Weather Delays Corn Planting but Optimal Window Remains Open

By Lizabeth Stahl, Jeff Coulter, and Dave Nicolai

Much of Minnesota has been covered in snow past mid-April and it will take some time for field conditions to dry enough for field work and planting to begin. Farmers are encouraged to consider the following as they wait for the 2018 corn planting season to begin.

Nutrient Management Podcast: Spring Nitrogen Outlook 2018

Spring is upon us! While there still may be snow on the ground, on this episode we have your spring nitrogen outlook. Guests Brad Carlson, Fabian Fernandez, Dan Kaiser, Greg Klinger and Anne Struffert answer some of your most frequently asked questions, including: How much N should I apply this spring? If I applied N in the fall, how much have I lost going into spring? What about starter fertilizers? How much N should I apply as starter? Is a preplant soil N test worth it this year? Should I use a nitrification inhibitor? What should I do about anhydrous if soil is too wet?

Respirator fit testing webinar

Do you have employees who need to wear a respirator this year? Or would you like to be a fit testing resource to your community? University of Minnesota, Extension is hosting a free fit test training webinar in collaboration with 3M on April 30th. 

Image: 3M

Evaluating Your Winter Wheat and Rye Stands

As wintery weather persists, you may wonder if your winter wheat or rye has survived this winter.  If you are really anxious or bored, you can dig up some crowns across the field and cut them longitudinal (lengthwise) with a very sharp knife or a safety razor blade. If the crowns look white/yellow to light green, they are healthy and have survived the winter to date. If you find crowns that have turned tan to brown and soft, they likely did not survive this winter.  A second method to check whether seedlings are alive is by trimming the roots and leaves down to about ¼  to ½ ” above and below the crown. Place these seedlings on a wet paper towel and place the towel in a Ziploc bag or plastic container that can be sealed. Place the container at room temperature and check for regrowth in 48 hours. Viable seedlings will show regrowth almost immediately (Photo 1). 

Photo 1 - Regrowth of young winter wheat seedlings after 36 hours incubation in a Ziploc bag at room temperature (photo courtesy of Blake Vandervorst)

Unfortunately, checking a single or a few crowns does not tell the whole story as winterkill is often patchy across a field (Photo 2).  To determine whether you need a plan B for these fields requires you to wait until the field starts to green up sufficiently in order to do a reliable stand count.  The more protected areas will green up first, while bare knolls or lower lying areas where water or ice may have been present sometime during the winter and early spring will be slowest to green up.

Photo 2 – Area with partial and uneven winter kill (photo courtesy of Joel Ransom).

To do a stand count, use one of the following two methods:

1.        Count the number of plants in a foot of row at several locations in the field.  Take an average and convert in plants per acre using Table 1.

2.        Take a hula-hoop, let it fall, and count the number of plants inside the hoop.  Repeat this at random several times across the field and calculate an average.  Use Table 2 to convert the count to an approximate population per square foot or acre.

Table 1 - Average number of plants per foot of row for different row spacing and plant densities per acre.

                                                                               

	Plants per acre (times 1 million)
Row Width	0.8	0.9	1.0	1.1	1.2	1.3	1.4	1.5
6”	9.2	10.3	11.5	12.6	13.8	14.9	16.1	17.2
7”	10.7	12.1	13.4	14.7	16.1	17.4	18.7	20.1
10”	15.3	17.2	19.1	21.0	23.0	24.9	26.8	28.7
12”	18.4	20.7	23.0	25.3	27.5	29.8	32.1	34.4

Table 2 - Adjustment factors to multiply the number of plants inside a hoop and convert the number into the number of plants per acre.

Hoop Diameter	Multiply by
30”	8,900
32”	7,800
34”	6,900
36”	6,200
38”	5,500

Uniform stands of 17 plants per square foot or approximately 750,000 plants per acre are sufficient to keep and do not require a plan B.  Consider replanting only those areas of the field where stands are below the threshold with, for example, spring wheat.  No-till seeding HRSW into standing HRWW is possible but creates some challenges later in the season because the two crops will reach growth stages at different times and complicate not just harvest but also the timing of herbicides and fungicides.

Small Grains: An easier way to establish (and grow) cover crops

Jochum Wiersma, Scotty Wells, and Jared Goplen

Establishing cover crops in corn and soybeans is not without its challenges in Minnesota.  There is little growing season left after harvest and soil moisture and herbicide carryover can often limit the ability to get a good cover crop stand when interseeding mid-season. In response to these growing season limitations, new interseeding technologies offer the promise to overcome some of the establishment issues in Minnesota (click here for more information). Even with the most advanced interseeding technologies, cover crop establishment success will be greater following short season crops. Wheat, barley, and oats make establishing cover crops much easier. There is plenty of growing season left following small grain harvest for reliable cover crop establishment. Oftentimes cover crops seeded following small grains accumulate enough biomass to be grazed or harvested for forage in the fall. 

Small grains also provide the opportunity to interseed cover crops. After all, interseeding alfalfa with oats is a common method to establish alfalfa. This approach can easily be extended to other legumes, including clovers and even grasses like annual ryegrass.  A common practice in NW Europe is to spread annual ryegrass with a fertilizer spreader over the top of winter wheat in early spring.  This strategy tends to work well for annual ryegrass and other species that require shallow seeding and light to stimulate germination. This strategy can probably be used successfully to interseed cover crops into wheat, barley, or oats in Minnesota.  

The biggest challenges when interseeding legumes in small grains is effective weed control, as many legume species are quite sensitive to the commonly used broadleaf herbicides. It is also important to select the proper legume species to avoid crop competition and harvest difficulty. Legumes like hairy vetch become very competitive when the small grain starts to mature, even to the point where plants impede harvest by reaching the top of the small grain canopy prior to harvest. Alfalfa and red clover are more appropriate choices to interseed with small grains, as UMN research has found they do not impede grain harvest and do not negatively affect hard red spring wheat yield. Other agronomic practices, including fertility management and seeding rates, can remain the same for interseeding small grains when compared to the practices for monocultures of wheat, barley, or oats.   More information on previous UMN research on intercropping alfalfa, red clover, and hairy vetch in hard red spring wheat can be found here.

Research on Woodland Management and Soybean Aphid: Cooperating Growers Needed

by Marcella Windmuller-Campione (Assistant Professor, Dept. of Forest Resources) and Robert Koch (Assistant Professor, Dept. of Entomology)

Looking for soybean growers in central and southern Minnesota to participate in a research study on soybean aphid population levels and buckthorn density in 2018

While there are several options for managing the destructive soybean aphid, including insecticides

and aphid-resistant soybean varieties, these options focus solely on the soybean field. However, it is very likely that buckthorn is lurking (and reproducing!) in your woodland or an adjacent publicly own forest, proving the required overwintering habitat for soybean aphid. Research in Ontario, as well as in Minnesota, has observed the relationship between proximity of buckthorn and early season

soybean aphid population levels. What has been little explored is if this relationship varies with buckthorn density – Does higher density buckthorn result in higher early season soybean aphid populations? If so, are there management techniques that we can implement to reduce buckthorn density, which could possibly reduce soybean aphid populations, thus improving quality and yield for soybean growers?  These questions require an interdisciplinary approach, bringing together research

faculty, Extension educators, and soybean growers with expertise in forestry, entomology, and agriculture.

Image of European buckthorn, which is the overwintering host for soybean aphid
(photo credit: Paul Wray, Iowa State Univ., Bugwood.org).

Do you have a soybean field adjacent to a woodland in central or southern Minnesota?... 

Why you need to use a preemergence herbicide on sugarbeet fields in 2018

Tom Peters, Extension sugarbeet agronomist

Waterhemp Cotyledons are more rowboat shaped than other pigweed species. True leaves are long and narrow (lanceolate) and are waxy and dark green. There are no hairs on the plant.

Waterhemp is the most widespread weed control challenge in sugarbeet. Growers attending the 2018 technical seminars and participating in the Turning Point survey of weed control and production practices reported waterhemp as their most important weed control challenge on 237,600 acres or over 35% of sugar beet fields in Minnesota and eastern North Dakota.

Sugarbeet planting date dictates the weed control strategy for waterhemp control. In 2017, many acres of sugarbeet were planted between April 10 and April 20. Early planting enables sugarbeet to grow to the 2-lf stage, or the sugarbeet growth stage when Dual-Magnum, Outlook, and Warrant is applied, before waterhemp gemination and emergence in mid-May (POST to sugarbeet, PRE to waterhemp). Split lay-by application of chloroacetamide herbicides or first application at the 2-lf stage followed by a repeat application 14 to 21 days later is the preferred approach for waterhemp control for early planted sugarbeet (Table 1).