Courtesy: United Soybean Board
Short growing seasons in South Dakota create difficulty for field activities following row crop harvest in the fall. Some crop producers in the state occasionally grow soybeans with varying maturity ratings for two major reasons: 1) to spread out the harvest resources in the fall, and 2) to avert any unpredicted weather circumstances such as early frost, mid-season hail occurrences, drought conditions, etc. With this approach, producers are not putting all eggs in the same basket. Planting soybeans other than recommended maturity group for the region, especially early maturing varieties, will allow producers to start harvest earlier in the fall and continue field activities such as establishing cover crops and/or timely winter wheat planting. In the past few seasons, growers have commented that early soybeans have performed equally well in terms of yield, if not better, than soybeans with recommended maturity ratings.
SDSU Extension Research
In collaboration with interested growers, SDSU Extension established a small plot trial during the 2017 growing season at two locations in Northeast SD: 1) SDSU NE Research Farm near South Shore, and 2) farmer cooperator field in Clark County, near Henry. The trial used two early varieties (rated 0.2 and 0.3) and two recommended varieties (rated 0.9 and 1.0) provided by Mycogen Seeds. All varieties were planted at two different dates: early (May 5th) and normal (May 23rd) on 10’x40’ plots with four replications for each planting date. Due to consistent rainfall in the second half of September harvesting was delayed more than normal and was only completed on October 3rd.
The results (Table 1) showed that yields, even though numerically quite different, were not statistically significant at the Henry location especially for the early planting date. This could be due to weed pressure and population loss as a result of heavy rainfall in late June. This site received nine inches of rain in three days in the last week of June which flooded almost half of the early planted plots. Some early flooded plot yields were not as consistent at harvest compared to the non-flooded plots. Therefore, the yields from flooded plots were not used while running statistics which may have contributed to large LSD values. This resulted in difficulty to statistically distinguish mean yields for the maturity ratings used in the study. At the NE Research Farm, yields from the earliest maturing soybean variety (i.e. 0.2) were significantly different from other three soybean varieties for both plating dates. These results suggest that planting soybean varieties that are earlier than half the maturity point than recommended for the region did not result in equal or higher yields in 2017 growing season. The research group plans to continue this study in the 2018 growing season.
|Table 1. Average Soybean Yields of varieties rated early and recommended for two Northeast SD locations: Northeast Research Farm by South Shore and farmer cooperator field by Henry.|
|May 5th||Henry||0.2||46.6||May 5th||NERF||0.2||47.5|
|May 5th||Henry||0.3||53.1||May 5th||NERF||0.3||56.2|
|May 5th||Henry||0.9||58.9||May 5th||NERF||0.9||63.1|
|May 5th||Henry||1.0||58.9||May 5th||NERF||1.0||67|
LSD(0.05)= Least Significant Difference value. Difference of yields higher than LSD values are considered statistically different at 0.05 probability level.