Delaware Agronomy Blog

University of Delaware Cooperative Extension

Category: Corn (page 2 of 7)

Biological Nitrogen Contributions Across Multiple Nitrogen Rates

October 31, 2023 / / Comments Off on Biological Nitrogen Contributions Across Multiple Nitrogen Rates

Quick summary: There was no boost in yield or tissue N from Pivot-Bio additions, however we did observe higher levels of Mn in corn ear leaves with the biofertilizer. Yield may have been limited by something other than N.

To examine Nitrogen (N) contributions from biological fertilizer amendments, Pivot-Bio was added across a range of N-rates (0-330 lbs/acre) in the spring of 2023. The irrigated plots were harvested in October where yields ranged from 50 to 200 bushels per acre (Figure 1). The only statistical difference in yield was 0 N with pivot bio, which was lower than all other treatments. A dry cool May potentially reduced N availability in 2023, and heavy rainfalls and field saturation may have also limited yields. Drone imagery taken during the season will be analyzed at a later date to determine when yield may have become limited.

Figure 1: Yields based on Nitrogen rates and Pivot-Bio additions.
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2023 Interactions Between Nitrogen, Planting Population, and Irrigation for Corn

October 28, 2023 / / Comments Off on 2023 Interactions Between Nitrogen, Planting Population, and Irrigation for Corn

Jarrod Miller, James Adkins

Quick summary: Irrigation boosted yields in southern Delaware by 30 bushels. Under irrigation, N-rates of 200 lbs averaged 247 bushels of corn, while maximum yield occurred at populations of 36,000 seeds acre-1. Rainfed conditions suppressed K uptake in the plant, while the opposite effect was observed with Mg.

Figure1: Research plots at the UD Warrington Irrigation Research Farm. Interactions include planting rates, nitrogen rates, and rainfed versus irrigated plots.

As part of research supported by the Maryland Grain Producers (https://marylandgrain.org/), we planted corn under irrigated and rainfed conditions under a range of populations (20-40,000 seeds acre-1) and nitrogen (N) rates (75-300 lbs acre-1). This research was performed at the University of Delaware Warrington Irrigation research farm (Harbeson, DE)  in the summer of 2023 (Figure 1), where variable rate irrigation was used to create rainfed conditions across the field.

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Effects of Cover Crops and Nitrogen Rates on Corn Yields

September 28, 2023 / / Comments Off on Effects of Cover Crops and Nitrogen Rates on Corn Yields

Quick summary: When available soil N is lower, rye cover crops may occasionally reduce yields while clover cover crops may occasionally improve yields. At adequate fertilizer levels, yields are not affected by cover crops on sandy, Delaware soils.

Figure 1: Corn nitrogen rate trials following cover crops in Georgetown, DE in the summer of 2023.

As part of the Precision Sustainable Agriculture network (https://www.precisionsustainableag.org/), a study was deployed across multiple states to examine the nitrogen (N) cycling that occurs with cover crops. Plots of rye, clover, and a rye-clover mix were seeded each fall over three years (2020-2023). In the spring, plots were terminated two weeks prior to corn planting and then sidedressed to reach total N rates between zero to 320 lbs N/acre. The visual response of the variable N-rates can be observed in Figure 1.

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Average Delaware Growing Degree Days (2019-2021)

June 22, 2022 / / Comments Off on Average Delaware Growing Degree Days (2019-2021)

The standard method used to follow and predict corn growth stages is using growing degree days (GDD). This is a calculation that uses average daily temperatures measure accumulated heat over the growing season. Using GDD works better than days from planting because cool spring temperatures slow early planted corn, while corn planted later in May can have a more linear growth pattern.

For the past three seasons in Georgetown we have followed our research plots and have these values as the average GDD for our area (Table 1). They will be similar to those found in other states, but represent averages and ranges for our region. You may find GDD values on our regional mesonet (DEOS) or through the Climate Smart Ag page at Cornell (edit the site location).

 EmergeV3V6V9V12VT
Average10926255687110671308
Range84-150220-310448–603787-950943-12721232-1363
R1R2R3R4R5R6
Average148616451891204422872824
Range1321-15941560-17431734-20671957-21872029-25092686-2926
Growing Degree Days (GDD) Average Accumulation to Reach Corn Vegetative and Reproductive Stages.

Cover Crop Biomass and Termination Considerations

March 25, 2022 / / Comments Off on Cover Crop Biomass and Termination Considerations

Jarrod Miller, Amy Shober, & Mark VanGessel

The benefits of cover crops to the following corn crop can include additional nitrogen (N) or weed suppression, but maximizing these benefits requires later termination to build greater biomass. These N and weed control characteristics are especially appealing this season as input costs are relatively high while supplies are relatively low. However, growers should take the time to estimate the additional costs of allowing a more robust cover crop to accumulate this spring, as surface residues reduce proper seed placement as well as limit seed to soil contact. This article will discuss the management of cover crops for both maximizing N benefits as well as weed suppression in the following corn crop.

Aerial picture of cover crop plots

Cover crop plots at the Carvel Research and Education Center.

Maximizing Cover Crop Biomass

Estimating the amount of N that could be available requires knowledge about 1) total cover crop biomass and 2) cover crop C:N ratio, both of which are affected by termination timing. The longer a cover crop is allowed to grow, the greater the amount of cover crop biomass will accumulate. Continue reading

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