Does Early Planting = Higher Soybean Yields?

D.B. Egli and P.L. Cornelius from the University of Kentucky recently took a number of planting date studies from across the US, including Ohio. and did an analysis of maximizing yield by planting date. What they found is that there was no consistent advantage to early planting. The study divided out results by region, midwest, upper south and deep south. They found very similar responses to planting data regardless of region. Planting dates from mid-April to late May resulted in similar yield averages. What the data did show was a definate yield loss when planting date was delayed past May 30 in the Midwest (0.7 % per day), June 7 in the upper south(1.1% per day) and May 27 in the deep south(1.2% per day).

The authors reasoned that the steady decline from late planting could be a response to changes in the plant or changes in the plant's environment or some combination of these factors. The discuss photosynthesis, temperature, reproductive versus vegetative among other issues that explain this response.

Their conclusion was if the soil is ready in late April farmers should start planting but realize it may not necessarily increase yields.

The full article can be found http://agron.scijournals.org/content/vol101/issue2/ under 'Production Agriculture'