Assessing Soybean Stands Under Cool Conditions

A significant portion of the state was planted and some (soybean) fields were planted right before this cold period.  With cold temperatures, it is going to take a longer period of time for plants to emerge.  Soil temperatures around the state:

These soil temperatures are cool enough to delay soybean emergence for as much as 2 weeks.  Warmer temperatures now forecast for the end of the week will help to alleviate this.  When seeds are in the ground under these cool and saturated soil conditions, they are vulnerable to many of the soil borne pathogens.  An effective fungicide seed treatment will help alleviate this and stands will not be affected.  But that is only if that fungicide seed treatment is effective towards the pathogen population in the field.  There have been lots of changes in the seed treatment industry in the past five years and each active ingredient does not control the full spectrum.  If after 2 weeks – you have spotty emergence and or seedlings have brown or pink lesions, send us the dying plants.  We can help sort out which fungicide may be more effective for your field – if we can recover the pathogens.  Send symptomatic seedlings to the Soybean Pathology Lab, OARDC, 1680 Madison Ave., Wooster, OH  44691.

Soybean plant population has been evaluated in many trials conducted by the Ohio State Agronomic Crop Team.  According to Agronomic Crop Team data, 95 to 98% soybean relative yield was achieved when soybean stand at harvest was between 127,000 and 171,000 plants per acre (see Figure 1).   However, soybean plants can achieve optimum yield over a wide range of plant populations if stand is even and uniform.  Some data indicates that 100,000 plants per acre at harvest can achieve maximum yield when planted in narrow rows prior to May 20.  Keep in mind this yield data is based on final plant population at harvest…not seeding rate.  Final population is a function of seeding rate, quality of the planting operation, seed germination percentage and environmental conditions (soil moisture, disease pressure, fungicide treatment, etc).  To quickly estimate stand, count the number of plants in 70 foot of row for 7.5 inch row spacing, 35 foot of row for 15 inch row spacing, or 17.5 foot of row for 30 inch row spacing.  These counts represent 1/1000th of an acre (i.e.,  120 plants in 35 foot of row grown at 15 inch row spacing represents a stand of approximately 120,000 plants per acre).

Source : osu.edu