Minnesota Crop News

Iron Deficiency Chlorosis Research in NW Minnesota

2013-05-09T14:32:04Z

By John Wiersma
Agronomist
Northwest Research and Outreach Center

High pH, highly calcareous soils, common in western Minnesota, restrict the availability of soil Fe needed for optimum soybean growth and yield. On such soils, the amount of Fe fertilizer applied must surpass a threshold before there is sufficient available Fe in the soil solution to induce a positive growth response. Only a limited number of management tactics designed to improve the availability of Fe have been studied with soybean. These include variety selection, seeding density, seed-applied or in-furrow materials, and foliar treatments.

]]> John Wiersma outlining research findings conducted over many years in the Red River Valley. Click on the link to the PDF file to read more.

Fe Chelates_Wiersma.pdf

Update on Iron Deficiency Chlorosis Research for Soybean

2013-04-29T20:00:55Z

By Daniel Kaiser
Extension Soil Fertility Specialist

Management of Iron (Fe) deficiency chlorosis (IDC) in soybean is seemingly and endless topic of research in soybean growing areas with high pH, calcareous, parent materials. We are just finishing a three-year summary of a series of IDC management strip trials that began in 2010. Our main focus for this work was to study the variability in response for a tolerant and susceptible variety to an oat companion crop and a 6% EDDHA-Fe treatment applied in-furrow (we used Soygreen at a rate of 3 lbs of product per acre). The field areas were selected to have some variation in the severity of IDC.

]]>
We have had mixed results with the oat companion crop the past three years. Our greatest risk with this strategy was reductions in yield if the oat crop was not terminated at the correct time. Our treatment was a 2 bu/ac rate broadcast seeded and dragged in immediately before planting. Our targeted time of termination was when the oat crop was 10 inches tall, which was challenging to say the least. With unpredictability in rainfall events the past three years we were only able to successfully terminate the oat crop at the correct stage about 50% of the time. The oat crop did increase yield, but the increase was seen only for the susceptible variety. Yield without oat for the tolerant variety was similar to the susceptible with oat. Thus, in terms of risk, the oat companion will work but is riskier than other management strategies.

The in-furrow iron treatment gave us the best chance for return with the lowest risk. No yield reductions occurred from the in-furrow application of the EDDHA-Fe fertilizer source. Yield responses were greatest in areas severely affected with IDC (soybean plants would generally die off during the season) and generally were still positive in areas that would show significant yellowing of leaves with some stunting of plants. There was no yield response in areas with little to no IDC pressure. The data we have strongly supports to only apply these products in field areas where moderate to severe IDC is present. Even with the in-furrow product, the susceptible variety could not out yield the tolerant. Again, selecting a tolerant variety is the best course of action.

There are a few unknowns with this work. First, we only tested at 1 rate of the product. Similar strip trials with multiple rates would be beneficial to determine variable rate applications. Second, predicting where the moderate and severe areas are can be difficult. When we speak to most growers, salts and carbonates are what is generally used to judge IDC severity in fields. However, these factors did not have much bearing on the severity of IDC in our studies. It generally followed that the field sites were we saw the best response to in-furrow Fe where higher in carbonates and had some higher EC values (electrical conductivity is used to assess the salt content). However, within the sites there was no clear correlation between the severity of IDC and these factors. What seemed to factor in greater than soil tests was precipitation in June. If we focus on past research the major driving force is soil moisture content. If you take soil from a field area affected by IDC, the severity of the problem has been shown to increase if with increasing level of water saturation of the soil. Thus, for our work in West-central Minnesota, soil moisture should be a major driving force where IDC will occur, but it is rarely if ever measured.

One thing we are doing for 2013 is trying to establish a set of IDC sentinel trials around the state. We currently are looking for 6 field locations where IDC has been present in the past. What we would prefer is:

1) Field site where IDC has been previously shown
2) Field area where only a tolerant variety will be planted and no in-furrow or foliar treatments will be applied
3) Close access to the road
4) Field that can be harvested with a combine equipped with a GPS and yield monitor

The idea behind this work is to look more closely at the causative factors, and if the funding is available, look across multiple years. In order to better establish variable rate guidelines we need to have a better understanding on why field areas vary in terms of IDC severity on a year to year basis.

We currently have one year of funding from the Minnesota Soybean Research and Promotion Council to launch this project. These studies are meant to be as non-invasive as possible. There will be no specific treatments to apply by the grower, the field areas need only to fit the criteria above.

We will install a time lapse camera to monitor the severity of IDC in the margins of the field and a data logger equipped with a probe to measure soil temperature, soil moisture, and soil electrical conductivity throughout the growing season. Everything will be installed after planting and prior to harvest.

A more intensive sampling will be conducted early in the season (mid-June is the target for sampling). An intensive grid sampling program will be used in order to take routine 0-6" soil samples as well as plant tissue. In addition the severity of the IDC and the soil moisture will be intensively mapped to look at spatial variation in these factors. This data can then be overlaid with per-existing soil maps and the yield data to look at correlating response.
We are hopeful that some insight on how to map fields for variable rate application can be achieved with this project. While we understand some of the causative factors there still are many questions in order to best be able to target moderate and sever areas for either targeted planting of differing varieties or for in-furrow application of Fe.

Interested parties can contact:

Daniel Kaiser
439 Borlaug Hall
1991 Upper Buford Circle
Saint Paul, MN 55108
612-624-3482
dekaiser@umn.edu

Does My Soybean Crop Need Sulfur?

2013-04-26T15:38:35Z

Daniel Kaiser
Extension Soil Fertility Specialist

I know there are still questions on the application of sulfur for soybean. Between me and a number of other researchers in Minnesota, we have been working on a number of projects focusing on sulfur management on corn, soybean, and spring wheat. Recently the soybean research has been fully summarized so I want to take a minute or two to highlight some of the findings to outline where we are at with the current guidelines for fertilizer management on soybean.]]>
We have been mainly focused on researching sulfur response for corn. One thing that seems to come to the forefront in this research is the overall importance of soil organic matter when considering where a yield increase will occur. For soybean it is not that simple. If you go through much of the research from around the country there is not much supporting evidence for recommendations for sulfur application to soybean. I believe much of any potential for response of soybean to sulfur is related to a few factors, the most important of which revolved around climatic conditions. Where we saw the response was in 2009 which was a year that saw very large responses to sulfur in many of our corn studies. With temperatures being cool and with most areas being relatively dry the potential for mineralization of sulfur from organic matter was low. Two other factors I think were important at the locations were the soil and the previous history of sulfur deficiency symptoms in other crops (alfalfa and corn). The site was on a silt loam soil in southeastern Minnesota with an organic matter concentration that averaged less than 2.0% in the top six inches. All these factors together created a perfect storm in terms of creating conditions were a sulfur application would benefit soybean.

Other than the field location in 2009, there was one other instance that I know of where sulfur benefitted soybean at the Southwest Research and Outreach Center at Lamberton. In this instance soybean yielded higher with sulfur, but the sulfur was applied before the previous corn crop. To follow up on this response we set up trials to look further into the sulfur cycling within corn-soybean rotations to better understand if there are greater benefits from application before the corn crop. One thing that we found in the studies in 2008 and 2009 is that we increased the amount of soybean plant material relative to the total grain produced, meaning we had more plant material per acre. When sulfur and phosphorus were added with N there was a large increase in soybean vegetative growth at all locations. This concerns me due to extra water usage in dry years and potential for disease pressure to increase.

So what are the overall benefits? Increased yield is the overall goal but I do not think that there is a widespread need for sulfur to be applied on all soybean acres. I think the best bet would be to look at fields that are in a areas prone to sulfur deficiency on corn or alfalfa, soil organic matter is around 2.0% or less, and the field has not had any sulfur (including manure) applied to it for several years. In this case 10-15 lbs of sulfur broadcast per acre should be enough for soybean. I would suggest not applying high rates of nitrogen and phosphorus with sulfur. In our field trials we broadcast potassium sulfate and did not see the large increases in plant mass. Another source that may work is gypsum.

I do not think sulfur needs to be applied to soybean if it was applied the previous year. Based on all of the data we have there does appear to be enough sulfur cycling from year to year that the soybeans crop should have enough. Sulfur does leach out of the soil but the relative rate it will leach is lower than some other anions. In coarse sand our data indicates that given enough rainfall any sulfate applied will be below the 2 foot depth in the soil by the middle of the growing season. Even with a small increase in clay content that rate can be reduced. At another site with a loam soil texture we just started to see elevated levels of sulfate by the end of the growing season. Thus, there will likely be some sulfate still in the profile for the soybean crop as long as rainfall is not too excessive.

The other aspect we have been studying is sulfur cycling in corn residue. Based on the information I had a few months ago there did not appear to be much, if any, sulfur that would mineralize from the breakdown of corn stover. However, a more recent set of data shows that it may be possible. From the data we have now, without sulfur, the ratio of carbon to sulfur tends to maintain at a point where the breakdown of corn stalks will not release or tie up sulfur. However, when we looked at the data from 10 and 20 lbs of sulfur applied to corn, the ratio became smaller indicating a potential for a small amount of sulfur to be potentially released. The amount released will again depend on soil temperature, moisture, and tillage to incorporate the residue. This cycling mechanism may explain some of the response we saw in 2009. We also studied higher rates, but the effect appeared to not extend past 20 lbs of sulfur.

To reiterate, if sulfur is applied before another crop I do not think it needs to be applied before soybean, especially corn where the chance of a profitable return is much greater. I think yield can still be increased without a direct application and we also have evidence to increases in grain protein concentration when sulfur was applied before corn. These increases have only been identified in our work in Southeastern Minnesota at this time. While most of our evidence does not support widespread use of sulfur on soybean, some of the isolated responses indicated that some changes needed to be made to our recommendations. Moving forward we will continue to study the cycling mechanisms in order to provide the most up to date information for our current guidelines.

Fertilizing Soybean in Minnesota

Safely Handling Treated Seed

2013-04-25T15:12:14Z

By Lizabeth Stahl, Extension Educator - Crops

Much of the seed planted this year will have been treated with a fungicide, insecticide and/or nematicide. As when working with any pesticide, care should be taken when handling treated seed so that exposure to the handler, non-target organisms, and the environment is reduced or prevented as much as possible.

]]> Exposure to the Handler: Although growers may be more familiar with checking an herbicide or insecticide label for the appropriate personal protective equipment (PPE) to wear when handling a product, every bag of treated seed will also list the proper PPE to be worn when handling the treated seed. Wearing the appropriate PPE will help reduce or prevent pesticide exposure when working with treated seed.

The PPE to be worn when handling treated seed will typically include a long-sleeve shirt, long pants, shoes, socks, and chemical-resistant gloves. Unless the seed bag label specifies the type of chemical-resistant gloves to be worn, there are several types a handler can choose from, varying in flexibility and durability. Note that leather or cloth gloves are not chemically resistant! Cloth and leather gloves can soak up pesticide residues and result in pesticide exposure each time they are worn.

Handlers of treated seed should also take care to limit exposure to any dust when opening or emptying out seed bags.

Exposure to non-target organisms and the environment: Treated seed is not to be used for food, feed or oil processing, and care must be taken to not contaminate grain that will be going into the food or feed market. There is ZERO tolerance for treated seed in the export market, meaning that a single seed could result in the rejection of an entire load.

Treated seed should also not be left on the ground surface as some products can be hazardous to birds and mammals, or may be toxic to fish and aquatic invertebrates. Any seed spills should be covered or cleaned up as soon as possible.

A number of products are also toxic to bees and pollinators, so care should be taken to minimize dust as much as possible when filling and emptying out planters. Avoid conducting these tasks near flowering plants where bees and pollinators may be foraging.

Disposal of leftover treated seed: The best and most preferred option is to plant out any leftover treated seed on fallow ground or an unused parcel of land. Depending on the seed treatment, there may be restrictions on planting rate and depth. Seed burial may also be allowed, although care must be taken avoid burial next to water sources. Other potential options include disposal in an approved municipal landfill, use as a fuel source for a power plant or kiln, or incineration by a waste management facility.

For more information: Always be sure to check the seed bag label for specific details and restrictions about the product you are using. Depending on the product, there may also be rotational, plant-back, grazing or feeding restrictions. Futher details can also be found on the U of MN Factsheet about this topic at: http://z.umn.edu/shtseed.

Soil Testing For K

2013-04-01T15:37:50Z

By Daniel Kaiser
Extension Soil Fertility Specialist

With spring finally approaching it is a good time to address some questions on soil testing that came up of the winter concerning testing soils in a field moist state versus the standard dried samples that are run through soil testing labs. First I would like to make it clear that the issue of drying of a soil sample mainly pertains to potassium. Most other tests routinely run through the lab are not affected by drying of the sample. The reason why potassium is different is due to its chemistry in the soil. We currently have finished the second year of potassium studies looking at both testing methods but will be continuing this work for the foreseeable future to gain a better understanding of what is going on within the soil.
]]> included from soil samples collected at a plot near Red Wing in the fall of 2012. This typifies some of our locations in the past two years where the field moist test has actually returned higher values than the air dry tests. With the dry soil conditions complicating matters, we really do not know whether one is actually correct in assessing the potential for a deficiency of K in out soils. The fact is that we are too early in our work to tell the difference between the two tests. If fact, our current calibration data shows that there is no difference in the assessment of crop response between a sample run field moist and air dry, even with the handful of locations testing higher with the field moist analysis. We currently are trying to expand research into poorly drained fields as these should represent conditions where the field moist potassium test has a better chance of coming back lower than the air dry test. The fact of the matter is that we know there are likely issues out there but have no concrete evidence to show where they are occurring.

Even with some of the issues noted I would like to make it clear that I have full confidence in the current analysis methods being used for testing K by soil testing labs in the state of Minnesota. Again, we are looking at these issues closely but the development of the field moist test and if we do find some evidence that it better predicts K response in some soils it will become publically available. The moist test is a different test than the air dried samples, and the value of the field moist cannot be directly converted to an air dry test. Because of this all new field calibrations will have to be established prior to any recommended use of the field moist test for potassium. This is very important for anyone thinking of having sample run at a lab using field moist testing for potassium. A few labs are currently running samples on a field moist basis, but until it is clearly demonstrated that the field moist test better predicts potassium response it will not be recommended for use in the state of Minnesota.

We currently are in the process of establishing a soil test sentinel program to study changes in soil test over time across the state of Minnesota. More information will be available in another e-news release on this program. One of the factors we intend to study is the difference between field most and air dried samples for testing for potassium and how they change at a fixed point in space, over time. What this program entails is taking soil samples from a fixed area of any field every 4 to 6 weeks and sending the sample to Daniel Kaiser at the Saint Paul campus. What we are attempting to research is how soils from around the state vary in the difference between the two tests to get a better understanding if and where problem soils may be found. With the diversity of soils this it is important to know how soils may differ. Support for this program is coming through check-off dollars supported by AFREC. Additional information will be available and can be obtained by contacting Daniel Kaiser at dekaiser@umn.edu.

U of MN Field Crop Trials Bulletin Available

2012-12-21T21:33:38Z

By Lizabeth Stahl

The University of MN Field Crop Trials Bulletin is now available in print and electronic forms. The new publication, dated January 2013, provides results from U of MN trials conducted in 2012 across the state. The varieties tested are from both public and private breeding programs and include U of MN developed forage, grain, and oilseed crop varieties.

]]> Plant varieties tested include alfalfa, barley, birdsfoot trefoil, canola, corn for grain, corn for silage, oat, soybeans, spring wheat, and winter wheat. Trials were conducted at Research and Outreach Centers across the state at St. Paul, Becker, Crookston, Grand Rapids, Lamberton, Morris, Rosemount and Waseca, and also in farmer's fields. Results are from replicated trials conducted at several locations, which allows growers to evaluate how varieties performed across various environments, while accounting for variability within a location and across locations.

The variety trials bulletin is available online through the Minnesota Agricultural Experiment Station website at http://www.maes.umn.edu/. A limited number of print copies will be available through the University of Minnesota Extension Store at http://shop.extension.umn.edu or by calling 1-800-876-8636. A limited supply of print copies may also be available at your local U of MN County Extension Office.

SCN Resistant Variety Plot Tour on Friday, August 24 from 1 - 2 PM at the SWROC

2012-08-20T18:30:11Z

One of the experiments at the U of M Southwest Research and Outreach Center (SWROC) is currently displaying interesting visual results which will rapidly fade as the season progresses. An impromptu tour on Friday, August 24 from 1 to 2 PM will give you a chance to see the effect of SCN resistance for yourself.

]]> A study with three sources of SCN resistance and a susceptible variety has been located at the SWROC for several years. Visual symptoms of SCN on soybean are especially pronounced this year. This is a good opportunity to see the effect of rotating resistance sources on soybean growth and SCN. This plot tour will highlight the effects of soil fertility on SCN and soybean aphids and show SCN interactions with soybean aphid, soybean disease and weed management.

If you plan on attending, please call the SWROC at 507-752-7372 or e-mail Molly Werner at werne022@umn.edu. There is no cost to attend the tour and beverages will be provided. The SWROC is located 1.5 miles west of Lamberton on Highway 14. For additional details, please view the SWROC website at http://swroc.cfans.umn.edu.

Spider mites: some points to consider

2012-07-25T23:01:19Z

From the University of Minnesota Extension Southeast Crop Connection newsletter

Spider mites are the concern today. Symptoms have become more obvious in some fields, especially along field edges, drought pockets and drier area in the region. Is this a "tornado watch" or "warning"? A watch in most fields, but we have touchdown (warning), with damage in some (more drought stressed conditions). You need to scout now. Here are some additional precautions and suggestions to consider.

We are entering the critical time for soybean growth--pod set and fill, determining yield.
When/If you pull the trigger and apply an insecticide now, this early in the season, plan on multiple application for multiple pests (aphids). You'll remove all beneficial insects and open the door to other pests.
When making multiple applications it is imperative that you choose multiple modes of action.
Canopy penetration is critical for good control.

Do not cheat on insecticide rates.
Do not cheat on water (gallons/acre applied).
Do not cheat on pressure--keep PSI up.

Consider preharvest interval (PHI) when planning multiple applications of insecticides. Average range, 18-45 days. You may need to use a product with a longer PHI first followed by one with a different mode of action and a shorter PHI second.
Insecticide/miticides will not kill spider mite eggs. Life cycle completed in 5-19 days (faster with temps above 90°)
Remember buffer zones, and setbacks to sensitive areas for the insecticides you use. Read the label.
Places to scout first: heaviest infestation usually occur along roadways, ditches, near alfalfa fields. Watch for spider mite movement from alfalfa to soybeans.

Read this article for more information on managing spider mites.

Crop revenues and costs resulting from drought

2012-07-23T20:04:24Z

Don Nitchie, Extension educator, dnitchie@umn.edu

How quickly crop conditions have changed from the wet weather of May.

Extreme heat and lack of rainfall throughout June has resulted in USDA Crop reports having been dramatically revised to reflect deteriorating crop progress throughout the U.S. Corn Belt. At the moment, conditions appear not quite as severe in SW Minnesota as in other regions but, that could change soon. I hope it is for the better as the result of rainfall.

Dry conditions threatening to generally impact final yields across the U.S. Corn Belt have historically had significant impacts on "old crop" and "new crop" prices. We have certainly seen that in the last few weeks. If market demand for corn or soybeans remain the same and stocks are tight, a relatively small change in expected supply leads to a larger change in prices.

]]> A larger change in expected supply leads to an even greater change in prices. We are certainly experiencing this now. This is not the case when we have more localized dry conditions which tend to mostly impact local supplies and therefore local basis relative to a mostly unchanged national price.

At your farm level, sometimes this greater price reaction of a general U.S. drought can compensate to a degree for your potential lost yield because of price compensations for reduced yields. This depends greatly on how widespread the U.S. crop impact is and what your yield impact is at your farm. However, it is important to remember that yields also impact your cost of production per final bushel of yield. At this time of year your costs per acre are virtually fixed for the year but, not your cost per bushel of production. Grain is priced per bushel not per acre, obviously, so sellers of grain will remain concerned with selling at desirable prices relative to their final cost per bushel. So, it is more important than ever, to continue to revise your final expected yields and update your costs per bushel of final yield. Yours will be different than the average and other producers.

To illustrate here are some examples of possibilities an average SWM farm could experience. Total costs include labor and management charge.

2012 Cash Rented Corn SW Minnesota

Yield	Price	Total rev/acre	Total cost/acre	Total cost/bu	Net return/bu
185	$4.70	$870	$733	$3.96	$.74
155	$5.80	$899	$733	$4.73	$1.07
125	$6.90	$863	$733	$5.86	$1.04

The above examples are only hypothetical at this point and some people will definitely have the opinion that things could turn out much worse or better than the extremes used in the example. However it is clear, that market price changes may compensate to a degree for yield reductions. How much depends on how our SW Minnesota weather and crop conditions progress from here until harvest, relative to the Corn Belt as a whole. It is also clear that you should continue to adjust your yield expectations and re-calculate your costs per bushel of that expected yield. It may change dramatically throughout the growing season. Not doing this may not help you realistically evaluate rapidly changing national and local corn and soybean prices.

Spider Mites in Soybeans

2012-07-09T01:30:30Z

We've been getting calls about spider mites in soybeans, not surprising given our high temps and the dry conditions in some locations. As temps get into the 90's, spider mite reproduction and development rates increase significantly. Drought also exacerbates spider mite populations, and when drought conditions are relieved by rain, spider mite populations may not necessarily decrease. Consequently, even after drought conditions pass, best to continue scouting for spider mites damage.

Spider mites are tiny and only large females are visible to the naked eye (unless you've got really good eyesight!). The best way to see spider mites is to shake a plant over a piece of white paper - any moving pieces of dirt are likely spider mites... So to scout for something that small, it's best to look for damage. Spider mite damage will first appear as small yellow spots (stippling) on lower leaves. There is currently no solid treatment threshold in soybeans, but If stippling reaches mid-canopy leaves, a treatment is likely necessary. Pyrethroids may flare spider mite populations, spreading mites and increasing their populations.

A good source for information on spider mite biology, scouting and thresholds was prepared last year by Bruce Potter and Ken Ostlie and is available at:

http://www.soybeans.umn.edu/crop/insects/spider_mites.htm

Keep scouting!

Assessing Hail Damage in Corn and Soybean

2012-06-22T23:15:00Z

By Jeff Coulter and Seth Naeve, Extension Agronomists

Recent storms left several areas affected by hail damage. Especially hard hit was a large area centered around Nicollet and Sibley Counties. Throughout this area, much of the corn was at the V8 stage (8 collared leaves) when damaged, and soybean had three to five fully developed trifoliolate leaves (V3-V5 stage).

In late June, assessing hail damage and making replant decisions can be difficult, with many variables to consider on your way to making a final decision to replant or maintain the existing stand. Many of the answers to questions regarding crop yield loss and the need for replanting can be found in the following online guides:

Corn Damage and Replant Guide: www.soybeans.umn.edu/pdfs/CornGuide.pdf

Soybean Damage and Replant Guide: www.soybeans.umn.edu/pdfs/SoybeanCropDamage.pdf

Survivability of corn plants:

Yield potential of hail-damaged corn depends primarily on the number of remaining plants per acre with healthy growing points that will recover, the amount of leaf area lost on these plants, and the growth stage at which the crop was damaged. To determine whether a corn plant will survive and regrow, split stalks and examine the growing point. In corn, the growing point remains below the soil surface until the V5 stage (5 collared leaves). Growing points located at or below the soil surface can be damaged by large hail stones landing on soft soil, and by freezing from hail accumulation around the base of the plant. At the V8 stage, the growing point is located about a foot above the soil surface and has a small tassel at the top of it. Healthy growing points will be firm and white to yellow in color. If damaged, the growing point will be watery and orange to brown in color. Plants with damaged growing points will not recover.

Another consideration is stem bruising. Severe stem bruising not only limits the plant's ability to translocate water and nutrients, but it also reduces standability. Plants with stem bruising should have their stalks split in order to determine the severity of the stem bruising, and whether the growing point has been injured. Plants with stem damage extending beyond the leaf sheaths and into the pith of the plant will either not recover or will likely have large reductions in yield. Fields with severe stem bruising should be harvested early to avoid significant losses from stalk lodging.

When there is whorl damage to corn, new leaves can have difficulty emerging through damaged tissue and can become tightly bound in the whorl. Plants with leaves that are tightly bound in the whorl can sometimes break free after about one week of growth. However, many of these plants are unable to recover. This makes it difficult to assess final plant population within just a few days after hail.

Survivability of soybean plants:

Soybean plants with significant amounts of green tissue remaining (more than one green cotyledon and/or remaining leaf tissue) are likely to survive early season hail damage, as they can regrow from axillary buds located at the juncture of the stem and leaves. Soybean plants cut below the cotyledons or entirely stripped of leaf tissue will not recover.

Estimating yield loss due to reduced plant population:

Hail damage is highly variable within fields. Thus, accurate estimation of the surviving plant population requires that surviving plant counts be made in as many locations within a management unit as possible. Making a replant decision based on a few stand counts near the field entrance will likely lead to a poor ultimate decision. Count several areas that are equal to 1/1000^th of an acre and take the average. Then, multiply by 1000 to get plants per acre.

Table 1. Length of row equal to 1/1000^th of an acre for various row widths.

Soybean can tolerate low populations very well, with only small reductions in yield potential across wide ranges in plant loss. For instance, populations near 100,000 plants per acre are likely to produce maximum yields, and those around 80,000 will yield about 90% of the maximum. However, expected yields drop more rapidly in stands below 50,000, with 39,000 plants per acre likely to produce about 75% of the normal yield. Yield potential for corn at various plant populations is listed in Table 2. When gaps of two feet or more are present throughout the field, assume an additional 5% reduction in corn grain yield.

Table 2. Relationship between corn plant population and yield in southern Minnesota. Source: Coulter (2009).

Estimating yield reductions due to leaf loss:

In addition to yield loss from a reduced stand, growers should consider added yield reductions due to leaf loss. Any green leaf area remaining on a plant will contribute to yield. Only consider leaf area lost if it is removed or brown in color. Information on corn yield and leaf loss is given in Table 3. For soybean, leaf loss up through the V4 stage (4 fully developed trifoliolate leaves) has little effect on yield.

Table 3. Relationship between corn grain yield and leaf loss. Source: Hicks et al. (1999).

Replanting considerations:

Replanting should be considered only in fields where the crop is a total loss. Replanting corn for grain at this time is not an option as the crop is not expected to reach black layer (maturity) before the first killing freeze. Replanting corn for silage may work if the corn is replanted very soon and a hybrid that is 15 or more relative maturity units earlier than a full-season hybrid is used. However, planting corn silage after about June 25 is not recommended in southern Minnesota.

Soybeans may be replanted, but yields will be limited by the short season remaining. Soybeans planted around the first of July routinely produce a yield of about half of that of normal planting dates. Experience with soybeans after peas has shown that planting a soybean variety that is at least one maturity group earlier than adapted to the region before July 4 will occasionally produce reasonable yields. Producers are seldom content with yields from crops planted a week or more after July 4. By this time, yield potentials fall to 40% of normal or less. Therefore, in fields that are a complete loss, replanting of soybean should occur as soon as possible.

Seed availability may be the primary determinant for replanting or not. Producers should contact their seed suppliers as soon as possible to confirm that early-maturity seed is still available.

Caring for your hail-damaged crop:

For those producers who choose to keep their existing crops, care should be taken to ensure that these fields produce as much as possible. Because the crop has been placed under tremendous stress, it is important to reduce the level of future stresses. The most important and difficult challenge in hail-damaged crops often revolves around weed control. Good weed control must be maintained season-long; however, contact herbicides that stress the crop should be avoided where possible.

While it is crucial to avoid further stress to your crop, foliar fungicides are not likely to improve crop recovery and yield. The most damaging diseases affecting corn and soybean after hail are bacterial in nature. Fungicides have no effect on these bacterial diseases. Furthermore, the defoliated crop is not likely to effectively take up the fungicide. Producers should instead focus on pests that they can control (like weeds and insects) and avoid costly applications of inputs that are not likely to increase yield.

References:

Coulter, J.A. 2009. Optimum plant population for corn in Minnesota. Available at http://www.extension.umn.edu/distribution/cropsystems/M1244.html. Univ. of Minnesota, St. Paul.

Hicks, D.R., S.L. Naeve, and J.M. Bennett. 1999. The corn growers field guide for evaluating crop damage and replant options. Available at http://www.soybeans.umn.edu/pdfs/CornGuide.pdf. Univ. of Minnesota, St. Paul.

Abundant Rainfall in Some Areas May Increase Soybean and Corn Seedling Disease

2012-06-04T17:12:13Z

By Dean Malvick

With most of the soybean and corn crop emerged and growing across Minnesota - it is a good time to assess fields for seedling disease problems and the potential benefits or failures of seed treatments. The recent fluctuating temperatures and abundant rainfall that resulted in surplus topsoil moisture in about 21% of the state last week (USDA-NASS data) have created good conditions for seedling diseases and root infection by a complex mix of pathogens in many fields. Scattered problems with seedling diseases have been reported.]]> Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4

Seedling infection can result in dead plants before or after emergence, stunted and discolored plants, wilting, and complete or partially rotted and discolored roots. The problems often occur in a circular or random pattern in the field. Seedling infection can also lead to damage that may not be seen until mid to late summer, as is common with Phytophthora rot and sudden death syndrome. Disease is just one of many stresses that seedlings are encountering in fields. Close inspection and thorough diagnosis are often required to accurately identify the cause.

The pathogens that cause these problems are widespread and persistent in Minnesota fields. Favorable conditions for infection and plant damage include wet and compacted soils, cool or warm soil depending on the pathogen, and poor seed quality. Slow plant emergence and growth, crusted soil, and fertilizer or herbicide injury may also enhance the problems. Seedling diseases can begin soon after the seed is planted and can continue for a month or more.

The most common soilborne fungi and fungal-like pathogens of soybean appear to be Fusarium, Pythium, Rhizoctonia, and Phytophthora. Each of these groups of pathogens, except for Phytophthora, also infect corn. These four pathogen groups are not composed of a single type of pathogen. We have been learning that these pathogens are more complex than previously known.

Recently we have learned that there are at least 10 different species of Fusarium in Minnesota that can cause root rot on soybean and possibly corn. There also appear to be over 15 different species of Pythium that infect soybean roots in Minnesota based on a 2011 survey of seedlings. The importance of these different species is unknown, but they may be infect under different environmental conditions, may have different levels of aggressiveness to soybean and corn, and might have different levels of sensitivity to seed treatment 'fungicides'. Several types of Rhizoctonia are known that preferentially infect different crops such as soybean, corn, and sugarbeet. Many different pathotypes (races) of Phytophthora occur in Minnesota, some of which can overcome Rps resistance genes in soybean.

Infected roots often show symptoms that can be caused by multiple pathogens and cannot be conclusively diagnosed without laboratory testing. For example, tan/brown, soft-rot symptoms on seedling roots caused by Pythium and Phytophthora are very similar. In contrast, the reddish- brown, often sunken lesions caused by Rhizoctonia are easier to recognize. The symptoms associated with Fusarium infection are typically light to dark brown lesions.

Scouting fields to identify when, where, and which diseases occur can assist in managing them in future crops and in understanding efficacy and or failures of seed treatments. Timely scouting is important because seedling diseases often develop rapidly and seedlings can degrade quickly. Intact, non-degraded plants are needed for diagnosis by the University of Minnesota Plant Disease Clinic (pdc.umn.edu/) or other diagnostic laboratories. Accurate diagnosis helps to focus management plans, which differ for different pathogens and diseases. More information on soybean seedling diseases can be found at Minnesota Crop Diseases web site (www.extension.umn.edu/cropdiseases/soybean/index.html).

Volunteer Corn - An Issue in Corn and Soybean

2012-05-23T19:12:11Z

By Liz Stahl and Jeff Coulter

Growers are finding high populations of volunteer corn in their fields this spring. Factors likely contributing to this include lodging in many fields last fall due to poor stalk quality and drought conditions, and higher harvest losses due to low grain moisture at harvest. Other factors that can lead to high populations of volunteer corn the following year include storm damage and ear droppage. The question arises: When are populations of volunteer corn high enough to warrant control? ]]>

Volunteer Corn in Corn - U of MN Research Results:

To help determine the effect of volunteer corn on corn yield and at what point a control tactic should be implemented, research trials were conducted by the University of Minnesota in 2007 and 2008 at the Research and Outreach Centers in Lamberton and Waseca. Extension Educators Liz Stahl and Ryan Miller along with Scientists Jodie Getting and Tom Hoverstad conducted the trials.

Treatments included seven populations of volunteer corn plants (target populations of 4,000, 8000, 12,000, 18,000, 24,000, 30,000, and 36,000 plants/acre), two populations of volunteer ears corresponding to 2 and 5% ear droppage (650 and 1,600 ear clumps/acre), three combination treatments of volunteer ears and plants (650 ears/acre plus 12,000, 24,000, or 36,000 plants/acre), and a control which contained no volunteer corn. Carry-over kernels and ears from a glyphosate-resistant hybrid planted the previous year were used for the volunteer corn treatments. Plots were hand-seeded with the carryover seed, with kernels being planted at two to three times the target population. Plots were field cultivated and then planted to a glyphosate-resistant corn hybrid at 32,000 to 33,000 seeds/acre in 30-inch rows. Acetochlor was applied preemergence for weed control followed by glyphosate postemergence. Within two weeks after the glyphosate application, volunteer plant and ear populations were assessed and plots were thinned to target volunteer populations where needed. Corn grain yield and moisture content were measured at harvest.

Effect of Volunteer Corn Plants on Corn Yield: Corn yield was significantly affected by volunteer corn in 3 of 4 site-years (Figure 1), although results were variable. In 2007, low germination of the carryover seed used for volunteer corn treatments contributed to variability among the plots, and average volunteer corn populations were 39 to 62% of the target population. In 2008, germination of the volunteer seed was much higher and plots were thinned to reach target populations of volunteer corn after the postemergence glyphosate application.

In 2007 at both locations, the lowest level of volunteer corn to impact yield (yield losses averaged 8% compared to the control) was at the 18,000 plants/acre target treatment. This corresponded to an average volunteer population of 8,000 and 11,000 volunteer plants/acre that year at Waseca and Lamberton, respectively. In 2008, corn yield was reduced at Lamberton by only the three highest volunteer populations evaluated (yield losses ranged from 23 to 26% compared to the control), or once volunteer populations reached at least 24,000 plants/acre. Yield was not significantly affected by volunteer corn populations at Waseca in 2008.

Effect of Volunteer Corn Ear Clumps on Yield: Except at Waseca in 2007, yield was not affected by the low (650 ear clumps/acre) or high (1600 ear clumps/acre) population of volunteer ear clumps (Figure 2). At Waseca in 2007, yield was reduced 9 to 11% by volunteer ear clumps compared to the control, although yields were similar between the two volunteer ear clump treatments. In 8 of 9 comparisons, yield was not reduced by the addition of 650 volunteer ear clumps to a low, middle or high population of volunteer plants (target populations of 12,000, 24,000, or 36,000 plants/acre). The only time yields were reduced in a combination treatment compared to the corresponding volunteer plant population was when ear clumps were added to the mid-level volunteer plant population at Waseca in 2007.

Other observations: In this trial, contribution to yield by volunteer plants appeared to be minimal. Emergence was typically delayed in volunteer plants compared to the planted hybrid, and volunteer plants were typically one to six leaf collar stages behind the hybrid. Most volunteer corn plants, particularly at higher volunteer populations, did not produce an ear and if ears were produced, they were small with poor seed set. Stalk lodging and harvest moisture were also evaluated, but no differences were detected among treatments.

What Does this Mean for Control of Volunteer Corn in Corn? This research demonstrates that volunteer corn can reduce corn yield, although the effects varied by growing environment. In this study, low levels of volunteer corn did not impact yield. In years where volunteer corn affected corn yield, volunteer corn populations had to reach at least 8,000 plants/acre before yield was reduced an average of 8 %. For a 200 bu/acre corn crop, that would be the equivalent of 16 bushels/acre. Using a corn price of $5.00/ bushel, this calculates to a break-even cost for a control tactic of $80/acre. At the populations evaluated, volunteer plants also had a greater impact on yield than ear clumps. These results demonstrate that if volunteer corn populations are high enough, control of volunteer corn in corn may be justified.

Volunteer Corn Control Options in Corn:

Control options for volunteer corn in corn are limited and complicated by the fact that most hybrids contain at least one herbicide resistant trait if not more. If a Roundup Ready (RR) hybrid was planted the previous year, glyphosate will not control volunteer corn the following year. Likewise, if a Liberty Link (LL) hybrid was planted the previous year, glufosinate will not control volunteer corn the following year. Glufosinate is an option to control volunteer RR corn, and glyphosate is an option to control volunteer LL corn. However, many hybrids are now stacked with both of these traits, making row cultivation the only option.

Volunteer Corn in Soybean:

Now that most growers in a corn/soybean rotation rotate RR corn with RR soybeans, volunteer corn has become one of the major weed issues in soybean fields today. Volunteer corn can be a major yield robber in soybean: Research conducted by Bill Johnson at Purdue University found that soybean yields can be reduced by populations of 8,000 to 16,000 volunteer corn plants/acre (Johnson, et. al., 2011). Although this population is similar to the population of volunteer corn that impacted corn yield in the U of MN trials described above, previous work by South Dakota State University demonstrates that volunteer corn is much more competitive in soybean than corn (Alms et al., 2007). Similar populations of volunteer corn (800 to 14,000 plants/acre) resulted in yield losses ranging from 0 to 13% in corn while losses in soybean ranged from 0 to 54%.

Yield impacts are not the only concern with volunteer corn in soybean. Volunteer corn can act as a bridge between corn crops for corn rootworm, and potentially encourage the development of resistance to Bt-corn rootworm hybrids (Potter, 2012). For long-term management of corn rootworm, control of volunteer corn in soybean is recommended.

Volunteer Corn Control Options in Soybean:

There are several effective herbicides that can be used to control volunteer corn in soybean. According to Jeff Gunsolus, U of MN Extension Weed Specialist, herbicide options include products with the ACCase mode of action such as: Assure II (quizalofop), Fusilade DX (fluazifop-P), Select Max (clethodim), and Fusion (fluazifop-P and fenoxaprop) (Gunsolus, 2009). Poast Plus (clethodim) is not as active on volunteer corn as the other products in this mode of action. The ACCase products are generally targeted on 12- to 24-inch tall corn. Another option is the ALS inhibitor Raptor, which is targeted to smaller volunteer corn (2 to 8 inch). For further details, check out the Minnesota Crop News article on volunteer corn management at http://blog.lib.umn.edu/efans/cropnews/2009/06/volunteer-corn-management-in-c-1.html.

Always check the herbicide label for the appropriate application rate and timing, information about tank-mixing with other products, and adjuvants guidelines. Row cultivation is also a viable option for control of volunteer corn in soybean.

Summary:

--Corn yield can be reduced by populations of volunteer corn. Volunteer corn populations of at least 8,000 plants/acre were needed before yield losses were observed in U of MN research trials.

--Volunteer ear clump populations simulating 2 and 5% ear drop contributed less to yield losses than the volunteer corn plant populations evaluated.

--Options to control volunteer herbicide resistant (HR) corn in HR corn are limited. Depending on the HR traits used, cultivation may be the only option for control when volunteer corn populations in corn are high enough.

--Volunteer corn is more competitive with soybean than corn, and soybean yield can be affected by populations of volunteer corn at 8,000 to 16,000 plants/acre.

--There are several effective tank-mix options with glyphosate for control of volunteer corn in soybean.

--Volunteer corn control in soybean should be considered not only for potential impacts on yield, but also for potential issues with long-term management of corn rootworm.

Acknowledgements:

Funding for the University of MN Volunteer Corn in Corn trial was provided by Monsanto Company.

References:

Alms, J., M. Moechnig, D. Deneke, and D. Vos. 2007. Competitive ability of volunteer corn in corn and soybean. Proc. North Central Weed Sci. Soc. 62:14.

Gunsolus, J. 2009. Volunteer Corn Management in Corn and Soybean. Minnesota Crop News. http://blog.lib.umn.edu/efans/cropnews/2009/06/volunteer-corn-management-in-c-1.html

Johnson, B., C. Krupke, and P. Marquardt. 2011. Volunteer corn: A pain in our Roundup Ready crops. Online Webinar, Plant Management Network. http://www.plantmanagementnetwork.org/edcenter/seminars/VolunteerCorn/player.html

Potter, B. 2012. Southwest Minnesota IPM stuff. Issue 7. http://swroc.cfans.umn.edu/prod/groups/cfans/@pub/@cfans/@swroc/documents/asset/cfans_asset_390134.pdf

On Farm IDC Management Strip Trials

2012-05-04T02:34:59Z

Daniel Kaiser

University of Minnesota Soil Fertility Specialist

Research on Iron Deficiency Chlorosis (IDC) has been identifying methods to manage the problem for soybeans. Since 2010 research has been conducted using strip trials within farmers' fields. Currently we are looking for a 5 acre area to conduct a field study looking at the effect of Soygreen and oat cover crops on areas of the field that range from no-IDC to severe IDC. Our goal is to determine the economic benefits of the treatments on varying IDC severity within fields planted with two soybean varieties with varying tolerances to IDC.

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Four field trials have been conducted since 2010. At two of the locations there was severe yield reduction from IDC. In sever areas, in-furrow application of an EDDHA-Fe fertilizer such as Soygreen significantly increased yield by an average of 5 to 6 bushels across the entire trial, and by as much as 10 bu/ac or more in the severe areas. The oats cover has also shown some positive yield benefits in sever IDC field areas. When comparing varieties, there was a large yield benefit with the variety that was less tolerant to IDC, but the tolerant variety still overall produced a higher yield level when IDC was present. When there was no IDC the less tolerant variety out yielded the tolerant. This indicates that 1) planting a tolerant variety is still the best option and 2) the application of EDDHA-Fe fertilizer in-furrow is advisable if possible in areas moderately or severely affected by IDC. A summary of the current and past work on this subject is available in the new publication "Managing iron deficiency chlorosis in soybean".

The area needed for this study is about 5 acres preferably with some variability in the severity of IDC. Our current research studies have been located in western Minnesota between highways 212 and 12. Compensation for the study area is available and all plot work from planting until harvest has been completed by the soil fertility research group at the University of Minnesota. Planting and harvesting are completed using small plot research equipment. Our goal has been to provide information on site specific management of soil fertility issues around the state of Minnesota. Advancements in variable rate technology have made it easier to vary inputs and studies like these have been crucial in determining the how to approach these problems with variable rate technology and whether it is economic to do so.

Conservation Tillage Conference, Rochester MN, Feb 7-8 2012

2012-01-17T19:59:04Z

Learn how conservation tillage can save soil, time, fuel -- and money.

University of Minnesota Extension will host the seventh annual Conservation Tillage Conference and tradeshow Feb. 7 and 8, at the International Event Center in Rochester, MN.

The day-and-a-half-long conference will provide practical, how-to information on nearly every aspect of conservation tillage. Learn how conservation tillage can save soil, time, fuel -- and money. Besides saving valuable soil resources, conservation tillage has been proven to save $25-45/ac in tillage costs. And that's not including your time.

The day-and-a-half-long conference will provide practical, how-to information on nearly every aspect of conservation tillage.

"Whether you are an experienced steward looking to fine-tune what you are doing, a crop consultant who helps growers, or a novice looking to get your feet wet, you should put this conference on your calendar now," says Jodi DeJong-Hughes, Minnesota Extension tillage specialist and conference coordinator.

Experts from the University of Minnesota, neighboring states will present the results of extensive research comparing tillage systems, including strip tillage. In addition, experienced conservation tillage farmers will answer questions and provide management tips.

Conference topics include:

Precision Ag solutions

Weed species shift and control

Nutrient management in high residue systems

Strip intercropping management

Soil health with reduced till systems

Vendor Sessions: Learn about new equipment, cover crops and technology

The popular "Farmer Panel" will be back again, offering practical insights and management tips from experienced northern strip tillers and ridge tillers.

Also back is "Beer & Bull," your chance to pick the brains of other farmers, consultants and researchers in a relaxed, informal setting.

The conference will open with a provocative keynote speech from Robert Recker: "Yield, Profitability, and Sustainability: Where to go from here?" Bob is the owner of Cedar Valley Innovation and a retired John Deere engineer, researching strip intercropping. He studies corn growth on a row by row basis trying to unlock the secrets of using technology and the sun to farm smarter.

The Conservation Tillage Conference runs from 9:00 a.m. to 4:30 p.m. on Tues., Feb. 7th, and from 8:00 a.m. to 12:15 p.m. on Wed., Feb. 8th. The tradeshow will be open both days.

The registration fee is $150 per person, which includes nine continuing education units (CEUs). An early bird fee of $120 per person is offered for those registering by Jan. 25, 2012.

More information, including schedules, maps, contacts and exhibitor registration is available at www.TillageConference.com. Or contact Jodi DeJong-Hughes at 320-815-4112 or dejon003@umn.edu.