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.

2014 WI Soybean Yield Contest is Announced

The Wisconsin Soybean Marketing Board launches the 5th 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 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.

Factors to Consider While Assessing Your 2014 Winter Wheat Crop

As the snow begins to melt and we finally put the 2013/14 winter behind us, many growers and consultants alike are beginning to venture out to their winter wheat fields to assess winter injury. Though it is a premature to make any rash decisions here are a few considerations for assessing your spring 2014 winter wheat stands.

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.
   

   

   2014 Arlington WI Winter Wheat Variety Trials

   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.

   

   Spring Root Regrowth in Winter Wheat

   
   If plants 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 remember that wheat grain in itself is only part of the revenue you capture with winter wheat. The price of winter wheat straw remains strong so please consider that revenue stream before any replant decisions are made.

WSMB Continues Enhanced Nematode Testing Program for 2014

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.

Figure 1. WI Counties Confirmed to Have SCN as of 2013.

In 2014, 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.