NDSU’s general soybean planting date recommendation is the first half of May when soil temperatures are consistently 50 degrees F or higher. Very early planted soybean in cold (and wet) soils may result in reduced seed germination (due to imbibitional chilling), increased risk of seedling disease and ultimately poor field stands. Emerged soybean plants are susceptible to air temperatures at 30 degrees and less. Also, the earliest insurance plant date for North Dakota is May 1. With the high possibility of an early spring and early planting season, farmers may have the opportunity to plant soybean earlier than normal.

NDSU conducted eight soybean planting date trials during 2011 through 2015 at Carrington, Hettinger, New Rockford, Prosper and Wishek (see graph below). The ‘early’ planting dates ranged from April 24 to May 5 and the ‘normal’ planting dates ranged from May 15 to 23. Soil tilth was appropriate with the early planting though soil temperatures at and following planting often were less than 50 degrees. Five of eight trials had a statistically significant (LSD 0.05 = *) yield advantage with early vs. late planting. Averaged across trials, early planted soybean yield was 9% or 3.9 bu/acre greater than with normal planting dates. Range of yield advantage with early planting among trials was -5.3 to 8.4 bu/acre.

Reasons for yield increase with early planting soybean include opportunity to use later-maturing varieties (generally with greater yield potential) and quicker canopy closure (advantages of capturing more sunlight, conserving soil moisture and increasing competition with weeds). Fungicide seed treatment is recommended if planting early.

In summary, though risks are involved with earlier than normal planting dates, the data indicates potential for higher soybean yield with no additional cost for early planting.

Greg Endres
Area Extension Agronomist