Soybean Planting Date
DuPont Pioneer research has consistently shown the value of timely soybean planting. Recent research efforts have also looked at the effects of planting varieties of different maturities at normal and earlier timings.
DuPont Pioneer scientists conducted a 2-year study evaluating planting dates to see if there is an advantage to earlier planting (late April and early May) at 9 Midwestern research locations. Results from this study indicate that yields were generally higher with a late April to early May planting date compared to later planting dates (Figure 1). These yield increases can be attributed to timing of soybean development stages and day length. Soybeans obtain higher yields when their critical developmental stages occur during longer summer days.
Figure 1. Soybean yield response to planting date in a 3-year DuPont Pioneer study (23 site-years in Iowa, Illinois, Minnesota and Nebraska.)
A subsequent research study evaluated the interaction of planting date and variety maturity on soybean yield. This study was conducted at 58 locations in Illinois and Indiana in 2011 and 2012.
In 37 locations, varieties differed by an average of 1 full maturity group. Results showed a significant interaction between planting timing and soybean variety maturity. Full-season adapted varieties had a greater average yield when planted early; whereas early maturing varieties yielded similarly across planting timings (Figure 2).
Figure 2. Influence of variety maturity at early (mid-April to early May) and normal (late May) planting times on soybean yield across 37 Illinois and Indiana locations in 2011 and 2012 where varieties differed by a full maturity group.
At the other 21 testing locations, varieties differed by half a maturity rating, on average. Varieties showed no significant interaction between planting timing and maturity (Figure 3).
Figure 3. Influence of planting timing and variety maturity on soybean yields at 21 Illinois and Indiana locations in 2011 and 2012 where varieties differed by one-half maturity group.
Sometimes conditions do not allow for early planting, and growers are forced to plant later. With later planting, growers may need to reconsider management practices to maximize yield.
- Refraining from switching to an earlier maturity variety may increase yield unless planting is severely delayed (later than June 15).
- Increasing planting rate by 10% might be beneficial after the first week in June.
- Planting in narrower rows may hasten canopy closure.
- Delaying planting might mean that harvest is delayed, leaving fewer available days for harvest.