Minnesota Crop News

Reports of yellowing in small grains have started to reach me. There are several reasons why young wheat, barley, or oat plants have a pale green/yellow color. Some of the more common causes of early season yellowing are:
Nitrogen deficiencySulfur deficiencyEarly tan spot infectionsHerbicide injuryBarley yellow dwarf virus (BYDV) infections Nitrogen deficiency Nitrogen (N) deficiencies can readily be identified as the symptoms are worst on the oldest leaves and start at the tip of the leaves, progressing towards the base as the deficiency gets worse. The causes of the N deficiencies are several, all which have common denominator, namely excess precipitation. Excessive rainfall causes leaching, denitrification, and an inability of the plants to take up available N.

Leaching is a potential problem in coarser textured soils. Saturated soils/standing water will cause both denitrification and inability to take up available N. Denitrification is a microbial process and slows down considerabl…

Bruce Potter - Extension IPM Specialist,  Senyu Chen,  Nematologist, Phil Glogoza, Extension Educator- Crops, Dean Malvick , Extension Plant Pathologist,  and Ryan Miller, Extension Educator-Crops

The soybean cyst nematode (SCN) is a serious pest of Minnesota soybean and has been managed with crop rotation and soybean varieties with resistance to SCN. This approach is becoming less effective, however, because SCN populations virulent on (able to reproduce on and damage) SCN resistant soybeans are increasingly widespread. A seed treatment biological (Clariva™ Complete, Syngenta Crop Protection®) has been labeled for management of SCN. 

Bruce Potter, IPM specialist, Madeleine Smith, Extension pathologist, and Ian MacRae, Extension entomologist

Photo 1. English grain aphid winged adult. Note the black on legs and cornicles (tailpipes). Unusually large numbers of aphids have been reported in some winter rye and wheat crops this spring. Last week, winged English grain aphids were predominant (Photo 1), but as of this week, there are already a few nymphs. Also present were a few nymphs and adults of bird cherry-oat aphids (Photo 2). Another cereal infesting aphid species, which is less commonly observed in MN, is the greenbug.

By Lizabeth Stahl, Extension Educator – Crops, Jeff Gunsolus, Extension Agronomist – Weed Science, and Jill Sackett-Eberhart, Extension Educator - Ag Production Systems
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As more farmers look to plant cover crops in their corn and soybean fields, the question “What should I do about my herbicide program?” often arises. There is not a one-size-fits-all answer to this question, and unfortunately there are many unknowns.

One of the hardest decisions with growing fall rye, winter wheat, or winter barley is evaluating the amount of winter kill and making the decision whether to keep a stand. Winter cereals are planted in the fall and develops in the spring during relatively ideal conditions for tiller development. Therefore the optimum plant stands of winter cereals can be less than that of their spring counter parts. A stand of 900,000 - 1,000,000 plants/acre or 21 - 23 plants/ft2 will be enough to maximize grain yield.

By Lizabeth Stahl, Extension Educator - Crops

Reading over the pesticide label is a key step in having a safe and productive cropping season. Even if you think you know a product well, read over the label each time you purchase and handle the product, as the label may have been updated, your practices may have changed, and because it can simply be difficult to remember all the details included on a pesticide label. Be sure to check the label that is attached to the container you are using as internet labels may differ. Reading over the label can help ensure the safety of yourself and others, the crop, the environment, and the food chain.

by Jeff Coulter, Extension corn specialist
Favorable soil temperature
Germination of corn requires that seed imbibe 30% of its weight in water and that soil temperature be 50°F or warmer. More time between planting and emergence increases the potential for stand establishment problems, since imbibition of water by seed is not greatly influenced by soil temperature. Risk of stand establishment problems is reduced if soil in the seed zone has reached or is near 50°F at planting and is expected to warm.

by Jill Sackett, Extension educator
Spring has sprung in the majority of Minnesota. It's now time to manage cover crops that were planted last summer or fall. Spring management of cover crops is as varied as the different farming operations across Minnesota. The plan of action any given farmer decides to do primarily depends on two things: 1) His or her reasons for using cover crops in the first place, and 2) the specific cover crops used.

An interesting e-mail from the United States Department of Agriculture (USDA)  reached my desk late last week. I have cited a portion of the e-mail below.
‘The NRCS will not recommend buckwheat in conservation plantings in areas in rotation with or adjacent to commodity wheat production that will be planted to wheat within the next 2 calendar years after planting buckwheat because of the potential for buckwheat seed to contaminate the wheat crop, and the health risks that potentially poses. The use of buckwheat in conservation plantings is still permitted in fields or areas that are not used for commodity wheat production.’
Why, may you ask, has the NRCS come out with this statement and updated a number of practice standards, including # 327 – Conservation Cover, 340 – Cover Crops, and 645 – Upland Wildlife Habitat Management?
As the use of cover crops has increased in recent years, contamination of wheat shipments to Japan with buckwheat has also increased.  Unfortunately, the popu…

by Bruce Potter, IPM specialist
Most corn hybrids contain at least one transgenic trait for insect or weed control. When it comes to Bt traits, remembering which Bt event does what can be challenging. Dr. Chris DiFonzo, field crop entomologist at Michigan State University, has revised her reference for Bt traits in corn to help keep things straight.

by Jeff Coulter, Extension corn specialist
First- and second-year corn following alfalfa usually benefit from increased yield potential, reduced or eliminated nitrogen requirement from fertilizer or manure, and reduced pest pressure. A recent Extension bulletin describes agronomic practices for alfalfa termination and the two subsequent corn crops that help maximize these benefits: http://z.umn.edu/rotation.

Fabián G. Fernández, John A. Lamb, and Anne M. Struffert
Corn in irrigated coarse-textured soils can be very productive with nitrogen applications, but excess nitrogen can increase groundwater contamination. To understand how much nitrogen is needed to optimize corn production and minimize the environmental impact of nitrogen fertilizers, a four-year study was done at the Rosholt Farm in Pope County and in Dakota County farmers’ fields.
Urea nitrogen rates ranged from 0 to 280 lb N/acre in 40 lb increments with half of the rate applied pre-plant and the other half at V4. Single pre-plant applications of enhanced efficiency fertilizers: ESN (a polymer coated urea), a blend of urea and ESN, and SuperU (urea with nitrification and urease inhibitors) were also studied. Lysimeters installed below the root-zone and water-balance calculations along with drain gauges were used to quantify the nitrate concentration and the amount of water and nitrate moving pass the root-zone.

Daniel Kaiser and Fabian Fernandez
University of Minnesota Soil Fertility Specialists

Over the winter we have done intensive data compilation and analysis and have a few updates to the corn guidelines publication. The primary update is on nitrogen application rates for corn following corn and corn following soybean. The updated publication is not finished yet, so this article will serve as the current rate guidelines starting spring of 2016.

The current guidelines still use the maximum return to nitrogen approach. The updated nitrogen guidelines reflect additional sites of nitrogen response data collected starting in 2011 through 2015. At this time, the data have not been uploaded into the online corn N rate calculator as the site is currently undergoing a scheduled maintenance. A future article will be released when the new data are available. The guidelines in Table 1 are for corn grown on non-irrigated soils in southern Minnesota. For growers with irrigation, please refer to…