Soil Science Society of America Journal · 2026
Nitrogen fertilization does not significantly increase soil carbon in most temperate corn‐based systems: Is initial carbon a key?
Blanco Canqui, H., Iqbal, J., Shapiro, C. A., Walters, D. T.
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Nitrogen fertilization does not significantly increase soil …
Abstract
Restoring the lost soil organic C (SOC) is the first step for regenerating soils. Nitrogen fertilization may contribute to the SOC restoration by boosting crop residue production. However, whether this practice increases SOC is still unclear. We integrated insights from a 40‐year experiment in a temperate Mollisol with a regional review to discuss SOC response to fertilization, compare results with those of global meta‐analyses, and identify potential influencing factors in temperate corn‐based systems. After 40 years, N fertilization did not significantly affect SOC to 1‐m depth, regardless of tillage system (moldboard plow, disk, and no‐till) or cropping system (continuous corn [ Zea mays L.] and corn‐soybean [ Glycine max L.]). These results concurred with our regional review (27 sites) in temperate corn‐based systems published up to April 15, 2026, in which N fertilization does not significantly increase SOC in 70% of sites. In 30% of sites, SOC accumulated at 0.15 ± 0.11 Mg C ha −1 year −1 with fertilization. These results differ from those of global meta‐analyses that stated N fertilization increases SOC by about 20% and highlight that SOC benefits of fertilization are highly context specific. Data from temperate regions suggest that initial SOC might be a potential predictor of SOC response to N fertilization, while tillage, crop, N rate, duration, and texture appear to have a lesser influence. Initial SOC was 1.5 times lower ( p = 0.01) in sites with (14 ± 5 g C kg −1 ) than without (21 ± 9 g C kg −1 ) fertilization effect, suggesting that N fertilization may preferentially increase SOC in low‐C soils (≤14 g C kg −1 ). However, initial SOC is predominantly the SOC in the unfertilized plots as 74% of studies did not report actual initial SOC. Overall, while N fertilization is important to optimize crop yield, it does not significantly accumulate SOC in most temperate corn‐based systems.
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Restoring the lost soil organic C (SOC) is the first step for regenerating soils. Nitrogen fertilization may contribute to the SOC restoration by boosting crop residue production. However, whether this practice increases SOC is still unclear. We integrated insights from a 40‐year experiment in a temperate Mollisol with a regional review to discuss SOC response to fertilization, compare results with those of global meta‐analyses, and identify potential influencing factors in temperate corn‐based systems. After 40 years, N fertilization did not significantly affect SOC to 1‐m depth, regardless of tillage system (moldboard plow, disk, and no‐till) or cropping system (continuous corn [ Zea mays L.] and corn‐soybean [ Glycine max L.]). These results concurred with our regional review (27 sites) in temperate corn‐based systems published up to April 15, 2026, in which N fertilization does not significantly increase SOC in 70% of sites. In 30% of sites, SOC accumulated at 0.15 ± 0.11 Mg C ha −1 year −1 with fertilization. These results differ from those of global meta‐analyses that stated N fertilization increases SOC by about 20% and highlight that SOC benefits of fertilization are highly context specific. Data from temperate regions suggest that initial SOC might be a potential predictor of SOC response to N fertilization, while tillage, crop, N rate, duration, and texture appear to have a lesser influence. Initial SOC was 1.5 times lower ( p = 0.01) in sites with (14 ± 5 g C kg −1 ) than without (21 ± 9 g C kg −1 ) fertilization effect, suggesting that N fertilization may preferentially increase SOC in low‐C soils (≤14 g C kg −1 ). However, initial SOC is predominantly the SOC in the unfertilized plots as 74% of studies did not report actual initial SOC. Overall, while N fertilization is important to optimize crop yield, it does not significantly accumulate SOC in most temperate corn‐based systems.
Restoring the lost soil organic C (SOC) is the first step for regenerating soils. Nitrogen fertilization may contribute to the SOC restoration by boosting crop residue production. However, whether this practice increases SOC is still unclear. We integrated insights from a 40‐year experiment in a temperate Mollisol with a regional review to discuss SOC response to fertilization, compare results with those of global meta‐analyses, and identify potential influencing factors in temperate corn‐based systems. After 40 years, N fertilization did not significantly affect SOC to 1‐m depth, regardless of tillage system (moldboard plow, disk, and no‐till) or cropping system (continuous corn [ Zea mays L.] and corn‐soybean [ Glycine max L.]). These results concurred with our regional review (27 sites) in temperate corn‐based systems published up to April 15, 2026, in which N fertilization does not significantly increase SOC in 70% of sites. In 30% of sites, SOC accumulated at 0.15 ± 0.11 Mg C ha −1 year −1 with fertilization. These results differ from those of global meta‐analyses that stated N fertilization increases SOC by about 20% and highlight that SOC benefits of fertilization are highly context specific. Data from temperate regions suggest that initial SOC might be a potential predictor of SOC response to N fertilization, while tillage, crop, N rate, duration, and texture appear to have a lesser influence. Initial SOC was 1.5 times lower ( p = 0.01) in sites with (14 ± 5 g C kg −1 ) than without (21 ± 9 g C kg −1 ) fertilization effect, suggesting that N fertilization may preferentially increase SOC in low‐C soils (≤14 g C kg −1 ). However, initial SOC is predominantly the SOC in the unfertilized plots as 74% of studies did not report actual initial SOC. Overall, while N fertilization is important to optimize crop yield, it does not significantly accumulate SOC in most temperate corn‐based systems.
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