Based on some observations in prior years, we planted irrigated corn on three different timings (April, May, and June) to observe three outcomes 1) yield, 2) nutrient uptake, 3) herbivory by deer. Average yields were all below 200 bushels, at 143, 175, and 128 bu/acre in the April, May, and June planted plots, respectively. Yield losses are potentially related to a range of factors, including deer feeding, weather, and soil nitrogen.
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.
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.
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.
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.
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 320lbs N/acre. The visual response of the variable N-rates can be observed in Figure 1.