Satisfaction across urban consumers of smallholder-produced teak (Tectona grandis L.f.) poles in South Benin     

Augustin K.N. Aoudji  Anselme Adégbidi  Jean C. Ganglo  Valentin Agbo  Armand S.I. Yêvidé  Charles De Cannière  Philippe Lebailly 《Forest Policy and Economics》2011,13(8):642-651

The study used the expectancy-disconfirmation framework to investigate the satisfaction among urban consumers of teak pole in South Benin, so as to identify the areas where interventions are needed to secure market opportunity for smallholder forestry. A survey was conducted in five cities; and 223 household-heads were interviewed using systematic sampling, with a random start. Data were collected on socio-demographic characteristics, teak pole consumption forms, behaviour patterns, and motivations. Respondents also rated their expectations and perceptions for a set of nine attributes on a 7 points Likert scale. Hierarchical ascending cluster analysis was performed to identify consumer segments; and satisfaction level was analysed per segment, by determining the gap between expectations and perceptions, for all attributes. Four consumer segments were identified; and sociodemographic profiles differed across those segments. Competitive price was an important purchasing motivation across the identified segments. Consumers were dissatisfied with price, availability, knot frequency, bending, length, hardness, and durability of teak pole. The efforts to meet the consumer expectations should be concentrated on building farmers' capacity in silvicultural management, and ensuring the availability of good planting material. The issue of competitive price might be addressed, through the improvement of the overall efficiency in the value chain.  相似文献   

Potassium Dynamics in US Coastal Plain Soils     

Charles C. Mitchell  Gobena Huluka 《Communications in Soil Science and Plant Analysis》2016,47(22):54-63

ABSTRACT

Potassium (K) deficiency in crops in southern US Coastal Plain soils has been documented since the l880s. Long-term soil fertility studies such as Alabama’s “Cullars Rotation” experiment (circa 1911) have been conducted with K since 1911. Other Alabama long-term experiments on several Coastal Plain and related Hapludults, Paleudults, and Kandiudults also contain K variable treatments which have been monitored since 1929. Soil test data from these long-term experiments have allowed us to answer some practical questions regarding K dynamics in Coastal Plain soils. Potassium movement through the soil profile is dependent on the soil’s cation exchange capacity (CEC) but relative accumulation is greater in the plow layer regardless of soil CEC. While subsoil K testing may be useful for identifying situations where subsoil K has been depleted, this extra effort and expense is not necessary for most cropping situations. A crop will remove most of its K from the plow layer if it is present in sufficient quantity based on soil test. Crop depletion of plow-layer K to the point where yield may be reduced is gradual and may take 10–15 years or more depending upon soil CEC and initial soil K concentration. Depletion is most rapid in low CEC soils as would be expected. However, soil test K can vary considerably during the course of a crop season with the lowest soil test K concentrations occurring immediately after harvest.  相似文献   

Identifying sources of snowmelt acidification with a watershed mixing model     

Douglas A. Schaefer  Charles T. Driscoll 《Water, air, and soil pollution》1993,67(3-4):345-365

We used ionic tracers to estimate the volume of old (soil and ground) water interacting with snowmelt in eleven Adirondack, NY watersheds. The contribution of old water varied from 66 to 90%, with no general relationship between old water % and soil depth to till. This approach also discriminated between watershed retention and release of particular ions to lake outlet water during snowmelt. Most watersheds released NO₃ ^? during snowmelt, in addition to the snowpack NO₃ ^?. Nitrification of snowpack NH₄ ⁺ explained part of the additional NO₃ ^? in lake out outlet water, but some NO₃ ^? was likely mineralized nitrogen from soil organic matter. All watersheds retained NH₄ ⁺ as well. Nitrogen release was greatest in the acidic watersheds in the southwestern Adirondacks, a region thought to be impacted by anthropogenic deposition. During snowmelt, Ca²⁺ and Mg²⁺ ions (presumably from soil exchange sites) were also released from most watersheds. In watersheds with acidic (minimum pH<4.6) lake outlet water, Al was also released during snowmelt. Thus, lake outlet water acidification during snowmelt was both buffered by cation release, and intensified by NO₃ ^? release. If the soil exchangeable cation pools were not replenished prior to snowmelt, or NO₃ ^? mobilization were increased, acidification during snowmelt would intensify.  相似文献   

Microbial immobilisation and turnover of N labelled substrates in two arable soils under field and laboratory conditions     

Louisa Wessels Perelo  Miguel Jimenez  Jean Charles Munch 《Soil biology & biochemistry》2006,38(5):912-922

Microbial biomass N dynamics were studied under field and laboratory conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The objective of the study was to determine the size and activity of soil microbial biomass in the soils of the different yield areas and to compare these data obtained under field and laboratory conditions. Soils were amended with ¹⁵N labelled mustard (Sinapis alba) residues (both experiments) and labelled nitrate (laboratory only) at 30 μg N g⁻¹ dry soil. Soil microbial biomass (SMB) N, mineral N (N_min) and total N content was monitored both in the field and in the laboratory. N₂O efflux was additionally measured in laboratory treatments. Isotope ratios were determined for SMB in both experiments, for all other parameters only in the laboratory treatments. In the laboratory less amounts of added substrate N were immobilised by the SMB in HY soils compared to LY soils, whereas in the field immobilisation of added N by SMB was higher in HY soils initially and slightly lower after 40 days of incubation. Calculated turnover times in the laboratory nitrate, laboratory mustard and field mustard amendments were 0.18, 0.27 and 0.74 years (HY) and 0.22, 0.61 and 1.01 years (LY), respectively. The turnover times of added substrate N always showed the trend to be faster in HY soils compared to LY soils. A faster turnover of nutrients in the HY soils may involve a better nutrient supply of the plants, which coincides with the higher agricultural yield observed in these areas.  相似文献   

Magnesium deficiency in Douglas-fir and Grand fir growing on a sandy outwash soil amended with sewage sludge     

Robert B. Harrison  Charles L. Henry  Dongsen Xue 《Water, air, and soil pollution》1994,75(1-2):37-50

Soil and plant samples were collected from chlorotic plantations of Grand fir (Abies grandis) and Douglas-fir (Pseudotsuga menziesii) in Winter, 1989. The soils had been amended in 1981 with an average of 300 dry Mg ha^?1 of municipal sewage sludge. The sludge amendment resulted in an N application rate of approximately 8000 kg ha^?1. Foliage analysis indicated a severe Mg deficiency (0.25 g kg^?1 in sludge-treated vs. 0.93 g kg^?1 in untreated area) might be the cause of chlorosis. No other nutrient showed concentrations in the deficient or toxic ranges. Trace metal levels in foliage were elevated significantly for Ni, Cd and Cr in sludge-treated sites, but not toxic levels. Soil samples taken to a depth of 1.4 m indicated the potential for soil acidification (up to 0.9 pH unit) in soil surface horizons. In addition, exchangeable Ca, Mg and K may have been depleted in surface horizons. Exchangeable Al and Fe were greater in the surface of sludge-treated sites. These observations and the loss of much of the nitrogen added during the sludge amendment indicated that nitrification and cation leaching was likely the mechanism for acidification and depletion of exchangeable cations. Fertilization of the plantation with MgSO₄ or dolomitic limestone was carried out in Spring 1990. New foliage collected in June, 1990 was non-chlorotic and significantly higher in Mg concentration than unfertilized foliage (1.1. vs. 0.7 g kg^?1, respectively). Results of this study indicate that it is important to assess the potential for initiating a nutrient deficiency due to secondary effects of sludge application in forest systems.  相似文献   

Production of phenolic metabolites by a soil pseudomonad     

David A. Bencini  Charles R. Howell  James R. Wild 《Soil biology & biochemistry》1983,15(4):491-492

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Input-Output Budgets of Inorganic Nitrogen for 24 Forest Watersheds in the Northeastern United States: A Review     

Campbell  John L.  Hornbeck  James W.  Mitchell  Myron J.  Adams  Mary Beth  Castro  Mark S.  Driscoll  Charles T.  Kahl  Jeffrey S.  Kochenderfer  James N.  Likens  Gene E.  Lynch  James A.  Murdoch  Peter S.  Nelson  Sarah J.  Shanley  James B. 《Water, air, and soil pollution》2004,151(1-4):373-396

Input-output budgets for dissolved inorganic nitrogen (DIN) are summarized for 24 small watersheds at 15 locations in the northeasternUnited States. The study watersheds are completely forested, free of recent physical disturbances, and span a geographical region bounded by West Virginia on the south and west, and Maine on the north and east. Total N budgets are not presented; however, fluxes of inorganic N in precipitation and streamwater dominate inputs and outputs of N at these watersheds. The range in inputs of DIN in wet-only precipitation from nearby National Atmospheric Deposition Program (NADP) sites was 2.7 to 8.1 kg N ha^-1 yr^-1 (mean = 6.4 kg N ha^-1 yr^-1; median = 7.0 kg N ha^-1 yr^-1). Outputs of DIN in streamwater ranged from 0.1 to 5.7 kg N ha^-1 yr^-1 (mean = 2.0 kg N ha^-1 yr^-1; median = 1.7 kg N ha^-1 yr^-1). Precipitation inputs of DIN exceeded outputs in streamwater at all watersheds, with net retention of DIN ranging from 1.2 to 7.3 kg N ha^-1 yr^-1 (mean = 4.4 kg N ha^-1 yr^-1; median = 4.6 kg N ha^-1 yr^-1). Outputs of DIN in streamwater were predominantly NO₃-N (mean = 89%; median = 94%). Wet deposition of DIN was not significantly related to DIN outputs in streamwater for these watersheds. Watershed characteristics such as hydrology, vegetation type, and land-use history affect DIN losses and may mask any relationship between inputs and outputs. Consequently, these factors need to be included in the development of indices and simulation models for predicting 'nitrogen saturation' and other ecological processes.  相似文献   

Water mobility in multicomponent model media as studied by 2H and 17O NMR     

Vittadini E  Dickinson LC  Lavoie JP  Pham X  Chinachoti P 《Journal of agricultural and food chemistry》2003,51(6):1647-1652

Molecular mobility of water was studied in a microbiological media containing complex and heterogeneous mixtures of cellulose, l-sorbose, and orange serum broth (OSB) using (2)H and (17)O high-resolution NMR. All mixtures showed Lorentian (17)O NMR spectra but complex (2)H NMR line shapes. Sorbose, when solubilized, caused line-narrowing where as cellulose-OSB mixtures showed wide peaks with flat plateaus. Presence of liquid or solvent water had a profound effect on a marked increase in T(2) relaxation time observed in sorbose-containing samples. (17)O NMR data were not composition dependent, while (2)H NMR data were highly sorbose dependent.  相似文献   

Making modern agriculture sustainable: Fam research network on agroecosystems     

Peter?Schr?derEmail author  Beate?Huber  Jean?Charles?Munch 《Journal of Soils and Sediments》2003,3(4):223-226

All forms of agriculture cause changes in the balances and fluxes of preexisting ecosystems, thereby limiting self-regulatory ecosystem (resiliency) functions. The intensive agriculture of the past, with its strong reduction of landscape structures and vast decoupling of energy and matter cycles, has caused stress and degradation of the production base; massive influence has also been exerted on neighboring compartments. This has resulted in the well known problems of pesticide loads, high phosphate loads to surface waters via over-fertilized soils or erosion as such. To overcome the economic, social and political inadequacies leading to ecological degradation, the demand for sustainable agricultural management needs to be transposed into knowledge-based practical instructions and political regulations on a regional scale. Thus, applied research for a sustainable and ecologically compatible land use aimed at sufficient food production is ever so important. In the FAM, thirty German research institutes have merged to perform research on this topic.  相似文献   

Toxicity of (+)- and (-)-gossypol to the plant pathogen,Rhizoctonia solani     

Puckhaber LS  Dowd MK  Stipanovic RD  Howell CR 《Journal of agricultural and food chemistry》2002,50(24):7017-7021

The dimeric sesquiterpene gossypol occurs naturally in cottonseed and other parts of the cotton plant. Gossypol exists as enantiomers because of the restricted rotation around the central binaphthyl bond. The (-)-enantiomer is toxic to nonruminant animals while the (+)-enantiomer exhibits little, if any, toxicity to these animals. Developing cotton plants with low levels of the (-)-gossypol could expand the use of cottonseed as a feed source. Gossypol also may play a role in protecting the plant from pathogens. The relative toxicity of (+)- and (-)-gossypol to plant pathogens has not been reported. We measured the concentration of (+)- and (-)-gossypol in roots from cotton seedlings that were treated with the biocontrol agent Trichoderma virens that induces biosynthesis of gossypol and related terpenoids in cotton roots. (-)-Gossypol was the minor enantiomer in control and treated roots, but levels were slightly higher in roots from T. virens-treated seed. We also determined the toxicity of the gossypol enantiomers and the racemate to the seedling disease pathogen Rhizoctonia solani. The (+)- and (-)-enantiomers of gossypol and the racemate are equally effective in inhibiting growth of this pathogen. The lethal doses of the gossypols required to kill the pathogen appeared to be similar, but their toxicities are significantly less than those of related cotton and kenaf sesquiterpenes. The results indicate that altering the enantiomeric ratio in cotton roots will not adversely affect the resistance of seedlings to the seedling pathogen R. solani.  相似文献