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  • 1
    Electronic Resource
    Electronic Resource
    Cation transport during unsaturated flow through two intact soils (1997)
    Oxford, UK : Blackwell Publishing Ltd
    European journal of soil science 48 (1997), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In the quest for better understanding of cation movement through undisturbed soils, leaching experiments on 300-mm long undisturbed soil columns of two contrasting soils were carried out. One soil was a weakly-structured alluvial fine sandy loam, the other a well-structured aeolian silt loam. About 2000 mm of solutions of MgCl2 and Ca(NO3)2 of 0·025 M were applied at unsaturated water flow rates of between 3 and 13 mm h−1. Solute movement was monitored over several weeks by collecting effluent under suction at the base. In the sandy loam anion transport was influenced by exclusion from the double layer, whereas in the Ramiha soil anion adsorption occurred. Cation transport was described by coupling the convection-dispersion equation with cation exchange equations. Good simulations of the Mg2+ and Ca2+ concentrations in the effluent and on the exchange sites were obtained if 80% of the exchangeable cations, as measured using the 1 M ammonium acetate method, were assumed to be active. Local physical or chemical disequilibrium did not need to be explicitly taken into account. About 400 kg ha−1 of native potassium was leached from the alluvial soil, but only about 10 kg ha−1 was leached from the aeolian soil. The convection-dispersion equation coupled with exchange theory was found to describe cation transport under unsaturated flow through undisturbed soil satisfactorily.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2389.1997.tb00206.x
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  • 2
    Electronic Resource
    Electronic Resource
    The effects of nitrogen fertilizer form on the plant availability of phosphate from soil, phosphate rock and mono-calcium phosphate (1987)
    Springer
    Nutrient cycling in agroecosystems 12 (1987), S. 269-283 
    Details
    ISSN: 1573-0867
    Keywords: Sechura phosphate rock ; plant-availability of phosphate rock ; nitrogen fertilizer/phosphate rock interactions ; phosphate rock dissolution and soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse trial using lettuce as the test crop, and laboratory incubations were used to evaluate the influence of various nitrogen fertilizers on the availability of phosphate from an unfertilized loamy sand soil and from the same soil fertilized with Sechura phosphate rock or monocalcium phosphate. The order in which nitrogen fertilizer form increased plant yield and P uptake from soil alone and from soil fertilized with the rock was ammonium sulphate 〉 sulphurised urea 〉 ammonium nitrate 〉 urea 〉 potassium nitrate. For each rock application (both 30 and 60 mg/pot) and for soil alone, increased P uptake by the plant correlated well with decreased soil pH. In soil fertilized with the soluble P form, monocalcium phosphate, the form of the nitrogen fertilizer had little effect on plant P uptake. Subsequent laboratory incubation studies showed that increased dissolution of soil-P or Sechura phosphate rock did not occur until acidity, generated by nitrification or sulphur oxidation of the fertilizer materials, had lowered soil pH to below 5.5. A sequential phosphate fractionation procedure was used to show that in soils treated with the acidifying nitrogen fertilizers, ammonium sulphate and urea, there was considerable release of Sechura phosphate rock P to the soil, amounting to 42% and 27% of the original rock P added, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01315111
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  • 3
    Electronic Resource
    Electronic Resource
    Single superphosphate-reactive phosphate rock mixtures. 1. Factors affecting chemical composition (1987)
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 223-239 
    Details
    ISSN: 1573-0867
    Keywords: exchangeable P ; free acid ; partial acidulation ; superphosphate ; reactive phosphate rock ; X-ray diffraction pattern
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of additon of reactive phosphate rock (RPR — North Carolina) on the degree of acidulation of unreactive phosphate rocks (PRs — Nauru and Christmas Island A) during the manufacture of single superphosphate (SSP) was examined using32P in isotopic dilution studies. Acidulation of unreactive PR during SSP manufacture continued through denning, granulation and drying. Even after 3 hours drying, between 20 and 30% of the total P remained as free phosphoric acid in the reaction mixture. The addition of North Carolina phosphate rock (NCPR) to ex-den SSP reaction mixture (3:7 NCPR:SSP reaction mixture) preferentially consumed the free phosphoric acid remaining in the reaction mixture. This resulted in reduced acidulation of the unreactive PR in the reaction mixture and partial acidulation (10–23%) of the RPR. Hence the SSP-RPR mixture contains more residual, unreactive PR than is present in SSP. The extent of partial acidulation of the RPR when mixed with SSP was determined by the nature of free acid remaining in the SSP reaction mixture, which in turn is affected by the type of unreactive PR used for SSP manufacture. The free acid in the Christmas Island A reaction mixture contained approximately 8 and 12 times as much Fe and Al respectively as that in the Nauru reaction mixture, and was only half as effective at converting the P in RPR to soluble P. Unless made with extended denning times and carefully chosen PR, SSP-RPR mixtures can contain (a) undesirable amounts of unreactive PR residues, and (b) low quality partially acidulated RPR, both of which have low agronomic value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066446
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of liming on phosphate extracted by two soil-testing procedures (1987)
    Springer
    Nutrient cycling in agroecosystems 14 (1987), S. 143-152 
    Details
    ISSN: 1573-0867
    Keywords: lime ; soil testing ; Olsen P ; Mehlich P ; coprecipitation ; constant pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Lime and phosphate (P) additions had a variable effect on Olsen- and Mehlich-extractable P in 4 acid soils from Fiji. Olsen-extractable P was at a minimum between pH values of 5.5–6.0, on either side of which it increased, particularly in soils which received large amounts of added P. The initial decrease in Olsen-extractable P is attributed to the removal of P from solution by precipitation during the Olsen extraction. The increase at higher pH values is thought to be due to the slow release of P from precipitated Ca-P compounds. There was a consistent decrease in Mehlich-extractable P with increasing soil pH. When the pH of the Mehlich reagent was kept constant, using an autotitrator, there was no decrease in Mehlich-extractable P, suggesting that in the absence of pH control the decrease in extractable P was largely due to the neutralizing effect of lime on the Mehlich reagent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066607
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  • 5
    Electronic Resource
    Electronic Resource
    Characterizing the dissolution of phosphate rock materials by electro-ultrafiltration (1987)
    Springer
    Nutrient cycling in agroecosystems 14 (1987), S. 161-171 
    Details
    ISSN: 1573-0867
    Keywords: Electro-ultrafiltration ; chemical reactivity ; dissolution rate ; ionic strength ; North Carolina phosphate rock ; Sechura phosphate rock ; Chatham Rise phosphorite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Electro-ultrafiltration (EUF) was evaluated as a potential technique for characterizing the dissolution and assessing the chemical reactivity of contrasting phosphate rock (PR) materials. The types of rock used were: three reactive rocks, Sechura phosphate rock (SPR), North Carolina phosphate rock (NCPR), and Chatham Rise phosphorite (CRP), which contains significant amounts of calcium carbonate; one unreactive rock, Tennessee phosphate rock (TPR); and one iron and aluminium phosphate, calcined Christmas Island “C” grade phosphate rock (Calciphos). Dissolution of SPR increased as the solution:solid ratio increased to 250:1, the voltage was increased from 0 to 400 V, and the ionic strength of the extracting solution was increased. The neutralizing effect of any CaCO3 present in PR materials, which is a major limitation with single chemical extraction procedures, does not appear to be a problem with EUF. A limitation of using de-ionized water as the extracting solution with EUF is the small amounts (1 to 6%) of total of P extracted. Addition of NaCl to the extracting solution increased the dissolution of all PR materials, although this varied with the PR. With both de-ionized water and NaCl as the extracting solution, EUF was inferior to 2% formic acid for assessing agronomic effectiveness of the PR materials. EUF appears to be of limited value in assessing the chemical reactivity of PR materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01066609
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  • 6
    Electronic Resource
    Electronic Resource
    An evaluation of water extraction as a soil-testing procedure for phosphorus II. Factors affecting the amounts of water-extractable phosphorus in field soils (1988)
    Springer
    Nutrient cycling in agroecosystems 15 (1988), S. 225-236 
    Details
    ISSN: 1573-0867
    Keywords: Soil P test ; water extraction ; seasonal variation ; sampling depth ; fertilizer P addition ; microbial biomass P
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of seasonal variation, sampling depth, and fertilizer P addition on water-extractable P values were investigated in two field experiments, involving soils of contrasting P retention capacity (Ramiha and Tokomaru) under permanent pasture over 12 months. The effects of the same parameters on Olsen-extractable P were also evaluated. The amounts of water-extractable P in soil were always lower than those of Olsen-extractable P. Over the 12-month period, the average value of water-extractable P in the unfertilized Ramiha soil (0–7.5 cm depth) was 1.8µg g−1 soil compared to an Olsen-extractable P value of 12.6µg g−1. The variability associated with water-extractable P at each sampling time was comparable with that for Olsen-extractable P. However, the relative seasonal variation over 12 months was larger for water-extractable P than for Olsen-extractable P. The results obtained with both extractants showed a seasonal fluctuation which was closely related to the pattern of pasture P uptake. The amounts of water- and Olsen-extractable P were higher in samples taken from the 0–4.0 cm than the 0–7.5 cm sampling depth. Fertilizer P addition resulted in larger increases in water-extractable P in the 0–4.0 cm sampling depth than in the 0–7.5 cm depth. The relative increase in water-extractable P following fertilizer P addition was larger than that of Olsen-extractable P. Seasonal changes in the soil microbial biomass P were not related to changes in either water-extractable P or plant uptake of P. Microbial biomass P may be a less sensitive index of soil P availability than is commonly thought.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051344
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  • 7
    Electronic Resource
    Electronic Resource
    An evaluation of water extraction as a soil-testing procedure for phosphorus I. Glasshouse assessment of plant-available phosphorus (1988)
    Springer
    Nutrient cycling in agroecosystems 15 (1988), S. 211-223 
    Details
    ISSN: 1573-0867
    Keywords: Soil P test ; water extraction ; plant-available P ; glasshouse experiment ; P-buffering capacity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A water extraction procedure was evaluated as a soil-testing procedure for phosphorus (P). In a glasshouse experiment using perennial ryegrass, the water extraction procedure was used to predict plant-available P in 20 New Zealand soils varying widely in P status and P retention capacity. Water-extractable P in the 20 soils was highly correlated with plant uptake of P (r = 0.90**). Although plant uptake of P and Olsen-extractable P were equally well correlated (r = 0.90**), relationships between plant uptake of P and Bray1 — and Truog-extractable P, and isotopically exchangeable P were less close. The prediction of plant-available P using water extraction was not improved by inclusion of an estimate of P-buffering capacity (obtained from P retention capacity or the slope of the P desorption isotherm), in contrast to the finding for Olsen-extractable P. Because the interpretation of the results obtained appears to be independent of P-buffering capacity and soil type, the water extraction procedure may have advantages over the other soil-testing procedures for P for soils containing reasonable amounts of water-extractable P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01051343
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  • 8
    Electronic Resource
    Electronic Resource
    Partially acidulated reactive phosphate rock (PAPR) fertilizer and its reactions in soil (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 281-293 
    Details
    ISSN: 1573-0867
    Keywords: MCP hydrolysis ; partially acidulated phosphate rock ; pH change ; phosphate diffusion ; solubility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract PAPR was made by partial acidulation of North Carolina phosphate rock with H3PO4. The PAPRs were incubated in bands in columns of two soils of contrasting P retention. The columns were sampled after freezing and sectioning with a cryomicrotome. The movement of P in soil incubated with33P-labelled PAPR was followed by autoradiography of polished epoxy impregnated sections of the freeze-dried soil column. PAPR solubility was also studied by a sequential dialysis process using distilled deionised water. The acid solution resulting from the dissolution of monocalcium phosphate (MCP) in PAPR moved into the surrounding soil, solubilizing soil minerals and creating a low-pH front with a high concentration of P. Depending on the soil, phosphorus moved 6–14 mm away from the fertilizer/soil interface by mass flow and diffusion in two days. The increase in 0.5 M NaOH extractable P above that of untreated soil showed a maximum at the same position as the pH minimum in the soil. In both soils, the total P movement from the fertilizer band after a two day period for 50% PAPR was comparable to that for 100% acidulation (≡triple superphosphate), indicating that acidulations above 50% did not necessarily increase the movement of soluble P from the fertilizer pellet. Variations in pH in the fertilizer-affected soil could be explained by the net balance of acidity resulting from incoming acid P solution and release of OH− during P sorption. The rock residue exhibited a transient loss in solubility which was reversed on subsequent dissolution, suggesting a possible surface alteration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054329
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  • 9
    Electronic Resource
    Electronic Resource
    Partially acidulated reactive phosphate rock (PAPR) fertilizer and its reactions in soil (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 295-304 
    Details
    ISSN: 1573-0867
    Keywords: Partially acidulated phosphate rock ; mineralogy ; phosphate fertilizers ; EDS analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The fertilizer reaction products formed during the dissolution of PAPR fertilizer applied to two soils of contrasting P retention were studied using electron microscopy and energy dispersive x-ray spectrum (EDS) analysis combined with common mineralogical analysis procedures. Monocalcium phosphate (MCP) and phosphate rock (PR) residue were the main components of the PAPR fertilizer at the time of application. Dissolution of MCP in PAPR led to the formation of dicalcium phosphate dihydrate (DCPD) which was morphologically distinct from the soil matrix and easily analyzed by the microprobe. The amount of DCPD at the granule site was greater in the soil of low P retention than in the soil of high P retention, consistent with a greater transfer of fertilizer-P to the soil in latter case. The mean crystallite size of carbonate apatite in the fertilizer residue suggested a preferential dissolution of very fine crystallites at acidulations less than 50% during phosphoric acid acidulation. Electron microscopy showed dissolution of primary mineral grains (e.g. clinopyroxene) in soil adjacent to the fertilizer pellet during the dissolution of PAPR fertilizer. The precipitated products in the soil near the PAPR fertilizer pellet were complex compounds containing P, Ca, Al, Fe and Si. There was no evidence of pure phases such as variscite and strengite. These changes were analogous to those occurring in and around fully acidulated P fertilizers (TSP) in soil; however, in the case of PAPR, the reactive phosphate rock residue and DCPD at the site of application may provide a continuous source of P for plants over a long period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01054330
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  • 10
    Electronic Resource
    Electronic Resource
    Lime-aluminium-phosphorus interactions and the growth of Leucaena leucocephala (1990)
    Springer
    Plant and soil 126 (1990), S. 1-8 
    Details
    ISSN: 1573-5036
    Keywords: aluminium ; aluminium toxicity ; Leucaena yield ; lime ; phosphorus ; phosphorus uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of lime and P addition on the amounts of soil extractable P and Al, and on the growth of the tropical legume Leucaena leucocephala were investigated in a factorial experiment under controlled climate conditions using 4 (Koronivia, Nadroloulou, Batiri, and Seqaqa) highly-weathered, acid (pH initially 3.9 to 4.9) soils from Fiji. Resin-extractable P increased with lime addition and then decreased above pH 5.5, whereas M KCl-extractable Al decreased to undetectable levels at or above pH 5.2. Plant growth was usually adversely affected at low and high pH, even in the presence of added P. The pH (in M KCl) at which maximum growth occurred in the 4 soils varied from approximately 4.4 to 5.2; values somewhat lower than those reported in the literature. Changes in dry matter yield with increasing soil pH were strongly influenced by P status and a positive lime × P interaction was obtained with 3 of the 4 soils. Above pH 5.2, liming decreased the yield of both tops and roots, for reasons which are discussed in part II. The data obtained for extractable soil P and plant P concentrations indicate that P deficiency is a major problem on these soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00041363
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