Our study showed that applying low rates of N fertilizers at planting generally created greater levels of available soil N in both growing seasons, however, grain yields were not improved when compared with the unfertilized control for any of the growing seasons. Rather, yields declined by 11.8 percent to 18.8 percent due to the N fertilizer addition as compared to the control in one of the study’s two years.

These results suggested that adding N fertilizer at planting was not an effective management practice to increase soybean yields, regardless of the sub-surface drainage managements, but could possibility increase the N that escaped to the environment.