTPA/TEA/CaCl₂, NaHCO₃/DTPA, 0.5M ammonium acetate solutions and water were less precise indicators of Fe availability. At media pH values of 5.5–6.0. 0.002M DTPA (1:1.5 volume) extracts need to contain at least 20 mg/L Fe and preferably 30 mg/L Fe for adequate Fe supply if ferrous sulphate is the source of added Fe. Some species need at least 40 mg/L Fe or must be grown at a lower pH. These criteria do not hold if the main source of Fe is FeEDDHA.