About

Jeffrey A Coulter is a Professor and Extension Agronomist in the Department of Agronomy and Plant Genetics at the University of Minnesota Twin Cities. He earned his Ph.D. from the University of Illinois in 2008 and was appointed as a faculty member in the same year. His research focuses on identifying and understanding agronomic practices that increase crop productivity, profitability, and sustainability within corn-based cropping systems. This work is conducted through field research at university research and outreach centers as well as on working farms, serving as the foundation for educational programs aimed at agricultural professionals and farmers. Coulter's extension education emphasizes corn-based cropping systems, and his research includes evaluating the effects of weather stressors, drought tolerance, nitrogen management, cover cropping, and interseeding practices on maize yield and sustainability. His contributions include advancing knowledge on how to optimize crop management under varying environmental conditions, with the goal of improving crop yields and sustainability in the Midwest region.

Research topics

• Agronomy
• Biology
• Environmental science
• Mathematics
• Chemistry
• Soil science
• Statistics
• Botany
• Animal science
• Materials science

Selected publications

• Precipitation influences pre‐sidedress soil nitrate thresholds for corn production

  Soil Science Society of America Journal · 2025-05-01

  articleOpen access

  Abstract Minnesota is a leading corn ( Zea mays L.) producer in the United States, requiring substantial nitrogen (N) inputs for optimal yields. Using an in‐season critical soil nitrate (NO 3 − ‐N) concentration threshold to adjust fertilization rates can improve N management and reduce environmental impacts. This study assessed corn grain yield response to in‐season (i.e., V4–V6 corn development stage) soil NO 3 − ‐N concentration to establish a critical pre‐sidedress soil NO 3 − ‐N test (PSNT) under Minnesota conditions. Data included were obtained from 34 field experiments conducted from 2012 to 2019 across the major corn production regions of Minnesota. Relationships between PSNT and relative corn grain yield were analyzed using a quadratic‐plateau regression model. Across the entire dataset, a PSNT of 20 ± 2.5 mg NO 3 − ‐N kg −1 soil was the critical level to reach 97% of maximum corn grain yield. To increase suboptimum PSNT concentrations up to the critical threshold, application of 13.8 ± 2.4 kg N ha −1 is needed per 1 mg kg −1 increase in soil NO 3 − ‐N concentration based on pre‐/at planting N application, but validation is needed for actual sidedress applications. When precipitation was lower or greater than the 30‐year mean, the critical PSNT value was 21.5 or 17.4 mg kg⁻¹, respectively. Nonetheless, the 20 ± 2.5 mg NO 3 − ‐N kg −1 PSNT critical value is applicable across the state as limited model improvements were achieved when the data were segregated according to soil characteristics, location, corn material, and/or previous crop.

  PublisherOA PDFDOI

• Maize yield response to mid‐season stalk breakage

  Agronomy Journal · 2025-07-01

  articleOpen access

  Abstract In 2022, over 198.8 million ha was insured across the United States, with indemnity payments exceeding $18.2 billion. In the US Midwest, strong wind gusts associated with thunderstorms often cause significant stalk breakage in maize ( Zea mays L.) fields. This study investigated whether crop insurance adjustment tables continue to be accurate when adjusting for maize yield after stalk breakage has occurred. Two experiments were conducted to assess the effect of below‐ear and above‐ear stalk breakage at four levels of severity (0%, 25%, 50%, and 75%) and at three timings (V13, V17, and tassel stage [VT]). Trials spanned nine site‐years across Iowa, Minnesota, and Nebraska from 2019 to 2022. Below‐ear breakage results in a loss of the primary ear, while above‐ear breakage reduces the size and weight of the harvestable ear. Plant density, primary and secondary ear counts, grain yield, and kernel mass were measured. The number of secondary ears was highly influenced by the damage type. When breakage occurred above the ear node, 25% damage severity resulted in a 35% increase in the number of secondary ears compared to the untreated control. When breakage occurred below the ear node, the impact was much more evident, with an 85% increase of secondary ears. On average, breakage above the ear resulted in a 9.5%, 18.6%, and 25.2% yield penalty for 25%, 50%, and 75% severity, respectively. As expected, for the same damage severity, below‐ear breakage resulted in much higher yield penalties (13.3%, 32.6%, and 55.0%). There was no clear relationship between damage severity and kernel weight.

  PublisherOA PDFDOI

• Should starter fertilizer rate be adjusted by initial soil test P concentration?

  Agronomy Journal · 2025-09-01

  articleOpen accessSenior author

  Abstract Starter fertilizers containing phosphorus (P) are applied to increase corn ( Zea mays L.) early growth and ultimately grain yield. This study determined the rate of starter P needed to increase corn early plant growth and grain yield at differing starting soil test phosphorus (STP) concentrations with or without broadcast P application. Field trials were established at 10 site‐years in Minnesota using a split‐plot design. Main blocks consisted of 0 or 59 kg P ha −1 broadcast pre‐plant. Sub‐plots consisted of liquid starter fertilizer (10‐15‐0 N‐P‐K): 0, 29, 58, and 87 kg ha −1 applied on the corn seed. Analysis was conducted across sites after classifying each block per site (low, medium, high, and very high STP) according to University of Minnesota guidelines. Corn plant mass and P uptake at V5–V7 increased linearly as the rate of starter P regardless of where broadcast P was applied and initial STP concentration. Corn yield was increased by P when STP was in the low or medium STP classification, and application of starter P alone did not maximize grain yield in low P soils. The data indicate that 29 kg ha −1 of the starter applied in this study is sufficient to increase early plant growth and corn yield compared to broadcast P only when STP was medium or higher. Broadcast P is needed to maximize yield when STP was low, and varying starter rates more than 29 kg ha −1 will not result in a greater yield potential across sites versus broadcast P alone regardless of STP concentration.

  PublisherOA PDFDOI

• Severe storm damage and short‐term weather stresses on corn: A review

  Crop Science · 2024-02-28 · 20 citations

  reviewOpen access

  Abstract Adverse weather conditions from acute events (e.g., storms causing lodging, flooding, or hail) or short‐duration weather patterns (i.e., periods of cold events; extended waterlogged field conditions) can result in yield losses, though management practices may play key roles in aiding with crop recovery or avoidance of these stress events. This review summarizes current knowledge (with emphasis placed on the US Midwest) related to corn response to short‐term weather stresses of (i) cold temperature, (ii) excess water, (iii) hail/defoliation damage, and (iv) wind damage. Each section presents summaries of how corn growth and yield are affected, provides context into past events experienced, identifies agronomic or production recommendations to correct or alleviate the stress condition, and proposes areas where future research is needed. This review also highlights challenges associated with controlled simulation work on these stressors, and also identifies key areas to expand future research efforts. In general, yield losses associated with strong storms and short‐term weather events often ranged from 5% to 35%, but extreme cases could result in up to 80%–100% yield loss. Much of the literature on these topics was published prior to 1995, though it still forms the basis for modern agronomic guidance, which is problematic given the changes in agriculture in the last 20 years in management practices, available genetics and technologies, and changing environmental conditions. Revisiting these foundational studies and expanding them to examine current and future weather conditions are critical for better informing agronomic recommendations, for devising mitigation strategies, and for determining accurate yield loss expectations following these stresses.

  PublisherOA PDFDOI

• Corn ¹⁵N uptake and partitioning in response to fertilizer application rate and timing

  Agronomy Journal · 2024-05-09 · 3 citations

  articleOpen accessSenior author

  Abstract Nitrogen (N) fertilizer applications near the time of planting are important for upper US Midwest corn ( Zea mays L.) production, but wet springs may result in significant N losses. Split applications may circumvent this problem and improve fertilizer uptake and use efficiency, but the relative contribution of N from the soil and fertilizer is poorly understood. A field study with six sites in Minnesota received 15 N‐labeled urea fertilizer in the first year and unlabeled urea in the second year to determine the effect of N rate and application timing on corn uptake and accumulation patterns of fertilizer‐derived N (FDN) and soil‐derived N (SDN) over two consecutive growing seasons. Corn responded positively to fertilization. The percentage of total N uptake as FDN was greatest closest to the time of application but decreased over time as SDN became the dominant N source. A split application (45 kg N ha −1 at planting, 90 kg N ha −1 at V4) significantly improved FDN uptake over the 135 kg N ha −1 preplant treatment but did not improve total N uptake in the first year at any site. Fertilizer‐N use efficiency (F 15 NUE) using the isotopic method was 2.8%–43.3% across all sites at the end of the first year with the majority partitioned to the grain. At the end of the second year, approximately 2.2% of the first‐year applied FDN was recovered in aboveground biomass. Fertilization ensures adequate N availability to the developing crop, but ultimately SDN contributed ≥61% of the total N uptake.

  PublisherOA PDFDOI

• Rate and time of nitrogen fertilizer application for winter camelina

  Agronomy Journal · 2024-06-05 · 7 citations

  articleOpen access

  Abstract Winter camelina [ Camelina sativa (L.) Crantz] is a potential third crop to diversify maize ( Zea mays L.)–soybean [ Glycine max (L.) Merr.] rotations in the upper Midwest. Although generally considered a low‐input crop, empirical evidence suggests that it responds to added nitrogen (N) fertilization. However, optimum agronomic N rates have not been extensively studied in the region. A study was conducted from fall 2018 to fall 2020 at three locations to assess the effects of N fertilizer application time (all N‐rate applied in spring and N‐rate split applied in fall and spring) and rates on biomass and seed yield, and quality of winter camelina. Nitrogen application time did not affect yields. Both biomass and seed yields were greatly affected by N rates at all locations. Nitrogen had minimal effects on the oil and protein content of seeds, although greater N rates were associated with a slight decrease in oil content and a slight increase in protein content. The number of branches and silicles per plant varied significantly with N rates in all locations. The seed‐to‐silicle ratio showed significant differences in two out of three locations. Residual soil N increased with increasing N rates. A fertilization rate of 67 kg ha −1 provided the highest camelina seed yield. While this study has determined the agronomic maximum rate for applied N, further economic analysis could provide comprehensive decision‐making for farmers.

  PublisherOA PDFDOI

• Carbon supplementation and bioaugmentation to improve denitrifying woodchip bioreactor performance under cold conditions

  Ecological Engineering · 2023-03-17 · 14 citations

  article
  PublisherDOI

• Corn response to long‐term seasonal weather stressors: A review

  Crop Science · 2023-09-10 · 22 citations

  reviewOpen access

  Abstract Long‐term weather patterns (environmental conditions or stresses exceeding 10 days in length) have the potential to influence corn ( Zea mays L.) growth, development, and yield. This review summarizes the current knowledge (with emphasis placed on the Midwestern U.S. production environment) on how long‐term weather conditions affect corn growth and yield, including (i) drought and heat stress, (ii) solar radiation, and (iii) distribution of heat unit accumulation during the season. Each section contains summaries of how these environmental factors influence corn growth and yield and provides context into past events experienced. The focus of the review is on dent corn grown for grain production, though relevant issues related to other types (i.e., silage corn) are included. This review also discusses agronomic recommendations or considerations to help alleviate the negative effects of stress conditions and identify areas where future research would be beneficial to continue improving the resiliency of corn cropping systems. Periods of high heat and water deficit as well as limited light availability challenge the ability to maximize yield production in corn. Temperature affects crop growth and development through the season, and accurately describing phenological progression using heat unit accumulation is a challenge. Advances in corn breeding and genetics, hybrid selection, and agronomic management practices will be key to ensuring long‐range productivity and fully leveraging possible benefits from the shifts in long‐range weather patterns.

  PublisherOA PDFDOI

• Temperature-Driven Developmental Modulation of Yield Response to Nitrogen in Wheat and Maize

  Frontiers in Agronomy · 2022-06-27 · 28 citations

  articleOpen access

  Nitrogen management is central to the economic and environmental dimensions of agricultural sustainability. Yield response to nitrogen fertilisation results from multiple interacting factors. Theoretical frameworks are lagging for the interaction between nitrogen and air temperature, the focus of this study. We analyse the relation between yield response to nitrogen fertiliser and air temperature in the critical period of yield formation for spring wheat in Australia, winter wheat in the US, and maize in both the US and Argentina. Our framework assumes (i) yield response to nitrogen fertiliser is primarily related to grain number per m 2 , (ii) grain number is a function of three traits: the duration of the critical period, growth rate during the critical period, and reproductive allocation, and (iii) all three traits vary non-linearly with temperature. We show that “high” nitrogen supply may be positive, neutral, or negative for yield under “high” temperature, depending on the part of the response curve captured experimentally. The relationship between yield response to nitrogen and mean temperature in the critical period was strong in wheat and weak in maize. Negative associations for both spring wheat in Australia and winter wheat with low initial soil nitrogen (< 20 kg N ha -1 ) in the US highlight the dominant influence of a shorter critical period with higher temperature; with high initial soil nitrogen (> 120 kg N ha -1 ) that favoured grain number and compromised grain fill, the relation between yield response to nitrogen and temperature was positive for winter wheat. The framework is particularly insightful where data did not match predictions; a non-linear function integrating development, carbon assimilation and reproductive partitioning bounded the pooled data for maize in the US and Argentina, where water regime, previous crop, and soil nitrogen overrode the effect of temperature on yield response to nitrogen fertilisation.

  PublisherOA PDFDOI

• Carbon supplementation and bioaugmentation to improve denitrifying woodchip bioreactor performance under cold conditions

  2022-09-13

  preprintOpen access

  Cold temperatures limit nitrate-N load reductions of woodchip bioreactors in higher-latitude climates. This two-year, on-farm (Willmar, Minnesota, USA) study was conducted to determine whether field-scale nitrate-N removal of woodchip bioreactors can be improved by the addition of cold-adapted, locally isolated bacterial denitrifying strains (bioaugmentation) or dosing with a carbon (C) source (biostimulation). In Spring 2017, biostimulation removed 66% of the nitrate-N load, compared to 21% and 18% for bioaugmentation and control, respectively. The biostimulation nitrate-N removal rate (NRR) was also significantly greater, 15.0 g N m-1 d-1, versus 5.8 and 4.4 g N m-1 d-1, for bioaugmentation and control, respectively. Bioclogging of the biostimulation beds limited dosing for the remainder of the experiment; NRR was greater for biostimulation in Fall 2017, but in Spring 2018 there were no differences among treatments. Carbon dosing did not increase outflow dissolved organic C concentration. The abundance of one of the inoculated strains, Cellulomonas sp. strain WB94, increased over time, while another, Microvirgula aerodenitrificans strain BE2.4, increased briefly, returning to background levels after 42 days. Eleven days after inoculation in Spring 2017, outflow nitrate-N concentrations of bioaugmentation were sporadically reduced compared to the control for two weeks but were insignificant over the study period. The study suggests that biostimulation and bioaugmentation are promising technologies to enhance nitrate removal during cold conditions. A means of controlling bioclogging is needed for biostimulation, and improved means of inoculation and maintaining abundance of introduced strains is needed for bioaugmentation. In conclusion, biostimulation showed greater potential than bioaugmentation for increasing nitrate removal in a woodchip bioreactor, whereas both methods need improvement before implementation at the field scale.

  PublisherOA PDFDOI

Frequent coauthors

• Qiang Chai

  Gansu Agricultural University

  20 shared

• Craig C. Sheaffer

  University of Minnesota

  19 shared

• Rodney T. Venterea

  19 shared

• Cai Zhao

  Gansu Agricultural University

  17 shared

• Aizhong Yu

  Gansu Agricultural University

  17 shared

• Junhong Xie

  Capital Medical University

  17 shared

• Emerson D. Nafziger

  17 shared

• Zhilong Fan

  Gansu Agricultural University

  16 shared

Education

• M.S., Crop Sciences

  University of Illinois at Urbana-Champaign

• B.S., Agronomy

  South Dakota State University

• Ph.D., Crop Sciences

  University of Illinois at Urbana-Champaign

Awards & honors

• Minnesota Future Farmers of America Honorary State Degree, 2…