Prediction of reference values for early leaf analysis for peach trees

Leaf analysis of peach (Prunus persica, L. Batsch) trees is restricted to midsummer (120 days after full bloom), which is the standard time for leaf sampling of fruit trees. In order to carry out foliar diagnosis in this plant at nonstandard times, reference values based on maximum yield exist for specific areas. When a diagnosis is applied with different objetives other reference values are needed. It may prove useful to bring forward the time when samples are taken. Samples taken 60 and 120 days after full bloom for two seasons, 1987 (using the late ripening cultivar “Calanda”; grafted on seedling) and 1992 (irrespective of cultivar or rootstock), were used to calculate the correlation between concentrations of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) present in leaves. The high significance gave rise to the following linear regression equations, which show the relationship between nutrients at the above mentioned times: N60days = 0.705N_{120 days} + 1.557; P_60days = 0.181P_120days + 0.244; K_60days = 0.444K_120days + 1.303; Ca_60days = 0.386Ca_120days + 0.639; Mg_60days = 0.386Mg_120days + 0.233. If we take these equations as a basis and knowing the standard mineral content at 120 days, it should be possible to obtain reference values needed to interprete the analysis of peach leaf samples taken 60 days after full bloom. If we compare the interpretation of several samples, by means of the DOP index, we find a remarkable similarity between the experimental and calculated reference values. This could lead to a new method of early diagnosis of nutritional status.     

Utilising biomass crops as an energy source: A European perspective

Biomass can be grown to act as a carbon (C) store, or as a direct substitute for fossil fuels (with no net contribution to atmospheric CO₂ if produced and used sustainably). There is great potential for the modernisation of biomass fuels to produce convenient energy carriers such as electricity and liquid fuels. Bioenergy accounts for about 15% of primary energy used throughout the world, and 4% of energy used in Western Europe. Several European countries plan to significantly increase their use of bioenergy and some already obtain over 10% of their energy from biomass fuels. The European Community (EC) is planning to implement policies which will more than double the use of biomass by 2005, with biofuels taking 5% of the motor vehicle fuel market, and a resultant reduction in CO₂ emissions of about 180 million tonnes (Mt), equivalent to 50 Mt C/yr. The potential contribution of biofuels is even greater, especially with all the ‘setaside’ land being taken out of production. Use of 15–20 million hectares (Mha) of agricultural land for biomass crops could represent an annual sink of some 90–120 Mt C or else offset between 50 Mt C and 120 Mt C from fossil fuel emissions, depending on the fuel displaced (7–17% of total EC carbon emissions). Policies are needed that will encourage the penetration of biofuels into the market such as increased support for research, development and demonstration, subsidies for biofuels, and carbon taxes on fossil fuels.     

Evaluation of the BCR sequential extraction for trace elements in European reference volcanic soils

Trace metal behaviour in volcanic ash soils displays distinctive features related to the soils’ large contents of metal‐binding phases and to the rapid release of trace metals from glasses and weatherable minerals. In this work, the BCR (Community Bureau of Reference) sequential extraction scheme (exchangeable + weak acid soluble, reducible, oxidizable, and non‐extractable metal fractions) was applied to selected COST‐622 European reference volcanic soils to determine partitioning of zinc and copper between various solid‐phase constituents, along with the major elements Al, Fe and Mn. The total extracted Al (ΣAl) was strongly correlated with acid ammonium oxalate extractable Al (Al_o) (ΣAl = 0.985Al_o+ 0.11, R²= 0.98), while the total extracted Fe clearly underestimated the amorphous fraction. Large values for the non‐extractable Al fraction were associated with the presence of gibbsite and phyllosilicates. Although the Zn and Cu contents of the soils were generally large, total amounts extracted (the potentially mobilizable fraction) were small, especially for Zn and for soils with crystalline secondary minerals. The fraction of the total Cu which was potentially mobilizable generally exceeded that of Zn. In the potentially mobilizable Cu the oxidizable fraction was generally dominant. Biocycling appears to play an important role in the surface enrichment of potentially mobilizable Zn and Mn. Although further methodological research seems necessary, the BCR sequential extraction appears to be a valuable tool for studies on metal dynamics in soils with andic properties.     

Microbiological assay for chloramphenicol residues

Procedures for the assay of chloramphenicol in milk, urine, serum, and muscle tissue are presented. The procedures specify an assay design with all standards as well as samples present on each plate, oxytetracycline in the buffer-diluent for greater sensitivity, a minimal medium to enhance the inhibitory effect of chloramphenicol on the assay organism, and a tetrazolium dye to improve the ability to measure the zones of inhibition. Recoveries of unbound chloramphenicol from bovine urine were 90.8%, from serum 88.3%, from milk 79.3%, from swine muscle 71.3%, and from beef and chicken muscle 61.0 and 61.4%, respectively. The lower levels of measurement in urine and serum were 0.25 microgram/mL, 0.025 microgram/mL in milk, and 0.10 microgram/g in muscle tissue.     

Analysis of foods for iodine: interlaboratory study

An accurate, reproducible method for less than or equal to 1 ppm iodine in foods is required for nutritional labeling. In order to ascertain the current status of iodine analysis in foods, 7 samples, representing different food classes, were analyzed by 8 laboratories. Six laboratories used their modifications of the Ce-As-I catalytic method preceded by alkaline dry ashing. Two laboratories used neutron activation analysis (NAA), with differing radiochemical separations. The study showed wide discrepancy in analytical results. Mean relative standard deviation for all laboratories was 77.9% between laboratories; 19.1% within-laboratories. Laboratories using NAA had only slightly better precision than did laboratories using the chemical method. The lowest level reported on the entire group of samples ranged among laboratories from 0.0089 to 0.65 ppm. Figures reported by a laboratory are, in general, consistently high or consistently low. The only differences in methodology which may possibly correlate with level of iodine obtained are the use of NAA technique and use of manual, rather than automated, colorimetry.     

Microbiological assays for antibiotics and vitamins: considerations for assuring accuracy.

Factors that may influence the accuracy and precision of microbiological manual and semiautomated turbidimetric methods as well as diffusion assays are discussed. Influence of kind of equipment, media, test bacteria, sample preparation, form of dose response lines, operations, and personnel on quality of assays is examined with the objective of reducing to insignificance those factors under control of the analyst that are responsible for low quality assays.     

Commonness and rarity in plants with special reference to the Sheffield flora part IV: A European context with particular reference to endemism

With respect to reasons for commonness and rarity, an attempt is made to compare the flora of the Sheffield region with that of Europe as a whole. Land use appears to exert a critical effect on species abundance in both floras. However, European endemics, a grouping poorly represented in the Sheffield region and indeed in N Europe, form a very different class of rare species. Unlike the rare species of the Sheffield region, which are particularly associated with primitive families (sensu Sporne, 1980), European endemics tend to be found in advanced families, the very families with the greatest proportion of common species. Thus, while the main factors controlling abundance in N Europe appear to be essentially similar to those operating in the Sheffield region, additional processes related to endemism must be taken into account in S Europe. Implications of these results for conservation policy are reviewed.     

Soil information for agricultural decision making: a New Zealand perspective

Understanding of the soil resource is pivotal to our ability to use, manage and modify soils effectively and responsibly. Yet those who make the most decisions concerning soil use and management – farmers and landholders – rarely have access to reliable soil information at scales suitable for farm decision making. By default, many rely on limited local soil knowledge when making decisions that determine farm performance and environmental impact. Providing detailed nationwide soil information that is appropriate for farm decision making is feasible, as demonstrated by the achievements of several European countries and the USA. For New Zealand, a stratified programme at scales of 1:10 000 for versatile land; 1:25 000 for other agricultural land; and 1:50 000 for non‐domesticated land, would cost NZD $280 million, or NZD $11.2 million per year if spread over the useful life of the information. This investment is small relative to the economic value of agriculture, and necessary if New Zealand is to make meaningful advances in reducing current agri‐environmental trends.     

Definition of a mechanical glass transition temperature for dehydrated foods

A new concept of the mechanical glass transition temperature (T(g)) is presented with application in dehydrated high-sugar/gelatin mixtures, fish, and fruits. The macroscopic basis and manner of relaxation processes during vitrification of these foodstuffs are developed using small deformation dynamic oscillation, the master curve of viscoelasticity, and the time-temperature superposition principle. The quantitative features of the mechanical T(g) are based on the combined framework of free volume/WLF theory and the Andrade equation. It is proposed that the thermal profile of storage modulus on shear is a fundamental index of monitoring changes in a glassy structure, and several cases are presented in support of this concept.     

Volatile organic compounds in foods: a five year study

A purge and trap procedure was used with gas chromatography-mass spectrometry determination to analyze 70 foods for volatile organic compounds (VOCs). The results from analyses over a 5 year period (1996-2000) are reported. VOCs were found in at least one sample of all foods tested, although no single compound was found in each of the foods. The total amount of VOCs found in a single food item over the 5 year period ranged from 24 to 5328 ppb, with creamed corn (canned) the lowest and cheddar cheese the highest. Benzene was found in all foods except American cheese and vanilla ice cream. Benzene levels ranged from 1 to 190 ppb, with the highest level found in fully cooked ground beef. Benzene was found in 12 samples of cooked ground beef, with an average of 40 ppb. Benzene levels above 100 ppb were also seen in at least one sample each of a cola (138 ppb), raw bananas (132 ppb), and cole slaw (102 ppb). This compares to a maximum contaminant level of 5 ppb set by the U.S. EPA for drinking water.     

Grapes and human health: a perspective

Grapes are a valuable source of numerous phytonutrients, including the intensively studied constituent, resveratrol. A question worth addressing is the potential of dietary grape consumption to positively modulate human health. Many studies have suggested cardiovascular benefits, and some work has indicated cancer chemopreventive activity. Data are particularly compelling in the area of skin cancer prevention. With financial support provided by the California Table Grape Commission, novel and exciting preliminary data are emerging from independent research suggesting beneficial activity against other less prevalent but devastating illnesses, such as Alzheimer's disease and urinary bladder dysfunction. It is further suggested that some of the copious amounts of data obtained with resveratrol may be relevant to grape consumption, especially responses that can be mediated by low concentrations of the substance. Whether future specific health claims will be sought from or allowed by regulatory authorities is not known, but based on existing data, it is clear that grapes should be considered an integral component of fruit and vegetable enriched diets that are recommended by health authorities and widely accepted as beneficial for human health and disease prevention.     

Microbiological method for assaying lincomycin in animal feed: collaborative study.

A microbiological assay for determining lincomycin in swine feed, supplement, and a vitamin-mineral premix was studied collaboratively in 16 laboratories. The design of the study involved a complete feed, feed supplement, and a vitamin-mineral premix covering a range of fortification from 20 to 80 g/ton and 80 to 2600 g/ton. Two methods of sample preparation were used depending on the concentration of lincomycin in the sample. Statistical evaluation of the results from the 2 methods indicated that 10 and 11 collaborators, respectively, had mean recoveries which were not significantly different from one another. Ten laboratories obtained a mean recovery of 112.2% (range 102.3--123.5%) for the lower level, and 11 laboratories obtained a mean recovery of 104.4% (range 100.0--107.7%) for the higher level. The method has been adopted as official first action.     

Cation exchange in forest soils: the need for a new perspective

The long‐term sustainability of forest soils may be affected by the retention of exchangeable nutrient cations such as Ca²⁺ and the availability of potentially toxic cations such as Al³⁺. Many of our current concepts of cation exchange and base cation saturation are largely unchanged since the beginnings of soil chemistry over a century ago. Many of the same methods are still in use even though they were developed in a period when exchangeable aluminium (Al) and variable charge were not generally recognized. These concepts and methods are not easily applicable to acid, highly organic forest soils. The source of charge in these soils is primarily derived from organic matter (OM) but the retention of cations, especially Al species, cannot be described by simple exchange phenomena. In this review, we trace the development of modern cation exchange definitions and procedures, and focus on how these are challenged by recent research on the behaviour of acid forest soils. Although the effective cation exchange capacity (CECe) in an individual forest soil sample can be easily shown to vary with the addition of strong base or acid, it is difficult to find a pH effect in a population of different acid forest soil samples. In the very acidic pH range below ca 4.5, soils will generally have smaller concentrations of adsorbed Al³⁺. This can be ascribed to a reduced availability of weatherable Al‐containing minerals and a large amount of weak, organic acidity. Base cation saturation calculations in this pH range do not provide a useful metric and, in fact, pH is modelled better if Al³⁺ is considered to be a base cation. Measurement of exchangeable Al³⁺ with a neutral salt represents an ill‐defined but repeatable portion of organically complexed Al, affected by the pH of the extractant. Cation exchange in these soils can be modelled if assumptions are made as to the proportion of individual cations that are non‐specifically bound by soil OM. Future research should recognize these challenges and focus on redefining our concepts of cation retention in these important soils.     

Nutritional reference values for Opuntia ficus‐indica determined by means of the boundary‐line approach

Optimum concentrations and/or sufficiency ranges of nutrients are useful for a correct diagnosis and improvement of nutrient status of cultivated plants. To develop boundary‐line approach (BLA) standards for Opuntia ficus‐indica L., a database of N, P, K, Ca, and Mg concentrations in 1‐year‐old cladodes and cladodes fresh‐matter yield was used. The BLA optimum concentrations (associated with estimated maximum yield) for O. ficus‐indica were: N = 13.1 g kg^–1, P = 3.2 g kg^–1, K = 44.4 g kg^–1, Ca = 38.1 g kg^–1, and Mg = 17.3 g kg^–1. The BLA sufficiency ranges at 95% yield were 8.4–20.3 g kg^–1 for N, 2.4–4.2 g kg^–1 for P, 38.2–50.8 g kg^–1 K, 31.8–45.2 g kg^–1 for Ca, and 14.3–20.9 g kg^–1 for Mg. The BLA standards are comparable to those obtained in a previous study using compositional‐nutrient‐diagnosis (CND) approach.