Impact of Residual Nitrogen Fertilizer on Nitrogen-Fixation and Nodulation in Peanut in a Corn-Peanut Rotation

Biological nitrogen fixation (BNF) is an important source of soil nitrogen (N) in agronomic systems, and has the potential to offset some of the costs of inorganic N fertilizer inputs. However, the helpful potential of this BNF may be suppressed by the application of N fertilizer at high levels, whether applied to the current crop or due to rates utilized during the prior growing season. The current evidence suggests that this suppression of BNF takes place in N-fixing legumes after being exposed to high levels of applied N fertilizer. However, there is comparatively less information about the possible effect of residual soil N from the previous growing season when peanut is rotated with crops requiring large amounts of N application; for example in a crop rotation such as corn and peanut. Given the high N demand of corn and the variability among producers in the rate of N applied, there is a potential benefit to better understanding the dynamics of rotating peanut with corn and the impact on the BNF balance in peanut following corn. If an optimal level of N use for corn can be determined that suppresses neither yield for the corn nor overall BNF for the subsequent peanut, there is potential to realize cost-savings and environmental benefits from efficient fertilizer use. The proposed study would investigate the observed impact of field history of N application in corn on BNF in peanut by assessing peanut root nodulation and nodule health, whole-plant N content, and chlorophyll fluorescence to monitor the impact on carbon assimilation. This should determine how N levels in the previous year's corn affect BNF in peanut.