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  • 21
    Electronic Resource
    Electronic Resource
    The nitrogen mineralization rate of legume residues in soil as influenced by their polyphenol, lignin, and nitrogen contents (1990)
    Springer
    Plant and soil 129 (1990), S. 251-259 
    Details
    ISSN: 1573-5036
    Keywords: 15N recovery ; nitrogen release ; nitrogen availability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A 12-week greenhouse experiment was conducted to determine the effect of the polyphenol, lignin and N contents of six legumes on their N mineralization rate in soil and to compare estimates of legume-N release by the difference and 15N-recovery methods. Mature tops of alfalfa (Medicago sativa L.), round leaf cassia (Cassia rotundifolia Pers., var. Wynn), leucaena (Leucaena leucocephala Lam., deWit), Fitzroy stylo (Stylosanthes scabra Vog., var Fitzroy), snail medic (Medicago scutellata L.), and vigna (Vigna trilobata L., var verde) were incorporated in soil at the rate of 100 mg legume N kg-1 soil. The medic and vigna were labeled with 15N. Sorghum-sudan hybrid (Sorghum bicolor, L. Moench) was used as the test crop. A non-amended treatment was used as a control. Net N mineralization after 12 weeks ranged from 11% of added N with cassia to 47% of added N for alfalfa. With the two legumes that contained less than 20 g kg-1 of N, stylo and cassia, there was net N immobilization for the first 6 weeks of the experiment. The legume (lignin + polyphenol):N ratio was significantly correlated with N mineralization at all sampling dates at the 0.05 level and at the 0.01 level at 6 weeks (r2=0.866). Legume N, lignin, or polyphenol concentrations or the lignin:N ratio were not significantly correlated with N mineralization at any time. The polyphenol:N ratio was only significantly correlated with N mineralization after 9 weeks (r2=0.692). The (lignin + polyphenol):N ratio appears to be a good predictor of N mineralization rates of incorporated legumes, but the method for analyzing plant polyphenol needs to be standardized. Estimates of legume-N mineralization by the difference and 15N recovery methods were significantly different at all sampling dates for both 15N-labeled legumes. After 12 weeks, estimates of legume-N mineralization averaged 20% more with the difference method than with the 15N recovery method. This finding suggests that estimates of legume N available to subsequent crops should not be based solely on results from 15N recovery experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00032420
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  • 22
    Electronic Resource
    Electronic Resource
    Field evaluation of several chemical indexes of soil nitrogen availability (1990)
    Springer
    Plant and soil 123 (1990), S. 83-88 
    Details
    ISSN: 1573-5036
    Keywords: maize ; nitrogen availability tests ; soil nitrate ; UV absorbance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The ability of several chemical soil N availability indexes to predict the N supplying capability (NSC) of soils to maize in the field was evaluated in 49 field experiments over 3 years in Pennsylvania. Two recently proposed indexes based on the amount of NH4 + released by treating soil with 2 M KCl at 100°C for 4 hr or with a pH 11.2 phosphate-borate buffer for 8 min were not good predictors of NSC (r=0.484 and 0.254, respectively). The absorbance of a 0.01 M NaHCO3 extract at 260 nm was also poorly correlated with field-measured NSC (r=0.412). The pre-sidedress soil NO3 − test (PSNT), the soil NO3 − concertration in the surface 20 cm of soil at planting, and the UV absorbance at 200 nm of a 0.01 M NaHCO3 extract of at planting soils were all moderately well correlated with NSC (r=0.672, 0.750, and 0.737, respectively). The latter two indexes are very simple, rapid, and inexpensive to perform and offer the possibility of improving the prediction of NSC in heavily manured fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00009929
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  • 23
    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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  • 24
    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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  • 25
    Electronic Resource
    Electronic Resource
    The effect of agitation on the morphology and penicillin production of Penicillium chrysogenum (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1011-1023 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Penicillium chrysogenum strain P1 was grown on complex media in 10 and 100 L agitated fermenters at various aeration rates and stirrer speeds. Samples were removed at intervals for measurements of the culture morphology. At high stirrer speeds (1000 and 1200 rpm) in 10-L fermentations the rate of decrease in the mean effective hyphal length was faster and the rate of penicillin production was lower than fermentations done at 800 rpm. At similar power inputs per unit volume in 100-L fermentations, the change in mean effective hyphal length was less and higher penicillin production rates were observed. This work comparing the results at two scales has shown that neither of the concepts of impeller tip speed or the dissipation rate of turbulence have general validity as a measure of hyphal damage. Our results are reasonaby well correlated by groups similar to circulation rate (NDi3/V) with lower circulation rates being beneficial. An adaptation of the van Suijdam and Metz relationship, expressed as P/Di3tc, was most successful. Our data are insufficient to demonstrate the generality of the relationship but do support the concept of a dispersion zone around the impellers in which mycelia may be damaged. The greater the frequency of circulation of mycelia through the zone the greater the damage and the lower the rate of penicillin synthesis by the culture.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260351009
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  • 26
    Electronic Resource
    Electronic Resource
    Synthetic sequence effects in polyurethane-poly(n-butyl methacrylate) mixtures: Grafting and mechanical properties (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 41 (1990), S. 1281-1298 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Morphology, stress-strain properties, and grafting have been investigated in highly phase-separated polyurethane (PU)-poly(n-butyl methacrylate) (PBMA) mixtures as a function of the sequence of formation of the components, both linear (l) and crosslinked (x), in the presence of each other. In the range of 0.3-0.7 weight fraction of PU, a morphology of PBMA particles in a PU matrix results. Particle size depends on matrix viscosity at the time of PBMA formation, decreasing as viscosity increases. The PBMA (l) particles are spherical; PBMA (x) particles are irregular in shape when formed in a fluid medium but tend to become spherical as the delay time before the onset of their formation is increased. Grafting, decreasing with increasing delay time, is observed between PBMA (l) particles and the PU (x) or PU (l) matrix. The grafting results from transesterification between BMA and the polyol precursors to the PU. Two families of mechanical properties are found, depending generally more on particle shape than size. Systematic trends of property values through a series of samples of constant composition, but increasing delay times, are observed with greater variation in the series with PBMA (x) particles; the trends are explainable in terms of matrix immobilization by the particles.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070410536
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