Grower Resource: Sooner Is Best But There’s More to Consider

Planting sooner is best for higher yields. But depending on where your farm is located, there’s much more to consider.

Our studies confirm that early May planting in Wisconsin increases yield (Gaspar and Conley, 2015). Why? In theory, a longer growing season means plants can intercept greater amounts of solar radiation. So longer maturity group (MG) soybean varieties may be better suited to maximize yield if they can mature before a hard fall frost.

Yet in some instances (weather or logistical problems) planting can be delayed or replanting may be needed. To advise growers better, we simply needed to know more.

To get the best data possible, we investigated the effect of different maturity group soybean varieties at multiple planting dates across the state. This 3-year study has been funded by the DuPont Pioneer and the Wisconsin Soybean Marketing Board and examines proper MG selection at 5 different planting dates across the state to maximize yield.

We conducted field trials at Arlington, Hancock, and Spooner, WI.  The five planting dates at each location were on or about: (1) May 7th, (2) May 20th, (3) June 1st, (4) June 10th, and (5) June 20th.  We tested two varieties within each realistic MG from a 2.5 all the way down to a 00.5 as shown in Table 1.  (We chose the cutoff of June 20th since planting after then is not recommended in WI.)  

Here’s what the preliminary data from 2014 and 2015 reveal:

Table 1. Maturity Groups 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

Starting with the easy Ag 101 answer, getting your soybeans in the ground ASAP maximizes yield.

Interestingly the yield decline for delaying planting was similar between years at Hancock and Spooner of approximately 0.46 and 0.23 bu/a/day, respectively.  However, at Arlington the yield decline was not as severe in 2015 compared to 2014, which was likely due to the abnormally late fall in 2015.  Nevertheless, if the soil is fit, soil temps are near 50 ˚F, and the forecast is favorable….. get the planter rolling!

Sooner is best

Figure 1. shows the effect of planting date across all MGs (varieties) tested in 2014 and 2015 and confirms the benefit of early planting on yield.

However, for many growers the question still remains: should you use a longer maturating variety in early planting situations (very possible again in 2016) or should you 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, during 2014 and 2015
Planting Date Arlington Hancock Spooner
1 (May 1th) 2.5 2.5 1.0
2 (May 20th) 2.5 2.5 1.0
3 (May 30th) 2.0 2.0 0.5
4 (June 10th) 2.0 2.0 0.5
5 (June 20th) 0.5 0.5 0.5
The numerically highest yielding MG for each planting date and location.  MG that are bold and colored red were significantly higher at the  P ≤ 0.05

Combining the 2014 and 2015 data, 8 out of 15 location x planting date combinations displayed a significant effect of MG on yield (Table 2).

At Arlington and Hancock, using the longest MG resulted in the highest yield within dates 1-4 and was significant 7 of 8 times.

Within planting date 5 the shortest MG (0.5) yielded the highest numerically, but this was not significant and the MG 1.5 varieties did not mature before the fall frost in 2014.

Bottom line: planting a portion of your acres to slightly longer MG than normal within May can provide the opportunity for greater yields with no additional dollars spent.

What’s more, when planting is delayed into June, switching to a variety much more than 0.5 MG earlier than a full season variety (2.5 MG) may limit yield potential.  However, if planting is delayed until mid to late June or more likely replanting is needed, a variety that is at least a full MG earlier should be considered to avoid fall frost damage.

At Spooner, MG selection was not as critical and only planting date 5 saw a significant effect of MG on yield where the 0.5 MG bested the 0.0 and ultra-early 00.5 MG varieties.  Therefore, northern WI growers can maximize yield and avoid fall frost damage using varieties within a narrow MG range (1.0  – 0.5). However, growers may consider trying a slightly longer maturing soybean on a portion of their acres when early planting is possible, because of the “potential”, but not guarantee, for higher yields with no additional dollars spent.

In conclusion, variety selection heavily based upon the MG is not a silver bullet to increasing yields, however it does provide the “potential” for higher yields with no additional dollars spent. While growers should consider MG when selecting varieties, past local and regional performance, disease package, SCN-resistance, etc. should take precedence in variety selection.


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.

(Editor’s note: This post was written by Adam Gaspar and Shawn P. Conley, and edited by David Schiff. The original article can be found here.)