Thursday, June 18, 2015

Soybean Flowers, Glyphosate Label, and Wheel Track Damage...Oh My!

Given the quick start to our soybean growing season we will begin to see many soybean fields begin to flower (R1) next week (6/21/15). 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.

Monday, June 1, 2015

A Tank Full of Sugar Helps the Profits Go Down


While in attendance at the 2015 Commodity Classic I was a bit dismayed at the number of featured speakers expounding upon the incredible in-season benefits of applying sugar to field crops. I have been sitting on this article for a few months now waiting for the right time to relaunch the below article originally entitled "Do Foliar Applications of Sugar Improve Soybean Yield".  I waited a bit too long as my colleagues at the University of Nebraska beat me to the punch with their articles linked here "Sugar Applications to Crops - Nebraska On-Farm Research Network Results" and "Research Results: Sugar Applications to Crops". I guess I shouldn't feel too bad though as this is the first time the Corn Huskers have beat the Badgers in anything for a long time....  

***UNL article spoiler alert*** In short the University of Nebraska team did not find a consistent yield increase in corn or sorghum and averaged 0.8 bu per acre in soybean (FYI: average cost of ground application in $7.55 and aerial is $10.60; 2015 Iowa Farm Custom Rate Survey and the average yield loss caused by sprayer wheel track damage in soybean in rows less than 20 inches is 1.9 or 1.3% with a 90 or 120 foot boom, respectively).

I also want to give credit to my colleague Chad Lee also wrote a nice article entitled "Could Sugar Help Drought Stressed Corn?" that discusses sugar rates, biological activity and actual costs of product. 

I am certain this article will stir up severe indignation, however when the local cash bids are averaging $8.88 ROI is more important than ever.   

Do Foliar Applications of Sugar Improve Soybean Yield (Originally published: June 14th, 2011)
High commodity prices have led growers to consider many novel soybean inputs. One input that has garnered considerable attention is the foliar application of sugar products to increase soybean yield. The objective of this research was to evaluate soybean yield in response to various sources of foliar-applied sugar across four states in the Midwest. Field research studies were conducted at Arlington, Wisconsin; Urbana, Illinois; St. Paul, Minnesota; and West Lafayette, Indiana in 2010.The four sources of sugar evaluated in this study were:
1.     granulated cane sugar
2.     high fructose corn syrup
3.     molasses
4.     blackstrap molasses.
All treatments were applied at the equivalent rate of 3 lb sugar a-1 and applied at 15 to 20 gal a-1. The treatments consisted of an untreated check, all four sources of sugar applied at V4, granulated cane sugar and blackstrap molasses applied at R1, granulated cane sugar applied at V4 and R1, and blackstrap molasses applied at V4 and R1.

No positive or negative (phytotoxic) effects were visually observed on the soybean foliage at any location within 10 days following foliar applications (data not shown). Furthermore, sugar did not increase soybean yield within location (data no shown) or across locations [P = 0.60 (Figure 1)], regardless of source. While this study cannot conclusively prove foliar applications of sugar will not increase soybean yield, the authors conclude that other management strategies to improve soybean yield should take precedence over applying sugar.
 
The source of this data is:

Furseth, B. J., Davis, V., Naeve, S., Casteel, S., and Conley, S. P. 2011. Soybean Seed Yield Was Not Influenced by Foliar Applications of Sugar. Crop Management. Accepted: 6/1/11.  

Please visit: http://www.plantmanagementnetwork.org/sub/cm/brief/2011/sugar/ to view the entire manuscript.

Tuesday, May 12, 2015

Last Night's Cold Temperatures Had No Impact on Emerged Soybean or Your Wheat Crop

Coauthored by Dr. Shawn P. Conley (15%) and Dr. Jim Specht (85%)

Last nights cold temperature has led to an influx of questions regarding the potential impact on either the wheat crop or emerged soybean seedlings. In short there is nothing to worry about in either crop. In the case of wheat, which is still in the jointing growth stage, cold temperature would need to reach 24 degrees F or less for 2 plus hours before injury occurred (Please see Recent Cold Temperatures will have Little Impact on WI Winter Wheat Crop for more details). 

In the case of soybean I was fortunate enough to be copied on this email from Dr. James Specht (please see below) which saved me a few hours of library time today so thank you Jim.

First of all 34F will not impact above-ground tissue.  Second, tissue freezing does not even take place at 32F because cell cytoplasm has solutes in it – like a modest anti-freeze, which depresses freezing point of the tissue a degree or two less than 32F - thus air temps surrounding the tissue have to get to below 31 or 30F before tissue freezing can occur.  Third, the soil surface is typically warmer than the air temperature (particularly when the soil is wet) and does not give up heat acquired during a sunny day as fast as the air does after sunset.  In actuality, the interface between soil surface temp and the air temp near that soil surface will be closer to the soil temp than to the air temp which most peopled measure on thermometers viewable at their height (not at ground level).  Biophysically, control of the soil temp over the air temp this is called the “boundary layer effect”).  So don’t trust air temperatures read on thermometers unless you know what the air temperature near the soil surface was (put a thermometer on the soil surface tonight where the cotyledons are and check it just before dawn (when the soil surface temp reaches its nadir for a 24-hour temperature cycle) and send out an e-mail blog to your producer colleagues early the next day.   Fourth, the cotyledons are a huge mass of tissue that are about 95% water.  That big amount of water-filled tissue is hard to freeze unless the exposure to temps of 30F at the soil-air interface is many, many hours.  Cotyledons will freeze faster (in fewer hours) but only if the soil surface temps get well below 30F (say 25F).  The only concern I would have is when cotyledons are no longer closed and protecting the young stem tip.  However, if that is in fact frozen off, the nodes to which the cotyledons are attached will regenerate TWO main stem tips.  Not an ideal way to start the growing season, but better than having to replant (0.5 bu/ac loss per each day that soybeans are NOT in the ground on May 1).

Thursday, April 16, 2015

Soybean Planting Date by Maturity Group Considerations for 2015

Article coauthored by Dr. Shawn P. Conley and Adam Gaspar

Early May planting in Wisconsin has been documented to increase soybean seed yield due to increased light interception (Gaspar and Conley, 2015).  In theory, earlier planting can potentially intercept greater amounts of solar radiation due to a longer growing season and therefore longer maturity group (MG) soybean varieties may be better suited to maximize yield if they can mature before a hard fall frost.  Unlike 2013 and 2014, 2015 may provide growers with an opportunity to plant their soybean crop earlier than ever before. Yet, in some instances (weather or logistical problems) planting will be delayed or replanting may be needed. Therefore, investigating the effect of different MG’s at multiple planting dates across the state would provide WI growers with BMP’s for soybean establishment regardless of planting timing.

To answer this question field trials were initiated at Arlington, Hancock, and Spooner, WI in spring of 2014.  The five planting dates at each location were planting roughly on: (1) May 7th, (2) May 20th, (3) June 1st, (4) June 10th, and (5) June 20th.  Planting after June 20th is not recommended in WI.  Two varieties within each MG from a 2.5 all the way down to a 00.5 were tested depending upon the location and planting date and are displayed in Table 1.


Table 1. Maturity Group’s tested within each location and planting date.
Planting Date

Arlington
Hancock
Spooner
1 (May 7th)

2.5, 2.0, 1.5
2.5, 2.0, 1.5
1.5, 1.0, 0.5
2 (May 20th)

2.5, 2.0, 1.5
2.5, 2.0, 1.5
1.5, 1.0, 0.5
3 (June 1st)

2.0, 1.5, 1.0
2.0, 1.5, 1.0
1.0, 0.5, 0.0
4 (June 10th)

2.0, 1.5, 1.0
2.0, 1.5, 1.0
1.0, 0.5, 0.0
5 (June 20th)

1.5, 1.0, 0.5
1.5, 1.0, 0.5
0.5, 0.0, 00.5













Let's start with the easy and redundant part, get your soybeans in the ground ASAP to maximize yield.  This is evident again in this trial, where Figure 1 shows the effect of planting date across all MG’s (varieties) tested in 2014.  If the soil is fit, soil temps are near 50 ˚F, and the forecast is favorable….. get the planter rolling!

Figure 1. Dots represent the mean yield within each planting date for each location.  The average yield loss per day for delaying planting past May 7th is presented in the legend.
However, the question still remains for many producers, should I use a longer maturity variety in early planting situations (very possible in 2015) and should I switch to an earlier maturing variety when planting is delayed?  

Table 2. Effect of Maturity Group on Yield tested within each location and planting date.
Planting Date

Arlington
Hancock
Spooner
1 (May 7th)

NS
NS
NS
2 (May 20th)

NS
NS
NS
3 (May 30th)

NS
**
NS
4 (June 10th)

NS
NS
NS
5 (June 20th)

**
NS
NS
** MG had a significant effect on yield at the  P ≤ 0.05 level














Based upon the 2014 data, only 2 out of 15 location x planting date combinations displayed a significant effect of MG on yield (Table 2).  So the moral of the story is that within a realistic MG range for your region and planting date, variety selection should be based heavily upon the varieties past local and regional performance, disease package, and etc.  Variety selection heavily based upon the MG is not a silver bullet to frequently increasing yields.

However, there are always caveats…… Growers may consider trying a slightly longer maturing soybean on a portion of their acres because there is a “potential”, but not guarantee, for higher yields with no additional dollars spent.  Within planting date 1, there was no significant MG effect, but MG 2.5 did yield the highest numerically in Arlington and Hancock with no fall frost damage, while the same is true for MG 1.5 in Spooner.  The longest MG tested within each planting date in our study numerically yielded the highest through June 10th (planting date 4). 

On the back end of the planting season, the inverse was seen.  Within planting date 5 at Arlington and Hancock, MG 1.5 did not mature before the first fall frost and was the lowest yielding.  Therefore, growers may consider switching to an earlier maturing variety as planting is delayed into June.  If switching to an earlier maturing variety, don’t use a variety less than 0.5 MG earlier than a full season variety (2.5 in southern WI) in early June.  However, if planting is delayed into mid to late June then a variety that is greater than or equal to a full MG earlier should be considered.

Acknowledgements: The authors would like to thank the Wisconsin Soybean Marketing Board and DuPont Pioneer for supporting this research.

References:
Gaspar, A.P. and S.P. Conley. 2015. Responses of canopy reflectance, light interception, and soybean seed yield to replanting suboptimal stands. Crop Sci. 55:377-385.