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  • 1990-1994  (5)
  • 1980-1984
  • 1930-1934
  • 1991  (5)
  • 1
    Electronic Resource
    Electronic Resource
    Oestrogen and androgen states in oligo-amenorrhoeic women with polycystic ovaries (1991)
    Oxford, UK : Blackwell Publishing Ltd
    BJOG 98 (1991), S. 0 
    Details
    ISSN: 1471-0528
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Summary. Oestrogen and androgen states have been studied in relation to ovarian morphology defined by ultrasonography in 65 women with oligo-amenorrhoea. Of the 48 women with polycystic ovaries (PCO), 44 (92%) had a withdrawal bleed following progestogen challenge (indicating oestrogenization) compared with just three (18%) of the 17 with non-PCO (P 〈 0.001). Median serum concentrations of oestradiol and oestrone were statistically significantly higher in the PCO group but the ranges overlapped widely. Of the four women with PCO but oestrogen deficiency, two were hirsute and had evidence of a severe form of the disorder. The other two were not hirsute and appeared to have hypo-thalamic dysfunction associated with weight loss overriding the disorder due to pre-existing PCO. Compared with the non-PCO group, the PCO subgroup without hirsutism (n = 31) had statistically significantly higher median values of LH, testosterone, androstendione, and dehydro-epiandrosterone sulphate concentrations, and free androgen index. Concentrations of androgen, but not LH, were significantly higher still in the PCO subgroup with hirsutism (n = 17).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-0528.1991.tb13396.x
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  • 2
    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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  • 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. 85-93 
    Details
    ISSN: 1573-0867
    Keywords: Phosphate rock ; soil pH ; andepts ; white clover ; ryegrass ; soil phosphorus ; monocalcium phosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The agronomic effectiveness of an unground reactive phosphate rock from Sechura, Peru, was compared with that of monocalcium phosphate in a severely P deficient and highly P retentive soil (vitrandept) over a period of three years. Soil pHs were adjusted to pH 5.1, 5.3, 5.6 and 6.4. The sward consisted mostly of ryegrass (Lolium perenne) and white clover (Trifolium repens). Fertilisers were applied at six rates at pH 5.3 and three rates at other pHs in the first year. For two of the rates fertilisers were reapplied in the second year. Dry matter yields, P uptake and ground cover of clover were determined during the experimental period. In phosphate rock treated plots a negative linear relationship was obtained between soil pH and the logarithm of yield. The agronomic effectiveness of phosphate rock relative to monocalcium phosphate increased with time at all pHs. Calculated at fertiliser rates which produced near maximum yields, relative agronomic effectiveness at soil pHs 5.1, 5.3, 5.6 and 6.4 were respectively 58, 60, 18, and 5 in year one; 118, 125, 77 and 38 in year three. At pH 5.3, as the rate of application increased the relative agronomic effectiveness of the phosphate rock generally decreased in year one but was enhanced in the intermediate rates in years two and three. The data for ground cover of clover gave a similar trend to that for herbage yield and P uptake.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048859
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  • 4
    Electronic Resource
    Electronic Resource
    Phosphate sorption approach for determining phosphorus requirements of wheat in calcareous soils (1991)
    Springer
    Nutrient cycling in agroecosystems 28 (1991), S. 67-72 
    Details
    ISSN: 1573-0867
    Keywords: Phosphate adsorption ; external P requirement ; wheat ; fertilizer requirements ; calcareous soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Five field experiments involving P application rates from 0 to 66 kg P ha−1 were conducted on irrigated wheat at Tandojam, Pakistan. The soils belonged to two great soil groups, Torrifluvent and Camborthid. All soils were calcareous. Olsen-P contents ranged from 3.5 to 6.3 mg P kg−1. Phosphate sorption curves were developed for soils from control (no P) plots at each site. Concentrations of P in solution established by fertilization in the field as estimated from the sorption curves ranged from 0.008 to 0.16mg P L−1. Actual grain yields were converted to relative grain yields and plotted against corresponding concentrations of P in solution. Yield response to P application was obtained in each experiment. Control plot yields ranged from 57 to 89% of maximum yield of respective experiments. Phosphorus requirements of wheat were 0.032 mg L−1 for 95% yield as determined from a composite yield response curve. Predicted quantities of P required to attain 0.032 mg P L−1 ranged from 18 to 29 kg P ha−1. The results of the study suggest that the P sorption approach can be used as a rational basis for making P fertilizer recommendations for various soil-crop combinations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01048857
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Plant-soil interactions associated with acid, weathered soils (1991)
    Springer
    Plant and soil 134 (1991), S. 65-72 
    Details
    ISSN: 1573-5036
    Keywords: acidity ; aluminium ; calcium ; citrus ; continuous-function design ; legumes ; manganese ; phosphorus ; soil mineral ; sulphur ; variable charge ; weathered soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plant-soil interactions in weathered soils are so complex that unqualified statements about a suitable pH for plants are risky. Conventional experimental designs and statistical methods may not be appropriate for investigating such complexities. Lime experiments using continuous function designs and observation of plant response to indigenous variability in soil pH permit detailed observations of plant-soil interactions that are frequently not detected. A graphical boundary-line approach to interpreting data can make good sense out of apparent confusion. Increasing the pH of variable-charge soils by adding lime or by indigenous means increased CEC and retarded cation leaching, but Ca solubility changed very little over the range pH 5 to 6. N fixation and yield was closely related to soil pH, soil Mn and Mn uptake by soybean. This result was clearly demonstrated regardless of numerous other limiting factors. Plant yield response curves resolved into distinct segments that corresponded with associated soil properties. Excess Al compounded by Ca deficiency is suspect in the pH range 〈5. Excess Mn, and Ca deficiency probably limited yields in the pH range 5.0 to 5.7. Yields were stable, and Ca and P were constant in the pH interval 5.7 to 6.0. Yields abruptly increased in the pH interval 6.0 to 6.3. This was associated with elevated Ca concentrations in soil solutions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010718
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