Search

Water balance influences soil development, and consequently plant communities, by driving weathering of soil minerals and leaching of plant nutrients from the soil. Along gradients in water balance, soils exhibit process domains where chemical properties are relatively stable punctuated by pedogenic thresholds where soil chemical properties change rapidly with little additional change in water balance. We ask if plant macronutrient concentrations in leaves also exhibit non-linear trends along water balance gradients, and if so, how these non-linearities relate to those in soils. We analyze foliar nutrient concentrations and foliar N:P ratios from eight species that span a range of growth forms along three water balance gradients (three of the species are found on multiple gradients). The gradients are located on basaltic substrate of different ages and have previously been characterized by studies on soil development. We find that maximum concentrations of foliar macronutrients occur at an intermediate water balance. As with soil nutrients, time mediates the effect of water balance on foliar nutrients, such that plants on older soils attain maximum nutrient concentrations at a lower water balance. On both a young, 20 ky and an old, 4100 ky water balance gradient, foliar nutrients reach peak concentrations at a water balance greater than the threshold for depletion of rock-derived nutrients in surface soils. Our findings suggest that plant acquisition of essential nutrients is imperfectly predicted by overall soil nutrient availability because the regulation of internal nutrient pools by plants makes nutrient pools within leaves partially independent of soil nutrient availability. [ABSTRACT FROM AUTHOR]

A field experiment was carried out to study the influence of nitrogen (N), phosphorus (P), and potassium (K) nutrient supply on weed flora in maize. The investigations were conducted in a long-term fertilization experiment launched in 2003 on a loamy chernozem soil with lime deposits, in Fejér County, Hungary. The composition, biomass weight, and density of weeds were determined in relation to different nutrient supplies. Seventy-five percent of weeds consisted of three species: Ambrosia artemisiifolia L., Datura stramonium L., and Helianthus annuus L. Density of weeds varied relative to the different nutrient treatments, with a range of 82–131 plants m−2. The total weed density was significantly lower by 19.9–37.8 percent in the N-containing treatments (NP, NPK) than in non-N treatments. The density of the nitrophilD. stramoniumL.,Chenopodium albumL.,Chenopodium hybridumL., andAmaranthus blitoidesS. Watson was higher when N supply was greater. [ABSTRACT FROM PUBLISHER]

ObjectiveTrinidad and Tobago has experienced an epidemiological transition over recent decades characterised by reduced rates of communicable diseases but rapidly increasing rates of obesity and non-communicable chronic diseases. The objective of the present study was to investigate the changes in energy and nutrient supply that have taken place in Trinidad and Tobago between 1961 and 2007.DesignFood balance sheets for each year between 1961 and 2007 were downloaded from the FAOSTAT database and daily per capita supply for seventeen food commodity groupings was calculated. After appropriate coding, energy and nutrient supply were determined using dietary analysis software.SettingFAO food balance sheets for Trinidad and Tobago from 1961 to 2007.SubjectsNone.ResultsThe food supply in 2007 provided an extra 1561 kJ (373 kcal)/capita per d than it did in 1961. Energy from carbohydrate as a percentage of total energy fell from 62 % in 1961 to 57 % in 2007, whereas energy from fat as a percentage of total energy increased from 26 % to over 30 % and now lies at the upper end of WHO recommendations. Sugars increased from 20 % to over 26 % of total energy and are well above WHO recommendations. When expressed on a nutrient density basis, supplies of vitamin A, folate and Ca are lower than WHO recommendations.ConclusionsNutritional imbalances in the Trinidadian food supply need to be addressed to combat the rise in nutrition-related chronic disease that is projected to cause increased disability and premature death in the country in the coming years. [ABSTRACT FROM PUBLISHER]

To assess the value of biochar to direct supply of crop nutrients we considered the release of phosphorus, magnesium and potassium from a hardwood biochar in a sequential leaching experiment with deionized water. Cumulative P release was proportionally large despite being quantitatively small, and the sixth extraction yielded 44-73% of the first, indicating that provision of soil P might be sustained for several seasons. Conversely, K release was quantitatively large but declined rapidly from first extraction to the last (6-18% of the first extraction). Only 6-27% of total Mg was recovered. These results indicate that these elements have contrasting associations with biochar that govern the trajectory and ultimate extent of their release. Fitting cumulative loss curves enabled these patterns to be quantitatively captured and compared and could provide a means to develop predictive capacity for the supply of nutrients from biochar to soil and plant. [ABSTRACT FROM AUTHOR]

The soil tillage study was carried out in Keszthely in 2006–2008. The study included different cultivation methods: no-till drill, disk tillage, conventional tillage (plowing), and five nitrogen (N) fertilizer rates. The bifactorial trial was arranged in a split-plot design with four replications. Crop rotation: winter wheat–winter wheat–maize–maize. Weeds were not killed before the investigation. The weed survey was made with Balázs–Ujvárosi coenological method on the first days of June. We collected all plants of every weed species by plot. The sample area was 1 m2. Five maize plants per plot were sampled. Maize was at the 3–4 leaf stage. Aerial parts of plants were collected and the fresh- and dry-matter weights were measured. The biomass production of each weed species was compared with maize to determine if weeds have an effect on maize during this early period of maize growth. Plow cultivation markedly reduced weed cover, the number of perennial and annual weeds in the weed flora and the number of occurring weed species. The most dominant weeds wereChenopodium album,Amaranthus retroflexus, andCirsium arvensewith 60% of the total weed cover. Seven of the 12 dominant weed species are annual weeds. The dry-matter weight of maize was reduced with less tillage. In this sample period the different N doses had no effect to the dry-matter weight of weeds. The N fertilizer increased the dry-matter weight of maize compared to no N fertilizer. [ABSTRACT FROM AUTHOR]

Using a dual-flow continuous culture fermenter system, this study evaluated the effect of timing of corn silage supplementation on ruminal digestion and nutrient flows following a short and intensive orchardgrass herbage meal. Treatments included 28 g dry matter (DM) of corn silage added either 9 h (9BH; 0700 h) or 1 h (1BH; 1500 h) before adding 42 g DM orchardgrass herbage or no corn silage (control; 70 g DM herbage). Herbage was fed as follows: 66% of the total herbage meal at 1600 h, 22% at 1720 h, and the remaining 12% at 1840 h. Effluent was analyzed for organic matter (OM), crude protein (CP), and neutral detergent fiber (NDF). Purine concentrations in effluent and bacterial isolates were used to estimate the partition of effluent N flow into bacterial and nonbacterial fractions, and to calculate true OM digestibility. Fermenters were sampled for pH, volatile fatty acids (VFA), and NH3-N at 0730, 1100, 1530, 1600, 1720, 1840, and 2000 h on d 10. Data were analyzed as a 3 × 4 Latin square experimental design. True digestibilities for OM (average of 78.5%) and CP (average of 84.6%), and apparent NDF digestibility (average of 82.7%) were not affected by treatment. Mean ruminal pH was lower for 9BH than for 1BH, averaging 5.6 and 6.5, respectively. Molar proportions of acetate were not affected by treatment. Propionate concentration was greater for 9BH than for 1BH, averaging 20.5 and 18.1 mM, respectively. Diurnal patterns of pH, NH3-N, and acetate:propionate ratio were affected by treatment: 9BH had the lowest values for all measurements as the day progressed. The NH3-N concentration and effluent NH3-N flow were higher for 1BH (11.4 mg/100 mL and 0.26 g/d, respectively) than for 9BH (8.8 mg/100 mL and 0.20 g/d, respectively). Effluent NH3-N flow (as a % of total N flow) was the lowest for 9BH. Bacterial efficiency was not affected by treatments, with a mean of 10.5 g of N/kg of OM truly digested. Under the same resource allocation (pasture plus supplement), a simple change in timing of corn silage feeding (9 rather than 1 h before an orchardgrass herbage meal) may alter ruminal fermentation pattern. These changes could increase the glucogenic nutrient supply and improve N utilization by reducing ammonia N losses. [ABSTRACT FROM AUTHOR]

The nutrient supply rates within the canopy of the economically important red algal species, Eucheuma serra J. Agardh were determined experimentally in a recirculating flow-chamber. A single individual was placed in the working section of the 2000 × 200 × 250 mm3 acrylic flow-chamber and subjected to unidirectional water velocities from 1.0 to 9.3 cm s−1. Rates of nutrient supply were determined using 9.7 mm diameter CaSO4 (gypsum) spheres that were attached to the thallus inside and outside of the canopy. The supply rates within the canopy were 56% less than outside of the canopy. Increases in internal and external water velocity asymptotically increased the nutrient supply rates regardless of location. A model was developed to examine how changes in ammonium and nitrate supply compared with the physiologically maximum uptake rates of these nutrients. The results suggest that when the ammonium concentration in the water was 20 µmol L−1 uptake rates were limited by the supply rate especially at velocities below 5 cm s−1, whereas in the case of 20 µmol L−1 of nitrate, the supply of nitrate was more than adequate to maximize nutrient uptake. [ABSTRACT FROM AUTHOR]

The hyphae of ectomycorrhizal and ericoid mycorrhizal fungi proliferate in nitrogen (N)-limited forests and tundra where the availability of inorganic N is low; under these conditions the most common fungal species are those capable of protein degradation that can supply their host plants with organic N. Although it is widely understood that these symbiotic fungi supply N to their host plants, the transfer is difficult to quantify in the field. A novel approach uses the natural 15N:14N ratios (expressed as δ15N values) in plants, soils, and mycorrhizal fungi to estimate the fraction of N in symbiotic trees and shrubs that enters through mycorrhizal fungi. This calculation is possible because mycorrhizal fungi discriminate against 15N when they create compounds for transfer to plants; host plants are depleted in 15N, whereas mycorrhizal fungi are enriched in 15N. The amount of carbon (C) supplied to these fungi can be stoichiometrically calculated from the fraction of plant N derived from the symbiosis, the N demand of the plants, the fungal C:N ratio, and the fraction of N retained in the fungi. Up to a third of C allocated belowground, or 20% of net primary production, is used to support ectomycorrhizal fungi. As anthropogenic N inputs increase, the C allocation to fungi decreases and plant δ15N increases. Careful analyses of δ15N patterns in systems dominated by ectomycorrhizal and ericoid mycorrhizal symbioses may reveal the ecosystem-scale effects of alterations in the plant–mycorrhizal symbioses caused by shifts in climate and N deposition. [ABSTRACT FROM AUTHOR]

Fire and herbivory are known to modify plant community structure. Many studies have suggested that fire ashes may increase soil nutrients in dystrophic soils. Herbivores may also change plant community structure through direct effects of herbivory and affecting nutrient cycling. Leaf-cutting ants were traditionally viewed as herbivores, although their role may be more complex, because their nests affect both chemical and physical soil properties, thus affecting plants indirectly. We investigated the effects of frequent burning and of leaf-cutting ants on the nutrient status of an herbaceous and a shrub species occurring in the Brazilian Cerrado, a habitat that is characterized by natural burnings. The proximity of ant nests resulted in an increase of nutrients in the leaves of both vegetation strata, whereas burning sometimes resulted in a decrease of nutrients. Our results do not lead to a possible positive effect of fire on plant nutrient content. On the other hand, ant nests may represent an important source of nutrients for plants on the nutrient-depleted Cerrado soils and may accelerate vegetation recovery after burning. [ABSTRACT FROM AUTHOR]

We suggest a method of analyzing the sustainability conditions for forestry from three major realms: environmental, social, and economic. The tools and methods were tested at sites in Sweden. Assessments were made for the long-term sustainability concerning the impact of present management practices on the balances of nutrients in monocultures and mixed-species stands. In the economic assessments, both traditional terms hut also costs and revenues from adaptation to defined biodiversity criteria and public service demands were accounted for. An alternative to traditional discounting was used for transferring monetary value over time, by introducing spruce pulp equivalent units. Several scenarios with unsustainable conditions could he identified as well as appropriate management measures that can be taken to correct the issue. Results showed that the changes in management methods needed are possible and feasible. No significant difference in the net profit from the Norway spruce monocultures and the deciduous-conifer mixed stands were found. An increased use of deep rooting tree species has the potential to increase the total sustainable harvest volume. [ABSTRACT FROM AUTHOR]

Beech (Fagus sylvatica L.) seedlings were cultivated from seeds sown in pots or directly in the ground in outdoor chambers that were transparent to solar radiation, and provided either ambient air or CO2-enriched air (ambient + 350 μmol mol−1). The rooting volume was high in all experiments. In the short-term experiment, potted plants were assigned to a factorial CO2 × nutrient treatment (optimal nutrient supply and severe nutrient shortage) for 1 year. In the long-term experiment, plants were grown directly in the ground and received an optimal supply of water and nutrients in both CO2 treatments for 3 years. [ABSTRACT FROM PUBLISHER]

Six-week-old wheat seedlings (Triticum aestivum) grown in pots with an alfisol soil with vertic properties and mulched at a rate equivalent to 10 t ha-1 with leaf prunings of Grevillea robusta, Erythrina abyssinica, Gliricidia sepium, Alhizia schimperiana, Acacia nilotica, Acacia polyacantha, Leucaena leucocephala, Leucaena pallida and Entada abyssinica were used to diagnose nutrient contributions by these tree species. A control treatment of 20 kg P + 30 kg N ha -1 was chosen as the reference treatment for the vector analysis applied to the mulch effects. Nitrogen was found to be the most important nutrient in seedlings mulched with L. pallida, L. leucocephala, Erythrina abyssinica and to a lesser extent A. schimperiana. Other nutrients of these mulches were also in the deficiency zone but with shorter vectors and therefore with lower impact. Since all these mulches showed increased values for shoot dry weight, nutrient concentration and nutrient uptake they have still reserves for further plant growth and appear therefore to be good mulch sources for annual crops. In contrast, wheat seedlings treated with A. polyacantha and Entada abyssinica had at least some vectors in the toxic zone due to an excess of nutrients while Grevillea treated plants showed a typical toxicity response with large vectors for all nutrients in between the toxic and the antagonistic zone. Allelopathic compounds might also have been involved. [ABSTRACT FROM AUTHOR]

Two components of root architecture (topology and link lengths) were measured in a group of 13 dicotyledon and eight grass species. under both high and low nutrient supply races. Predictions were made, based on a simulation analysis, that root systems from plants grown in low nutrient conditions and those from plants characteristic of such conditions should have the more herringbone topology (branching principally on math axis) and longer links. Both these predictions were confirmed for the dicots, but data from grasses agreed with the predictions only in terms of geometry (link lengths) and not topology. The ecological character of the species was assessed on the assumption that species of low inherent relative growth rate were characteristic of infertile soils. Taxonomic patterns were also evident, indicating that some variation in root system architecture may be historical rather than adaptive. [ABSTRACT FROM AUTHOR]

One of the most dramatic effects of infection by vesicular-arbuscular mycorrhizal fungi on the physiology of the host plant is an increase in phosphorus absorption. When phosphorus is limiting, the maximum extent to which mycorrhizal infection can improve plant performance is thus predicted to be a function of the phosphorus deficit of the plant, the difference between phosphorus demand and phosphorus supply. Phosphorus demand is defined as the rate of phosphorus absorption that would result in optimum performance of the plant as measured by growth rate, reproduction or fitness. The phosphorus supply is defined as the actual rate of phosphorus absorption under the prevailing conditions. Variation among plant taxa in morphological, physiological or phenological traits which affect either phosphorus demand or phosphorus supply (and thus phosphorus deficit) is predicted to lead to variation in potential response to mycorrhizal infection. The actual response to mycorrhizal infection is predicted to be a function of the increase in phosphorus uptake due to mycorrhizal infection and the phosphorus utilization efficiency of the plant. Demonstrated variability in responsiveness to mycorrhizal infection among plant taxa suggests that mycorrhizal fungi may play an important role in determining the structure of plant communities. Mycorrhizal infection may alter the phosphorus deficit or phosphorus utilization efficiency independently from its direct effect on phosphorus uptake, making the prediction of response to mycorrhizal infection based on the traits of non-mycorrhizal plants quite difficult. For example, infection may at times increase the rate of phosphorus accumulation beyond that which can be currently utilized in growth, reducing the current phosphorus utilization efficiency. Such momentary 'luxury consumption' of phosphorus may, however, serve a storage function and be utilized subsequently, allowing mycorrhizal plants ultimately to outperform non-mycorrhizal plants. [ABSTRACT FROM AUTHOR]

Senecio vulgaris (groundsel), healthy or inoculated with rust (Puccinia lagenophorae), was grown in a nutrient-poor sand-soil mixture amended with a compound fertiliser to provide a range of nutrient regimes. The greatest number of pustules per plant occurred on unamended soil but fertiliser addition increased the sporulating area of each pustule: the leaf area occupied by by pustules was unaffected by nutrient supply. Since total leaf area increased with increasing nutrient supply, the percentage of total area that was infected declined. Plant and root dry weights increased with nutrient supply and decreased with rust infection. Infection also reduced root fresh weight and length, which were little changed by nutrient supply, but reduced leaf area only under the most nutrient-rich conditions. The ratios of root length; leaf area (R:L) and, especially, root: shoot dry weight (R:S) were reduced by infection. Root length per unit root weight was increased by infection when expressed on the basis of dry weight but not on the basis of fresh weight. Conversely, increasing nutrient supply decreased root length: weight only on basis of fresh weight. The concentrations of P and K per unit dry weight were increased in rusted leaves but that of N was unchanged. Because infection increased the dry weight: fresh weight ratio (d. wt: f. wt) of leaves, concentrations of P and K on a fresh weight basis increased by up to 3-fold over those in controls and that of N was also substantially increases. On a dry weight basis, the concentration of N and K, but not P, increased in the roots of rusted plants. However, since d. wt: f. wt of roots was decreased in infected plants, the concentrations of N and K were unchanged on a fresh weight basis and that of P was significantly reduced. Rates of uptake of N, P and K were significantly increased in rusted plants both on the basis of root dry weight and root length. This was attributed to increased 'shoot demand' on each unit of root which, in turn, reflected the decreased R:S and R: L of infected plants. [ABSTRACT FROM AUTHOR]

An experiment was set up in order to investigate semelparity and seed output of Daucus carota L., Linum catharticum L., Picris hieracioides L. and Scabiosa columbaria L. in relation to various levels of nutrient supply. Some plants of Daucus carota and Scabiosa columbaria were found to flower within one growing season, when nutrient supply was at its highest, whereas the other species did not flower. In the second growing season almost all plants receiving a maximum supply of nutrients flowered and produced seeds. In Linum catharticum flowering plants were recorded in all treatments. The reproductive plants of all species died after seed shedding, except those of Picris hieracioides and Scabiosa columbaria under high nutrient conditions which formed lateral shoots. These plants survived and were iteroparous. Seeds produced early in the fruiting period were most numerous and heaviest in the treatments with highest levels of fertilization. In Daucus and Scabiosa a positive linear relationship between seed weight and germination success was found. Thus, the plants grown under the highest nutrient supply conditions showed the highest seed output in all species, although this was less clear in Linum. The significance of these results for the field situation is discussed. [ABSTRACT FROM AUTHOR]

We show that temporal variability in root populations can depend upon the scale of measurement (particularly the sampled soil volume). The presence of roots in a range of volumes of soil was studied using perspex tubes installed horizontally into the soil around three mature kiwifruit vines. Roots Intercepting lines scored on the tubes were counted using a periscope. For small volumes of soil (c. 2.4 cm3) the root counts varied with time in a very irregular manner, and as the interval between measurements increased the autocorrelation between the measurements decayed rapidly. At about half of the locations monitored there was no significant autocorrelation between measurements 27 d apart. Linear interpolation In these time series was unreliable, and where the correlation dimension could be resolved it was usually non-integer (suggesting chaotic behaviour). The time series measured at different locations were poorly correlated, indicating weak coordination. As the observed soil volume increased, the coordination between locations improved, the autocorrelation function increased, and linear interpolation errors decreased (although these remained substantial). Clearly there are considerable fundamental constraints on our ability to predict the root behaviour of kiwifruit vines at scales that are appropriate for mechanistic models of nutrient and water uptake. We discuss the need for a new conceptual model of the fine-root systems of kiwifruit and similar species. [ABSTRACT FROM AUTHOR]

Abstract: The objetive of this work was to study if the addition of nutrients to the irrigation water modified ‘Manzanilla de Sevilla’ olive pulp and pit growth. The experiment was carried out during the 2003 fruit-growth period in an irrigated orchard near Seville, southern Spain. Fruit samples were taken in July and September, at 12 and 21 weeks after full bloom (AFB) respectively, in trees irrigated with (T1) or without (T0) the addition of nutrients (N–P–K). The nutrient availability of T1 fruits increased the fruit fresh and dry weight, longitudinal and equatorial diameters, and the pulp-to-pit ratio, characteristics particularly appreciated for table olives. The balance of growth between the fruit mesocarp (pulp) and endocarp (pit) was modified because those two tissues were affected differently. Mesocarp fresh weight was significantly higher at both 12 and 21 weeks AFB in the fertilized treatment, as was mesocarp dry weight at 12 weeks AFB. Neither the endocarp fresh and dry weight nor shape (the ratio of the equatorial and longitudinal diameters) was altered at either of the two studied dates. These results emphasize the importance of an appropriate fertilization management in irrigated olive orchards, particularly for table olives, and also confirm the olive endocarp as a strong sink tissue that competes with the mesocarp during early development. [Copyright &y& Elsevier]