Delaware Agronomy Blog

University of Delaware Cooperative Extension

Page 2 of 19

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.
Continue reading

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 (, 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.

Continue reading

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 (, 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.

Continue reading

Fall Establishment of Small Grains for Tillers

Proper establishment of small grains will ensure success when springtime temperatures begin to warm. Some practices that help with planting include germination tests, tillage (after corn), and planting during the optimal window ( When considering planting rates, research at UD has not seen increased yields above 1.5 million seeds per acre ( This follows many regional recommendations, but without good seed to soil contact, moisture, or N, you may still have a slow start.

Continue reading

2022-2023 Cover Crop Growth and Tillage

For all crops, initial establishment is as important as fertility in maximum yield. The same principles adhere to cover crop growth, with earlier establishment and good seed to soil contact necessary for good coverage.

Figure 1: Fields in March 2023 of a) turbo tilled rye cover crop after rainfed corn, b) no-till broadcast rye after irrigated corn, c) flown on after full-season + double crop soybeans and d) turbo-tilled rye after irrigated corn.
Continue reading
« Older posts Newer posts »