Watch for Imbibitional Chilling Injury to Soybean in 2013

Imbibitional chilling injury is an annual issue associated with field corn but we rarely associate this damage to soybean. Why am I raising this red flag in 2013… many reports of soybean seed containing low seed water content (dependent upon the area where the seed was grown). Bedi and Basra (1993), defined imbibitional chilling injury as sensitivity of seed to a combination of low seed water content and imbibition at cold temperatures. As we all know some of our 2013 soybean seed is of decreased seed quality caused by the drought of 2012. We couple this fact with the current forecast and our eagerness to plant and I foresee potential issues on the near horizon.  The challenge for growers and agronomists is the strong genetic predisposition for this phenomenon. Bramlage et al (1979) screened soybean cultivars for sensitivity to imbibitional chilling injury. All were susceptible to some injury but that susceptibility varied greatly. Some showed no injury at 45° F (7 C) whereas others were damaged at 63° F (17 C). This means as your scouting and trying to deduce stand issues your suspect field may look like a train wreck whereas neighboring fields look great.        

Lastly I know the question of seed treatments will arise. It is unclear to me the role that todays seed treatments or polymer coatings have in mitigating imbibitional chilling injury. Therefore unless you are absolutely certain you have high quality seed that is 13% moisture with a perfect seed coat I would suggest we just wait a week for warmer weather before we start pounding our seed into this cold wet soil. 

WI Soy Podcast with Pam Jahnke: Soybean Seed Quality and Chilling Injury

Literature cited.

Bedi, S. and A.S. Basra. 1993. Chilling injury in germinating seeds: basic mechanisms and agricultural implications. Seed Science Research. 3:219-229.

Bramlage, W.J., A.C. Leopold, and J.E. Specht. 1979. Imbibitional Chilling Sensitivity Among Soybean Cultivars. Crop Sci. 19:811-814.

2013 WI Soybean Yield Contest is Announced

The Wisconsin Soybean Marketing Board launches the 4th annual Wisconsin Soybean Yield Contest. The objective of this program is to encourage the development of new, innovative management practices and show the importance of sound cultural practices in Wisconsin soybean production.

Wisconsin soybean growers have until August 1, 2013 to enter the Wisconsin Soybean Yield Contest. Two winners from each of four geographical districts in the state will receive awards (Image 1.).  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 February 6, 2014 during the Corn/Soy Expo at WI Dells.  

For more detailed information regarding the program and contest rules please visit www.coolbean.info or 2013 Wisconsin Soybean Yield Contest Rules. 

Entry forms can be found at 2013Wisconsin Soybean Yield Contest Entry Form.

A list of the 2012 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 2013 growing season!

Image 1. Yield Contest Districts

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

With cold temperatures, snowfall, and ice accumulation predicted over the next two days (April 12 and 13) 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. Remember the winter wheat crop is just coming out of dormancy and remains in the tiller phase (Feekes 2). At this growth stage the wheat crop can withstand temperature down to 12 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)

Wheat Stand Assessment: I can tell you if it is alive..too early to say if it is dead!

Ice covered wheat fields coupled with strong corn and soybean prices and no field activity have growers and consultants considering tearing up their winter wheat fields. Before we get to crazy here are a few points to consider while we wait for spring to arrive.

1. As you look across your wheat landscape vibrant green patches will be interspersed with drab brown areas. The brown areas do not necessarily indicate those plants are dead.
   
    
   
   
   Growers and consultants can either reassess in a week or pull plants from the field and place in warm environments. Milk houses and kitchens work perfect. Root regrowth will appear from the crown and will appear as vibrant white roots as shown below.
   
   
   If plans do not recover our critical threshold for turning over a field is 12 to 15 live plants per square foot. Below this threshold is an automatic replant. For more detailed information on assessing winterkill please view Wheat Stand Assessment, Winterkill Yield loss, and Nitrogen Application.
2. Evaluate tiller number and make the N timing decisions. It is important to remember that the functional purpose of spring N is to 1. stimulate tillering and 2. provide crop nutrition. If ample tillering (> 70 tillers per square foot) has occurred growers can delay N applications up to pre-joint (Feekes 4-5; Zadoks 30). This practice will aid in minimizing early spring N loss. Applications of N made after this growth stage may lead to wheel track damage. If growers have < 70 tillers per square foot it is important to get across those fields as soon as possible to minimize yield loss due to low tiller/head counts. For more information on tiller counts and spring N timing please view my YouTube video entitled: Wheat Stand Assessment and Nitrogen Timing. 
3. Lastly the frost is coming out of the ground. Be cautious as you make your way out to the wheat fields to make your stand assessment or you will be spending your time or more importantly my time time digging out your truck!
   

WSMB Continues Enhanced Nematode Testing Program for 2013

Four out of every five animals on earth today is a nematode so it is not surprising that agricultural fields are home to many nematode species. Fortunately, most nematodes are beneficial to crop growth and soil health because their activities help decompose crop residues and cycle nitrogen and other nutrients. Pest nematodes do not threaten yield if their numbers remain low. The key to avoiding population explosions of nematode pests is to be proactive – know what the situation is and take appropriate measures when nematode numbers indicate a problem is brewing. 

The WSMB sponsors free nematode testing to help producers stay ahead of the most important nematode pest of soybean, the soybean cyst nematode (SCN) (Figure 1). 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 2013, the WSMB is again offering the expanded 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 at 
(freescntest@mailplus.wisc.edu).

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.

Management Summary of the 2012 WSA Soybean Yield Contest Finalists

Image 1. Geographic Divisions

2012 was the third year of the WSA sponsored soybean yield contest.  The format was changed in 2012 to allow more growers to compete against their peers from areas of Wisconsin that had equal yield potential.  Four geographic divisions were created based on county historic yield data (Image 1.).  As expected, the winning yields in each division were proportional to, and reflected the productivity of the regional yield potentials. 

A management summary of the nine finalists is as follows (Table 1.)

• The mean planting date was May 12^th
• The mean seeding rate was 156,000 seeds/acre.
• 67% used seed applied inoculant
• 89% used fungicide and insecticide seed treatments. 
• 56% used a foliar insecticide and a fungicide.
• 100% rotated following corn
• 67% were in a row spacing less than 30”

The most important variable that was key to high yields was variety selection.  Among this year’s first place winners, three of the four varieties planted were starred (not significantly different than the highest yielding variety) in the Wisconsin Soybean Variety Test Results. Other than variety selection, there was no single management factor that separated the winners from the other contestants. Yields achieved were the result of a combination of good management and favorable environmental factors.

Cultural Weed Management Practice Changes in the Midwest

Dr. Kevin Bradley from the University of Missouri is conducting an on-line survey across the Midwest to assess the changes that glyphosate-resistance has caused for cultural weed management practices and recommendations.  I have personally been through this survey and it is very simple and should only take a few minutes to complete.  This survey will only be up a short amount of time, so please if you’ve read this far please just quickly complete the survey now and help represent WI with a good response rate: https://www.surveymonkey.com/s/59GJBCX   

I thank you very much in advance! 

Vince M. Davis, Extension Weed Scientist

Shawn P. Conley, Extension Soybean and Small Grain Specialist