Thorburn, Peter J., Biggs, Jody S., Puntel, Laila A., Sawyer, John E., Everingham, Yvette L., and Archontoulis, Sotirios V. (2024) The nitrogen fertilizer conundrum: why is yield a poor determinant of crops’ nitrogen fertilizer requirements? Agronomy for Sustainable Development, 44. 18.

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Abstract

The application of nitrogen (N) fertilizer both underpins high productivity of agricultural systems and contributes to multiple environmental harms. The search for ways that farmers can optimize the N fertilizer applications to their crops is of global significance. A common concept in developing recommendations for N fertilizer applications is the “mass balance paradigm” – that is, bigger crops need more N, and smaller less – despite several studies showing that the crop yield at the optimum N rate (Nopt) is poorly related to Nopt. In this study we simulated two contrasting field experiments where crops were grown for 5 and 16 consecutive years under uniform management, but in which yield at Nopt was poorly correlated to Nopt. We found that N lost to the environment relative to yields (i.e., kg N t-1) varied +/- 124 and 164 % of the mean in the simulations of the experiments. Conversely, N exported in harvested produce (kg N t-1) was +/- 11 and 48 % of the mean. Given the experiments were uniformly managed across time, the variations result from crop-to-crop climatic differences. These results provide, for the first time, a quantitative example of the importance of climatic causes of the poor correlation between yield at Nopt and Nopt. An implication of this result is that, even if yield of the coming crop could be accurately predicted it would be of little use in determining the amount of N fertilizer farmers need to apply because of the variability in environmental N losses and/or crop N uptake. These results, in addition to previous empirical evidence that yield at Nopt and Nopt are poorly correlated, may help industry and farmers move to more credible systems of N fertilizer management.

Item ID:	85911
Item Type:	Article (Research - C1)
ISSN:	1773-0155
Copyright Information:	This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/
Date Deposited:	19 Jun 2025 03:21
FoR Codes:	30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3004 Crop and pasture production > 300411 Fertilisers (incl. application) @ 50% 30 AGRICULTURAL, VETERINARY AND FOOD SCIENCES > 3004 Crop and pasture production > 300403 Agronomy @ 50%
SEO Codes:	26 PLANT PRODUCTION AND PLANT PRIMARY PRODUCTS > 2601 Environmentally sustainable plant production > 260199 Environmentally sustainable plant production not elsewhere classified @ 100%
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