Showing papers on "Phosphorus published in 1977"

Simulation of Phosphorus Cycling in Semiarid Grasslands

Abstract: A simulation model of the phorphorus cycle in semiarid grasslands was developed and tested. When used with appropriate data sets for biotic and abiotic driving variables at the Pawnee (Colorado) and Matador (Saskatchewan) Sites, this model predicted plant and decomposer uptakes and turnover rates of the principal phosphorus compartments. Daily phosphorus requirements for plant and decomposer uptake are taken from pools of labile inorganic phosphorus in each soil layer. Mineralization of labile organic phosphorus and leaching of water-soluble forms from standing dead biomass and litter are the main sources of replenishment of the labile inorganic pools. Phosphorus solubility, soil-water content, and rates of diffusion of phosphorus through soil are the primary controls on rates of uptake by the active fraction of the live-root biomass.

The Assessment of Plant-Available Cadmium in Soils

Abstract: Three pot experiments were conducted to test the utilization of ash from different kinds of animal manures and vegetative crop residues as source of phosphorus fertilizer. Corn (Zea mays L.) yield grown on phosphorus-deficient soil (Aiken loam), treated with acidified ash at rates equivalent to 200, 400, 800, and 1,200 ppM P, responded almost like concentrated super phosphate (CSP) at the same rates. Yields from pots treated with ash acidified at 50% of its base equivalent were slightly less than those at 100% acidification. The leached acidified ash of agricultural waste materials proved to be a comparable source to CSP fertilizer.

Nitrogen, Phosphorus and Water Contents During Grain Development and Maturation in Wheat

Abstract: Plants of five cultivars of wheat were grown under controlled-environmental conditions in order to analyse the effect of cultivar and of temperature and illuminance after anthesis on the accumulation of nitrogen and phosphorus by grains in relation to dry matter. The water relations of the grain during maturation were also examined, using calcium content as an index of water entry. The nitrogen and phosphorus contents of grains increased linearly throughout the grain growth period. The percentage of nitrogen and phosphorus in grains fell sharply during the first few days after anthesis but rose progressively thereafter. The higher the temperature, and the lower the illuminance, the higher was the percentage of nitrogen in the grain of all cultivars. Such conditions also reduce final grain size, but their effects on nitrogen concentration in the grain were apparent early in grain development. No evidence was found of a flush of nitrogen or phosphorus into the grain late in its development. Water entry into the grain continued at a steady rate until maximum grain dry weight was reached, then ceased suddenly. No evidence was found of an increased rate of water loss by the grain at that stage, and the rapid fall in water content at the cessation of grain growth may have been due to blockage of the chalazal zone of entry into the grain by the deposition of lipids. Accumulation of dry matter, nitrogen and phosphorus and entry of water into the grain all ceased at the time of lipid deposition in the chalazal zone.

Vesicular‐arbuscular infection and soil phosphorus utilization in lupinus spp.

Abstract: SUMMARY Lupinus angustifolius, L. cosentinii and L. luteus were weakly infected (<10% of root length) with vesicular-arbuscular endophytes and hence VA mycorrhizas were not considered of any value in their phosphorus uptake on the nutritionally poor sandy soils of Western Australia. Vesicles were present in approximately 30% of field plants and less often in the glasshouse. Arbuscules were observed on only one specimen of L. cosentinii in a restricted section of one lateral root. Infection was reduced further when soil moisture was high and by small additions of phosphorus to the soil. Under certain conditions, VA mycorrhizal infection in L. cosentinii was stimulated by the growth of red clover. ‘Proteoid’ -like rootlets were observed on lupins and these had specialized root-soil surface properties that may be responsible for improved phosphorus uptake.

Respiration and excretion by the ctenophore Mnepiopsis leidyi

Abstract: Respiration (dissolved oxygen and carbon dioxide) and excretion (dissolved organic carbon, inorganic and organic nitrogen and phosphorus) rates were measured for a variety of sizes of Mnemiopsis leidyi over a temperature range of 10.3° to 24.5°C. Both respiration and excretion rates were a direct linear function of animal weight and very temperature sensitive (Q10≊4). Oxygen uptake ranged from 155 to 489 μg at O/(g dry weight) day-1 and carbon dioxide release from 43 to 166 μM. Organic carbon made up about 38% of the total carbon released. Inorganic nitrogen excretion, exclusively in the form of ammonium, comprised 54% of the total nitrogen release and ranged from 10 to 36 μM NH4/(g dry weight) day-1. Average release of dissolved primary amines (expressed as glycine equivalents) equaled 43% of the organic nitrogen fraction. Inorganic phosphorus release ranged from 2.0 to 4.9 μM/(g dry weight) day-1 and made up about 72% of the total phosphorus loss. The turnover of elements in the body was calculated as 5 to 19% per day for carbon and nitrogen, depending on the temperature, and an even higher 20 to 48% per day for phosphorus. These values are comparable to rates observed for small, active zooplankton.

Interaction between effects of vesicular–arbuscular mycorrhiza and fertiliser phosphorus on yields of potatoes in the field

Abstract: MANY experiments in controlled environments have shown that vesicular–arbuscular (VA) mycorrhizas may benefit the phosphorus uptake and growth of plants1–4, depending on the nature and level of indigenous inoculum, the phosphorus status of the soil and other factors5–7. But there have been few reports of attempts to obtain larger crops, or reduce phosphorus fertiliser requirement, by manipulation of VA mycorrhizal infection in field crops8–12. We report here the effect on potatoes of an artificial increase in the level of VA infection. Potatoes are known to have VA mycorrhizas13–16, and their sparse rooting systems17 and heavy phosphorus demand suggest that they should respond to infection. This is the first report of a successful field inoculation experiment on a major field crop in temperate zone conditions.

The uptake and release of dissolved phosphorus by reef corals1*2

Abstract: The fluxes of dissolved reactive, organic, and total phosphorus into and out of nonfeeding corals were measured by chemical and radiochemical techniques. A net uptake of reactive phosphorus from seawater by corals containing zooxanthellae was not, at typical ambient phosphorus levels, sufficient to offset simultaneous losses of organic P. Consequently, there was a net loss of total P. A coral without zooxanthellae was unable to remove net amounts of reactive P from solution even at levels above ambient. Reactive phosphorus uptake was light sensitive, was highly temperature dependent, showed characteristics of Michaelis-Menten kinetics, and could be inhibited by arsenate. An active transport mechanism appears to be involved. The kinetics of net reactive phosphorus uptake were described by a Michaelis-Menten equation modified to include a correction for an efflux of reactive P accompanying uptake. The mean half-saturation constant (K) for uptake was 377 nM and the mean maximum rate of uptake (unlax) was 293 ng atoms P * mg Chl a-l . h-l. Although the symbiotic corals tested cannot obtain all of the phosphorus they require by means of reactive phosphorus uptake at typical environmental concentrations, the ability of corals to obtain part of it in this manner, and the presence of mechanisms for efficient recycling of phosphorus within the symbiotic association, may help enable corals to flourish in waters low in phosphorus sources.

Kinetics of phosphate limited algal growth

Abstract: The kinetics of phosphate limited growth of two green algae Chlorella pyrenoidosa and Selenastrum capricornutum have been studied in chemostats. Several kinetic models which express the specific growth rate as a function of the intracellular phosphorus content have been examined, and one of the models was found to be significantly better than the other models. The principles of this model were described in a recent paper by Nyholm. The kinetics of phosphate uptake have been investigated by adding pulses of phosphate to the chemostats, The uptake by phosphorus deficient cells could be described by Michaelis-Menten kinetics for phosphate concentrations below approximately 500 microng P/liter. Further, with the assumption of a discontinuous adjustment of the uptake rate at the onset of phosphorus deficiency, a complete kinetic model for growth and phosphate removal is proposed. The mean cell size and the contents of chlorophyll a and RNA per unit dry weight have been measured for C. pyrenoidosa as a function of the dilution rate.

Nutrient transport in surface runoff and interflow from an aspen-birch forest

Abstract: Nutrients transported in surface runoff and interflow from an undisturbed aspen-birch (Populus tremuloides Michx., and Betula papyrifera Marsh.) forest (6.48 ha) in northern Minnesota were measured for 3 years. Surface runoff from snowmelt accounted for 97% of the average annual surface runoff and for 57% of the average annual water loss. Slope aspect influenced the amount, rate, and time of snowmelt runoff. In surface runoff, organic nitrogen (N) comprised 80% of the total N load, and organic (+ hydrolyzable) phosphorus (PI comprised 45% of the total P load. The quantities of cations in surface runoff were in the order of calcium (Ca) > potassium (K) > magnesium (Mg) > sodium (Na). More than 96% of all the nutrients in surface runoff were transported by snowmelt. The annual volumes of interflow varied only slightly during the 3 years. Compared with surface runoff, the amounts of all the nutrients (except Na) and their weighted concentrations decreased in interflow. These nutrient losses from the ecosystem can accumulate in surface waters.

Studies on mineral ion absorption by plants

Abstract: The effect of Al and P on the growth of lucerne (Medicago sativa) was studied in nutrient solutions in which aluminium phosphate did not precipitate. Al and P retained in the free space of the roots was washed out with 0.1N HCl/O4 at 5°C. The inhibitory effect of Al on growth was much less at pH 5 than at pH 4.5, although 3 to 4 times as much Al was found in the roots and shoots of the pH 5 plants. It is suggested that the low toxicity of high contents of Al was due to a portion of the uptake at pH 5 being in the form of polymeric aluminophosphate complexes of low net charge density. The optimum pH for the formation and polymerization of such complexes is around 5, and their composition depends on the P/Al mole ratio of the initial solutions. Washing32P-labelled roots in unlabelled P solutions containing Ca showed that 12–43 per cent more of the total label diffused out of the Al-treated roots at pH 5 than from control roots. This was consistent with estimates by solution analysis of 16–36 per cent (depending on the P/Al mole ratio) of the P present in the original uptake solutions being complexed with Al.

Paleolimnology and trends in the phosphorus and iron budgets of an old man‐made lake, Barton Broad, Norfolk

Abstract: SUMMARY. Barton Broad, Norfolk is a shallow, eutrophic lake. During the last 30 years submerged macrophytes have declined and phytoplankton numbers have increased. This change is traced through the stratigraphy of a 60-cm mud core. Diatom frustule counts of 1-cm sections of the core showed that an epiphyte-dominated diatom community was replaced by a planktonic community. From chemical analysis and radio-isotope dating of the core, sedimentation rates and past phosphorus and iron loadings are estimated. Sedimentation rates were between 1.2 mm and 3.1 mm year−1 during the early part of the core but doubled in the 1950s to 5 mm year−1, doubled again in the 1960s and have increased to 12 mm year−1 in the 1970s. Retention of phosphorus in the sediment increased from 0.5 g m−2 year−1 to 18–21 g m−2 year−1 in two steps. A similar trend is shown for iron. The diatom species composition and chemistry of the core sections are correlated with increased nutrient loading and the decline of macrophytes. Contemporary phosphorus and iron budgets are calculated from inflow–outflow data and balanced using sediment retentions estimated from the core data. It is believed a large proportion of phosphorus and iron enters the Broad by movement of sediment along the river bed. A reduction of 25% of the 1975 phosphorus loadings would probably permit re-establishment of some macrophytes. The present chemistry and algal communities of Barton Broad and the River Ant are described.

Chlorophyll production, in response to nutrient additions, by the algae in Lake Rotorua water

Abstract: Batch cultures of water and algae from Lake Rotorua were subjected to nitrogen, phosphorus, and trace element additions, singly and in combination, at monthly intervals between June 1975 and May 1976. The algal responses to the additions were assayed after 5 d incubation, by extracting the chlorophyll from the algae and estimating the concentration by fluorescence. The chlorophyll production consistently responded positively to the addition of nitrogen, while responses to the addition of phosphorus and trace elements were minor by comparison. Although the chlorophyll responses to nitrogen may not have been paralleled by actual growth, the consistent pattern of behaviour by algae in the batch cultures was interpreted as evidence of persistent shortage of nitrogen in the Lake Rotorua environment.

Interactive Effect of Salinity and Phosphorus on Sesame1

Abstract: A solution culture experiment was conducted with a short-season sesame [Sesamum indicum L. (Selection 333)] to observe interactive effects of osmotic potential (—0.4, —1.4, —2.4, and —4.4 bars NaCl added to a complete nutrient solution), and P concentration (0.5, 5, 25, and 50 mg P/liter) on water relations, mineral nutrition, and yield characteristics. Salinity reduced yields linearly with a 50% decrease in pod yield at an osmotic potential of approximately —2.7 bars. Increasing P concentrations increased yields only at low salinity levels; at higher salinity levels, yields decreased progressively as P increased. Salt tolerance was reduced by the higher P additions. A multiple regression equation for pod yield as a function of salinity and P in combination was developed (R = 0.76). Leaf water potential at the early flowering stage decreased with pod yield as salinity and P concentrations increased. Leaf NO3 concentrations decreased as salinity increased. Additional Index Words: leaf water potential, short-season sesame, salt tolerance. View complete article To view this complete article, insert Disc 4 then click button8

Nutrient exchanges between brackish water marshes and the estuary

Abstract: Two irregularly flooded brackish marshes of the Chesapeake Bay estuarine system were studied to detect patterns of tidal nutrient exchange and utilization A 57 ha marsh on the Choptank River was monitored monthly from October 1974 to August 1975 for dissolved inorganic nitrogen and phosphorus During these diurnal samplings, nutrient exchange with the estuary was eliminated by a tidal gate and total aquatic oxygen metabolism was measured During winter, photosynthesis exceeded respiration, and total nitrogen increased to 80 μg-at liter−1 and declined through spring to 8 μg-at liter−1 Phosphate varied erratically from 08 to 43 μg-at liter−1 Tidal import and export of the above nutrients were also monitored monthly from January to June 1975 During winter, there appears to be a net flow of inorganic nitrogen and phosphorus to the estuary In spring this pattern is reversed for both nutrients Two years tidal flow data from a larger 127 ha marsh on the Patuxent River revealed that dissolved inorganic nitrogen is also taken up in May, June and July However, when the dissolved organic fraction is also consisered, net nitrogen flow was always to the estuary in every month sampled It is estimated that the dissolved nitrogen flux from the marsh was 414 g m−2 yr−1, or about 18-82% of the estimated nitrogen of the vegetation Also, the net annual flux of dissolved phosphorus was 019 g m−2 yr−1 to the estuary or 8-23% of the phosphorus in standing crop Data from both marshes suggest that, in contrast to previously studied high salinity marshes, brackish marshes act more as sources of nutrients to the estuary However, these marshes may be trapping some nutrients, either from upland areas surrounding them, or possibly from infrequent massive river deposition