Delaware Agronomy Blog

University of Delaware Cooperative Extension

Category: Fertility (page 1 of 4)

Corn Yield Responses to In-furrow Biological Products

James Adkins, Extension Engineer, adkins@udel.edu,  Jarrod Miller, Extension Agronomist

In 2023, the University of Delaware evaluated the corn yield response to 14 biological products at 3 nitrogen fertility levels (optimum, 80%, and 50% rate).  While some of the products claimed to provide nitrogen fixation others were designed to improve plant health and root structure.  Products tested include:        

Invigorate (AMVAC)   

Ion Strike (Planet Earth Agronomy)

Zypro (Helena)   

BioGrowth (Willard Ag)

UtrishaP (Corteva)     

Source (Sound Ag)

ProveN40 (Pivot Bio)   

Blaine (Farmer 2 Farmer)

Accomplish Max (Loveland)     

Blaine with humic (Farmer 2 Farmer)

RioZyme Supreme (Schaeffer’s)   

Nexia (Innvictis)

RioZyme Plus (Schaeffer’s)     

Launch (Ag Concepts)

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Potassium Applications in Delaware Soils

Jarrod Miller, Extension Agronomist

University of Delaware recommends potassium (K) applications for low (0-70 ppm) and medium (71-140 ppm) soil test categories. However, soils in Delaware may have K that is not accounted for in a normal soil test, with minerals slowly release K over the growing season. Some of this was established by UD soil chemists in the 1980s, who observed high total K (not all plant available) in our soils, particularly in the sand fraction (https://www1.udel.edu/soilchem/Parker89SSSAJa.pdf). This means that some soils may need less K than is recommended by a regular soil test.

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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

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

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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