Soybean Harvest in Wisconsin is at a Crawl

Wisconsin growers are struggling to get their soybean crop harvested and we are no exception. As of today the WSRP (WI Soybean Research Program) have only harvested 18% of all of our plots and projected weather outlooks show no real extended harvest window in sight. One of our combine crews just called from Chippewa Falls, WI minutes ago. We opened up the field and were treated with soybean moisture's in the low to mid 20's. Nothing left for us to do but shut it down for the day and hope for some drying weather. As we continue to struggle through harvest soybean seed quality, drying, and storage issues will continue to arise. Below are a few sources of information that may prove useful as harvest pushes forward.

• Soybean seed quality: Be aware of the differences between sclerotinia, phomopsis, and purple seed stain. Please see Common Soybean Diseases in Wisconsin, Soybean Quality Issues in 2009, and Discolored Soybean Seed.
• Soybean Grain Drying, Conditioning and Aeration: Drying Soybeans in 2009, Harvesting, Drying and Storing Frost-Damaged Corn and Soybeans and, Drying Soybeans Requires Special Considerations
• More info on grain quality please see Chat n chew cafe and grain harvest.
  

Note of Interest: John Gaska called from the field after the initial post and indicated that all of the pods he inspected remain tightly sealed and no germination was occuring. Grain quality at the Arlington location still looked good to excellent.

Drop Dead Date for Seeding Winter Wheat

Given our 7- day weather outlook and the fact that the winter wheat we planted on October 1^st is barely spiking it is obvious that the drop dead date for trying to get the rest of our winter wheat planted in 2009 is quickly approaching. Unfortunately assigning a strict calendar date to end planting is difficult given the fact that we don't know what the weather will be like from now until Christmas or the ground freezes (whichever comes first). What we do know is:

• From our data at our Arlington and Lancaster winter wheat sites we see significant yield loss as planting date is delayed from mid-September to mid-to-late October (Table 1)

Table 1. Planting date effect on grain yield and winter survival at Lancaster and Arlington WI, 2009.

Planting date	Grain Yield	% Yield Loss
Lancaster, WI
17-Sept	74.9	-
30-Sept	68.3	8.8
13-Oct	54.2	27.6
Arlington, WI
18-Sept	101.9	-
1-Oct	93.3	8.4
17-Oct	73.9	27.5

• At this point of the season crop insurance coverage is reduced to 60% of the original guarantee (see Recommendations for Winter Wheat Establishment in 2009 for more details).
  

• A warm November or December can do wonders. Our winter wheat variety trial was planted at our Janesville location on November 8^th 2006 and averaged 76 bu per acre whereas our Arlington site was planted on September 28^th 2006 and yielded 78 bu per acre. However given our record cool season I would not mortgage the farm on a warm November/December.

• If a grower is still planning on planting winter wheat it is likley for reasons other than just yield (i.e. manure ground, straw, setting up a rotation, etc.). To ensure the best possible success given our planting and growing environment:

1. Plant "new seed
2. Plant fungicide treated seed
3. Plant a minimum of 1.75 million seeds per acre (more would be better, up to 2.2 million)
   

For additional information regarding wheat establishment please see Recommendations for Winter Wheat Establishment in 2009

The Fall is a Good Time to Pull Soil Samples for SCN

The UW Agronomy Department, in cooperation with the Wisconsin Soybean Marketing Board, is again offering free SCN testing for Wisconsin growers. This program is intended for growers to sample up to three of their fields in order to identify if SCN is present and at what levels. Growers will be responsible for collecting soil from fields suspected to have SCN and then sending the sample to the SCN testing laboratory. They will receive a lab report back with the SCN egg count and a brochure to help plan future rotations and other cultural practices to lower the level of infestation.

We have a limited number of these free kits available and will furnish them on a first come - first served basis. Each kit has a bag and a prepaid mailer for one soil sample which should represent about 10-15 acres. Both the postage and lab fees are prepaid. Before or right after harvest are great times to collect soil samples for routine soil fertility analysis and for SCN monitoring.

Soil sample test kits are available now and can be requested from Colleen Smith at clsmith8@wisc.edu or at 608-262-7702.

Preliminary Soybean Yields

Delayed maturity and inclement weather has greatly delayed/slowed our harvest progress. The rain however has given us a chance to get accurate early yield estimates at a few of our sites. Across the seven experiments we have harvested to date soybean grain yield has ranged from 48 (one of our Mn x glyphosate experiments) to 65 bushels (one of our inoculant experiments) per acre. We have only harvested sites near Arlington and Waterloo WI. As soon as it dries out and our beans become harvest ripe we hope to hit the road and begin harvest at our other out-state experimental sites.

Yield Loss and White Mold

We have been receiving multiple questions about the potential yield loss in soybean fields where white mold has been observed in 2009. As soybean moves into the R6 and R7 growth stages, this is an excellent time to assess your fields for plant mortality. Measures to consider include incidence, or the percentage of plants showing symptoms of white mold divivided the total number of plants assessed (multiplied by 100 to obtain the percentage). Also, the severity of white mold can be assessed by examining individual plants and rating each plant using a 0-3 scale (Grau et al. 1982), where:

0 = no symptoms

1 = lesions on lateral branches only

2 = lesions on main stem, no wilt, and normal pod development

3 = lesions on main stem resulting in plant death and poor pod fill

As you scout your fields, the more plants that are rated as a 3 would indicate a increased severity of white mold in the field.

What does this all mean in terms of potential yield loss? Previous studies across Wisconsin has indicated that for every 1% plant mortality, yield loss is 0.25-0.50 bushels per acre. So, for example, if there was 10% plant mortality, yield loss may be from 2.5 to 5 bushels per acre.

For further information, a new video available through UW-Extension YouTube discusses symptoms and risk factors associated with white mold.

References:

Grau, C.R., Radke, V.L., and Gillespie, F.L. 1982. Resistance of soybean cultivars to Sclerotinia

sclerotiorum. Plant Dis. 66:506-508.

Planting date effect on winter wheat grain yield and winter survival

As we prepare for the 2009/10 winter wheat production year it is good time to reflect back on the problems that we encountered and devise practical solutions that we can integrate into our upcoming field season. The most widespread issue in our 2009 wheat crop was winter-kill. In our field assessments winter survival was impacted by four major factors, three of which growers have direct control over.

1. The most obvious factor during a drive-by assessment was location within a field. Areas that were sheltered from driving winds as well as areas that held snow such as fence lines or shaded/wooded areas provided protection for crown tissue and increased winter survival.
2. Planting depth: Variability across a field with no topographical effect was mainly driven by planting depth. Wheat that was planted at less than 0.5 inches demonstrated more winterkill than wheat planted at the 1 inch depth. Please see: (Recommendations for winter wheat establishment in 2009 for more information).
3. Genetics (winter-hardiness) played a huge role in 2009. Winter survival ratings ranged from 16 to 69% at our Chilton WI variety trial site and 22 to 73% at our Arlington WI variety trial site. For specific information regarding varietal winter survival ratings please see Wisconsin winter wheat performance tests - 2009.
4. Planting date: Results from our Lancaster and Arlington WI research sites show that yield and winter survival decreased as planting date was delayed (Table 1. and Image 1.). Given the delayed maturity of Wisconsin's field corn and soybean crop and the fact that delayed planting decreases winter survival growers should put greater weight in 2009 on selecting winter-hardy wheat varieties.
   

Table 1. Planting date effect on grain yield and winter survival at Lancaster and Arlington WI, 2009.
Lancaster, WI
Planting date	Grain yield	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	Winter survival (%)
18-Sep	101.9	83.8
1-Oct	93.3	55.3
17-Oct	73.9	30.0

Figure 1. Planting date impact on winter survival at Arlington, WI in 2009.

Impact of Cool Temperatures on Soybean Seed Fill

Delayed crop development due to decreased heat units coupled with forecasted cool nighttime temperatures over the next week have many questioning the fate of the WI soybean crop. The soybean fields that I have scouted over the last week range from the R5.5 growth stage to the R6 growth stage (full seed: pod containing a green seed that fills the pod cavity at one of the four upper most nodes on the main stem with a fully developed leaf). The minimum temperature range required for soybean seed ripening is 46.4 to 48.2 °F; whereas the optimal range is 66.2 to 68°F (Holmberg 1973). A survey of the literature suggests that though cool temperatures during grain fill may adversely affect yield, the more serious impact to soybean would likely be increasing the number of days to physiological maturity and the threat of a killing frost (Image 1).

Image 1. Average date for first killing frost in Wisconsin.

On average a soybean plant remains in the R6 growth stage for 18 days; however the range can be as short as 9 days or as many as 30. The risk to WI growers is that the longer we remain below the optimal temperature range for seed development the longer our crop may remain in the R6 growth stage. As we move through the R6 growth stage and into R7 soybean (physiological maturity) seed moisture declines thus decreasing the risk of yield loss due to frost. Judd et al. (1982) found that seed in green pods which contain 65% moisture are injured at 28 °F whereas seed found in brown pods at 35% moisture was not injured at 10 °F.

Though chilling may adversely impact soybean yield a more important issue may be the effect of chilling on seed quality of yellow hilum soybean. Morrison et al. (1998) found that seed coat discoloration in yellow hilum soybean increased with the accumulation of daily minimum temperature ≤ 59 °F during seed development.

Literate cited:

Holmberg S. A. 1973. Soybeans for cool season climates. Agric. Hort. Genet. 31:1-20.

Judd, R., T.M. Tekrony, D. B. Egli, and G.M. White. 1982. Effect of freezing temperatures during soybean seed maturation on seed quality. Agron J. 74:645-650.

Morrison, M. J., L. Pietrzak, and H Voldeng. 1998. Soybean seed coat discoloration in cool-season climates. Agron J. 90:471-474.