Ridge tillage (RT) is a Precision Zonal Management (PZM) system, most commonly used in corn-soybean rotations, that creates raised beds for planting through the repeated relocation of soil and residues from between rows. Several studies have found that with long-term management, the ridge and furrow spaces develop distinct biological and physical profiles. The creation of these zones has important implications for nitrogen (N) availability in RT systems. To examine how RT might alter patterns of N distribution and mineralization, we conducted experiments in a tillage study fully replicated at two sites in Urbana, Illinois (IL) and Mason, Michigan (MI). Over the 2012 growing season, fine resolution soil monitoring was done in zero-fertilizer sub-plots for inorganic N, potentially mineralizable N, particulate organic matter, ion exchange N, and plant N status. Consistent with previous research, we found that RT increased labile N pools, as well as in situ measurements of N mineralization by ion exchange resins in the ridge positions relative to the furrow. As well, mean cumulative NO3 adsorption summed across all positions, depths, and sampling points was greater in RT treatments than in CP treatments. Higher per plant yields and total plant and grain N concentrations also indicated that the effect of RT on soil N pools may have increased N uptake in RT plants relative to CP plants. Results were consistent with RT having the potential to create distinct soil functional zones with the potential to improve spatial N synchrony in agricultural systems.
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