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Title:Use of 15N-labeled anhydrous NH3 to determine the efficiency of fall N fertilization for corn production
Author(s):Griesheim, Kelsey Luella
Advisor(s):Mulvaney, Richard L.
Department / Program:Natural Res & Env Sci
Discipline:Natural Res & Env Sciences
Degree Granting Institution:University of Illinois at Urbana-Champaign
anhydrous ammonia
fertilizer N uptake efficiency
field-plot research
nitrification inhibitor
soil N mineralization
Abstract:Fall application of anhydrous ammonia (NH3) is a common practice for corn (Zea mays L.) production in the Midwestern USA, but evaluations to date have relied entirely on yield comparisons that provide no means of distinguishing fertilizer from soil N uptake. A more rigorous evaluation of this practice requires the use of 15NH3, which has long been impeded by the difficulties and safety hazards inherent to a liquefied gas that must be handled and applied under pressure. A manifold system is described for transferring known quantities of NH3 from labeled and unlabeled sources to obtain a desired 15N enrichment, and for collecting the mixture cryogenically in a tank specifically configured for knifed applications using a tractor-mounted tool bar. Enrichments of 1.2–1.5 atom % 15N were obtained for 3 kg of NH3 prepared within a normal working day by a fifteen-fold dilution with 10 atom % 15N as the starting label. A collection capacity of such magnitude represents a 3000% upscaling over systems previously described for this purpose, providing an essential prerequisite for field plot research to realistically assess the fate and fertilizer value of anhydrous NH3. In using this system, six field trials were conducted between 2016 and 2018 by applying 224 kg N ha-1 with and without the use of nitrapyrin (NP) or an experimental alternative (EP) for inhibiting nitrification. Significant grain yield response to fall N fertilization averaged 46% at five of the six sites studied in both years of the experiment. Isotopic estimates of fertilizer N uptake efficiency (FNUE) ranged from 12 to 34% for grain and from 16 to 42% for total aboveground biomass, while in both cases N derived from fertilizer (NDFF) never exceeded 50%. A significant increase in FNUE occurred with NP but not EP at only two sites studied, whereas site differences in soil organic C and potentially mineralizable N had a much larger effect on crop uptake of 15N. The results show that, even with the addition of NP, the majority of the N applied in the fall as anhydrous NH3 is not taken up by the following corn crop. If this practice is to be used, uptake efficiency can be improved by accounting for soil N mineralization.
Issue Date:2019-04-12
Rights Information:Copyright 2019 Kelsey Griesheim
Date Available in IDEALS:2019-08-23
Date Deposited:2019-05

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