Minnesota Crop News

Daniel Kaiser, Paulo Pagliari and Fabian Fernandez Late fall can present challenges when it comes to fertilizer application. If you don’t apply fertilizer at the right time in the fall, you risk loss of nutrients via runoff. As soil temperatures move toward freezing, the chance of nutrients getting held in the soil decreases and the risk for nutrient loss goes up. Here are some best practices for late fall fertilizer management to keep in mind.

Greg Klinger and Anne Struffert, Extension Educators  Not all fall-applied nitrogen sources are equal. Fall-applied anhydrous ammonia behaves very differently than fall-applied urea. Anhydrous ammonia is as harmful to microorganisms as it is to people, so the microbes that convert ammonium to nitrate in the soil are typically killed in the area right around the injection band. These microorganisms will eventually recolonize the injection zone and ammonium will begin converting to nitrate. Urea does not inhibit the activity of these microorganisms. As a result, anhydrous ammonia delays the conversion to nitrate by at least 2 weeks longer than urea and other fertilizer forms. 

Greg Klinger and Anne Struffert, Extension Educators  Substantial nitrogen loss from fall applied fertilizer can happen under a few key conditions: Warm temperatures (especially above 50°) that increase the activity of nitrifying microorganisms A large portion of nitrogen in the soil in the form of nitrate nitrogen (NO3-N), usually due to nitrifying microorganisms, Significant precipitation.

By Sara Berg, South Dakota State University; John Thomas, University of Nebraska Lincoln; Lizabeth Stahl, University of Minnesota; Josh Coltrain, Kansas State University Photo: Sara Berg, SDSU Extension With technology being so prevalent in today’s culture, data and marketing information has become a key part of life. Farmers especially have been targeted with large quantities of new technology to generate more efficient farming systems and easy real-time data access. With large amounts of data and fast access to information and product marketing being the new norm, producing a commodity requires many decisions. While the number of US farms has dropped, average farm size has risen 23 percent from 2009 to 2016 (USDA, 2017). At the same time, producers have seen a shift in the types of ag services available. With such a wide scope of products and options available, it can be difficult to determine what products or technologies to invest in and what to leave on the shelf.

Paulo Pagliari, Nutrient Management Specialist Among the major nutrients (nitrogen, phosphorus and potassium), phosphorus (P) has the least mobility. As the fertilizer granule dissolves, most of the P in the fertilizer will likely only move a couple eights of an inch away from the granule, primarily by diffusion. The dissolved P will then start to react with cations in solution such as calcium, aluminum, and iron, and will start to adsorb onto soil particles. In general, tie up of P as calcium phosphates is a concern when the soil pH exceeds 7.3. Soils will become more acidic over time if they are not limed. With the decrease in pH, the availability of P will change. When the pH of soils range between 4.8 and 5.5, P is more reactive with aluminum in the soil and is tied up as aluminum phosphates that are not available to the plants. Liming of the soil can help to increase P availability from Fe and Al bound forms. The reaction of sorption and precipitation will limit P availabilit

Melissa Wilson, Manure Management Specialist Animal manure - or “brown gold” as some like to call it - is a valuable source of nutrients for growing crops when applied at agronomic rates. In Extension, we often get questions about how to manage manure nutrients. Unfortunately, there is not a simple answer. The nutrient content and availability depend on many factors.

By Liz Stahl, Dave Nicolai and Jeff Coulter Photo: Liz Stahl There is a significant amount of corn to be harvested throughout the Upper Midwest. Grain moisture for most of this corn is not at a level safe for long-term storage, ranging from 17 to 20 percent. Dr. Kenneth Hellevang, Extension Engineer with North Dakota State University, is a regional expert on corn storage issues. Suggestions from Dr. Hellevang and publications for dealing with wet corn and a late harvest include the following:

Daniel Kaiser, Soil Fertility Specialist Once you’ve taken the basal stalk nitrate test , it’s time to interpret your results. Remember that this test is diagnostic, not predictive. The results will come in measurements of PPM, or parts per million. This is an indication of nitrogen availability throughout the season. Watch the video below for more on how to interpret these results.

Fabian Fernandez, Nutrient Management Specialist The basal stalk nitrate test is a diagnostic test taken at the end of the growing season in corn. Results will show how well you did with your nitrogen management during the season. While this test won’t tell you how much N you need to apply next year, over time it can reveal a picture of your fertilizer management practices.

Ken Hellevang, North Dakota State University Extension Service, and Dave Nicolai, UM Extension Each year brings challenges for crop production, North Dakota State University Extension Service grain drying expert Ken Hellevang warns. The U.S. Department of Agriculture estimates that 82 percent of the Minnesota corn crop is mature compared with a five-year average of 93 percent. As of Oct. 15, only 7 percent of the Minnesota corn crop had been harvested, compared with a 38 percent average.

Jeff Gunsolus, Lisa Behnken and Fritz Breitenbach As we enter the fall harvest, many will be evaluating what soybean variety to select for next year. No longer is the focus solely on yield and tolerances to disease, iron chlorosis, and nematodes. This fall, farmers, consultants and advisors will be asking questions regarding how label modifications, if any, to the newly introduced dicamba formulations of Xtendimax, FeXapan, and Engenia might affect their variety selection decisions. The conundrum is that discussions at EPA and State Departments of Agriculture assessing the impact of this year’s off-target events on next year’s label will likely extend well into the fall. As you strategize future weed management plans, we would like for all of us to rethink the dicamba issue. Think about what brought on this issue in the first place: weed resistance to multiple groups of herbicides. As herbicide resistance increases and spreads, farmers are compelled to shoulder added risk an

By Lizabeth Stahl, University of Minnesota; Sara Berg, South Dakota State University; Josh Coltrain, Kansas State University; John Thomas, University of Nebraska Lincoln Tillage plots at the Southwest Research and Outreach Center, Lamberton, MN. Photo: Liz Stahl Utilizing sound research results to help make decisions on the farm is a wise business practice. It can be confusing, however, when you see two numbers that are clearly not the same labeled as "not significantly different." One can quickly calculate the value of a few bushels per acre over hundreds of corn or soybean acres. It is key to look at just what this terminology means and its practical importance when using this information to make decisions.

By: Jared Goplen and Eric Mousel Photo 1: Forage cover crops have the potential to reduce feed costs. Photo: Eric Mousel. Now is the prime time to be seeding small grain stubble fields with a cover crop to be grazed this fall, winter or next spring. One of the many benefits of incorporating small grains into the crop rotation is the ability to get a forage cover crop established by the end of August, which is a great way for beef and dairy producers to add value to their crop fields by extending the grazing window or adding to the forage supply.

By: Jared Goplen and Dave Nicolai Photo 1: Mow fencelines now to minimize deposits to the weed seed bank. Photo: Jared Goplen. As summer field activities wind down, harvest will soon be in full swing. Take the time now to mow fenceline weeds to prevent or minimize seed production. Fencelines are often where weed infestations start. By eliminating fenceline weeds, we prevent combine harvesters from picking up weed seeds from the field edges and pulling them into the field, where they can be further spread by harvesting and tillage equipment.

prepared by Phillip Glogoza, Jochum Wiersma and Ian McRae Wheat stem sawfly (WSS) are being found at significant levels in Polk County. Field surveys were conducted from August 14 to 18, 2017 to learn more about the levels of infestation and the possible size of the area impacted.  The inspected fields had infestations  on the field margins  ranging from a low of 0 to a high of 15 WSS/row foot. Every field inspected had fewer infested stems as sampling moved further into the field. Edge effects are pretty strong with this insect as they overwinter in stubble and migrate to nearby wheat the next year.

Jeff Gunsolus, Extension weed scientist Earlier Crop News articles focused on dicamba’s potential routes of injury, injury symptomology, soybean sensitivity and yield loss potential. In this article, I would like to explore in greater detail the factors that could contribute to dicamba volatility's role as a potential route of injury. I will be working off the assumption that the primary cause of dicamba volatility is due to degradation of the new dicamba formulations to dicamba acid, dicamba’s most volatile form. A 1979 Weed Science publication by Behrens, R. and W. E. Lueschen titled "Dicamba Volatility" will serve as my reference (Weed Sci. 27:486-493).

By Jared Goplen, Tom Peters, and Dave Nicolai Waterhemp in a wheat stubble field in Ottertail Co., Minnesota. Photo: Dave Nicolai One of the many benefits of including small grains in crop rotations is improved broadleaf weed control and breaking up weed lifecycles. Although freshly harvested small grain fields have a clean look, they often have weeds hiding in the stubble. The most prominent weeds in stubble fields are often late-emerging weeds like waterhemp and other pigweed species that emerged after early season herbicide applications were made. Control escaped weeds now to prevent seed production and weed seed bank replenishment.

Bruce Potter, IPM specialist and Bob Koch, Extension entomologist Photo 1. Thistle caterpillar leaf feeding and webbing. Photo: Bruce Potter The second 2017 MN generation of thistle caterpillars continue to cause concern in some soybean fields. Most of the reports of Minnesota high populations are from SW, SC, C, and the WC part of the state. Adults and egg-laying are now tapering off but more than two weeks of painted lady butterfly egg-laying activity means that there is a wide range of larval sizes out there.

Prepared by Phillip Glogoza, Jochum Wiersma and Ian McRae As wheat harvest moves northward, we are detecting infestations of Wheat Stem Sawfly in fields in Polk County. Recent storms and strong winds have helped bring these problems to front and center.    Farmers have noticed lodged stems, particularly on field margins, where in some cases plants are 100% lodged for 50+ feet from the edge inward.  In those cases, the cut stems could be grabbed and picked up in a bundle (Figure 3) and the stubble below was all cut (Figure 4). As we  inspected the interior of these fields, the percent lodging, declined, but there was still evidence of Wheat Stem Sawfly damage.  Infestations have been found in the areas around Crookston and westward toward East Grand Forks.  We urge farmers to pay attention to lodged areas of fields to determine if sawfly are a contributing cause of the problem. While driving the combine, lodged stems should be visible from the cab (Figures 1 and 2). Infested ste

by Jeff Gunsolus, Extension weed scientist Xtendimax drift onto non dicamba-tolerant soybean. Photo: Liz Stahl As you continue to assess and document the impact of dicamba injury on soybean yield, I thought it would be timely to make you aware of an excellent summary of Dr. Andy Robinson’s research conducted when he was a graduate student at Purdue University. This summary came from Purdue Extension and was authored by Joe Ikley and Bill Johnson: https://z.umn.edu/2vhs The published manuscript can be accessed at: https://z.umn.edu/dicamba-purdue

By Jared Goplen, Dave Nicolai, Lisa Behnken, Jeff Gunsolus Giant ragweed escapes in soybean. Photo: Dave Nicolai Despite your best weed-control efforts this year, you still ended up with patches or fields with weeds coming through the crop canopy. Now that August has rolled around, what options are available to control weeds and prevent them from going to seed? What can we do differently to prevent this problem next year? August is a good time to evaluate your current weed management plan and develop strategies for next year. Is there a herbicide available for rescue treatment? The short answer is no. Although it would be great to have a herbicide rescue treatment to control escaped waterhemp and other weed species that are now 3+ feet in height in soybean, there are no control options available. The crop stage at this point is generally advanced far enough that products, such as Roundup, Liberty, Flexstar, dicamba, and others are no longer labeled for use in soybean. Alth

by Jeff Gunsolus, Extension weed scientist Photo 1. Leaf cupping symptoms of dicamba injury in soybean. Photo Bruce Potter As we enter August, the big unknown in fields presenting dicamba injury symptoms will be dicamba’s impact on soybean yield. Unfortunately, due to the sensitivity of non-Xtend soybeans to dicamba, injury symptoms are not reliable indicators of yield loss. The level of yield loss depends on exposure at vegetative or reproductive stage of growth, persistence of injury symptoms, and growing conditions post-exposure. Relationship of injury symptomology to yield Dicamba injury symptoms range from cupping and strapping of newly emerged leaves to height reduction and injury to growing points. Symptoms will reflect the level of exposure to dicamba. A publication written by Rodrigo Werle, Richard Proost and Chris Boerboom contains color photos of dicamba injury symptoms, mimics and assessment of yield loss: Soybean injury from dicamba Photo 2. Xtend so

By Carl Rosen, Professor and Head Department of Soil, Water and Climate Vince Fritz, Professor, Horticultural Science New research conducted at the Southern Research and Outreach Center in Waseca shows that the optimal N application rate for new sweet corn hybrids following soybeans in non-irrigated, on medium- to high-organic matter soils is higher than the current recommended rate of 110 lbs N/ac.

by Jeff Gunsolus, Extension weed scientist Leaf cupping symptoms of dicamba injury in soybean. Photo: Fritz Breitenbach Dicamba injury to non-target soybeans has been widely reported in south central and southwest Minnesota. Symptoms range from cupping and strapping of newly emerged leaves to height reduction and injury to growing points. At low dicamba concentrations, symptoms were slow to emerge, showing up 14 to 21 days after exposure. The big unknown, of course, will be impact on soybean yield, which will require negotiations now to determine the most accurate in-field yield comparisons later.

The USDA-NASS' July 1 yield forecasts for barley, oat, and spring wheat were 67, 71, and 61 bushels per acre, respectively.  This would mean a new state record for spring wheat, while the forecast for barley and oats are 10 and 7 bushels off the records set in 2015. To estimate yield the USDA-NASS collects farmer's assessment of yield prospects throughout the growing season, i.e. the USDA-NASS asks producers to predict their final yield. At first glance, this may seem a bit unscientific and not very accurate. The statistical methods that are used to crunch the collected data and have it confess a forecast, however, are robust and because enough producers are surveyed, the forecasts have been proven predictive at the aggregate level.  This is, in a way, a testament that you each know you crop and operation pretty well. The completely methodology can be found here .

By Dan Kaiser, Extension Soil Fertility Specialist The ultimate goal of nutrient management is to ensure that the plant has enough nutrients to produce maximum potential yield. This involves monitoring soil nutrients and crop uptake, and often supplementing nutrients that the crop is lacking. But what happens when the plant takes up more than enough of a certain nutrient? That’s called luxury uptake. Though it isn’t usually a problem for crops, it can become an issue if a nutrient reaches toxic levels in a plant. In Minnesota, the main concern is with Boron in soybeans and other broadleaf plants.

Robert Koch (Extension Entomologist), Ian MacRae (Extension Entomologist), Bruce Potter (Extension IPM Specialist), and Phil Glogoza (Extension Educator – Crops) By now you should be scouting your soybean fields for soybean aphid on a regular basis. Soybean aphid can be found in most fields throughout the state and populations have reached economic threshold (250 aphids per plant) in some fields in northwest Minnesota and have require insecticide application to protect soybean yield. In northwest Minnesota (especially around Norman County), applications of pyrethroid insecticides are failing to adequately control aphid populations in some, but not all, fields. This is the third year in a row that we have received reports of failures of pyrethroids to control soybean aphid in Minnesota. In 2015 and 2016, field-level failures of pyrethroid insecticides were reported (Figure 1) and pyrethroid resistant populations of soybean aphid were confirmed in Minnesota, particularly in parts