Long-term effects of nitrogen sources on yields, nitrogen use efficiencies, and soil nitrogen and carbon sequestration in irrigated, tilled corn

Authors: Delgado, Jorge; D Adamo, Robert; Stewart, Catherine; Floyd, Bradley; Del Grosso, Stephen; Manter, Daniel; Halvorson, Ardell; Brandt, Amber

Submitted to: Agronomy
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2024
Publication Date: 11/5/2024
Citation: Delgado, J.A., D Adamo, R.E., Stewart, C.E., Floyd, B.A., Del Grosso, S.J., Manter, D.K., Halvorson, A.D., Brandt, A.D. 2024. Long-term effects of nitrogen sources on yields, nitrogen use efficiencies, and soil nitrogen and carbon sequestration in irrigated, tilled corn. Agronomy. 14(11). Article e2618. https://doi.org/10.3390/agronomy14112618.
DOI: https://doi.org/10.3390/agronomy14112618

Interpretive Summary: We conducted long-term research about the effects of various combinations of tillage systems (no tillage, strip tillage, and conventional tillage) and types of fertilizer (for example, manure, urea fertilizer, enhanced efficiency fertilizer, among others) on corn grown at a site in Fort Collins, Colorado. We found that corn grown using conventional tillage and manure is a better practice for increasing the aboveground production and harvested grain yields while capturing carbon and nitrogen in the soil (improving the health of the soil) and also helping ensure that the increased yields could be sustained over time, compared to growing corn with tillage and inorganic fertilizer. Additionally, the harvested grain yields of corn grown using conventional tillage and manure fertilizer were higher than when strip tillage or no tillage was used. We found that the best overall combination to increase corn productivity and yields was when we used a combination of manure (30% of the nitrogen applied) with enhanced efficiency fertilizer (70% of the nitrogen applied).

Technical Abstract: Although corn is the most important and nitrogen (N)-fertilized crop, there is a lack of long-term data on the effects of organic and inorganic N fertilizers on the N balance and losses for corn systems under different tillage approaches. From 2012 to 2023, we assessed the effects of the N source on the grain yields from cultivated continuous corn receiving irrigation at a site with minimal erosion in Fort Collins, Colorado, USA, and compared these effects to no-till (NT) and strip till (ST) systems receiving inorganic N. An N balance accounting for N and carbon (C) sequestration found a system nitrogen use efficiency (NUESys) for organic N fertilizer (manure) with a tillage of 86.6%, which was higher than the NUESys of 62.6% with inorganic N fertilizer (enhanced efficiency fertilizer, EEF). Conventional tillage with manure use is a good management practice that contributed to higher grain yields (2 of 11 years), C sequestration (p < 0.05), soil organic N content (p < 0.05), and soil phosphorus (P) content than inorganic N fertilizer with tillage (p < 0.05). The tilled systems, whether receiving organic or inorganic N fertilizer, had higher yields and grain N content than the NT and ST systems receiving inorganic N fertilizer (p < 0.05). The grain production of the cultivated system receiving organic N fertilizer did not decrease with time, while the yields of the cultivated system receiving inorganic N fertilizer decreased with time (p < 0.05), suggesting that cultivated systems receiving organic N fertilizer may be more sustainable and better able to adapt to a changing climate. Additionally, a combination of manure (30% of N input) with EEF (70% of N input) contributed to a synergistic effect that increased the agronomic productivity (harvested grain yields).