Impact of Prior Corn Nitrogen Fertilizer Application on Peanut Nodulation and Life History Analysis of Nodule Senescence in a Corn-Peanut Rotation.

Biological nitrogen fixation (BNF) is an important source of soil nitrogen (N) in agronomic systems. However, BNF may be suppressed by N fertilizer application at high levels. While most research is focused on N application to the legume, relatively little is known about possible effects on nodulation from fertility applications in a prior rotational crop. This may be occurring in a common southeastern U.S. rotation, when corn (Zea mays L.) is followed by peanut (Arachis hypogaea L.). To quantify prior N application effects from corn on a following peanut crop, this study investigated the impact of three levels of corn N application (157, 247, and 336 kg N ha^-1) on peanut nodulation patterns at six regular harvests during the growing season. To assess nodulation, root system samples of these plants were selected and nodules were removed from taproot and lateral root subsamples. Images of these nodules were scanned and digital image analysis protocols determined the average size and total number of nodules per sample. Dissected nodules were digitally assessed for internal color, which is indicative of BNF activity. Chlorophyll fluorescence and plant N content were assessed as physiological correlates with BNF. Preliminary analysis indicated interaction between prior corn N treatments and sampling date for numbers of nodules and nodule dry mass. The 157 kg N ha^-1 prior N application lagged behind the other two treatments, peaking at 5.2 nodules cm^-1, 138 DAP, while both 247 and 336 kg N ha^-1 treatments peaked 103 DAP, with 4.0 and 4.4 nodules cm^-1, respectively. Nodule dry mass followed a similar pattern. Furthermore, differences in nodule activity (internal color) and average nodule size were observed between lateral root and taproot segments across N treatments. This study presents new information on life history of peanut nodules through the season, providing insight into BNF processes.