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Extension > Minnesota Crop News > April 2017

Tuesday, April 25, 2017

Sufficiency or Build and Maintain? Best Bets for Phosphorus Management

Karina Fabrizzi, Daniel Kaiser and Albert Sims

When it comes to phosphorus management, there are two schools of thought: 1) the sufficiency approach, which is designed to maximize economic return for each dollar of P fertilizer applied; and 2) the build and maintain approach, which seeks to mitigate risk by keeping soil test P at a level that minimizes the potential for yield loss. In 2011, University of Minnesota, with funding provided by the Agricultural Fertilizer Research and Education Council (AFREC), set out to test these phosphorus management strategies in long-term replicated field experiments.

Thursday, April 20, 2017

Alfalfa winter injury in Minnesota

Jared Goplen, Lisa Behnken, and Dan Martens

winter-injured-alfalfa
Photo 1. Severely winter-injured alfalfa in Carver County, 2013. Photo courtesy of Dave Nicolai
As the weather warms and the 2017 growing season gets rolling, it is time to evaluate alfalfa stands for winterkill and winter injury. There have been numerous reports of alfalfa fields across Minnesota with varying levels of winter injury and winterkill. Many reports are of low areas in the field suffering the greatest damage, with affected field areas ranging from 10 – 40%. Lack of snow cover along with cold temperatures, freezing and thawing in February, and ice sheeting are some possible causes for winter injury and winterkill this year.

Tuesday, April 18, 2017

Southern Minnesota research and demonstration highlights - 2016

Lisa Behnken, Fritz Breitenbach, and Phyllis Bongard


Photo 1. Field day highlighting weed management at Rochester, MN.
A research team comprised of faculty from Extension, the Research and Outreach Center at Waseca, and the University of Minnesota St. Paul campus conduct field research and demonstration trials annually in southern Minnesota to address local, timely crop production issues. Highlights from the 2016 research report include demonstrating 1) the benefits of using preemergence (PRE) herbicides in corn and soybeans, 2) systems to control giant ragweed and waterhemp, 3) new herbicide technologies used in soybeans, and 4) use of mechanical cultivation for waterhemp control in soybeans.

Friday, April 14, 2017

Cutting Production Cost in HRSW

This post may be a day late and a dollar short as the drills are already rolling across much of Minnesota.  Nonetheless, I'm going to share some thoughts about how to reduce input cost in HRSW without sacrificing much, if any, yield. Consider whether you really need to:


  • Use a seed treatment - only if you have scabby seed with poor germination, know that you had a loose smut in the field that you saved for seed, and/or have a history of common root rot and/or wire worm in a field should you consider a seed treatment.   
  • Use a grass herbicide across every acre - Wild oat is a very competitive weed and already causes yield losses at very low densities.  Fortunate, presence of wild oat tends to be patchy and therefor you may not need a grass herbicide across every acre. The use of Roundup Ready crops has reduced wild oat pressure over the years in many fields, further reducing the need to use a grass herbicide across every single acre. 
  • Use a fungicide mixed in at he time of weed control -  If there is no tan spot, powdery mildew, or stripe rust already present, tank mixing a fungicide at the time of weed control doesn't make sense as the application will not protect any new growth anyway. Research has shown that only when disease was already present at the time of application that an economic return could be expected.
  • Use an insecticide mixed in with your fungicide at the time of your late season disease control - Likewise if there are no or very few aphids present at Feekes 10.51, you shouldn't expect an economic return of the insecticide.
  • Use a pre-harvest glyphosate application to control any late season weeds. Research has shown that in Minnesota, there is little to no advantage to using pre-harvest glyphosate to speed-up dry-down of the HRSW crop itself.

The last inputs to debate their need are fertilizer (in particular N) and the late season fungicides. Ultimately it is not about being the lowest cost producer per acre but being the lowest cost producer per bushel.  

Evaluating Winter Cereal Stands

One of the hardest decisions with growing 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.

Winter kill is to be expected in Minnesota. The least amount of winter kill is to be expected with rye, while winter barley is only marginal winter hardy for Minnesota. This past winter was not very cold but snow cover was intermittent which means that some winter kill is likely this year. Roots are generally less winter hardy than crowns and regrowth may be slower than expected.

This past week was probably the first time that evaluating surviving plant density was fairly straightforward. The problem that remains, however, is that winter survival in all likelihood will variable within a field and depending on topography (windblown hilltops having less stand than protected areas of the field). If stands are reduced uniformly across the field, stands of 17 plants/ft2 can still produce near maximum grain yields. If there are bare areas due to desiccation or drown-out consider replanting a spring cereal in those areas.  

Mixing of Hard Red Spring and Hard Red Winter wheat varieties maybe not ideal for management of the field itself as the areas will likely grow and mature at different rates but it should not pose a problem with marketing as they are not contrasting classes of grain as defined by the Federal Grain Inspection Service.


Thursday, April 13, 2017

Spring Management of Cover Crops

By Jill Sackett Eberhart and Liz Stahl

winter-rye-may
Winter rye cover crop planted in September ready for termination in late May.
Spring management of cover crops is as varied as the different farming operations across Minnesota. The plan of action any given farmer decides to follow will lean heavily towards two things: his or her reason for using cover crops in the first place and the specific cover crops planted.

Monday, April 10, 2017

Got waterhemp? Layer residual herbicides to maintain control

Lisa Behnken, Fritz Breitenbach, Jeff Gunsolus, Liz Stahl, and Phyllis Bongard

waterhemp-in-soybeans
Photo 1. Waterhemp in soybeans. Photo: Liz Stahl
Tall waterhemp (Amaranthus tuberculatus) is expanding its reach across Minnesota, and herbicide-resistant populations are becoming more commonplace. Most waterhemp populations have been resistant to ALS (Group-2) herbicides, such as Pursuit, for a while. In addition, glyphosate-resistant (Group-9) populations were first reported in 2007, and PPO-resistant (Group-14) populations were confirmed in southern Minnesota the past two growing seasons. Herbicides in Group-14 include Cobra, Flexstar and Spartan. To add to management challenges, some waterhemp populations have developed resistance to two or all three herbicide groups. In this situation, what herbicide control options are left?

Thursday, April 6, 2017

Key factors for successful corn planting

by Jeff Coulter, Extension corn specialist
corn-planting

Soil conditions


Avoid tillage and planting when soils are wet. In general, a field is ready for seedbed preparation when soil in the depth of tillage crumbles when squeezed. Pre-plant tillage when soils are wet can create a cloddy seedbed that reduces seed-to-soil contact. Achieving excellent seed-to-soil contact is essential for rapid and uniform imbibition of moisture by seeds and uniform emergence. Tillage when soils are wet can also create a compacted layer below the depth of tillage that can restrict root development.

Wednesday, April 5, 2017

Updated nitrogen and agronomic guidelines for corn following alfalfa

By Jeff Coulter, Extension corn specialist

alfalfa-field
First- and second-year corn following alfalfa usually benefit from increased yield, reduced or eliminated nitrogen requirement from fertilizer or manure, and reduced pest pressure.

Nitrogen management guidelines for first- and second-year corn following alfalfa were updated in 2016 and are available at http://z.umn.edu/fertilizingcorn.
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