Abstract
For maize (Zea mays L.), nitrogen (N) fertilizer use is often summarized from field to global scales using average N use efficiency (NUE). But expressing NUE as averages is misleading because grain increase to added N diminishes near optimal yield. Thus, environmental risks increase as economic benefits decrease. Here, we use empirical datasets obtained in North America of maize grain yield response to N fertilizer (n = 189) to create and interpret incremental NUE (iNUE), or the change in NUE with change in N fertilization. We show for those last units of N applied to reach economic optimal N rate (EONR) iNUE for N removed with the grain is only about 6%. Conversely stated, for those last units of N applied over 90% is either lost to the environment during the growing season, remains as inorganic soil N that too may be lost after the growing season, or has been captured within maize stover and roots or soil organic matter pools. Results also showed iNUE decrease averaged 0.63% for medium-textured soils and 0.37% for fine-textured soils, attributable to fine-textured soils being more predisposed to denitrification and/or lower mineralization. Further analysis demonstrated the critical nature growing season water amount and distribution has on iNUE. Conditions with too much rainfall and/or uneven rainfall produced low iNUE. Producers realize this from experience, and it is uncertain weather that largely drives insurance fertilizer additions. Nitrogen fertilization creating low iNUE is environmentally problematic. Our results show that with modest sub-EONR fertilization and minor forgone profit, average NUE improvements of ~10% can be realized. Further, examining iNUE creates unique perspective and ideas for how to improve N fertilizer management tools, educational programs, and public policies and regulations.
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Claims 6
Claim · model-written summary
Incremental nitrogen use efficiency at the economic optimum was about 6% for nitrogen removed in grain.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“iNUE for N removed with the grain is only about 6%”
e1“maize (Zea mays L.)”
Claim · model-written summary
Over 90% of the final units of nitrogen applied were outside grain removal, across loss or other pools.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“for those last units of N applied over 90% is either lost to the environment during the growing season, remains as inorganic soil N that too may be lost after the growing season, or has been captured within maize stover and roots or soil organic matter pools”
Claim · model-written summary
Incremental NUE decrease averaged 0.63% on medium-textured soils.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“iNUE decrease averaged 0.63% for medium-textured soils”
e1“maize (Zea mays L.)”
Claim · model-written summary
Incremental NUE decrease averaged 0.37% on fine-textured soils.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“iNUE decrease averaged 0.63% for medium-textured soils and 0.37% for fine-textured soils”
e1“maize (Zea mays L.)”
Claim · model-written summary
Excessive or uneven rainfall was associated with low incremental NUE.
Verbatim
e0“Conditions with too much rainfall and/or uneven rainfall produced low iNUE”
Claim · model-written summary
Modest sub-optimal nitrogen fertilization could improve average NUE by about 10% with minor foregone profit.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“with modest sub-EONR fertilization and minor forgone profit, average NUE improvements of ~10% can be realized”
e1“maize (Zea mays L.)”
The same questions in other papers
fertilization · nutrient: efficiency · Zea mays (maize)Results differ
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- no effect
- negative
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See all 189 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.