Delaware Agronomy Blog

Page 3 of 19

Effects of Cover Crops and Nitrogen Rates on Corn Yields

September 28, 2023 / Jarrod Miller / Comments Off

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.

Fall Establishment of Small Grains for Tillers

September 21, 2023 / Jarrod Miller / Comments Off

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 (https://sites.udel.edu/weeklycropupdate/?p=12483). When considering planting rates, research at UD has not seen increased yields above 1.5 million seeds per acre (https://sites.udel.edu/agronomy/2020/10/01/2018-2020-wheat-seeding-rate-yields/). This follows many regional recommendations, but without good seed to soil contact, moisture, or N, you may still have a slow start.

2022-2023 Cover Crop Growth and Tillage

September 21, 2023 / Jarrod Miller / Comments Off

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.

Grid Sampling Soils to Improve Understanding of Soil Variability

March 22, 2023 / Jarrod Miller / Comments Off

Jarrod Miller and James Adkins, University of Delaware

Variability in soil land landscape characteristics reduces yield response to management techniques, particularly regarding seeding rates and fertilizer additions. Yield maps provide a spatial map of yield, which can be associated with drainage issues, soil nutrient holding, or nutrient concentrations. One method to uncover soil variability and crop response is to use precision soil sampling, including either grid or zone methods. Both increase the cost of taking soil samples, and each have their value depending on the desired outcomes.

Soybean Yield Response to Planting Populations, Row Spacing and Irrigation

January 27, 2023 / Jarrod Miller / Comments Off

To update our recommendations for soybean population, the Delaware Soybean Board sponsored a study of five different planting populations (60, 90, 120, 150, and180,000 seeds per acre), two row spacings (15 and 30”), and included irrigated and rainfed treatments under variable rate irrigation. Overall, no differences in yield were observed by population, while 15″ rows boosted yields by 10.6 bushels and irrigation boosted yields by 25.9 bushels.

**Figure 1**: a) aerial image of planting populations and row spacings at our Irrigation research farm, b) rainfed plots senescing earlier under our variable rate linear irrigation field.

Project Summary

Soybeans (maturity group 4.3) were planted at the UD Warrington Irrigation Research farm in May 2022 and harvested in November 2022 with a plot combine. The results were analyzed statistically as a randomized complete block design with three factors (population*row-spacing*irrigation) with means separation by Fisher’s LDS (alpha = 0.1).