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, and drought have left some 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 surpassing $13.00 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 last year, 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 envirnoment 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)

Planting winter wheat into dry soil

Dry soil conditions have sparked many questions from growers on how best to establish their winter wheat crop. As we were reminded last year and this there is no substitute for rain (unless you have irrigation), however here are a few ideas to consider to mitigate your risk.

• Conserve soil moisture. If possible no-till your winter wheat. If this is not possible due to equipment limitations, limit your tillage passes across the field. 

• Increase your seeding depth (e.g. plant to moisture). As stated in the Top 7 Recommendations for winter Wheat Establishment: Wheat should be planted ~1.0 inch deep depending upon soil moisture conditions. Wheat planted more than 1.5 inches deep may result in death due to pre-mature leaf opening or poor tiller development and winter survival. 

• As a grower there is little you can due to prevent pre-mature leaf opening. This phenomenon is rare unless seeded extremely deep and compaction also occurs. 
• You can increase tiller development or effective head number by increasing your seeding rate. 
• I do not have yield loss or winter kill data implicitly from seeding depth experiments however deep seeding will delay emergence which may be similar to delayed planting. Data from our 2009 Lancaster and Arlington WI planting date experiments show that yield and winter survival decreased as planting date was delayed (Table 1.).
• Deeper planting may expose germinating and emerging wheat seed to greater potential for herbicide carryover. However if you explicitly followed the herbicide label restrictions for rotational crops you have a basis to contact the company if problems occur. Remember the label is the law.   

Table 1. Planting date effect on grain yield and winter survival at Lancaster and Arlington WI, 2009.
Lancaster, WI
Planting date	Grain yield (bu/a)	Winter survival (%)
17-Sep	74.9	88.5
30-Sep	68.3	70.0
13-Oct	54.2	58.0
Arlington, WI
Planting date	Grain yield (bu/a)	Winter survival (%)
18-Sep	101.9	83.8
1-Oct	93.3	55.3
17-Oct	73.9	30.

• Remember to use a fungicide seed treatment. Even though you are planting into dry soil and the overall pathogen load may be lessened, you are planting deeper and delaying emergence especially as soil temps continue to decrease. 

• Remember your crop insurance and planting date restrictions. In a spring seeded crop we would often say wait until it rains to establish the crop however we have a short window to get the crop established and still get your full crop insurance coverage. Please talk to your crop insurance agent for specific dates for your county.

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 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 14 days from R6 to R7. Note: we have seen crop development expedited the past few weeks due to heat and drought conditions. 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 9/7/13 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

Late Planted Drought Stricken Soybean II: More Valuable as a Forage or Green Manure?

Now that we have checked the label and determined we can legally harvest our soybean crop as a forage now lets consider the calendar for our full suite of options. The average number of days it will take from R6 (full seed) to R7 (beginning maturity) soybean is 15-18 days. If you are in R6 now look at your historic killing frost date and extended weather forecast. If the odds are in your favor roll the dice and cut the beans for grain. If you are not at R6 yet or there is a strong chance of a killing frost in your extended forecast prior to R7 lets realistically consider our options for best utilizing this standing soybean crop.

Option # 1: Soybean haylage considerations

• What is my realistic tonnage expectations?
• Late planted drought stricken soybean will yield ~1 to 2 tons of dry matter per acre.
• What is it going to cost me to harvest and put this crop up?
• The average cost on a hourly basis to harvest and ensile a soybean forage according to 2013 Iowa Farm Custom rate survey are as follows:  
• Mowing ($11.45 per hour)
• Swathing ($13.50 per hour)
• Haylage (chopping/hour/ ft head width; $12.71)
• Hauling ($ not listed))
• Fill silage bags ($10.15 per foot of bag)
• How should I price this crop?
• Soybean silage pricing will fall between good quality hay ($233.10 per ton) and poor quality hay ($112.50 per ton); personal communications from P. Hoffman and R Shaver.  Source: FeedVal 2012 predicted dairy feed prices and rankings for August 2013. V.E. Cabrera, P. Hoffman, and R. Shaver.
• If you were to price the soybean forage based on expected grain yield (assuming the crop would mature) and CBOT then realistic yield levels would range from 12 - 18 bu per acre at $14.35 per bu. Expected forage value range would be $172.20 to $258.30 per acre. 

Option #2: Green manure considerations

• I am tired of throwing money at this crop..........
• Though you will save on harvest costs the average cost of a plow down disk operation is $16.05 per acre.
• How much will I save on next years fertilizer bill?
• By not harvesting the crop you will not remove the 30# P and 85# K (estimated removal rates of P2O5 and K2O for 15-25 bu per acre soybean grain and straw (A2809)).
• You may contribute 20-40 pounds of N to next years corn or wheat crop. 
• I need the feed so this is not an option (please refer back to option #1 above).

Neither of these prove to be particularly attractive options. However I would encourage growers, crop consultants, and nutritionists to weigh the true economical value of each option carefully before proceeding.