If soybeans are grown for the first time in a field and the inoculant was not used, N fertilization will be needed. N rates will be about 200 lbs N/acre, costing about $80/acre. Inoculant will cost $1 to $2 per acre.
Generally, soybean seed should be inoculated with proper product and procedures. On fields without prior history of successful soybean production, soil N levels at the 0- to 2-foot depth should be about 50 lb/acre. If a field has a history of 2 to 3 years of successful soybean production (good nodulation, minimal iron deficiency chlorosis, and acceptable yield), soil N levels can be below 50 lb/acre. POST N application is not recommended if soybean plants are healthy and the root system contains viable nodules.
Preplant/starter N applications have been shown to provide no benefit. Residual N, mineralized N, and N that comes with P fertilizers have not been found to be detrimental to soybean yields. Even N applications for double cropped soybeans (soybean after wheat) have not shown yield benefit. Late season N (R3-R5) applications do not tend to reliably increase yields. In rare situations, high yielding irrigated fields can benefit from application of small quantities (<60 #) during early seed filling.
“For more information on this or other topics related to soybean production, contact your state extension specialist or your local extension educator/agent.”
The following is the link to the soybean extension specialists: state extension soybean specialist
