Wet spring planting conditions have caused a delay in the soybean planting across the state. In the latest Crop Progress and Condition report from Kansas Agricultural Statistics (June 15, 2015), soybeans planting was at 57% complete, well behind the 85% for 2014 and the long-term average. Total soybeans emerged is also behind normal by a similar amount. East central, northeast, and southeast Kansas seem to be the regions most impacted by wet spring conditions. The most active planting dates for soybeans are between May 15 and June 20 (USDA NASS). The total number of days suitable during the “most active” planting dates for soybean over the last 33 years by Crop Reporting District can be found in Griffin and Ciampitti in the Agronomy eUpdate Issue 501 (April 3, 2015).
Where soybean planting has been delayed, producers should consider a few key management practices. Planting soybeans in the right soil conditions is essential for establishing an adequate soybean canopy and improving chances to increased yield potential.
Figure 1. Late-planting soybeans (June 10) into adequate soil conditions. Photo by Ignacio A. Ciampitti, K-State Research and Extension.
Maturity group factor: From our planting date x maturity group study in 2014, late planting did not clearly result in a yield reduction at the dryland sites, and caused only a minimal yield reduction at the irrigated site. Medium maturity groups (ranging from 3.8 to 4.8) yielded better, depending on the site (Fig. 2). More information related to this study can be found at: http://newprairiepress.org/kaesrr/vol1/iss2/21/ [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.]
Figure 2. Soybean yields under varying planting dates (early, mid, and late) and maturity groups (E = early, M = medium, L = late maturing groups) for Manhattan (dryland), Topeka (irrigated), Ottawa (dryland), and Parsons (dryland) during 2014 growing season.
Seeding rate factor: Increasing the seeding rate of late-planted soybeans by 10-20% as compared to optimal seeding rate can help compensate for the shortened growing conditions. Research information on seeding rate and late planting of soybeans is currently being investigated further, with more updates on this topic in future issues of the eUpdate. The same soybean cultivar planted early in the planting window, under normal conditions, will develop nearly 50% more productive nodes than when planted in late June: 19-25 nodes when planted early vs. 13-16 nodes when planted late. For soybean seeding rates and optimum plant populations, see eUpdate Issue 508 (May 1, 2015).
Row spacing factor: Information on late-planted soybean across multiple row spacings suggests that narrow-rows (e.g. 7” or 15” vs. 30”) can hasten canopy closure, increasing season-long light interception, weed suppression, and potentially improving biomass and final yield. In some cases, the likelihood of finding yield responses to narrowing rows increases as the planting is delayed later in the season.
Finally, proper identification of soybean growth stages can make a difference in yield. We have worked recently with the United Soybean Board and the Kansas Soybean Commission recently to produce a soybean growth and development chart. It can be downloaded at:
More information about key aspects of each growth stage and management practices can be found in that soybean chart. Weekly and timely updates on soybean are also provided via Twitter @KSUCROPS and @KStateAgron, and on our Facebook page.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist
Doug Shoup, Southeast Area Crops and Soils Specialist
Stu Duncan, Northeast Area Crops and Soils Specialist