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  • 1
    Electronic Resource
    Electronic Resource
    Influence of low-molecular-weight organic acids on the solubilization of phosphates (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 311-319 
    Details
    ISSN: 1432-0789
    Keywords: Phosphate adsorption ; Organic acids ; Stability constants ; Lolium rigidium ; Mitscherlich equation ; Relative agronomic effectiveness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A range of low-molecular-weight organic acids were identified in rhizosphere soil, leaf litter, and poultry manure compost. Laboratory and greenhouse experiments were carried out to examine the effects of seven low-molecular-weight organic acids on phosphate adsorption by soils, and the solubilization and plant uptake of P from soil pre-incubated with monocalcium phosphate and North Carolina phosphate rock. Acetic, formic, lactic (monocarboxylic), malic, tartaric, oxalic (dicarboxylic), and citric (tricarboxylic) acids were used in the study. The addition of organic acids decreased the adsorption of P by soils in the order tricarboxylic acid〉dicarboxylic acid〉monocarboxylic acid. The decreases in P adsorption with organic acid addition increased with an increase in the stability constant of the organic acid for Al (logK Al). Organic acids extracted greater amounts of P from soils meubated with both monocalcium phosphate and phosphate rock than water did. Although more phosphate was extracted by the organic acids from monocalcium phosphate — than from phosphate rock — treated soils in absolute terms, when the results were expressed as a percentage of dissolved phosphate there was little difference between the two fertilizers. The amount of P extracted by the organic acids from both fertilizers increased with an increase in logK Al values. The addition of oxalic and citric acids increased the dry matter yield of ryegrass and the uptake of P in soils treated with both fertilizers. The agronomic effectiveness of both fertilizers increased in the presence of organic acids and the increase was greater with the phosphate rock than with the monocalcium phosphate. The results indicated that organic acids increase the availability of P in soils mainly through both decreased adsorption of P and increased solubilization of P compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00570634
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  • 2
    Electronic Resource
    Electronic Resource
    Assessment of the influence of phosphate fertilizers on the microbial activity of pasture soils (1996)
    Springer
    Biology and fertility of soils 21 (1996), S. 284-292 
    Details
    ISSN: 1432-0789
    Keywords: Basal respiration ; Long-term effect ; Metabolic quotient ; Microbial biomass ; Osmotic potential ; Pasture soil ; Phosphate fertilizers ; Substrate-induced respiration (SIR)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of the present work was to examine the effects of phosphate fertilizers on the microbial activity of pasture soils. Various microbial characteristics were measured using soils from an existing long-term phosphate fertilizer field trial and a short-term incubation experiment. The measurements included basal respiration, substrate induced respiration, inhibition of substrate-induced respiration by streptomycin sulphate (fungal activity) and actidione (bacterial activity) and microbial biomass C. The long-term field trials was initiated during 1985 to examine the effectiveness of different sources of phosphate fertilizers (single superphosphate, North Carolina phosphate rock, partially acidulated North Carolina phosphate rock, and diammonium phosphate) on pasture yield. The incubation experiment was conducted for 8 weeks using the same soil and the sources of phosphate fertilizers used in the field trial. In the incubation experiment the fertilizer addition caused an initial decrease in basal and substrate-induced respiration but had no effect on total microbial biomass. The initial decline in basal and substrate-induced respiration with the fertilizer addition was restored within 8 weeks after incubation. In the field experiment the fertilizer addtion had no significant effect on basal respiration but increased substrate-induced respiration and microbial biomass C. The short-term and the long-term effects of phosphate fertilizer addition on the microbial characteristies of the soils are discussed in relation to its effects on pH, salt concentration, and the nutrient status of the soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334905
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  • 3
    Electronic Resource
    Electronic Resource
    Characteristics of earthworm casts affecting herbicide sorption and movement (1996)
    Springer
    Biology and fertility of soils 22 (1996), S. 367-372 
    Details
    ISSN: 1432-0789
    Keywords: Atrazine ; Casts ; Earthworm ; Herbicides ; Leaching ; Metsulfuron methyl ; Sorption ; 2,4-d
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Various physical and chemical characteristics of earthworm casts collected from a laboratory incubation and a field experiment were examined in relation to their effect on the sorption and the movement of three 14C-labelled ionic herbicides: atrazine, 2,4-dichlorophenoxyacetic acid, and metsulforon methyl. The earthworm casts contained higher levels of fine fractions and total and soluble C. This is attributed to the grinding action of the earthworm gut and selective feeding on zones with higher organic matter and fine size fractions. The earthworm casts had a higher pH than the source soil, resulting in a higher number of surface negative charges. The earthworm casts sorbed higher amounts of herbicides than the source soil, mainly due to the increases in the amount of organic C and fine size fractions. The incrased sorption of herbicides by the casts resulted in decreased leaching.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00334585
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  • 4
    Electronic Resource
    Electronic Resource
    Enhanced dissolution of phosphate rocks in the rhizosphere (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 169-174 
    Details
    ISSN: 1432-0789
    Keywords: Key words Dissolution ; Open leaching ; Organic acids ; Phosphate rocks ; Plant uptake ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Dissolution of two phosphate rocks (PRS) which vary in their chemical reactivity was examined using two soils in the absence (closed-incubation and open-leaching) and presence (thin-layer) of plants. Greater dissolution was obtained in the presence than in the absence of plants. In the absence of plants, open-leaching resulted in higher dissolution than the closed-incubation system. Removal of the dissolved Ca from the zone of PR dissolution is considered to be the main reason for the increased dissolution in the open-leaching columns. In the case of the thin-layer experiment, removal of Ca and P through plant uptake and the supply of protons (H+) through the release of organic acids are considered to be the main reasons for the enhanced dissolution of PRs in the rhizosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050226
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Single superphosphate-reactive phosphate rock mixtures. 2. The effect of phosphate rock type and denning time on the amounts of acidulated and extractable phosphate (1988)
    Springer
    Nutrient cycling in agroecosystems 16 (1988), S. 179-194 
    Details
    ISSN: 1573-0867
    Keywords: Exchangeable P ; chemical extractants ; dioxan-acetone quenching ; free acid ; single superphosphate ; reactive phosphate rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Ground samples of Nauru (N), Christmas Island A (X), Jordan (J) or North Carolina (NC) phosphate rocks (PRs) were acidulated with32P ‘spiked’ sulphuric acid to produce single superphosphate (SSP) reaction mixtures. Subsequently, single superphosphatereactive phosphate rock (SSP-RPR) mixtures were manufactured by adding reactive phosphate rock (RPR) as either ground or unground NCPR or ground JPR to SSP reaction mixtures that had been denned for either 22 or 47 minutes after acid addition. The solubility of P in the final SSP-RPR products was assessed either by extraction with water, 2% citric acid, 2% formic acid or 1M neutral ammonium citrate (NAC), or by calculation of the exchangeable P content of the fertilizer by isotopic dilution techniques. The measurement of exchangeable P allowed calculation of the amounts of acidulated P in the ex-den SSP and the amount of RPR P acidulated on addition to ex-den SSP containing free phosphoric acid. Among the PRs used for SSP manufacture, the highest degree of acidulation at the ex-den stage was obtained for NCPR (92%) and the lowest was obtained for XPR (75%). As a consequence, the presence of XPR in the SSP reaction mixture decreased the amount of exchangeable P in the SSP-RPR mixtures. Whereas initially the conversion of PR P increased with time of acidulation at 22 minutes and 47 minutes (i.e. the time of addition of RPR) the differences in the degree of acidulation of PR in the ex-den SSP were not large and hence had no significant effect on the extractability of P in the SSP-RPR mixtures. The nature of the RPR added to the ex-den SSP reaction mixture had a significant effect on the solubility of P in the SSP-RPR mixtures. SSP-RPR mixtures with added unground NCPR or ground JPR had lower P solubility than when ground NCPR was added. RPR P constituted between 38 and 46% of the total P in the SSP-RPR mixtures and at acid/PR (A/R) ratios of 0.60 to 0.70, between 28 to 49% of the RPR P was acidulated by the free acid in the SSP reaction mixture during manufacture. The results also indicate that RPR mixtures made using ex-den SSP made from unreactive PRs will always contain more unreactive PR residue than those made with mature SSP. However, given the practical difficulties of producing the SSP-RPR mixtures with mature SSP, denning times should be extended for as long as practicably possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01049773
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Dissolution of phosphate rocks in soils. 2. Effect of pH on the dissolution and plant availability of phosphate rock in soil with pH dependent charge (1990)
    Springer
    Nutrient cycling in agroecosystems 24 (1990), S. 125-134 
    Details
    ISSN: 1573-0867
    Keywords: Phosphate adsorption ; phosphate rock dissolution ; plant uptake ; relative agronomic effectiveness ; soil pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of soil pH on the dissolution of phosphate rocks (PRs) and the subsequent availability of the dissolved inorganic phosphorus (Pi) to plants was examined in a volcanic soil adjusted to different pH values. Potassium dihydrogen orthophosphate (KH2PO4) and three PRs, Nauru (NPR), Jordan (JPR) and North Carolina (NCPR) were incubated with the pH-amended soils at a rate of 800µg P g−1 soil for 84 days. The extent of PR dissolution was determined by measuring the increases in the amount of 0.5 M NaOH extractable Pi (ΔNaOH-P) in the PR treated soil over the control soil. The amount of plant available P was measured either by extracting with 0.5 M NaHCO3 or by growing ryegrass in soil samples incubated with the phosphate sources. At each pH the order of the extent of PR dissolution followed NCPR 〉 JPR 〉 NPR, which was consistent with the decreasing order of their chemical reactivities. As the pH decreased from 6.5 to 3.9 the dissolution of PRs increased from 29.3% to 83.5%, from 18.2% to 78.9%, and from 12.5% to 60.3% for NCPR, JPR and NPR, respectively. In contrast, as the soil pH decreased from 6.5 to 3.9, the proportion of the dissolved P extracted by 0.5 M NAHCO3 decreased from 38% to 5% and the proportion taken up by ryegrass plants decreased from 46% to 7%. This decrease in plant available P corresponded to an increase in the adsorption of inorganic P with a decrease in pH. However, the uptake of P from PR relative to that from KH2PO4 was higher at low pH than at high pH. Further, the amount of P taken up by plants was more closely related to the amount of NaHCO3 extractable P than to the amount of dissolved P present in the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073580
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  • 9
    Electronic Resource
    Electronic Resource
    Evaluation of methods of measurement of nitrogen in poultry and animal manures (1990)
    Springer
    Nutrient cycling in agroecosystems 24 (1990), S. 141-148 
    Details
    ISSN: 1573-0867
    Keywords: Ammonia volatilization ; animal manures ; composting ; forms of nitrogen ; Kjeldahl nitrogen ; poultry ; total nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Kjeldahl nitrogen (N), total N and forms of inorganic N (ammoniacal (NH4)-N, nitrate (NO3)-N and nitrite (NO2)-N) were measured in a range of animal manures. The manures include fresh samples of poultry manure, sheep manure, horse manure, dairy slurry and pig slurry and composted poultry manure. Kjeldahl N was measured by standard micro-Kjeldahl digestion. For total N measurements, NO3-N and NO2-N were recovered during Kjeldahl digestion by pretreatments with various oxidizing and reducing agents. Inorganic forms of N were measured by extraction with 2M KCl solution. Kjeldahl digestion alone allowed measurement only of organic N and NH4-N. Amongst various modifications to the Kjeldahl, pretreatment with either acidified (H2SO4) Zn-CrK(SO4)2 or acidified (H2SO4) reduced Fe achieved complete recovery of NO3-N. Nitrite N was only recovered by first oxidising the NO 2 - to NO 3 - with KMnO4 followed by reduction to NH4-N with acidified (H2SO4) reduced Fe. More than 95% of the total N in fresh animal manure was present as organic N and NH4-N which were recovered by the standard Kjeldahl digestion. In the case of fresh manures there was no difference between the amount of total N measured by the Kjeldahl digestion and its modified methods. However composting of poultry manure or drying of poultry manure, pig slurry and dairy slurry resulted in an increase in NO3-N which was not recovered during Kjeldahl digestion alone. Under these conditions the total N could be measured by pretreating the samples with KMnO4 and reduced Fe prior to Kjeldahl digestion. Drying of animal manures caused a decrease in organic N and NH4-N, especially in poultry, pig and dairy manures. There was a slight increase in NO3-N; but most of the decrease in N content with drying was attributed to the volatilization loss of ammonia (NH3). Amongst various drying methods examined air drying caused maximum loss of N as NH3 whereas freeze drying caused minimum loss of N. This suggests that fresh animal manures can be freeze dried for analysis of N which causes minimum loss of N.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01073582
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  • 10
    Electronic Resource
    Electronic Resource
    Preparation, forms and properties of controlled-release phosphate fertilizers (1993)
    Springer
    Nutrient cycling in agroecosystems 35 (1993), S. 13-24 
    Details
    ISSN: 1573-0867
    Keywords: Calcined phosphate ; fused phosphate ; partially acidulated phosphate rocks ; phosphate rock ; thermal phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Controlled-release phosphate fertilizers include phosphate rocks (PRs) for direct application, partially acidulated phosphate rocks (PAPRs) and thermal phosphates. Phosphate rocks contain apatite as the main P containing mineral, the composition and the chemical nature of which vary between PRs. Based on the solubility in chemical extractants PRs are broadly grouped into ‘reactive’ and ‘unreactive’. The ‘reactivity’ of PRs is influenced strongly by the extent of carbonate substitution for phosphate in the apatite minerals. Under certain soil and climatic conditions reactive PRs (RPRs) can be used as a source of P for direct application. Partially acidulated phosphate rocks (PAPRs) are produced either by direct partial acidulation of PRs with mineral acids or by mixing PRs with fully acidulated superphosphate reaction mixtures. Partial acidulation of PRs with H3PO4 generally results in higher water soluble P contents than those acidulated with H2SO4. Mixing of RPRs with superphosphate reaction mixtures sometimes results in the preferential consumption of free acid and thereby increases the amounts of residual unreacted PRs. Thermal phosphates are produced by either heating PRs below melting point both in the presence and the absence of silica (calcined phosphates) or heating PRs with silica above melting point (fused phosphate). These phosphates are alkaline in nature and hence suitable for acidic soils.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750216
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