Increased inputs of phosphorus (P) and heavy metals to agricultural soils have caused considerable concern. Information on accumulation and chemical forms of the elements in soils is needed as a ...guide for the judicious application of agricultural chemicals and organic manures. The focus of this study was to assess accumulation of P and heavy metals among various fractions of a sandy soil with a 25 year history of vegetable crop production and primarily inorganic fertilization. The results demonstrated that long-term vegetable production practices changed concentrations and partitioning of P and heavy metals in the soil. Phosphorus, Cu, Zn, and Mn were significantly accumulated and moved downward along the soil profile. Most of the total Cr in the vegetable soil accumulated in the upper 0-15 cm. However, there was no significant accumulation and transport of Cd, Co, Mo, Ni, and Pb in the vegetable soil. Major P fractions in the vegetable soil were NaHCO
3
-P, followed by HCl-P and residual P. Copper, Zn, and Mn accumulated predominantly in the CaCO
3
fraction or oxide fraction, whereas Cr accumulated mainly in the organically bound fraction, indicating that P, Cu, Zn, and Mn in the vegetable soil have greater mobility potential. Compared with adjacent forest soil, the vegetable soil had a lower percentage of P, Cu, Zn, and Mn in the residual fractions, and a higher percentage of P, Cu, Zn, and Mn in the CaCO
3
fractions or organically bound fraction.
Compost amendment to agricultural soils has been reported to reduce disease incidence, conserve soil moisture, control weeds, or improve soil fertility. Application rate and placement of compost ...largely depends on the proposed beneficial effects and the rate may vary from 25 to 250 Mg ha
−1
(N content up to 4 percent). Application of high rates of compost with high N or P levels may result in excessive leaching of nitrate, ammonium, and phosphate into the groundwater. Leaching could be a serious concern on the east coast of Florida with its inherent high annual rainfall, sandy soils and shallow water table. In this study, five composts (sugarcane filtercake, biosolids, and mixtures of municipal solid wastes and biosolids) were applied on the surface of an Oldsmar sand soil (in 7.5 cm diameter leaching columns) at 100 Mg ha
−1
rate and leached with deionized water (300 ml day
−1
, for five days; equivalent to 34 cm rainfall). The concentrations of NO
3
-N, NH
4
-N, and PO
4
-P in leachate reached as high as 246, 29, and 7 mg L
−1
, respectively. The amount of N and P leached accounted for 3.3-15.8 percent of total N and 0.2-2.8 percent of total P in the compost. The leaching peaks of NO
3
-N occurred following the application of only 300-400 ml water (equivalent to 6.8-9.1 cm rainfall).
Fertilization is critical for sustainable production of citrus on sandy soils. However, information on nutritional diagnosis standards for grapefruit (Citrus x paradisi Macfad. ) is lacking and this ...information is needed for implementation of best management practices (BMPs). A field experiment was conducted from 1997 to 2000 on a Riviera fine sand (loamy, siliceous, hyperthermic, Arenic Glossaqualf) with 30-yr-old+ white Marsh grapefruit trees on sour orange (Citrus aurantium L.) rootstock to evaluate irrigation and fertilization effects on fruit yield and quality and to validate leaf nutrient concentration standards for guiding fertilization of grapefruit. Fertilizers were applied as water soluble granular (WSG, 3 applications yr-1), by fertigation (FRT, 15 applications yr-1), or as controlled-release fertilizers (CRF, 1 application yr-1) and at five rates (0, 56, 112, 168, or 224 kg N ha-1 yr-1) with an N:P:K blend (1.0:0.17:1.02). Fruit yield and quality were not affected by irrigation treatments or fertilizer sources. There was a significantly positive correlation between leaf N concentrations and N rates (r = 0.98**). Fruit yield was linearly related to N rates or leaf N concentrations. At 90% of maximum yield, leaf N concentrations (dry weight basis) were 22 to 23 g kg-1. Fruit quality parameters such as soluble solid concentration (SSC), juice, and total soluble solids (TSS) were positively correlated with leaf N concentrations, whereas fruit titratable acidity (TA) was negatively related to leaf N concentrations or N rates. The effect of N rate on TA outweighed that on SSC and consequently, the SSC/TA ratio decreased with increasing N rates or leaf N concentration. Fruit size was quadratically related to N rate or leaf N concentration. Overall, fruit sizes and SSC/TA ratios were acceptable for fresh marketing or processing at leaf N concentrations of 22 to 23 g kg-1. Therefore, this leaf N concentration of 22 to 23 g kg-1 can be considered the optimal concentration guideline for fertilization of grapefruit provided that other nutrients are sufficient.
Afforestation in sandy soils can cause soil acidification and affect Cu and Zn release. The behaviors of Cu and Zn release from contaminated arable sandy soils were investigated in the laboratory ...with the methods of simulated acidification of the soils. The results showed that soil acidification could change chemical forms of Cu and Zn in the soils, impel the transformation of Cu and Zn from carbonate associated fractions to exchangeable, organic matter and oxides associated fractions, and thus increase the release potential of Cu and Zn in the soils. The effect of the acidification on Zn leaching was more significant than that of Cu. Water solubility of Cu and Zn in the soils was increased with decreasing pH, and the solubility of Cu and Zn was increased exponentially at pH 3.8–4.5, and 6.2–6.5, respectively.
Sedum alfredii Hance has been identified to be a zinc (Zn) hyperaccumulating plant species native to China. In this study, growth responses, uptake and accumulation of cadmium (Cd) and Zn by S. ...alfredii were examined at Cd/Zn combining supply levels. The results showed that optimal growth for both shoots and roots was found when the plant grew at the Cd/Zn level of 100/500 μmol L
−1
. The concentrations of Cd and Zn in leaves and Sstems of Sedum afredii H increased with increasing Cd and Zn supply levels. The distributions of the metals in different plant parts decreased in the order: stem > leaf ≫ root for Zn and leaf > stem ≫ root for Cd. The highest concentrations of Zn (23.2 mg g
−1
) in the stems and Cd (12.1 mg g
−1
) in the leaves were noticed when the plants were grown at the Zn/Cd levels of 1000/50 and 500/400 μmol L
−1
, respectively. The maximum Cd and Zn accumulations in the shoots were 5.1 and 11.2 mg plant
−1
at the Cd/ Zn combining levels of 400/250 and 100/500 μmol L
−1
, respectively. Zinc supply levels <500 μmol L
−1
enhanced Cd concentrations in stems and leaves at the Cd levels <100 μmol L
−1
and Cd concentration in roots at the Cd levels <50 μmol L
−1
. Cadmium at the supply levels ≥100 μmol L
−1
decreased considerably root Zn concentrations for all the Zn levels, slightly increased leaf Zn concentrations at the Zn levels ≥250 μmol L
−1
, but had minimal effect on leaf Zn concentrations at the Zn levels ≥500 μmol L
−1
. The results indicate that S. Alfredii has an extraordinary ability to co-tolerate Cd/Zn toxicities, and to absorb and hyper-accumulate Cd and Zn under a range of Cd/Zn combining levels. Zinc addition at relatively low levels could stimulate Cd uptake and translocation, whereas Cd supply enhanced Zn translocation and partition to the shoots. Sedum alfredii is a Zn/Cd hyperaccumulator, which can be a valuable material for further study on the mechanisms of metal uptake and accumulation and for phytoremediation of the soils with Zn/Cd combined contamination.
Field evaluation of release and availability of nutrients and potentially toxic elements from composts is necessary to estimate their nutrient contribution to crops, potential effect on soil and ...environmental quality. A biosolids (BSD), a yard waste (YW), and a West Palm Beach cocompost (WPCC) were incubated under field conditions in a citrus grove on an Oldsmar fine sandy soil (sandy, siliceous, hyperthermic Alfic Arenic Haplaquods). The incubation columns and the soil underneath each column were sampled on 0, 240, and 360 days after incubation and analyzed for KCl extractable NH
4
-N and NO
3
-N, 0.5 M NaHCO
3
extractable P, and Mehlich 3 extractable K, Fe, Mn, Zn, Cu, and microbial biomass. The total concentration and extractable proportion of each element greatly varied among the three organic amendments. Approximately 34-73% of K, 1-14% of Fe, 7-68% of Zn, 7-47% of Mn, and 2-34% of Cu in the three organic amendments were extractable by the Mehlich 3 reagent at the beginning of incubation. Incubation of these amendments under field conditions for a period of 1 yr increased the availability of N, P, K, and several micronutrients including Fe, Cu, Zn, and Mn. Microbial biomass-C and -P were markedly increased during the field incubation. However, the BSD, containing high total C and other nutrients, produced less microbial biomass-C than the two composts. The rapid increase in concentrations of available metals including Cu, Zn, and Mn in the BSD during the incubation may have adverse effects on microbial biomass growth and proliferation in this compost. A combination of BSD and YW improved conditions for the microbial biomass growth as evidenced by the increase in microbial biomass C and P of this combination during the course of incubation.
It is generally believed that the interception of rain by the citrus tree canopy can substantially decrease the throughfall under the canopy as compared to that along the dripline or outside the ...canopy (incident rainfall). Therefore, the position of placement of soil-applied agrichemicals in relation to the tree canopy may be an important consideration to minimize their leaching during rain events. In this study, the distributions of rainfall under the tree canopies of three citrus cultivars, 'Marsh' grapefruit (Citrus paradisi Macf.), 'Hamlin' orange (Citrus sinensis L. Osbeck), and 'Temple' orange (Citrus hybrid), were evaluated at four directions (north, south, east, west), two positions (dripline and under the canopy), and stem flow. There was not a significant canopy effect on rainfall amounts from stem flow or dripline, compared with outside canopy, for any citrus cultivar or storm event. However, throughfall varied significantly among the four cardinal directions under the canopy of all three citrus cultivars and was highly related to the wind direction. Among the three citrus cultivars evaluated in this study, throughfall, stem flow, and canopy interception accounted for 89.5% to 92.7%, 0.5% to 4.7%, and 5.8% to 9.3% of the incident rainfall, respectively
Many glycoproteins contain multiple glycosylation sites that can present multi-valent epitopes for antigenic recognition. Release of the oligosaccharides results in loss of avidity of antibody ...binding, which has been overcome by reforming clustered ligands, usually by reductive amination of free reducing oligosaccharides to poly-amine groups. We have adapted this approach to hydrazinolytic release of O-linked chains of mucin glycoproteins and ‘one-pot’ microscale coupling to poly-
l-lysine (PLL). The conjugated PLL adheres to nitrocellulose membranes through washing procedures required for antibody or lectin overlay and detection. We show evidence for the applicability of this technique using lectin and antibody reactivity to the oligosaccharides of pigeon intestinal mucins, which have been implicated in the allergic disease pigeon fanciers’ lung.
We report a case of chronic traumatic paraplegia in which epidural electrical stimulation (EES) of the lumbosacral spinal cord enabled (1) volitional control of task-specific muscle activity, (2) ...volitional control of rhythmic muscle activity to produce steplike movements while side-lying, (3) independent standing, and (4) while in a vertical position with body weight partially supported, voluntary control of steplike movements and rhythmic muscle activity. This is the first time that the application of EES enabled all of these tasks in the same patient within the first 2 weeks (8 stimulation sessions total) of EES therapy.
PDF
