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.
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Claims 11
Claim · model-written summary
The manifold prepared 3 kg ammonia at 1.2–1.5 atom % enrichment in a working day.
- Taxon
- corn
Zea mays subsp. mayst0 - Outcome
- Enrichmentse0
- Value
- 1.2–1.5 atom % 15Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Enrichments of 1.2–1.5 atom % 15N were obtained for 3 kg of NH3 prepared within a normal working day”
t0“corn”
Claim · model-written summary
Collection capacity was 3000% above prior systems.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- upscalinge0
- Value
- 3000%e0
- Comparator
- systems previously describede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a 3000% upscaling over systems previously described for this purpose”
t0“corn”
Claim · model-written summary
Fall nitrogen raised grain yield by an average 46% at five sites.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- fall N fertilizatione0
- Outcome
- grain yielde0
- Value
- 46%e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant grain yield response to fall N fertilization averaged 46% at five of the six sites studied”
t0“corn”
Claim · model-written summary
Grain fertilizer nitrogen uptake efficiency ranged 12 to 34%.
- Taxon
- cornZea mays subsp. mayst0
- Organ / stage
- graine0
- Outcome
- fertilizer N uptake efficiencye0
- Value
- 12 to 34%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Isotopic estimates of fertilizer N uptake efficiency (FNUE) ranged from 12 to 34% for grain”
t0“corn”
Claim · model-written summary
Biomass fertilizer nitrogen uptake efficiency ranged 16 to 42%.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- total aboveground biomasse0
- Value
- 16 to 42%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“from 16 to 42% for total aboveground biomass”
t0“corn”
Claim · model-written summary
Fertilizer derived nitrogen never exceeded 50%.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- N derived from fertilizere0
- Value
- 50%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N derived from fertilizer (NDFF) never exceeded 50%”
t0“corn”
Claim · model-written summary
Nitrapyrin significantly increased uptake efficiency at only two sites.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A significant increase in FNUE occurred with NP but not EP at only two sites studied”
t0“corn”
Claim · model-written summary
The experimental alternative did not significantly increase uptake efficiency.
- Taxon
- cornZea mays subsp. mayst0
- Treatment
- EPe0
- Outcome
- FNUEe0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A significant increase in FNUE occurred with NP but not EP at only two sites studied”
t0“corn”
Claim · model-written summary
Soil organic carbon and mineralizable nitrogen differences had larger effects on corn labeled nitrogen uptake.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- crop uptake of 15Ne0
- Direction
- largere0
- Setting
- sitee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“site differences in soil organic C and potentially mineralizable N had a much larger effect on crop uptake of 15N.”
t0“corn”
Claim · model-written summary
Most fall applied ammonia nitrogen was not taken up by the following corn crop.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- N applied in the fall as anhydrous NH3 is not taken upe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the majority of the N applied in the fall as anhydrous NH3 is not taken up by the following corn crop.”
Claim · model-written summary
Accounting for soil nitrogen mineralization can improve uptake efficiency.
- Taxon
- cornZea mays subsp. mayst0
- Outcome
- uptake efficiency can be improved by accounting for soil N mineralizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“uptake efficiency can be improved by accounting for soil N mineralization.”
t0“corn”
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