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  • 1
    Electronic Resource
    Electronic Resource
    Changes in net surface charge of hydrous alumina with phosphate adsorption (1976)
    [s.l.] : Nature Publishing Group
    Nature 262 (1976), S. 45-46 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The hydrous alumina used has been described elsewhere3 and the pH value at the point of zero charge (PZC) was 9.3. The phosphate adsorbed and the hydroxyl ions released at different phosphate concentrations were measured at a constant pH (see ref. 3). The experimental conditions were: pH 5.0; 0.01 ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/262045a0
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  • 2
    Electronic Resource
    Electronic Resource
    Adsorption of divalent phosphate on hydrous aluminium oxide (1975)
    [s.l.] : Nature Publishing Group
    Nature 253 (1975), S. 434-436 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The preparation and properties of the aluminium oxide used have been described elsewhere1. The sample was predominantly amorphous and had a surface area (B.E.T.) of 197 m2 g"1. The point of zero charge (PZC) pH (ref. 2) was 9.3. The phosphate adsorption and hydroxyl ion release were determined ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/253434a0
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of pH, time and rate of application on phosphate rock dissolution and availability to pastures (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 95-101 
    Details
    ISSN: 1573-0867
    Keywords: Phosphate rock dissolution ; soil pH ; solution phosphorus ; phosphorus fractionation ; monocalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Soil Samples were collected from a field experiment conducted to evaluate the agronomic effectiveness of a reactive phosphate rock (PR), Sechura sand, relative to that of monocalcium phosphate (MCP) at different soil pHs and rates of application. The samples were analysed for P soluble in the soil solution and bicarbonate extractable P. The rate of dissolution of PR was calculated from the data on the fractionation of inorganic P. In MCP plots P in the soil solution decreased sharply with time especially at low pHs and high rates of fertiliser application. In PR plots the concentration remained with time at the same as or a slightly higher level than that was found one month after application. Solution concentration of P was lower at very high rates of PR application than at intermediate rates. In both MCP and PR plots bicarbonate extractable P decreased with increasing pH. Bicarbonate extractable P was linearly related to MCP but not to PR applied. The rate of dissolution and the proportion of PR dissolved decreased with increasing rates of PR application but the amount dissolved increased. Phosphate dissolved at high level of PR application did not seem to enhance proportionately either the concentration of P in soil solution or bicarbonate extractable P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048860
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  • 4
    Electronic Resource
    Electronic Resource
    Reducing fertilizer requirements for hybrid squash (Cucurbita maxima L.) with localized applications of phosphorus and potassium and use of partially acidulated phosphate rock (1987)
    Springer
    Nutrient cycling in agroecosystems 13 (1987), S. 169-180 
    Details
    ISSN: 1573-0867
    Keywords: Phosphorus ; potassium ; fertilizer placement ; triple-superphosphate ; partially acidulated phosphate rock ; hybrid squash ; Cucurbita maxima L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two experiments examined options for reducing the inputs of P and K fertilizers for hybrid squash (Cucurbita maxima L.) at Pukekohe, New Zealand. The first experiment examined the effects of elevating the NaHCO3-soluble P from 32 to 130 mg kg−1 and the exchangeable K from 140 to 350 mg kg−1 within strips from 0 to 0.75 m around rows of hybrid squash planted 1.5 m apart. From both P and K, crop yield increased as the width of the fertilized strip was increased up to 0.25 m, while wider fertilized strips had no further effect. These results followed similar effects on plant dry matter and tissue P or K concentration during early growth, and are explained in terms of the P and K accumulation by the crop, the decline during growth of the sensitivity of the crop to soil P and K fertility associated with declining rates of P and K uptake per unit length of root. Implications for fertilizer management for hybrid squash are also discussed. The second experiment compared the effects of partially acidulated phosphate rock and triple-superphosphate on soil P fertility, growth and yield of hybrid squash. Partially acidulated phosphate rock had smaller effects than those of triple-superphosphate on NaHCO3-soluble P levels in the soil, plant dry weight and tissue P concentration soon after emergence, and subsequently crop yield. On average, partially acidulated phosphate rock increased crop yield by about 70% of that following the application of the same quantity of P as triple-superphosphate. This lower effectiveness of partially acidulated phosphate rock for hybrid squash is explained in terms of its lower solubility and hence smaller effect on NaHCO3-soluble P in the soil during early growth, when the crop is most sensitive to soil P fertility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01064830
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  • 5
    Electronic Resource
    Electronic Resource
    Preface (1993)
    Springer
    Nutrient cycling in agroecosystems 35 (1993), S. v 
    Details
    ISSN: 1573-0867
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750227
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  • 6
    Electronic Resource
    Electronic Resource
    Use of low grade phosphate rocks as biosuper fertilizer (1981)
    Springer
    Nutrient cycling in agroecosystems 2 (1981), S. 199-209 
    Details
    ISSN: 1573-0867
    Keywords: allophanic soil ; biosuper ; low grade phosphate rock ; marine phosphorite nodule ; phosphate rock/sulphur granule ; ryegrass ; Thiobacillus spp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot trial was conducted for 10 months to evaluate the fertilizer value of two low grade phosphate rocks applied either as biosuper (phosphate rock/sulphur granules, PR/S*) or as untreated granulated rocks. The phosphate rocks were Chatham Rise nodules (CR), a marine deposit containing calcium phosphate and calcium carbonate, and the ‘C’ grade ore from Christmas Island (CC) containing predominantly aluminiumiron phosphate and free oxides of iron and aluminium. Perennial ryegrass was grown as the test crop in a highly phosphate retentive allophanic soil, limed to pH 6.2. Single superphosphate was used as the standard fertilizer. Phosphate uptake and dry matter yields showed that biosuper prepared from CR was agronomically as effective as superphosphate whereas that prepared from CC was less effective. At the highest rate of application CR increased the yield of ryegrass by 80% over that of control but granulating it with sulphur increased the yield by 143%. The corresponding values for CC and CC/S were 39% and 50%. The time lags from the addition of CR/S and CC/S to apparent maximum phosphate availability were less than 18 and 49 days respectively. Olen bicarbonate extractable phosphate of soils increased by 100% and 33% respectively when CR and CC were added as biosuper in comparison with addition as phosphate rock granules. Liming the soil to raise its pH from 5.1 to 6.2 lowered the quantity of superphosphate needed to reach 90% of maximum yield by 23%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01834813
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  • 7
    Electronic Resource
    Electronic Resource
    Differential availability of partially sulphuric and phosphoric acidulated phosphate rocks I. Plant response (1996)
    Springer
    Nutrient cycling in agroecosystems 47 (1996), S. 251-259 
    Details
    ISSN: 1573-0867
    Keywords: Partially acidulated phosphate rock ; residual PR ; P uptake ; soil pH ; agronomic effectiveness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A glasshouse study was conducted to determine the influence of soil pH on the agronomic effectiveness of partially phosphoric (Phos-PAPR) and partially sulphuric (SA-PAPR) acidulated phosphate rocks (PR). For Phos-PAPR ground North Carolina PR (NCPR) was acidulated with 10, 30 and 50% of acid needed for complete acidulation. For SA-PAPR a blend of NCPR, Arad and Khouribga PRs were acidulated with 60% of the acid needed. The relative agronomic effectiveness of these PAPRs were compared with superphosphate (SSP) and ground NCPR. A highly phosphate (P) retentive and P deficient pasture soil was used. Prior to addition of fertilizers to soil, the pH of soil was adjusted to 5.1 (initial soil pH) 5.4, 5.7 and 6.1 by applying varying amounts of Ca(OH)2. Ryegrass (Lolium perenne) was grown as the test plant over a period of eight months. Fertilizers were applied at three rates plus control. Soil pH was monitored and continuously adjusted to the desired levels throughout the experimental period. The dry matter yields and P uptake in SSP treated pots were not influenced by soil pH. With increasing soil pH, agronomic performance of Phos-PAPRs and NCPR significantly (P〈0.01) decreased but that of SA-PAPR was not affected. On the basis of per unit water-soluble P applied, uptake of P by plants was greater from PAPRs than SSP. Using the P uptake values of SSP and NCPR (which was used to prepare the PAPRs), the dissolution of P from the residual PR component of the PAPRs were calculated. The residual PR component of the Phos-PAPRs apparently dissolved in greater quantities than unacidulated NCPR. Dissolution of the residual PR was enhanced with increasing degree of acidulation. However, in the case of SA-PAPR, the agronomic performance of the PAPR was mostly dependent on the water-soluble P component of the PAPR. The uptake of P from the residual PR component of the SA-PAPR was insignificant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01986280
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  • 8
    Electronic Resource
    Electronic Resource
    Partially acidulated phosphate rocks: Phosphorus release characteristics (1990)
    Springer
    Nutrient cycling in agroecosystems 22 (1990), S. 109-117 
    Details
    ISSN: 1573-0867
    Keywords: Partially acidulated phosphate rock ; inorganic phosphate fractionation ; phosphate dissipation ; phosphate release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Five phosphate rocks varying in formic acid P solubility from 18.9 to 52.7%, expressed as percentage of total P, were acidulated with phosphoric or sulphuric acids to 0, 20%, 33% and 50% of full acidulation and granulated. In an incubation experiment fertilizer granules of diameter 1–2 mm were mixed with two acid soils and after 1 week incubation soil samples were extracted with a 0.5 M NaOH solution. In a dissipation experiment single fertilizer granules of 4 mm diameter were implanted into soil, incubated for 1 and 4 weeks and inorganic P fractionation in the residual granules and the surrounding soil was performed. Dissipated P was greater than the water soluble P content of the partly acidulated phosphate rock fertilizers indicating the dissolution of the non-acidulated phosphate rocks. The amount of P dissipated was related to the initial water soluble P content and to the formic acid solubility of phosphate rocks used for manufacturing the fertilizers. The P dissipated increased with an increase in soil acidity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01116184
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  • 9
    Electronic Resource
    Electronic Resource
    Partially acidulated phosphate rocks: Controlled release phosphorus fertilizers for more sustainable agriculture (1994)
    Springer
    Nutrient cycling in agroecosystems 37 (1994), S. 69-78 
    Details
    ISSN: 1573-0867
    Keywords: fertilizer efficiency ; partially acidulated phosphate rocks ; permanent pastures ; phosphate rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Phosphate rocks partially acidulated either with H3PO4 or H2SO4 were compared against SSP or TSP as phosphate fertilizers for permanent pasture. Eleven field trials were conducted over periods of up to 6 yrs. Fertilizers were surface applied annually. Initial soil pHw values ranged from 5.5–6.3 and Soil P retention from 25% to 97%. The PRs used for partial acidulation were unground or ground North Carolina PR, ground Khouribga PR, and a blend of ground PRs of North Carolina, Arad and Khouribga PRs. From the DM yields, fertilizer substitution values were calculated: fertilizer substitution value was the ratio of total P applied as superphosphate to total P as PAPR required to produce the same DM yield. Rates of dissolution of the PR component of PAPRs were also determined in soils collected from two trials. Agronomic results demonstrated that 30% acidulated phosphoric PAPRs (about 50% of total P as water-soluble P) were as effective as TSP, when the PR acidulated was from unground North Carolina PR. Results from one field trial indicated that when PAPR was from ground North Carolina PR, 20% acidulated product (water-soluble P 30–40% of total P) was equally effective as TSP. Replacement of ground North Carolina PR by a less reactive Khouribga PR did not appear to decrease the yield. Results indicated that per unit P released into soil solution, PAPRs were more efficient fertilizers than TSP. With annual applications, fertilizer substitution value of PAPR 30% tended to increase with time. Sulphuric PAPRs prepared from North Carolina PR were generally inferior to phosphoric PAPRs containing similar amounts of water-soluble P. This was attributed to the presence of CaSO4 coatings.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750675
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  • 10
    Electronic Resource
    Electronic Resource
    Use of partially acidulated phosphate rocks as phosphate fertilizers (1993)
    Springer
    Nutrient cycling in agroecosystems 35 (1993), S. 47-59 
    Details
    ISSN: 1573-0867
    Keywords: Partially acidulated phosphate rocks ; phosphate rock reactivity ; soil pH ; compaction ; cogranulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Partially acidulated phosphate rocks (PAPRs) are manufactured by acidulation of PRs with less than the stoichiometric amounts of, usually, phosphoric or sulphuric acids. Products of similar composition to PAPRs are also prepared by cogranulating superphosphate with PRs. For most crops the agronomic value of PAPRs is determined by the availability to plants of their water-soluble P as well as their PR P component. The acid unreacted PR present in the directly acidulated PAPR, is considered to be less reactive than the original PR. This is probably the result of surface coatings of chemical compounds formed during acidulation. Under some soil conditions, in the presence of plants, the PR component probably dissolves faster than the original PR. For seasonal crops, except for fast growing ones such as squash (Cucurbita maxima), reactive PRs partially acidulated so that the final products contain about 50% of its total P in water-soluble form, are generally as effective as fully acidulated superphosphate. For permanent pastures the water P content may be reduced to about 40% of total P without reducing their agronomic effectiveness of the product. In medium P retentive soils pH seems to have little or no influence on the agronomic effectiveness of PAPRs. In highly P retentive soils increasing soil pH reduces the agronomic effectiveness of phosphoric PAPRs apparently by reducing the solubility of the PR component of PAPRs. Even at low pH the dissolution of unreacted PR in sulphuric PAPRs is less than that in phosphoric PAPRs, probably due to the possible coating of calcium sulphate on the residual PR in sulphuric PAPRs. Results on the agronomic effectiveness of PAPRs prepared from unreactive rocks were highly variable and no generalisation could be made regarding the degree of acidulation needed for the products to be consistently effective. Single superphosphate (SSP) cogranulated with reactive rocks (SSP/PR) was agronomically less effective than SSP, and also than phosphoric PAPRs of similar water-soluble P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750219
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