Showing papers on "Phosphorus published in 1984"

Soil Nutrient Bioavailability: A Mechanistic Approach

Abstract: Chemistry of Soil-Nutrient Associations. Nutrient Absorption by Plant Roots. Nutrient Uptake by Plant Roots Growing in Soil. Modeling Nutrient Uptake by Plant Roots Growing in Soil. Interaction of Plant Roots with the Soil and Environment. Rhizosphere Microorganisms, Mycorrhizae, and Root Hairs. Nitrogen. Phosphorus. Potassium. Calcium. Magnesium. Sulfur. Boron. Copper. Iron. Manganese. Molybdenum. Zinc. Water. Application of the Mechanistic Uptake Model. Index.

Litterfall, Nutrient Cycling, and Nutrient Limitation in Tropical Forests

Abstract: Patterns of nitrogen, phosphorus, and calcium cycling through litterfall were evaluated using published information from 62 tropical forests. In general, lowland tropical forests have more nitrogen and lower dry mass/nitrogen ratios in litterfall than most temperate forests, while nitrogen return in montane tropical forests is comparable to that in temperate forests. Calcium return is also high in most tropical forests studied, but many tropical forests (lowland and montane) have little phosphorus return and very high dry mass/phosphorus ratios in litterfall compared to most temperate forests. Phosphorus appears to be cycled highly efficiently in such forests. Fine litterfall in the range of tropical forests studied was predicted from climate, and the residuals of this regression were positively correlated with phosphorus but not nitrogen concentrations in litterfall. The amount of fine litterfall (uncorrected for climate) was also significantly correlated with phosphorus concentrations in moist and wet lowland tropical forests. These analyses suggest that phosphorus but not nitrogen availability limits litterfall in a substantial subset of intact tropical forests. Sites on old oxisols and ultisols, especially those in Amazonia, appear to be particularly low in available phosphorus.

Phosphorus versus nitrogen limitation in the marine environment1

Abstract: Limnological and marine geochemical opinion favors phosphorus limitation of organic production in aquatic environments, while marine biological opinion favors nitrogen limitation. Clues in the literature and nutrient budgets for selected marine ecosystems suggest that phosphorus vs. nitrogen limitation is a function of the relative rates of water exchange and internal biochemical processes acting to adjust the ratio of ecosystem N:P availability.

Pathways of Phosphorus Transformations in Soils of Differing Pedogenesis

Abstract: Nine different organic and inorganic soil phosphorus fractions were obtained by a sequential extraction of samples from 168 USDASCS benchmark soils, representing eight soil orders of the Soil Taxonomy The distribution of P across the different fractions (resin, bicarbonate, hydroxide, sonification-2nd hydroxide, acid, and acidperoxide digest fractions with separate organic and inorganic P determinations) and their relationships to other soil chemical properties were used to evaluate the effects of different soil development on phosphorus composition Correlation and regression analyses of P distribution and chemical analyses confirmed the partial dependence of organic matter accumulation on available forms of P Weathering indicators such as base saturation were related to the formation of secondary P forms The relative proportions of available and stable as well as organic and inorganic P forms were dependent upon soil chemical properties and related to soil taxonomy Path analysis of relationships between labile and stable P forms showed that in Mollisols much of the labile resin extractable P was derived from inorganic bicarbonate and hydroxide extractable P forms In more weathered Ultisols, 80% of the variability in labile P was accounted for by organic P forms, suggesting that mineralization of organic P may be a major determinant of P fertility in these soils Additional Index Words: organic phosphorus, inorganic phosphates, sequential phosphorus extraction, soil taxonomy, path-analysis View complete article To view this complete article, insert Disc 4 then click button8

A comparison of the abilities of freshwater algae and bacteria to acquire and retain phosphorus1

Abstract: Extant physiological and in situ data provide contradictory answers to the question of whether the bacterioplankton can outcompete the phytoplankton for phosphorus at natural concentrations. Two phytoplankton species and three bacterial spccics isolated from the epilimnion of Lake Memphremagog, Quebec, were grown in phosphorus-limited continuous cultures and their abilities to take up and retain phosphorus compared. The algae showed orthophosphate uptake kinetics comparable to those reported elsewhere. In contrast, the specific orthophosphate uptake rates (i.c. uptake per unit cell P) by the bacteria were variable, but much higher than the algal rates at the low P concentrations characteristic of natural waters. Algal and bacterial alkaline phosphatase activities were similar and provided no evidence that the algae could utilize organic P more efficiently than the bacteria. The bacteria showed some tendency to excrete P more readily than the algae but mixed culture experiments indicated that excretion did little to alter the long term partitioning of phosphorus between the algae and the bacteria. The kinetic data suggest that planktonic bacteria are unlikely to be limited by phosphorus in situ. Furthermore, our results are consistent with the hypothesis that the bacteria should bc markedly superior competitors at natural phosphate concentrations.

Effect of dietary phosphorus on circulating concentrations of 1,25-dihydroxyvitamin D and immunoreactive parathyroid hormone in children with moderate renal insufficiency.

Abstract: The hyperparathyroidism characteristic of patients with moderate renal insufficiency could be caused by decreases in the plasma concentration of ionized calcium (Ca++) evoked by: (a) recurring increases in the plasma concentration of inorganic phosphorus that may be detectable only in the post-prandial period; (b) a reversible, phosphorus-mediated suppression of renal 25-hydroxyvitamin D-1 alpha-hydroxylase that decreases the plasma concentration of 1,25-dihydroxyvitamin D (1,25-(OH)2D) enough to decrease both gut absorption and bone resorption of Ca++; (c) both of these. In a group of eight children with moderate renal insufficiency, mean glomerular filtration rate (GFR) 45 +/- 4 (SE) ml/min per 1.73 M2, ages 6-17 yr, we tested these hypotheses by determining the effect of short term (5 d) restriction and supplementation of dietary intake of phosphorus on the plasma concentration of 1,25-(OH)2D, the serum concentrations of immunoreactive parathyroid hormone (iPTH) and phosphorus, and the fractional renal excretion of phosphorus ( FEPi ). When dietary phosphorus was normal, 1.2 g/d, the serum concentrations of phosphorus throughout the day were not greater than those of normal control children, and the serum concentrations of carboxyl-terminal iPTH (C-iPTH) were greater, 59 +/- 9 vs. 17 +/- 3 mu leq/ml, and unchanging; the serum concentration of intact-iPTH was also greater, 198 +/- 14 vs. 119 +/- 8 pg/ml. The plasma concentration of 1,25-(OH)2D was lower than that of age-matched controls, 27 +/- 3 vs. 36 +/- 2 pg/ml (P less than 0.01). When dietary phosphorus was restricted to 0.35 g/d, the plasma concentration of 1,25-(OH)2D increased by 60% to a mean value not different from that of normal controls, while serum concentrations of C-iPTH and intact-iPTH decreased by 25%, the latter concentration to a mean value not different from that of controls. FEPi decreased from 31 to 9%. When dietary phosphorus was supplemented to 2.4 g/d, the plasma concentration of 1,25-(OH)2D decreased 32%, while those of C-iPTH and intact-iPTH increased by 131 and 45%, respectively; FEPi increased from 27 to 53%. Plasma concentrations of 25-hydroxyvitamin D remained normal and unchanged, and GFR did not change when dietary phosphorus was manipulated. The data demonstrate that in children with moderate renal insufficiency: (a) A normal dietary intake of phosphorus in attended by a decreased circulating concentration of 1,25-(OH)2D and an increased concentration of iPTH, but not by recurring increases in the serum concentration of phosphorus at any time of the day; (b) Dietary phosphorus is, however, a major determinant of the circulating concentrations of both 1,25-(OH)2D and iPTH, which vary inversely and directly, respectively, with dietary intake of phosphorus, and increase and decrease, respectively, to normal values when phosphorus is restricted for 5 d; (c) Restriction and supplementation of dietary phosphorus induces changes in the serum concentration of iPTH that correlate strongly but inversely with those induced in the plasma concentration of 1,25-(OH)2D (r = -0.88, P < 0.001); and (d) The physiologic responsiveness of the renal tubule to changes in dietary phosphorus is to a substantial extent intact. The data provide support for the second hypothesis stated.

The prediction of internal phosphorus load in lakes with anoxic hypolimnia1

Abstract: Lakes with anoxic hypolimnia (anoxic lakes) have significantly lower values for phosphorus retention than do lakes with aerobic hypolimnia (oxic lakes). This difference may reflect an increased internal phosphorus load from the anoxic hypolimnia. Two models are given to predict internal phosphorus load (L;,,) in such lakes. The first predicts internal load as the difference between the observed phosphorus retention in anoxic lakes and that predicted (Rpred) by a formula that adequately describes phosphorus retention in oxic lakes. The second predicts internal load as the product of an average rate of phosphorus release from anoxic sediments, the surface area of the anoxic sediment, and the period of anoxia. Predictions of the first model compare favorably with 17 observed values of internal load; further data are required to test the second model. These models suggest that mean phosphorus concentration (TP) in anoxic lakes can be predicted in two ways. One can use whole-lake phosphorus budget models which implicilly incorporate internal phosphorus load, because they include a measurement of phosphorus retention. Alternatively, a term to account for the internal load can be added to current models based on external load (L,,,) and predicted retention (I&J, where

The effect of phosphorus on the formation of hyphae in soil by thevesicular‐arbuscular mycorrhizal fungus, glomus fasciculatum

Abstract: Summary Hyphae formed in soil by the vesicular-arbuscular (VA) mycorrhizal fungus, Glomusfasciculatum (Thaxter sensu Gerd.) Gerd. and Trappe were extracted using the membrane filter techniqe and their length was estimated by the grid intersection method. The effect of phosphorus on the formation of this external mycelium was assessed after sampling procedures had been investigated. Phosphorus supply was varied from amounts severely deficient to those adequate for the growth of subterranean clover. After 6 weeks, the alleviation of severe phosphorus deficiency increased both the length of infected root and the length of external hyphae per centimetre of infected root. Further additions of phosphorus decreased both of these measurements. However, the level of added phosphorus at which the most external hyphae was formed per centimetre of infected root was higher than the level of phosphorus which gave the greatest length of infected root. The increase in phosphorus supply which gave the greatest increase in the length of external hyphae per centimetre of infected root also decreased the formation of vesicles within infected roots. At phosphate levels adequate for growth of mycorrhizal plants, there was little development of either external hyphae in soil or vesicles within the mycorrhizal roots.

Soil characteristics and nutrient status in a Northern Australian mangrove forest

Abstract: The results of a study of soil factors in relation to plant growth for a tropical mangrove forest in northern Australia are presented and discussed. Basic soil properties are described briefly in terms of particle size distribution, bulk density and total carbon, nitrogen and phosphorus. Soil redox potential, pH, salinity and extractable nitrogen and phosphorus were monitored monthly over a 14 month period commencing April 1979. Sampling was carried out at 9 sites along a 370 m transect which exhibits strong gradients in topography, above ground biomass, canopy height and species distribution. Statistical analysis of the data shows that above ground biomass correlates significantly with the following soil factors, averaged over depth within the rooting zone and over time: Extractable P (r=0.85, p<0.01), redox potential (r=0.89, p<0.01) and salinity (r=−0.79, p<0.05). The strong biomass-EH correlation may be partly due to oxygen translocation by the plants to the root zone. Soil ammonium levels were within the range of 1–14 μg N per g (dry wt) and, unlike the above parameters, showed only minor variation with position along the transect. Variation of ammonium levels with time was apparent, but no significant correlation with rate of new shoot growth could be demonstrated, although depth profiles indicated depletion of ammonium by plant uptake during rapid growth periods. In addition neither soil ammonium, extractable phosphorus nor rate of plant growth showed any definite seasonal periodicity in this tropical system.

Phosphorus Cycling in a Northern Hardwood Forest: Biological and Chemical Control

Abstract: Phosphorus is tightly conserved within the northern hardwood forest ecosystems at Hubbard Brook, New Hampshire. Detailed analyses of the soil system indicate that biological and geochemical processes, stratified within the profile, regulate phosphorus retention.

The relative importance of bacterioplankton and phytoplankton in phosphorus uptake in freshwater1

Abstract: In several studies of orthophosphate cycling in lakes, most of the phosphorus uptake has been associated with the smallest limnetic particles. The hypothesis that bacteria rather than phytoplankton are responsible for most P uptake in situ was tested in Lake Memphremagog by means of size fractionation of [32P]orthophosphatc uptake, [14C]glucose uptake (as an indicator of bacterial activity), and both [r4C]bicarbonate uptake and chlorophyll a (as indicators of algal activity). In biweekly samples from May to October, particles ~3.0 pm accounted for 72-98% (median 94%) of the uptake of orthophosphate. There was no diel variation in the fraction of uptake by particles ~3.0 pm. The bacterial contribution to the total community uptake of orthophosphate was estimated to range between 97 and 100% over all samples collected. However, the phosphorus released (shown not to be orthophosphate) was taken up almost entirely by the phytoplankton. The bacterioplankton apparently strongly dominates orthophosphate cycling in situ, while the phytoplankton seems to obtain most of its phosphorus from excreted organic P compounds.

Zooplankton community structure, but not biomass, influences the phosphorus-chlorophyll a relationship

Abstract: Simultaneous observations were made of total phosphorus (TP), chlorophyll a (Chl a), and zooplankton biomass and community structure at 12 sites in the Eastern Townships (ET) region of Quebec to de...

Effect of soil compaction on root growth and uptake of phosphorus

Abstract: Zea mays L. andLolium rigidum Gaud. were grown for 18 and 33 days respectively in pots containing three layers of soil each weighing 1 kg. The top and bottom layers were 100 mm deep and they had a bulk density of 1200 kg m−3, while the central layer of soil was compacted to one of 12 bulk densities between 1200 and 1750 kg m−3. The soil was labelled with32P and33P so that the contribution of the different layers of soil to the phosphorus content of the plant tops could be determined. Soil water potential was maintained between −20 and −100 kPa.

Potential mobility of phosphorus in different types of lake sediment

Abstract: The fractional composition and potential mobility of sediment phosphorus was investigated in a number of Swedish lakes with different characteristics. Differences between sediments regarding P release patterns in laboratory experiments with varying pH and redox conditions could largely be explained by differences in the fractional composition of the sedimentary P. Sediments from sewage-loaded lakes contained considerably more loosely adsorbed P than unpolluted lakes. P release was redox-sensitive and strongly favoured by high pH values in sediments with a high content of aluminium and iron-bound P. Other sediments released primarily organic and loosely adsorbed P, and in such cases less P was released and redox and pH conditions had less effect. Comparisons with P release rates determined by mass balance calculations were made.

Cadmium accumulation by a Citrobacter sp.

Abstract: SUMMARY: Cadmium accumulation by a Citrobacter sp. growing in the presence of the metal occurred as a sharp peak during the mid-exponential phase of growth, but cultures showed considerable inhibition of growth compared to cadmium-free controls. This problem was overcome by pregrowing the cells in cadmium-free medium and subsequently exposing them to the metal in the resting state, under which conditions higher concentrations of cadmium were tolerated and metal uptake was enhanced. This ability was retained when the cells were immobilized and then challenged with a flow containing Cd2+; 65% of the metal presented was removed from solution. The influence on uptake of the composition of the exposure buffer and of various cell treatments were investigated and the results are discussed with respect to the anticipated speciation of the cadmium presented to the cells and also with respect to the probable mechanism of metal uptake. This is thought to occur through the activity of a cell-bound phosphatase, induced during pre-growth by the provision of glycerol 2-phosphate as sole phosphorus source. Continued enzyme function in resting cells would then precipitate the metal as cell-bound cadmium phosphate.

A Simplified Soil and Plant Phosphorus Model: II. Prediction of Labile, Organic, and Sorbed Phosphorus

Abstract: Surface samples and soil chemical, physical and taxonomic data for 78 soils from the continental U.S. and Puerto Rico were obtained from the U.S. Soil Conservation Service National Soil Survey Lab. Phosphorus was extracted with the following: NHF + HCl (Bray 1 P), NaHCO (Olsen P), HCl + HSO (North Carolina P), and anion exchange resin (labile P). Organic P and an index of fertilizer P sorption were also measured. Soils were divided into three groups based on soil taxonomy and weathering. Regression analysis was used to obtain equations to predict labile P, organic P, and a P sorption index from soil chemical and physical properties. Labile P was related to extractable P; organic P to total N and pH; and P sorption to clay, CaCO, labile P, and base saturation. These parameters accounted for up to 84% of labile P variation, 64% of organic P variation, and up to 78% of P sorption variation. Although the equations are empirical, independent variables chosen in the stepwide regression were consistent with P mineralization and sorption relationships previously reported. These relationships were tested using independent data sets. They can be used to generate inputs for the soil P component of the Erosion-Productivity Impact Calculator crop management model from soil test P and data available in U.S. Soil Conservation Service/State Agricultural Experiment Station Soil Survey Investigation Reports.

A 31P nuclear magnetic resonance study of the phosphorus species in alkali extracts of soils from long‐term field experiments

Abstract: SUMMARY The different forms of phosphorus (P) in 0.5 m sodium hydroxide extracts of soils from long-term field experiments at Rothamsted were characterized by 31P-nuclear magnetic resonance spectroscopy (NMR). The extract from an old grassland soil (pH 4.6) from a plot of the Park Grass Continuous Hay Experiment that had received no fertilizer or lime for at least 125 years contained the following forms of P: inorganic orthophosphate (22% of the extracted P), orthophosphate monoesters (49%), orthophosphate diesters (14%), phosphonates (3%), pyrophosphate (4%) and two unidentified forms of P (7%). The soil extract from a Park Grass plot given inorganic phosphate fertilizer (35 kg P ha−1) annually for 121 years contained the same forms of P and, in addition, a small amount of polyphosphate. There was also evidence of an increase in the orthophosphate monoester fraction. Another old grassland soil, of pH 6.1, contained more total and organic P than Park Grass but the extract contained fewer forms of P: inorganic orthophosphate (14% of the extracted P), orthophosphate monoesters (39%), orthophosphate diesters (34%) and an unidentified form (13%). An area of this grassland that had been ploughed up 20 years previously, and kept bare since, contained less organic P. The extract contained less of the phosphate diesters but the more stable monoesters remained relatively unchanged.

Seasonal Dynamics of Nutrient Limitation in a Tropical High-Altitude Lake (Lake Titicaca, Peru-Bolivia): Application of Physiological Bioassays

Abstract: Five types of physiological assay were applied to samples from three sites in Lake Titicaca, PeruBolivia (16”s) to assess the magnitude and seasonality of N or P limitation of algal growth. Phosphorus appeared to be in abundant supply relative to growth requirements throughout 1982. Alkaline phosphatase levels were low (~3 nmol substrate converted.cc.g-‘Chl aeliter-l), 3zP0.,3turnover times were always long (> lo3 min in the main body of the lake), and little or no phosphorus was accumulated by the seston during short term enrichments. Ammonium enhancement assays suggested a persistent cellular shortage of nitrogen throughout all seasons in the plankton of a large shallow bay, and in the main basin when the water was stratified. High ammonium uptake capacities, as measured with the NH,+ analogue [L4C]methylammonium, and selective accumulation of nitrogen from N plus P enrichments provided supportive evidence of cellular N deficiency. Winter mixing brought large quantities of NO,- and SRP into the surface euphotic zone of the main basin, and throughout this period neither N nor P appeared to be limiting. Polymixis in the shallow bay resulted in large variations in nitrogen supply and deficiency, and these effects were modulated in part by changes in depth of the euphotic zone. Nitrogen was always in low abundance relative to phosphorus in Lake Titicaca, but the extent of nutrient control on algal growth varied considerably with site and time of year.

Biological Availability of Soluble Reactive Phosphorus in Anoxic and Oxic Freshwaters

Abstract: The availability of hypolimnetic phosphorus was assessed by a short-term bioassay, based on 32P uptake kinetics. In the anoxic hypolimnia of eight lakes and in anoxic model systems (core tubes), at...

Role of Internal Phosphorus Loading in Two Shallow, Productive Lakes in Alberta, Canada

Abstract: The contribution of internal loading from the sediments to the total phosphorus (TP) budget and to the [TP] in the surface water was investigated from May to November in Nakamun and Halfmoon lakes, Alberta. During the summer, Nakamun Lake was intermittently stratified and Halfmoon Lake was weakly, thermally stratified. During the stratified periods, water overlying the sediments was anoxic, TP levels increased in the deep water, and sediments were the main source of TP, contributing 1468 and 147 kg of TP to Nakamun and Halfmoon lakes, respectively. During these same periods, internal loading to Nakamun and Halfmoon lakes (12.7 and 15.6 mg∙m−2∙d−1, respectively) were slightly higher than the rates predicted from laboratory experiments on sediment cores (9.7 and 7.2 mg∙m−2∙d−1, respectively). Quantitative estimates of vertical water exchange in Nakamun Lake and in-lake TP budgets for both lakes indicated that phosphorus released from the sediments was transported to the surface water during mixing. After ei...