In certain cases, producers may be required to apply supplemental nitrogen fertilizer to soybeans.
Manitoba Agriculture Crop Nutrition Specialist John Heard says there are several reasons why inoculation failures may occur including acid soils, or drowning in flooded soils.
He explains the targeted rescue application is the R3 or R4 stage or the start of seed filling.
"It seems that we can grow a vegetative plant fine, with the nitrogen that's in the soil and the nitrogen that mineralizes from organic matter but for that yield, that seed filling, that's where the supplemental nitrogen is advantageous."
Source : Portageonline