Nitrogen application for optimized corn yield in the USA
Present status, challenges and prospects
Effective application of nitrogen (N) is crucial in corn production to overcome current environmental, economic, and crop-yield-related issues. Adoption of site-specific cropping systems, precision agriculture, and collaboration with economists, extension specialists, and policymakers can assist in creating a climate-resilient and N-efficient production structure. For this, we need to understand the present status of the corn and N relationship, address the relevant challenges, and develop a corn system with better N use efficiency. Addressing questions related to effective N application for achieving improved corn yield can help farmers overcome higher input costs and achieve their target yield while reducing their environmental footprint.
The USA is the largest corn (Zea mays L.) producer in the world in terms of area, production, and value with half of the country’s total corn produced coming from the U.S. Corn Belt region. Corn is the most important crop not just for food, but also for forages for livestock and poultry and ethanol for the fuel industry. In fact, 60% of the total corn grain in the USA goes to animal feed production (Klopfenstein et al., 2013) although the shift keeps on changing depending on the market demand.
In 2024–2025, the national average corn yield was 11.26 tons ha–1, a 6.5% increase since 2015–2016 (USDA-IPAD, 2025). To meet the food, feed, and industrial demand, research is being conducted to improve corn yield. It is estimated that approximately 145 million metric tons of synthetic fertilizers along with other chemicals are applied for global agricultural production (Sandhu et al., 2020), causing environmental degradation and higher input costs. In the USA, half of the national synthetic N application goes to corn production (Mirzaee & Nafchi, 2025).
From seedling growth to ear development, corn growth stages are significantly impacted by N application. However, there is a big concern from the environmental health perspective. Analysis has shown that over the past three decades, the economic optimum nitrogen rate has increased by 2.7 kg N ha⁻¹ yr⁻¹, corresponding to an annual increase of approximately 1.2% in U.S. corn production (Baum et al., 2025). This trend highlights the growing complexity of nitrogen management and underscores the need for integrated strategies that balance productivity with environmental sustainability.
In this review, we examine the current status of nitrogen application in U.S. corn systems, associated agronomic and environmental challenges, emerging technologies for improving nitrogen use efficiency (NUE), the role of extension services and farmer education, and future prospects for yield optimization. To guide this discussion, Figure 1 presents a systems-based conceptual framework illustrating how agronomic practices and precision technologies interact under climate and soil variability to enhance NUE, ultimately generating economic and environmental benefits supported by policy and extension networks.
Present status of nitrogen application in the USA for corn production
It is an established fact that N application has increased over the years in an almost linear trend along with the increased crop yield. However, according to USDA findings, N fertilizer quality also has improved compared with the fertilizers in 1940s (Njuki et al., 2024). Similarly, the global N application rate for corn increased 141.3% between 1961 to 2020 (Adalibieke et al., 2023), contributing 63% of total global reactive N due to human action (Dobermann & Cassman, 2005).
The requirement for N fertilizer depends on the cropping system; for example, a corn–corn rotation will consume more synthetic N than a corn–soybean rotation as soybean fixes N biologically in the soil, reducing the total N requirement. Similarly, pre-plant or N application at planting time is necessary for corn crops in a corn–corn rotation as opposed to corn in a corn–soybean system.
Currently, corn NUE ranges between 25 and 30% (Kaur et al., 2024), and most of the N applied is lost through volatilization, denitrification, leaching, runoff, or erosion, causing severe environmental consequences. To reduce the negative impact on the environment and improve NUE, it is suggested to split the total N requirements and follow 4Rs—right source, right rate, right time, and right placement.
Split application provides the farmer a chance to decide on the rate of a second N fertilizer application depending on the crop performance and the weather conditions. For instance, regardless of agronomic management practices, high temperature causes N loss through N2O emissions (Kabir et al., 2021).
Under conservative tillage conditions, especially for spring N application on no-till soils, polymer-coated urea (PCU) or sulfur-coated urea (SCU) can be an option for surface broadcast as urea is prone to greater loss through nitrification than anhydrous ammonia. However, banding is more efficient than broadcast application (Nattrass et al., 2024).
Urea ammonia nitrogen (UAN) solution is better placed using Y-drops, but direct contact with the plant needs to be avoided to prevent leaf burning, particularly at an advanced vegetative stage. Some studies suggest application of 50-50 split N application between planting and V12 (Kosola et al., 2023) whereas some suggest cover cropping (cereal rye) and a split N application (pre-plant and sidedress) to reduce annual N loss (Preza-Fontes et al., 2021b). Spring N application is often found more efficient than fall application (Lasisi et al., 2021).
For calculating optimum N rate, depending on various sources of N and profitability, the Corn Nitrogen Rate Calculator was developed for U.S. Corn Belt region and is an excellent resource for farmers.
Nitrogen stabilizers such as urease inhibitors, nitrification inhibitors, and slow-release coated fertilizers slow the hydrolysis or nitrification process of urea and thus improve NUE and reduce N loss in the environment (Qi et al., 2021; Sha et al., 2020). Nitrification inhibitors (NIs) restrict the nitrification process and enhance the efficiency of N fertilizer.
Recently a few studies have been conducted on microbial (fungal arbuscular mycorrhiza, Trichoderma, plant-growth-promoting rhizobacteria, Azotobacter, and Azospirillium) and non-microbial (seaweed products, chitosan, protein hydrolysates, and humic substances) biostimulants for improving NUE (Gajula et al., 2025). Despite the positive impact on crop yield in general, more research is required to find the efficacy of biostimulants in increasing NUE in corn.
Because of the climatic and soil variations, N requirement varies. As we move from north to south in the U.S., the temperature gets warmer, and precipitation increases from west to east. Hence, N application rate varies from region to region.
An observation through geospatial analysis confirmed that in the past 100 years, a higher synthetic N application trend shifted from the southeastern and eastern U.S. to the Midwest, the Great Plains, and the Northwest (Cao et al., 2018), which also lets us know the cropping system shift (towards corn cultivation) in those regions (Rathore et al., 2024).
Agronomic and environmental challenges of nitrogen application
Since N is a crucial factor determining yield and profitability and because of government incentive policies, farmers tend to apply more N than what is required. However, excess N application does not lead to a significant increase in corn yield. On the contrary, in some cases, it may negatively impact biomass growth (Ordóñez et al., 2021), and most of the time, that extra N gets lost in the environment, causing water quality issues (through leaching or runoff) or air pollution (nitrous oxide or ammonia emission).
Furthermore, agriculture is the largest contributor to nitrous oxide, ammonia, and nitrate emissions, leading to ozone injury to our atmosphere (Ribaudo, 2011).
Corn, being a N fertilizer-intensive crop, receives high N compared with other major crops. A higher dose of N causes several environmental problems such as disruption of soil microbes’ status, decrease in organic carbon soil, and nutrient ion balance in the soil.
It is estimated that approximately half of the total applied N is recovered in cereal crops (Bhatt et al., 2025) while the remainder is lost as previously discussed. This points out the importance of crop residue management to recover a portion of the N from the harvested crop parts to the soil. Likewise, organically enhanced N fertilizers can be an option for reducing N loss and significantly less greenhouse gas emissions (Singh et al., 2012).
Nitrous oxide (N2O) emission from corn fields has been documented. Research shows that approximately 5.6 kg of N2O–N is emitted annually per hectare of corn field in U.S. Corn Belt region (Lawrence et al., 2021).
Excessive N application causes ground water quality deterioration, and this ultimately affects surface water quality, leading to eutrophication, hypoxia, and even deadly zones (Liu et al., 2024).
Advanced technologies for optimum nitrogen use efficiency in corn
Established techniques like crop rotation, for instance, can improve corn yield and NUE (e.g., corn followed by soybean instead of corn followed by corn; Attia et al., 2015). Likewise, cover crops such as cereal rye and hairy vetch are known to improve corn yield (Pokhrel et al., 2025; Sun et al., 2025).
Even though the concept of enhanced-efficiency fertilizers (EEF) (e.g., controlled-release fertilizer use or techniques to reduce nutrient reaction loss) has been in the research community since the 1960s, there are less research works on this topic (Lyons et al., 2024). According to Hergert (2010), EEF can be “fertilizer additives, physical barriers, or different chemical formulations,” which reduce N loss through volatilization, denitrification, leaching, or some other losses. Some researchers have found field level efficiency using EEF (Verburg et al., 2022).
Most corn farmers apply N fertilizer uniformly. Nevertheless, to improve corn production, increase crop NUE, and reduce N losses and associated environmental consequences, there is an urgent need to use advanced scientific technologies for optimum economic return and environmental benefits.
Variable-rate N application or variable-rate technology (VRT) allows farmers to check field N variations; address spatial variability such as soil type, slope and curvature, and drainage issues; and apply accordingly instead of uniformly, which ends up being inefficient.
Some other precision agriculture tools, namely drones, satellite imagery, GPS technology, remote sensing, and Geographic Information Systems (GIS), collect information on weather, soil, and crop health while smart soil sensors and automated control systems can help remote monitoring or management and artificial intelligence (AI) can help with data analysis (Mansoor et al., 2025). Although precision agriculture technologies are still at an early stage for field-level popularity, these tools are expected to assist in maintaining ecological balance and improved crop yield.
Preza-Fontes et al. (2021a) developed an online system for tracking seasonal changes in soil N concentration in corn from the USDA gSSURGO soil database, a process-based model for soil and crop N cycling, and a publicly available online decision support tool that could potentially assist with N fertilizer management. Ransom et al. (2023) used a computer simulation crop model combined with other regular tools (yield goal, pre-plant and late season soil nitrate tests, and canopy reflectance sensing) for precise N recommendation in a corn field.
Finally, progress in development of genetically N-efficient modern corn hybrids has simultaneously improved both crop yield and NUE (Ordóñez et al., 2025). Long-term analysis has found that short-season corn hybrids have been improved in the past four decades (King et al., 2024).
To synthesize the diverse approaches discussed above, Table 1 summarizes the major nitrogen management strategies currently used or proposed for corn systems, highlighting their underlying mechanisms, agronomic performance, environmental benefits, and practical adoption barriers. While each strategy contributes to improved nitrogen use efficiency in a different way, their effectiveness depends strongly on site-specific soil and climate conditions, economic feasibility, and farmer management capacity.
| Strategy | Mechanism | Yield impact | Environmental benefit | Adoption barrier |
|---|---|---|---|---|
| Split N application | Synchronizes supply with uptake | Neutral–positive | Reduced leaching | Weather dependency |
| Cover crops | N capture | Positive | Reduced runoff | Management complexity |
| VRTa precision N | Spatial targeting | Positive | Reduced excess | Equipment cost |
| N stabilizers | Slowed transformation | Variable | Reduced emissions | Cost uncertainty |
| a VRT, variable-rate technology. | ||||
This comparison illustrates that no single practice is universally optimal; rather, integrated adoption of complementary strategies is more likely to achieve both yield stability and environmental sustainability.
Extension services and farmers’ education on nitrogen use efficiency
The USDA-ARS advises farmers to develop and employ a nutrient management plan, particularly “SMART Nutrient Management,” at the local level, which NRCS conservationists can help with. The Nutrient Management (Ac.) (590) Conservation Practice Standard highlights site-specific nutrient management practices in the USA considering soil and manure tests, nutrient loss risk estimation, and 4R strategy.
Economic incentive programs—Environmental Quality Incentives Program (EQIP) and Conservation Stewardship Program (CSP)—motivate farmers to adopt conservative strategies that help reduce N pollution. The USEPA provides information about nutrient restoration methods.
Each state has nitrogen management programs. Minnesota has a “Nitrogen Management Financial Assistance Pilot Program” for farmers who adopt agricultural practices such as (i) cover cropping, (ii) manure testing, (iii) cultivation of a perennial crop or small-grain crop (namely oats, barley, rye, wheat), (iv) relay cropping, (v) N testing in the spring before planting, and (vi) precision agriculture to decrease groundwater contamination through nitrogen leaching.
Similarly, there are other state-level nitrogen management programs, including the Iowa Nitrogen Initiative, Minnesota Pollution Control Agency, USEPA Gulf Hypoxia Program (GHP; Louisiana), and the Indiana State Nutrient Reduction Agency. Land grant universities in the respective states conduct field days, workshops, and training programs on advanced technologies in precision agriculture and provide nutrient management guidelines to farmers and related stakeholders.
Regulatory guidelines of the USEPA Total Maximum Daily Loads (TMDLs) pose a limit on the pollutant disposal to a waterbody to maintain water quality. In short, for achieving optimum NUE in corn, both voluntary and regulatory approaches are required so that farmers can obtain unambiguous guidance.
Future prospects for improved corn nitrogen use efficiency
Considering the current changes in weather patterns, N fertilizer application in corn is going to be affected by the weather variables much more than the previous decades. Quan et al. (2024) found that temperatures above 28°C cause an increase in N demand in corn plants to meet the corn production level. One explanation for this could be that at higher temperatures, the plant metabolic activity rate also increases, which requires more energy and hence, more N intake.
Likewise, continuous rainfall for several days leads to soil water saturation. This causes N loss through leaching and denitrification, and it means that water pollution and the cost of controlling N pollution will increase under an excessive rainfall scenario (Choi et al, 2023).
Development of a flexible and site-specific climate-resilient N management plan in consultation with state soil nutrient specialists can solve this problem to a greater extent. Additionally, recent rapid progress in AI helps in more accurate analysis of weather patterns and soil and crop health, ensuring better decision making for farmers.
Integration of machine learning and genetics can potentially support scientists to develop more N-efficient corn hybrids (Chen et al., 2024; He et al., 2025; Wang et al., 2021). Nevertheless, efficient N management requires effective interdisciplinary collaborations to understand the agronomical, economical, physiological, biochemical, molecular, and sociological aspects of N optimization for improved corn yield along with the support of the policymakers.
Conclusion
Understanding and formulating a meaningful optimum N management plan is crucial for corn in terms of economic and environmental sustainability and meeting the present growing demand. Hence, effective advanced precision agriculture technologies and developing a site-specific cost-effective suitable cropping system can address the current N optimization issues.
However, research findings need to reach farmers through regular extension work to obtain their feedback. Collective effort of various segments of the scientific research community, economists, extension specialists, and policymakers can provide us with a feasible climate-resilient N management plan for a yield-efficient and environmentally sustainable ecosystem.
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