747 research outputs found
Mineral Nutrition
Many reviews have been published on plant mineral nutrition. Some of these are
specific for forages. Fertilization of forages, including cool-season grasses was
reviewed in a book edited by Mays (1974). Wilkinson and Mays (1979) reviewed
the mineral nutrition of tall fescue, and Turner (1993) discussed nutrient deficiencies
and toxicities of turfgrass. The most thorough treatment of mineral nutrition
of higher plants was provided by Marschner (1986). The chemical composition
of cool-season grasses was presented in Spedding and Diekmahns (1972).
Shuman (1994) provides information on uptake, translocation, and enzyme activity
of mineral elements. Trace elements in soils and plants were thoroughly
discussed by Kabata-Pendias and Pendias (1992). Barber (1995) has published a
mechanistic approach to soil nutrient bioavailability. Graham and Webb (1991)
reviewed the role of micronutrients and disease resistance and tolerance in plants.
Nicholas and Egan (1975), Reid and Horvath (1980), and Spears (1994) provided
excellent reviews of minerals in the soil–forage plant–animal system. This
chapter presents details about minerals in the soil/cool-season grass/animal system
compiled for those interested in production and herbage utilization of cool-season
grasses
Yield and mineral concentration of HiMag compared to other tall fescue cultivars grown in the Southern Piedmont
HiMag is an experimental cultivar derived from Missouri 96 (Mo96) and
Kentucky 31 (K31) tall fescue (Festuca arundinacea Schreb.) parentage for
increased calcium (Ca), magnesium (Mg), and reduced potassium (K)/
(Ca+Mg). Our objective was to determine productivity and mineral
characteristics of endophyte-free (E-) HiMag in relation to standard tall fescue
cultivars when grown in the Southern Piedmont Land Resource Area. In
experiment 1, HiMag (E-) and K31 (E-) were grown at two levels of
phosphorus (P), K, and lime additions to both severely eroded, and non-eroded
Cecil soil (clayey, kaolinitic, thermic family of Typic Hapludults).
Herbage Ca and Mg were greater and K/(Ca+ Mg) and yield were less for
HiMag than for K31. Phosphorus and K concentrations were not different.
Herbage yields, P, Ca, and Mg concentrations were increased by P, K, and
lime additions. In experiment 2, HiMag(E-), K31(E-), endophyte-infected
K31(E+), Mo I(E+), Mo II (E+), and AU Triumph (E-) were planted either in
a prepared seedbed or planted without tillage into the Cecil soil. HiMag
yields were not different from Mo-I, Mo-II or K31(E±), but were less than
those of AU Triumph (E-). HiMag yield response to no-till planting, past
soil erosion, and fertilizer level was similar to that of K31 (E±). Fertilizer
level, and soil condition affected the magnitude of differences in mineral
levels in HiMag and K31 (E±), but K/(Ca+Mg) values were more favorable
in HiMag. All tall fescue cultivars established equally well in no-till or
prepared seedbeds. Aside from a slightly lower first harvest yield there were
no important effects of planting no-till versus planting in a prepared seedbed.
HiMag's agronomic attributes, while not superior to other cultivars, were
sufficient to justify further testing to improve Mg nutrition of grazing animals
Soil factors affecting magnesium availability in plant-animal systems: A review
Soils provide the support, water and most of the nutrient elements, including Mg,
needed for plant growth. Magnesium uptake by plants depends largely on the amount,
concentration and activity of Mg in the soil solution and the capacity of the soil to
replenish Mg in the soil solution. The availability of Mg depends on the activity or
proportion of Mg relative to soluble and exchangeable amounts of K, Ca, Na, Al and Mn.
In humid regions, Mg losses from leaching are often greatest from agroecosystems
receiving heavy N fertilization. Cool-season grasses produce nearly maximum growth at
herbage concentrations of 1 to 1.5 g Mg/kg, 25 g K/kg and 30 g N/kg of dry matter. At
these concentrations of N and K, herbage should contain about 2.5 g Mg/kg to avoid
inducing hypomagnesemic grass tetany in ruminants. To increase herbage Mg concentration
to this level often requires, except on sandy soils, an uneconomically large addition of
Mg fertilizer. Adjusting soil conditions to produce grasses with a low-tetany potential may
not always be possible physically. The risk of tetany can be reduced by a judicious
program of well-timed N, K and Mg fertilizer applications. However, direct Mg
supplementation of grazing ruminants is considered more cost-effective than is Mg
fertilization to prevent grass tetany
A comparison of terrestrial laser scanning and structure-from-motion photogrammetry as methods for digital outcrop acquisition
Terrestrial laser scanning (TLS) has been used extensively in Earth Science for acquisition of digital outcrop data over the past decade. Structure-from-Âmotion (SfM) photogrammetry has recently emerged as an alternative and competing technology. The real-world performance of these technologies for ground-based digital outcrop acquisition is assessed using outcrops from North East England and the United Arab Emirates. Both TLS and SfM are viaÂble methods, although no single technology is universally best suited to all situations. There are a range of practical considerations and operating conditions where each method has clear advantages. In comparison to TLS, SfM benefits from being lighter, more compact, cheaper, more easily replaced and repaired, with lower power requirements. TLS in comparison to SfM provides intrinsically validated data and more robust data acquisition in a wide range of operating conditions. Data post-processing is also swifter. The SfM data sets were found to contain systematic inaccuracies when compared to their TLS counterparts. These inaccuracies are related to the triangulation approach of the SfM, which is distinct from the time-of-flight principle employed by TLS. An elaborate approach is required for SfM to produce comparable results to TLS under most circumstances
Momentum transfer using chirped standing wave fields: Bragg scattering
We consider momentum transfer using frequency-chirped standing wave fields.
Novel atom-beam splitter and mirror schemes based on Bragg scattering are
presented. It is shown that a predetermined number of photon momenta can be
transferred to the atoms in a single interaction zone.Comment: 4 pages, 3 figure
Finite temperature effects in Coulomb blockade quantum dots and signatures of spectral scrambling
The conductance in Coulomb blockade quantum dots exhibits sharp peaks whose
spacings fluctuate with the number of electrons. We derive the
temperature-dependence of these fluctuations in the statistical regime and
compare with recent experimental results. The scrambling due to Coulomb
interactions of the single-particle spectrum with the addition of an electron
to the dot is shown to affect the temperature-dependence of the peak spacing
fluctuations. Spectral scrambling also leads to saturation in the temperature
dependence of the peak-to-peak correlator, in agreement with recent
experimental results. The signatures of scrambling are derived using discrete
Gaussian processes, which generalize the Gaussian ensembles of random matrices
to systems that depend on a discrete parameter -- in this case, the number of
electrons in the dot.Comment: 14 pages, 4 eps figures included, RevTe
Grass tetany
Grass tunny is a metabolic disorder of ruminant animals that results from a deficiency of
available Mg in the diet. The etiology of tetany is complicated by the many soil, plant, and animal
factors that influence Mg availability to plants and in tuns to animals. This review will highlight
some of these factors and provide management information which will minimize the impact of this
disorder. Only the most recent and pertinent literature citations are included. A more detailed
bibliographic list is available from the authors
Magnesium in plants: uptake, distribution, function, and utilization by man and animals
Plants provide man with his primary needs--nutrition, clothing, and
shelter as well as medicinal, recreational, and esthestic benefits.
There are over 500,000 species of plants distributed over the earth.
Magnesium is an essential nutrient for plants and animals.
The criteria for the essentiality of elements for plants are as follows:
(1) the plant will be unable to complete its life cycle if
the element is removed from the plant nutrient medium; (2) the element
has a specific function which cannot be replaced by other elements;
or (3) the element is a necessary component of an essential
metabolite [1]. The relative abundance of Mg in plant life is less
than N, K, Ca, and similar to S and P. Intensive crop production
practices with fertilizers, improved plant cultivars, and best management
practices are commonly used today. These intense cultural
practices may mean an increasing frequency of Mg deficiencies as well
as the need for knowledge on economically sound practices to prevent
such deficiencies.
Plants are an important source of Mg to satisfy human and animal
requirements, and factors affecting Mg bioavailability need to
be identified. The objective of this chapter is to assess the importance,
distribution, function, and utilization of Mg in plant
growth and metabolism and in grazing ruminant animal production and
human health
Quantum phase transition of condensed bosons in optical lattices
In this paper we study the superfluid-Mott-insulator phase transition of
ultracold dilute gas of bosonic atoms in an optical lattice by means of Green
function method and Bogliubov transformation as well. The superfluid-
Mott-insulator phase transition condition is determined by the energy-band
structure with an obvious interpretation of the transition mechanism. Moreover
the superfluid phase is explained explicitly from the energy spectrum derived
in terms of Bogliubov approach.Comment: 13 pages, 1 figure
Gravity-induced Wannier-Stark ladder in an optical lattice
We discuss the dynamics of ultracold atoms in an optical potential
accelerated by gravity. The positions and widths of the Wannier-Stark ladder of
resonances are obtained as metastable states. The metastable Wannier-Bloch
states oscillate in a single band with the Bloch period. The width of the
resonance gives the rate transition to the continuum.Comment: 5 pages + 8 eps figures, submitted to Phys. Rev.
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