June Planted Soybeans

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How does late planting affect soybean maturity and yield?

A one month delay in planting generally results in a 9 day delay in maturity (OMAFRA Agronomy Guide Pub 811).  The vegetative period is shortened, causing a reduction in nodes per plant and plant height.  The flowering and pod-filling periods are also shortened which causes fewer pods per plant and smaller bean size. This could result in a reduction in yield by about 0.30 bu/ac/day (OMAFRA trials 2010-2012).

What factors should be considered when switching to a shorter maturity?

1. Is the grower planning to plant winter wheat after?
2. Is the variety they currently have chosen adapted for their maturity zone?
3. Does the grower have their own combine and dryer?

What is an adapted variety?

An adapted variety corresponds to the maturity group (MG) in the area that it’s planted in. Each decimal unit equals approximately one day of maturity. For example, a MG 1.0 variety matures about 5 days before a MG 1.5 variety. Selecting adapted varieties allows maximum yield opportunity by making use of the full growing season, given normal planting dates. Below is a map of Ontario soybean maturity groups (OMAFRA Pub 811).

When should you consider switching to a shorter soybean variety?

1. If plans were to grow a variety that is considered long for its maturity zone, then switch to an adapted variety after June 1.
2. If planning to grow an adapted variety and you are
   1. not planning to plant winter wheat after, then switch around June 15.
   2. planning to plant winter wheat after, then switch around June 10.

What management factors can be adjusted to improve yield of a late planted soybean after June 15th?

1. To compensate for the decrease in pods per plant and shorter plants in late planted soybeans, consider increasing planting population by 10% to a minimum of 200,000 seeds/ac in narrow (7.5”) rows.
2. Planting on narrow rows will decrease the time to row closure which allows for maximum sunlight interception compared to 15” or 30” rows.

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