Trends in Kansas
In recent years, Kansas producers have shifted soybean planting dates to earlier dates at a 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 influenced final soybean yields.
Figure 1. Trend in the date at which 50 percent of planting progress was achieved for soybean planted area in each year from 1980 to 2013 in Kansas. Source: USDA-NASS.
Kansas planting date recommendations
Soybean can be planted over a wide range of planting dates (Fig. 2) under adequate soil moisture conditions, although germination and emergence could be reduced and delayed in cool soils (less than 50 F).
Figure 2. Recommended soybean planting dates across Kansas. Source: K-State Soybean Production Handbook, C449.
A summary of research studies comprising information on planting dates and yield benefits for early planting in Kansas is presented Table 1. For general guidelines, the outcomes from the planting date information is evaluated by diverse regions around the state:
Northeast and North Central Kansas:
- For Topeka and Manhattan sites, planting a bit earlier (early May) than normal 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.
- 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.
Table 1. Soybean planting dates and sites/years across Kansas. The information in this table was calculated as the yield obtained in the early May planting date compared to each planting date following this date (mid-late May, early-mid June, and mid-late June).
- East Central: In Ottawa, planting in mid-May resulted in a yield benefit of 6.6 bu/acre compared to planting in early May.
- 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 maximized 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 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 and planting dates did not affect actual yields.
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, under high risk of drought (sites with low soil moisture at planting, environments more prone to drought) diversifying planting dates may be a good approach to consider.
- When planting early, seed should be treated with a fungicide and insecticide. Varieties with resistance to soybean cyst nematode and sudden death syndrome are advisable to be employed. Do not plant into soils that are too wet, however. Also, do not plant until soil temperatures are at least 50 degrees. 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.
Ignacio Ciampitti, Crop Production and Cropping Systems Specialist