Delaware Agronomy Blog

University of Delaware Cooperative Extension

Using Foliar Manganese Applications to Correct Deficiencies

Amy L. Shober, Professor and Extension Specialist, Nutrient Management and Environmental Quality,; Jarrod O. Miller, Assistant Professor and Extension Specialist, Agronomy,; Mark Reiter, Associate Professor and Extension Specialist, Soils and Nutrient Management, Virginia Tech,


This image shows areas of the field where the soybeans that were growing in a field ditch (yellow arrow) showing less Mn deficiency symptoms than areas that have better tilth. Figure credit: Jarrod Miller, UD

Soybean is susceptible to manganese (Mn) deficiency, especially when grown on sandy, low organic matter soils like we have in Delaware. Soil Mn availability is a function of both Mn concentration and soil pH. Soil Mn converts to unavailable forms as soil pH increases. So when soil pH starts creeping above 6.2, we can start to see Mn deficiency symptoms. While Mn deficiency can be widespread across the field, we can also see Mn deficiency symptoms in small pockets in a field, often occurring after liming. Deficiency symptoms can be prevalent in areas where lime applications overlapped or where the soil is sandier than the general field; thereby changing pH more quickly and becoming higher than soils with more clay, loam, and/or organic matter. Manganese deficiencies may also reveal themselves with dry soil conditions like we have seen this summer (especially when soils were tilled soils) because soil Mn also becomes less available to plants. Interestingly, Mn deficiencies are less likely in areas of the field that stay wetter (e.g., compacted wheel tracks, field ditches) as wetter soils are less oxygenated, promoting plant available forms of Mn (as seen in the photo below). Continue reading

2020 Mid Atlantic Crop Management School

The 2020 Mid Atlantic Crop Management School will be held virtually this year. Mark your calendars for the week of November 16-20th. Sessions will be held online daily from 8:30 am to 12:30 pm with each session offering one continuing education credit in the areas of Nutrient Management, Pest Management, Crop Management, and Soil and Water Management . Credits will also be available for various regional nutrient management and pesticide programs. Paid registrants will receive access to recordings for all sessions for viewing outside the scheduled session times. Registration will open in early September with early-bird pricing, our full list of speakers, and regional credit availability.


Nutrient Deficiencies and Toxicities Related to pH, Ca and Mg

We are observing a range of deficiency issues this year in corn, many of which have similar symptoms. Last week we had some images of a field with pale yellow leaves and some interveinal chlorosis that turned out to be a sulfur deficiency ( This week we have similar symptoms, but a different diagnosis. Across this field (Figure 1), some corn appears pale and stunted, and upon closer inspection (Figure 2), there is also some stripping (interveinal chlorosis) along the leaves. Continue reading

Do You Need Micronutrients in Your Starter?

Whether or not you need micronutrients in your starter should come down to last years soil or tissue tests. Over the last two years, our research projects have not revealed a deficiency in many micronutrients, but we still understand it is out there. In 2018, we conducted a study at the Carvel Research and Education Center (Georgetown, DE) with two rates of (Mn), zinc (Zn), and boron (B) in the starter. We observed no effect on yield, which was expected as these soils were adequate in Mn and Zn based on UD recommendations. Although starter B had no effect on yield, B did have a positive correlation with yield in the starter study. This implies that with increase tissue B concentrations, yield also increased. Correlations imply relationships, but not necessarily why this occurred. An environmental variable may have influenced both B uptake and yield in this case, such as saturated soils leaching B while reducing yield. Continue reading

Current Soil Temperatures and Corn Planting

The preferred soil temperature for corn germination is 50°F, which allows the seed to begin root and shoot growth. When soils fall below this temperature, germination may be limited and seeds may rot in the ground. Many of the weather stations on DEOS ( have soil temperature as an option, so you can track current conditions. Continue reading

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