Should We Be Using Soybean Maturity Group as a Tool for Variety Selection?

Over the last decade I have noticed a subtle shift across much of the northern soybean growing region towards planting later maturity group soybeans. This shift, either conscious or unconscious, may be attributed to earlier planting dates, relatively favorable fall harvest windows, and the drive for maximum yield as influenced by high commodity prices. As with all trends sooner or later, we have a correction year: 2014 was that year for many farmers. As farmers, consultants, and the battered and bruised seed suppliers sort through the plethora of product offerings for 2015, a common question arises: "In 2015, how much weight should we really give to maturity group in these seed decisions?". For those of you with short attention spans like me, the short answer for soybean is not much....for the rest of you please read on to understand my reasoning.

In 2011, the WI Soybean Research Program published an article in the journal Crop Management entitled: "Optimal Soybean Maturity Groups for Seed Yield and Quality in WI" (Furseth et al, 2011). In this data set we looked at 893 varieties across 6 growing seasons (2004-2009) and three production regions in WI . Within each region we identified the optimal maturity group range for maximum yield. Those were 2.6-2.9, 2.1-2.4, and 2.0-2.2 for our southern, central and north central regions respectively.  After I make this provocative statement this is usually where the audience either falls asleep, starts texting their neighbor about the lame and inept speaker (me), or uses the restroom and fails to hear as the great Paul Harvey would say ......the rest of the story.

Within each figure below you will also notice a maroon line directly below the black yield regression slope. This maroon line indicates the range of maturity groups that lie within 10% of maximum yield. These figures suggest that regardless of growing region in WI growers can select a variety that is almost one full maturity group earlier than the optimal maturity group range for maximum yield and still be within 10% of maximum yield.

These data further support Joe Lauer's assertion that "Every hybrid (or in our case cultivar or variety) must stand on its own" (Happy Thanksgiving JGL, you were positively quoted in a soybean article). In our recently released 2014 WI Soybean Variety Test Results book the maturity group range that included a starred variety (starred varieties do not differ from the highest yield variety in that test) was 1.9-2.8, 1.1-2.4,and 0.9-2.0 in our southern, central and north central regions respectively. This amplifies my assertion that the "relative" maturity group rating is trumped by individual cultivar genetic yield potential.

Lastly, since I brought it up lets also discuss our "relative" soybean maturity group rating system. If anyone has ever observed a multi-company variety trial in the fall, they may have notice many differences in maturity amongst varieties that have the same MG rating. For example in our 2014 Southern Region Glyphosate Tolerant Soybean Test we noted a 7 day maturity date range among all the 2.4 maturity group varieties listed. This may not seem important at the end of September, but in years when we plant late (Table 1), have a cool growing season and apply a fungicide those few days may matter. 

As seed decisions are made for 2015, it is fine to keep the relative maturity rating on your check list, just don't have it near the top!

Table 1. Calendar date for reaching R5 (beginning seed fill) and R7 (beginning maturity) growth stage (G.S.) by planting date and maturity group (M.G.) for the 2014 growing season at Hancock WI.

		Timing of G.S. Initiation
Planting Date	M.G.	R5	R7
5-May	1.9	29-Jul	3-Sep
	2.1	3-Aug	13-Sep
	2.1	29-Jul	3-Sep
	2.1	29-Jul	3-Sep
	2.3	29-Jul	3-Sep
	2.3	1-Aug	6-Sep
	2.4	3-Aug	6-Sep
	2.5	29-Jul	6-Sep
	2.5	30-Jul	6-Sep
	2.5	31-Jul	13-Sep
22-May	1.9	12-Aug	12-Sep
	2.1	9-Aug	20-Sep
	2.1	12-Aug	16-Sep
	2.1	12-Aug	20-Sep
	2.3	12-Aug	20-Sep
	2.3	9-Aug	20-Sep
	2.4	12-Aug	16-Sep
	2.5	12-Aug	16-Sep
	2.5	12-Aug	20-Sep
	2.5	12-Aug	20-Sep
11-Jun	1.9	23-Aug	27-Sep
	2.1	23-Aug	2-Oct
	2.1	23-Aug	30-Sep
	2.1	23-Aug	2-Oct
	2.3	23-Aug	2-Oct
	2.3	23-Aug	30-Sep
	2.4	23-Aug	1-Oct
	2.5	23-Aug	2-Oct
	2.5	23-Aug	2-Oct
	2.5	23-Aug	2-Oct

Literature cited: 

Furseth, B. J., Zhao, Y., Conley, S. P., Martinka, M., and Gaska, J. 2011. Optimum Soybean Maturity Groups for Seed Yield and Quality in Wisconsin. Crop Management. Online. Crop Management doi:10.1094/CM-2011-0622-01-RS.

Finalists for the 2014 WI Soybean Yield Contest are Announced

The 2014 growing season proved to be yet another challenging year for many WI soybean growers.  Given these widespread challenges, we again experienced great interest in the 2014 WSA/WSMB Soybean Yield Contest.  The top two entries in each division (in no particular order) were:

Division 4: 

• Tim McComish, Shullsburg (planted Channel 2402R2 Brand)
• Kevin Bahr, Darlington (planted Channel 2402R2 Brand)

Division 3:

• Travis Van De Hey, Kaukauna (planted DuPont Pioneer P22T69R)
• Ron Ellis, Walworth (planted Jung 1250RR2)  
• *WI Bean Team (Adam Gaspar, David Marbuger, Ethan Smidt), Madison (planted DuPont Pioneer P28T33R) 

*The WI Bean Team is ineligible for official prizes as they are grad students of Dr. Conley; however their efforts are still unofficially recognized.  

Division 2:

• Steven Stetzer, Melrose (planted NK Brand 17G8) 
• Steven Kloos, Stratford (planted  DuPont Pioneer 91Y90) 

Division 1: 

• Paul Graf, Sturgeon Bay (planted DuPont Pioneer 90Y90) 
• Jerry Koser, Almena (planted DuPont Pioneer 91M10)

The final ranking and awards will be presented at the 2015 Corn Soy Expo to be held at the Kalahari Convention Center, Wisconsin Dells on Thursday January 29^th during the WSA/WSMB annual meeting.

The contest is sponsored by the WI Soybean Program and organized to encourage the development of new and innovative management practices and to show the importance of using sound cultural practices in WI soybean production.

For more information please contact Shawn Conley, WI State Soybean Specialist at 608-262-7975 or spconley@wisc.edu

Fall is Still a Good Time to Sample for SCN and Other Plant Parasitic Nematodes

The WI Soybean Marketing Board (WSMB) sponsors free nematode testing to help producers stay ahead of the most important nematode pest of soybean, the soybean cyst nematode (SCN). Eggs of SCN persist in the soil between soybean crops so a sample can be submitted any time that is convenient. The soil test report indicates the number of eggs in the sample and is useful for selecting the right variety for the next soybean crop. Retests of fields planted with SCN-resistant varieties over multiple years shows how the nematode population is responding to variety resistance and provides an early warning should the nematode population adapt to host genetics.

In the spring of 2012, the WSMB expanded the nematode testing program to include other pest nematodes in addition to SCN. These nematodes are less damaging to soybean than SCN but can cause enough yield loss to warrant treatment. As is the case for SCN, there are no rescue treatments for nematodes so the primary purpose of this year’s soil test is to plan for next year’s crop. Soil samples collected in corn for nematode analysis have predictive value for explaining yield if they are collected before the corn V6 growth stage. Sampling early in the season will provide information about the risk potential for the current corn crop AND the next soybean crop.

The assays used to recover nematode pests other than SCN in soil require that the nematodes are alive. So, it is important to keep the samples moist and at least room temperature cool. Collecting a sample that includes multiple cores ensures that there will be plenty of root pieces to assay. It is not necessary to include live plants in the sample. The soil test report will indicate which pest nematodes are present and at what quantities and their damage potential to soybean and corn based on the numbers recovered.  

Free soil sample test kits are available now and can be requested from Jillene Fisch at (freescntest@mailplus.wisc.edu) or at 608-262-1390.

For more information on SCN testing and management practices to help reduce the losses from this pest, please contact: Shawn Conley: spconley@wisc.edu; 608-262-7975 or visit www.coolbean.info.

Remember the first step in fixing a nematode problem is to know if you have one! The WSMB sponsored nematode testing program provides you that opportunity.

Harvest Considerations for Variable Soybean Maturity

Variable soil types, knolls, flooding and drought have left many growers with extreme in-field variability of soybean maturity.   There are areas in fields where the soybean seed is 13% or less moisture adjacent to areas with green seed.  The prevailing question is “When should the grower harvest?” Obviously there is no simple answer, as each field is different. However here are a set of guidelines to consider:

1.    The easiest answer is harvest the field at two different times. Take what is dry today and come back in two weeks and harvest the rest. The challenge with this approach is that today’s equipment is large and not easily moved from field to field. Furthermore many growers rent or own land over large areas where this is impractical and the whole field must be taken at once. So……

2.     The next simple answer is wait until the whole field is ready to go. As noted in our article Drought Induced Shatter, we are seeing areas across the Midwest where shattering is occurring. The general rule of thumb is 4 seeds per square foot = one bushel yield loss. At local cash prices dipping below $10.00 per bushel this is hard to see happen and not harvest. Furthermore, waiting will also lead to moisture loss in the field. As we learned the past few years, you do not get compensated for harvesting below 13% moisture. So…..

3.     If growers are concerned with shatter and/or other harvest losses the next logical approach is harvest ASAP. This opens a whole new can of worms. Harvesting ASAP will lead to a mixture of dry, wet, and immature (green) soybean seed. Be aware that if you harvest this mixture regardless of the ratio, your combine moisture sensor may not detect the correct moisture, be prepared for that initial shock when the elevator tests the grain. Next be prepared for the dockage. Most combines will leave more beans in the pod when they are wet or immature.   These beans may end up on the ground or in the grain tank as unthreshed soybeans. Harvesting seed with this variability will be very similar to handling frosted soybean seed so discounts may occur due to moisture shrink, damage (green beans are considered damage), foreign material (this is usually higher when harvesting wet beans), test weight, and heating. If you choose on farm storage to address some of the dockage concerns please refer to Soybean Drying and Storage for questions.  

4.  The last consideration I would bring forward is that the mature areas are likely going to be the low yielding pockets due to drought whereas the yet to mature areas will likely be the higher yielding areas within the field. So, in short, which yield environment would you rather focus your time and efforts to protect?  

      The question ultimately comes down to the bottom line and where you make the most $$$. If shatter is not occurring and you have good equipment that does not incur significant harvest loss, will harvesting grain that is over-dry make you more money than harvesting seed that may incur significant dockage? My guess is yes but you tell me!

Image 1. Variable Maturity (M. Rankin)

Odds My Soybean Crop Will Mature Before A Killing Frost Hits

The Wisconsin soybean crop is slowly starting to mature, however many growers and crop consultants are still concerned about the risk of frost damage to late planted fields.  In soybean an extended period (several hours) of temperatures 28 degrees F or lower is required to completely kill a soybean plant, though temperatures 32 degrees or less can still damage top growth. Those growers considering the state of their soybean crop and wondering the odds of making it to maturity before significant yield loss occurs must first correctly identify the soybean growth stage.

Once the crop growth stage has been determined we can estimate the number of days it will take for your field to reach R7 or physiological maturity.  Across our Arlington and Hancock field sites in 2014 it has taken 5-8 days to go from R3 to R4, 7-8 days to go from R4 to R5, 10-14 days from R5 to R6 and 15-20 days from R6 to R7. As a point of reference our June 20th planted soybean at both locations just hit R6 this week. Next using the three figures below that show the 10th percentile, median, and 90th percentile date when you can expect a freeze event you can estimate the risk of a frost based on your crop growth stage.

For example: If you lived in SW Marathon county there is a 10% chance that a freeze event would have occurred prior to September 11-20, a 50/50 chance that a freeze event would occur prior to September 21-30, and a 90% chance a freeze event would have occurred prior to October 1-10. So if your soybean crop just entered the R5 crop growth stage today 9/8/14 there is a greater than a 50/50 chance that crop won't make grain based on historical weather data.

Lastly if you are concerned about a freeze event please refer to Table 1 below that provides yield loss estimates of freeze damage by crop crop stage. This may help you decide whether you should risk taking the late planted soybean field as a grain crop or would that field be more valuable as a forage or green manure?

Table 1. Soybean Response to Freeze Damage
Growth Stage	Yield Reduction
R4 - Full pod	70%-80%
R5 - Beginning seed	50%-70%
R6 - Full seed	15%-30%
R7 - Beginning maturity	0%-5%
R8 - Full maturity	0%

Source: Saliba et. at. Kansas State University, 1982

Do Not Plant Saved Wheat Seed This Fall!

The race to turn the 2014 wheat crop into 2014/15 seed is on and early lab samples confirm that the percent germination from on farm sampled wheat is low. The Wisconsin Crop Improvement Association has received over 100 samples to date and over 30% have exhibited visual signs of Fusarium Head Scab (FHB) or scab. The % germ from the infected samples range from 53 to 98% (variety dependent) with an average % germ of 79%. First class certified wheat requires a minimum % germ of 85%. Furthermore invest in a wheat fungicide seed treatment this fall. Seed applied fungicides can increase % germination. On a small sample size (N = 4) the average percent germination from the addition of a seed applied fungicide increased average germination from 76 to 93%. Lastly all signs point to a late wheat establishment season. With that in mind remember to plant certified or private new seed, use a fungicide seed treatment and starting increasing your seeding rate after October 1. For more information on wheat establishment please see: Top 7 Recommendations for Winter Wheat Establishment in 2014.

2014 WI Soybean Yield Contest Entry Deadline is September 1

Wisconsin soybean growers have until September 1, 2014 to enter the Wisconsin Soybean Yield Contest. Two winners from each of four geographical districts in the state will receive awards (Image 1.).  "Please note the divisional lines were redrawn for 2014 based on a rolling 10 year average yield".   The first place award in each district includes a $1,000 cash prize; second-place honors include a $500 prize. Winners will be selected for having the highest soybean yield based on bushels per acre at 13% moisture. The awards ceremony is scheduled for January 29, 2015 during the Corn/Soy Expo at WI Dells.  

For more detailed information regarding the program and contest rules please visit www.coolbean.info or 2014 Wisconsin Soybean Yield Contest Rules. 

Entry forms can be found at 2014Wisconsin Soybean Yield Contest Entry Form.

A list of the 2013 winners and a management summary of their practices is also provided. 

For more information please contact Dr. Conley at spconley@wisc.edu. Good luck and have a safe and productive 2014 growing season!

Image 1. Geographic Division Map.

Think Twice Before Applying Nitrogen to Poorly Nodulated Soybean Fields

Over the last 3 days my phone, email and twitter account has been blowing up with questions surrounding poorly nodulated soybeans and my thoughts regarding applying foliar nitrogen to alleviate those symptoms. I have been reluctant to write this article for two reasons. 

1. This article will contradict some of my colleagues’ thoughts (Identifying and responding to poor nodulation in soybean) however I would agree with their scenario of applying nitrogen to early-seeded, non-nodulating soybean planted on virgin ground.
2. I like to speak from data and I don't have a ton of data to speak from 

So with these caveats in mind here is my thought process for asking growers and crop consultants to think twice before applying nitrogen to poorly nodulated soybean fields. 

First lets start with the problem. A record number of soybean acres were planted in 2014. To get those acres both virgin ground as well as long term continuous corn acres were converted to soybean. For the most part (unless someone forgot) those acres did receive a 1x or 2x rate of inoculant. Unfortunately the perfect storm of delayed planting, poor planting conditions, compaction and poor environmental conditions all led to saturated anaerobic soil conditions that limited rhizobia infection.  These poor establishment conditions were then followed by poor early season growth conditions (cool saturated soils) delayed herbicide applications, increased herbicide rates and weed competition that further stressed the plants and limited infection. 

So with all this stress in mind why do I suggest no additional nitrogen?

1. Once soils dry out and aerobic conditions resume the ethylene stress response in plants quickly dissipates and normal N-fixation can resume. This will lead to nodulation occurring on lateral roots as infection occurs behind the root tip of actively growing root. Furthermore once plant roots resume normal growth they will be able to take advantage of residual and mineralized soil nitrogen which will alleviate the pale green coloration.
2. Be realistic with your yield potential. Many of the fields in question are late planted, with stunted soybeans and thin stands.  A short soybean crop will require much less N than a big one.  Salvagiotti et al; (2008) indicated in "Nitrogen uptake, fixation and response to fertilizer N in soybeans: A review" that the most likely soybean response to additional nitrogen was in high yield environments. 
3. Be realistic with your expected yield loss in non-nodulated virgin soil environments. Somehow the idea of a 20 bu yield loss has been floating around the coffee shops. Our most recent data from a virgin soil site in 2010 showed an average +4.6 bu yield gain (range: -0.9 to 9.6 bu depending upon product) from inoculants. The untreated uninoculated check averaged 73.5 bu per acre. Also remember no history of soybean = low soil borne disease pressure and beautiful healthy roots!
4. What are your 2014 beans marketed at $14.00 or $11.92 and dropping?
5. What source of nitrogen are you going to apply and what is that cost per pound coupled with application cost and crop damage?

•  Simple math equation (please insert your number for mine). 70 pounds of urea @ $0.55 per pound  + $8 application cost + $10.26 yield loss from running down soybeans (90 foot applicator = 1.9% on 45 bu $12 beans) = $56.76. At $12 soybeans you would need 4.73 bu to break even. Our average response in 2010 was 4.6 bu.

I know not everyone will agree with my thought process but understand that I am cognizant of the realities of today’s production ag world….high land rent costs coupled with high commodity prices = grower risk aversion. If you do apply nitrogen please leave at least one yield check and be fair to that yield check placement. Given our climate variability this will not be the last time we deal with this question and having data to streamline recommendations in future years makes us all better stewards and producers.

*Reviewed by Dr. Seth Naeve, Extension Soybean Agronomist, University of Minnesota.

Harvest Considerations for a Fusarium Head Blight (Scab) Infected Wheat Fields

Subsection taken from Smith and Conley 2014. Fusarium Head Blight and Other WinterWheat Diseases in Wisconsin, 2014

A survey of the Wisconsin Winter Wheat Variety Trials indicates that some fields will be at risk for dockage or outright rejection of winter wheat grain later this month. Environmental conditions that lead to high risk coupled with susceptible genetics and the grower’s inability to simply get fungicides applied all contributed to this issue.  As we move forward into harvest here are a few point to consider to help mitigate dockage and deoxynivalenol (DON or vomitoxin) risk moving forward.

1.      Scout your fields now to assess risk. Wheat near our Fond du Lac location is maturing making it very difficult to assess the incidence and severity of the infection. Understanding a fields risk will help growers either field blend or avoid highly infected areas so entire loads are not rejected.

2.      Adjust combine settings to blow out lighter seeds and chaff. Salgado et al. 2011 indicated that adjusting a combine’s fan speed between 1,375 and 1,475 rpms and shutter opening to 90 mm (3.5 inches) resulted in the lowest discounts that would have been received at the elevator due to low test weight, % damaged kernels, and level of the mycotoxin deoxynivalenol (DON; vomitoxin) present in the harvested grain.  

3.      Know your elevators inspection and dockage procedure (each elevator can have a different procedure).

4.      Scabby kernels does not necessarily mean high DON levels and vice versa.

5.      DON can be present in the straw so there is concern regarding feeding or using scab infected wheat straw.  DO NOT use straw for bedding or feed from fields with high levels of scab (Cowger and Arellano, 2013).

6.      Do not save seed from a scab-infected field. Fusarium graminearum can be transmitted via seed. Infected seeds will have decreased growth and tillering capacity as well as increased risk for winterkill.

7.      Do not store grain from fields with high levels of scab.  DON and other mycotoxins can continue to increase in stored grain.

8.      For more information on Fusarium head blight, visit this information page: http://fyi.uwex.edu/fieldcroppathology/fusarium-head-blight-scab-of-wheat/

References

Cowger, C., and Arellano, C. 2013. Fusarium graminearum infection and deoxynivalenol concentrations during development of wheat spikes. Phytopathology 103:460-471.

Salgado, J. D., Wallhead, M., Madden, L. V., and Paul, P. A. 2011. Grain harvesting strategies to minimize grain quality losses due to Fusarium head blight in wheat. Plant Dis. 95:1448-1457.

Bloomin Beans, Glyphosate, and Wheel Track Damage

The WI soybean crop ranges anywhere from just planted (JP) to beginning flower (R1). As we enter the soybean reproductive growth phase there are a few things to keep in mind. The first is that soybean will produce flowers for ~3 to five weeks, depending upon planting date and environment. During that time soybean will abort anywhere from 20 to 80% of the flowers that they produce. Generally it is the first and last flush of flowers produced that are most likely to be aborted.

R1 soybean growth stage

Next, the timing window for glyphosate applications in our early planted soybean is quickly closing. Glyphosate labels indicate that applications can be made through R2 or full flower. The R3 growth stage begins when one of the four top nodes with a fully developed leaf has a 3/16 inch long pod. Applications made after the R3 stage begins are off-label applications. On average it takes ~ 4 days to move from R1 (beginning flower) to R2 (full flower) and ~10 days from R2 to the start of R3 (beginning pod).

Last but not least, wheel track damage made from ground applications may start to reduce yield. Sprayer wheel traffic from first flower (R1) through harvest can damage soybean plants and reduce yield (Hanna et al. 2008). Our research suggests that an adequate soybean stand (more than 100,000 plants per acre) planted in late April though mid-May can compensate for wheel tracks made when a field is sprayed at R1. Yield loss can occur, however, when wheel tracks are made at R1 or later in thin soybean stands (less than 100,000 plants per acre) or late planted soybeans. Regardless of stand, plants could not compensate for wheel tracks made at R3 (early pod development) or R5 (early seed development). The average yield loss per acre is based on sprayer boom width (distance between wheel track passes). In our trials yield losses averaged 2.5, 1.9, and 1.3% when sprayer boom widths measured 60, 90, and 120 foot, respectively. Multiple trips along the same wheel tracks did not increase yield loss over the first trip.

Spraying soybean at the R1 crop growth stage

Wheel track damage to drilled soybean at R1

Hanna, S., Conley, S. P., Shaner, G., and Santini, J.  2008.  Fungicide application timing and row spacing effect on soybean canopy penetration and grain yield.  Agronomy Journal: 100:1488-1492.

Delayed Planting: Top Three Considerations for Switching Corn Acres to Soybean

A tremendous number of corn and soybean acres have been planted over the past 10 days; however C, NC, and NE WI continue to get hammered for the second year in a row with awful planting weather.  It seems like those growers are constantly 1/2 day away from the soil being fit to go. Over the past two weeks we have  discussed maturity switch dates for corn grain, corn silage and soybean cultivars. What about switching corn ground to soybean.

1. Check your herbicide label. Several burn-down or early pre-plant programs have labels for both crops. However tankmix partners or rates may differ between the two. Maker sure you verify rates, timings, and plant back restrictions before you make the switch. Even with the intense rainfall we have experienced don't bank on these products being gone.   

2. Fall applied anhydrous or spring applied urea. How much N is too much to not even consider the switch?  Biologically I don't think that number really exists. Economically that number is a moving target given yield penalty, corn drying costs, etc. What I can surmise and you would likely agree with is that over the last 4 weeks the amount of N readily available to the late planted corn crop or in this case the soybean crop has declined, though some N is still readily in the soil profile. We were somewhat prepared for this question a year ago given the likelihood of residual N following the 2012 drought stricken corn. In that article I stated:

In excess situations soybean will generally utilize the background nitrogen prior to initiating maximum N fixation. This may lead to luxurious early season growth, which in fields with a history of white mold, may cause problems if weather conditions are conducive. High soil N reserves may also lead to increased lodging. In either case, manage your soybean crop accordingly to minimize risk of white mold or lodging. This can be accomplished through variety selection (e.g. white mold tolerance, short statured soybean cultivars or good lodging tolerance), decreasing seeding rates, and proper scouting to time fungicide applications if needed.    

The only change I would make to this paragraph would be to increase seeding rates to compensate for delayed planting. Remember when I wrote this article in 2013 I was under the assumption that soybean would be planted the first week in May not the first week in June.

3. Should I use an inoculant even when excess N is present? The simple answer is yes and here is why....excess N limits N fixation (Lit review excerpt quoted with permission from Eric Wilson; M.S. Thesis; Shaun Casteel Adviser; Purdue University)

Nitrate uptake of soybean plants did not appear to directly damage the BNF capacity (Streeter, 1985; Arrese-Igor et. al, 1997). Streeter (1985) concluded that carbohydrate deprivation and nitrate toxicity did not inhibit BNF. It is hypothesized that additional nitrate increased the oxygen diffusion barrier of the nodule, which limited oxygen supply and restricted nitrogenase activity and nodule respiration (Vessey and Waterer, 1992). This hypothesis was supported by Arrese-Igor et al., 1997. However, additional oxygen supplied to the nodules did not markedly increase BNF (Heckmann et al., 1989; Serraj et al., 1992).

Literature cited:

Arrese-Igor, C., F.R. Minchin, A.J. Gordon, and A.K. Nath. 1997. Possible causes of the physiological decline in soybean nitrogen fixation in the presence of nitrate. Journal of Experimental Botany 48:905-913.

Heckmann, M.O., J.J. Drevon, P. Saglio, and L. Salsac. 1989. Effect of oxygen and malate on NO₃- inhibition of nitrogenase in soybean nodules. Plant Physiology 90:224-229.

Serraj, R., J.J. Drevon, M. Obaton, and A.Vidal. 1992. Variation in nitrate tolerance of nitrogen-fixation in soybean glycine-max. - Bradyrhizobium symbiosis. Journal of Plant Physiology 140:366-371.

Streeter, J.G. 1985. Nitrate inhibition of legume nodule growth and activity .2. short-term studies with high nitrate supply. Plant Physiology 77:325-328.

Vessey, J.K., C.D. Raper, and L.T. Henry. 1990. Cyclic variations in nitrogen uptake rate in soybean plants - uptake during reproductive growth. Journal of Experimental Botany 41:1579-1584.

Recent Cold Temperatures will have Little Impact on WI Winter Wheat Crop

With cold temperatures predicted over the next few days (May 15-17) there are some questions regarding the potential impact on this year’s winter wheat crop. Based on the predicted temperatures reported, widespread significant crop injury is unlikely. The winter wheat crop is several weeks behind "normal" and remains in the tiller (Feekes 2) to jointing (Feekes 6) growth stages. At these growth stages the wheat crop can withstand temperature down to 24 degree F for up to 2 hours before crop injury occurs (Table 1).  For more detailed information I have attached a link to a publication entitled Spring Freeze Injury to Kansas Wheat.  For ease I have also removed a table from that publication to stress the importance of growth stage on damage potential  (Table 1).

Lastly, growers may also be questioning the impact of temporary flooding within fields. Though crop injury from this flooding may occur that damage will likely be limited due to cool temperatures and slowed crop respiration. Any crop injury that does occur will directly be related to the duration of the flooding event.

Table 1.  Wheat Resistance to Freeze Injury (From: Spring Freeze Injury to Kansas Wheat)

Top 5 Recommendations for Soybean Establishment and Yield

I awoke this morning to the gleeful announcement from my two year old yelling at the top of her lungs "Dad....snow....outside''. I feigned excitement only because I know we are still missing 75 entries for our soybean variety test program (hint hint to those that are delinquent) and suboptimal soil temperatures (Figure 1).

Figure 1. Soil temperature (2") at Arlington WI April 9-15, 2014.

As past experience has taught many of us that live in the "frozen tundra", a WI spring can appear rapidly so here are a few thoughts to mull over before we all get busy and throw recommendations out the window to get those crops in the ground.

1. Planting date matters for northern soybean growers. Dr. Specht et al. from UNL did a very good job discussing "Why planting soybean early improves yield potential".  Furthermore, our recent planting date data is also very supportive of early planting.  Not only have we seen a synergistic yield response with today's genetics to early planting, we also average ~0.36 bu per day cost to delaying planting past the first week of May (please see Figure 2. below).   

Figure 2. Soybean yield response to planting date at Arlington and Hancock WI 2012-13.

2. Use a fungicide and insecticide seed treatment. Given today's seed input costs and commodity price our data suggests reduced economic risk and increased profitability utilizing these inputs.

3. Plant your soybean seed 1" deep. I know I know MSU just came out with new information regarding soybean planting depth, but I am not completely sold on planting early soybean at 1.75 inches in Wisconsin. If it is June 5th, soil temps are 72 degree F, and I am planting to moisture due to drought conditions and no rain in the forecast then maybe I could be convinced.   

4. In short....if rotating with corn no tillage is required!

5. Last but certainly not least, invest in a residual herbicide program for your soybean crop. Not only is it an effective tool for herbicide resistance management (remember we have two confirmed (one suspect) glyphosate resistant weed populations in WI) it also widens the application window for glyphosate and it often provides growers with a positive ROI.