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  • Geography  (4)
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  • 1
    Online Resource
    Online Resource
    Comparison of a Forced‐draft Technique to Nitrogen‐15 Recovery for Measuring Ammonia Volatilization Under Field Conditions
    Wiley ; 1987
    In:  Soil Science Society of America Journal Vol. 51, No. 1 ( 1987-01), p. 124-128
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 51, No. 1 ( 1987-01), p. 124-128
    Abstract: Reliable field measurements of NH 3 volatilization are necessary for evaluating N‐fertilizer efficiency for sod crops and conservation crop production systems. This study was conducted to compare NH 3 loss measurements under field conditions using a forced‐draft technique and recovery of urea‐ 15 N. Measurements were made from urea solution applied at a rate of 100 kg N ha −1 to a bare or mulched Cecil sandy loam soil (Typic Hapludult). In an adjacent area, microplots were established to which urea enriched with 15 N was added. Ammonia losses from the bare and mulched soil were 49 and 72% of the applied N by the forced‐draft technique, and 14 and 46% of the applied N by 15 N recovery. The air flow rate with the forced‐draft technique was shown to exceed the actual wind speed near the soil surface 10 and 50% of the time for bare and mulched soil, respectively. These results raise serious questions about the validity and accuracy of the forced‐draft technique. The usefulness of the forced‐draft technique may be limited to relative comparisons of N sources, N rates, and various management practices.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1987.03615995005100010027x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1987
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Location Call Number Limitation Availability
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    Online Resource
  • 2
    Online Resource
    Online Resource
    The Magnesium Problem in Nitrate Determination by Steam Distillation
    Wiley ; 1980
    In:  Soil Science Society of America Journal Vol. 44, No. 6 ( 1980-11), p. 1326-1327
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 44, No. 6 ( 1980-11), p. 1326-1327
    Abstract: Steam distillation of NH 3 is commonly used to quantify the amount of mineral N in soil and plant materials. A problem with NO 3 ‐ recovery by this method was encountered in an NH 3 volatilization study. When NH 4 NO 3 solutions were collected in acid and analyzed for NH 4 + ‐N and NO 3 ‐ ‐N, incomplete recovery of NO 3 ‐ occurred. As the volume or normality of H 2 SO 4 added to the distilling solution increased, more of the MgO used to raise the pH of the distilling solution was solubilized, which caused NO 3 ‐ recovery in the first 25ml of distillate to decrease. Only 80% NO 3 ‐ ‐N recovery was obtained with 20 ppm of Mg 2+ in the distilling solution. Soils with 3 meq exchangeable Mg 2+ /100 g depressed NO 3 ‐ ‐N recovery by 15% using the standard distillation procedure. An interaction between Mg 2+ and Devarda's alloy evidently inhibits NO 3 ‐ reduction.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1980.03615995004400060040x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1980
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Location Call Number Limitation Availability
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    Online Resource
  • 3
    Online Resource
    Online Resource
    Corn Responses to Ammonium‐ and Nitrate‐Nitrogen Fertilization
    Wiley ; 1992
    In:  Soil Science Society of America Journal Vol. 56, No. 4 ( 1992-07), p. 1166-1171
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 56, No. 4 ( 1992-07), p. 1166-1171
    Abstract: Studies have indicated that, by maintaining relatively high solution culture or soil NH + 4 /NO ‐ 3 ratios during the reproductive growth stage, certain corn ( Zea mays L.) genotypes have a higher yield potential. Unfortunately, few data on soil NH + 4 and NO ‐ 3 levels have been reported. A 3‐yr field experiment was conducted in northeastern Kansas in 1987, 1988, and 1989 to evaluate the effects of time and form of applied N on fertilizer band NH + 4 /NO ‐ 3 ratios and on the N nutrition, dry‐matter accumulation, and grain yield of two corn hybrids. Urea, urea‐NH 4 NO 3 , urea plus Ca(NO 3 ) 2 , NH 4 NO 3 , and Ca(NO 3 ) 2 solutions having NH + 4 /NO ‐ 3 ratios of 1:0, 3:1, 1:1, 1:1, and 0:1, respectively, were used at equivalent N rates. The nitrification inhibitors, nitrapyrin [2‐chloro‐6‐(trichloromethyl) pyridine] and dicyandiamide, as well as two‐way and three‐way timing of application schemes were used to maintain N as NH + 4 . Split applications of ammoniacal N with a nitrification inhibitor were effective in maintaining elevated soil NH + 4 concentrations from planting through early grain fill. In 1988 only, grain yield was increased slightly (3–9% higher) when corn was fertilized with ammoniacal N compared with NO ‐ 3 only. Overall, manipulation of soil NH + 4 /NO ‐ 3 ratios had few effects on corn development or yield.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1992.03615995005600040027x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1992
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Location Call Number Limitation Availability
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    Online Resource
  • 4
    Online Resource
    Online Resource
    Modified‐Quadratic/Plateau Model for Describing Plant Responses to Fertilizer
    Wiley ; 1990
    In:  Soil Science Society of America Journal Vol. 54, No. 6 ( 1990-11), p. 1784-1789
    Details
    In: Soil Science Society of America Journal, Wiley, Vol. 54, No. 6 ( 1990-11), p. 1784-1789
    Abstract: Accurate estimation of optimal fertilizer rates is becoming more critical because of growing economic and environmental concerns associated with fertilizer use. Curve‐fitting techniques are often used to estimate optimal fertilizer rates, but significant problems exist in selecting a proper model for a particular cropping situation. One solution is to develop a model sufficiently general to preclude the need for selecting a proper model for each cropping situation. We developed a modified‐quadratic/plateau (MQ/P) segmented model (four or five parameters) and demonstrated its general applicability compared with the quadratic/plateau (MQ/P) segmented model (three parameters) for describing fertilizer responses. The MQ/P model contains an efficiency index ( E x ) that is a quadratic function of the applied rate of nutrient X . In the Q/P model, E x remains constant relative to the rate of nutrient X . The MQ/P and Q/P segmented models set yield equal to the maximum yield ( Y m ) when the rate of nutrient X is greater than that required to achieve Y m . The general applicability of the MQ/P model in comparison with the Q/P model was evaluated by determining how well these models fit hypothetical input data calculated with linear/plateau (L/P), Mitscherlich (M), and square root/plateau (SR/P) functions. The MQ/P model gave R 2 values 〉 0.99 and predicted economically optimum fertilizer rates (i.e., rates at which the first derivative of yield response functions equaled the fertilizer/crop price ratio) close to those calculated with the input functions. The Q/P model gave R 2 values ranging from 0.95 to 0.99, but gave poor predictions of economically optimum fertilizer rates. The ability of the MQ/P model to fit functions as diverse as L/P, M, and SR/P, and to predict economically optimum N rates associated with these functions, suggests that the MQ/P model has utility as a general curve‐fitting technique for responses in which the right‐hand segment is a plateau. An advantage of the MQ/P model is that the regression parameters can be interpreted as physically meaningful constants.
    Type of Medium: Online Resource
    ISSN: 0361-5995 , 1435-0661
    URL: Article
    DOI: 10.2136/sssaj1990.03615995005400060047x
    RVK:
    RA 4845
    Language: English
    Publisher: Wiley
    Publication Date: 1990
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
    Online Resource
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