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Department of Agronomy

Kansas State University

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Manhatan, KS 66506

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Extension Agronomy

Soybean planting dates and maturity group: Trends and K-State recommendations

Trends in Kansas

In recent decades, Kansas producers have been planting soybeans slightly earlier through the years -- at the rate of about a half-day per year (Fig. 1). After considering the effects of genetic yield potential and the environment, planting date is one of the primary management practices under the farmer’s control that can highly influence soybean yields.

Figure 1. Trend in the date at which 50 percent of planting progress was achieved for soybean in each year from 1980 to 2014 in Kansas. Source: USDA-NASS.

 

Kansas Planting Dates and Maturity Groups

Soybean can be planted over a wide range of planting dates (Fig. 2a) under adequate soil moisture conditions, although germination and emergence could be reduced and delayed in cool soils, less than 50 degrees F. Recommended maturity groups vary by the area across the state (Fig. 2b).

 

 

Figures 2a and 2b. Recommended soybean planting dates and suggested maturity groups across Kansas.

 

K-State research: Planting Dates

 

A summary of K-State research studies on planting dates and relative yield advantages or disadvantages of early May planting in Kansas is presented Table 1. 

 

Table 1. Effect of planting dates on soybean yields at seven locations in Kansas, based on K-State research. The information in this table was calculated as the yield obtained in early May planting date compared to the yield at later planting dates (mid-late May, early-mid June, and mid-late June).

 

Planting Date

 

Mid-Late May

Early-Mid June

Mid-Late June

Location, Year

Yield (bu/acre) compared to Early May planting

Powhattan, 2000-021

1.7

11.4

-9.0

Belleville, 1999, 20011

4.4

-26.2

-55.2

Topeka, 2000-021

-4.8

-15.1

-19.2

Ottawa, 1999-20021

6.6

-0.3

-25.8

Belleville, 2009-10

 

-6.5

 

Scandia, 2009-10

 

-4.5

 

Manhattan, 2010

-7.7

-15.3

-26.1

1 No seed treatment in these studies

 

The results can be summarized as follows:

  • For Topeka and Manhattan sites, planting in early May consistently produced higher yields than other planting dates. Each day that planting was delayed from early May up to mid-late June, yields declined at an overall rate of close to 0.5 bu/acre/day.
  • In Belleville (1999, 2001), mid-May planting presented a small yield benefit (4.4 bu/acre) compared to the early May time, with yields declining as the date was delayed beyond mid-late May. Research at Belleville and Scandia in 2009-2010 confirmed this trend, with a clear yield advantage for early May as compared with early-mid June planting.
  • In Powhattan, under lower soybean yield (<30 bu/acre) environments, yields declined with mid-late June planting dates, and was maximized with the early-mid June planting time. Thus, for Powhattan, there was no yield benefit in planting in early May.
  • In Ottawa, planting in mid-May resulted in a yield benefit of 6.6 bu/acre compared to planting in early May.

 

Recommendations for other regions:

Southeast: Planting from mid-May to the end of June is recommended for this region (Fig. 2). For Parsons, early-to-mid June and early July planting dates maximizes yield production. Those planting dates tend to increase soybean production because they usually allow the beans to avoid heat-drought stress and increase the probability of catching summer rains during the reproductive period.

South Central: Early planting dates are recommended for this region. For Hutchinson and Wellington, yields in K-State tests were maximized by planting in late April, which is a couple of days before the range of dates recommended in our K-State soybean management guide for planting dates (Fig. 2).

Western Kansas: Low yields were recorded in the western Kansas tests and planting dates did not affect yields.

K-State 2014 research: Planting date by maturity group

A summary of four studies on soybean planting date by maturity group performed during the 2014 growing season was recently published: Ciampitti, I. A.; Shoup, D. E.; Sassenrath, G.; Kimball, J.; and Adee, E. A. (2015) "Soybean Planting Date × Maturity Group: Eastern Kansas Summary," Kansas Agricultural Experiment Station Research Reports: Vol. 1: Iss. 2. http://newprairiepress.org/kaesrr/vol1/iss2/21/

The primary outcome is that the optimum combination of soybean planting dates and maturity groups was governed by the environment (site) evaluated.

In this research, three soybean varieties (early, medium, and late maturity groups) were planted at three planting dates during the 2014 season, at Topeka, Manhattan, Parsons, and Ottawa. Maturity groups at Topeka and Manhattan locations were 2.0, 3.8, and 4.8. Planting dates were April 22, May 15, and June 3 at Manhattan; and May 2, May 20, and June 18 at Topeka. Maturity groups at Ottawa were 3.7, 4.2, and 4.8; and planting dates were May 5, May 28, and June 26. At Parsons, maturities 3.9, 4.8, and 5.6 were planted May 2, June 3, and June 26.

Under rainfed conditions at Manhattan, the mid-maturity group (3.8) was the highest-yielding at both early and late planting date. The late maturity group (4.8) outyielded the other maturity groups at the mid planting date of May 15 (Fig. 3).

Under irrigation at Topeka, group 3.8 and 4.8 (medium and late) varieties maximized yields at the earliest planting date (May 2), with yields >70 bu/a (Fig. 3). Lower yields were observed for the mid-May vs. early planting date, with the exception of the late-maturing group (4.8). For the late planting time (June 18), group 3.8 (yields >60 bu/a) significantly outyielded groups 2.0 and 4.8 (yields <45 bu/a).

 

Figure 3. Soybean yields with different planting dates (early, mid, and late) and maturity groups (E = early, M = medium, L = late maturing groups) for Manhattan and Topeka.

 

Under rainfed conditions at Ottawa, yields were similar, but generally greater for May 28 (mid-planting date) as compared with May 5 (early) across all maturity groups (around 35 bu/a) (Fig. 4). At the late planting date (June 26), yields increased with the later maturity groups.

At Parsons (rainfed), group 3.9 (early) outyielded the other maturity groups for the May 2 planting date. On the opposite side, later-maturing soybean groups yielded better for the other planting dates (June 3 and 26) (Fig. 4). Although a trend in the data supported timing of planting to capture fall rains to enhance yield, the results were not statistically significant between the later maturity groups.

Figure 4. Soybean yields with different planting dates (early, mid, and late) and maturity groups (E = early, M = medium, L = late maturing groups) for Ottawa and Parsons.

 

Conclusions and recommendations

  • Ultimately, weather patterns dictate soybean yields, especially under dryland conditions. There is no guarantee that any certain planting date will always work out the best when it comes to soybean yields in Kansas. In fact, the distribution and amount of rainfall and the day/night temperature variations around flowering and during the grain filling periods have large impacts in defining soybean yield potential. Thus, when the risk of drought stress during the growing season is high, diversifying planting dates may be a good approach to consider.
  • When planting early, seed should be treated with a fungicide and insecticide. Selecting varieties with resistance to soybean cyst nematode and sudden death syndrome is advisable. Do not plant into soils that are too wet, however. Also, do not plant until soil temperatures are at least 50 degrees F. If planted into soils cooler than that, seedlings may eventually emerge but will have poor vigor.
  • In drier areas of Kansas and on shallow soils, yields have been most consistent when planting soybeans in late May to early June. By planting in that timeframe, soybeans will bloom and fill seed in August and early September, when nights are cooler and the worst of heat and drought stress is usually over.
  • In our 2014 planting date by maturity group study, interactions with the environment are the primary factor in the yields and maturity group responses. Under full irrigation, the earliest planting date maximized yields with groups close to 4 and 5 maturity at Topeka. For our rainfed sites, there is not one rule that can apply to all conditions, but late planting showed good yields at Ottawa and Parsons (June 26) with later-maturing groups.
  • New studies are planned for the 2015 growing season for similar locations.

 

 

Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
ciampitti@ksu.edu