Delaware Agronomy Blog

University of Delaware Cooperative Extension

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 (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.

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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.
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Grid Sampling Soils to Improve Understanding of Soil Variability

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.

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Soybean Yield Response to Planting Populations, Row Spacing and Irrigation

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).

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Exchangeable Cation Uptake by Irrigated and Rainfed Soybeans (2021-2022)

Although Ca, Mg, and K are all exchangeable nutrients that are considered plant available, soil chemistry and plant root interactions result in different uptake and bioavailability. Within the soil, Ca and Mg can move with soil water or by diffusion, while the lower K concentrations do not readily move with soil water. This results in differences in uptake for soils with adequate moisture versus those under drought stress. Understanding how concentrations of each nutrient, the soil CEC, and soil moisture content interact is important for giving future nutrient recommendations.

Irrigated and rainfed dry corners in a Delaware field.

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