To use NO₃-N concentration (hereafter, simply "NO₃-N") as an indicator of agricultural management effects on shallow groundwater quality requires understanding groundwater NO₃-N controls, patterns, and correlations over spatial and temporal scales. Over a 2-yr period, we determined groundwater NO₃-N patterns, correlations, and natural controls at various spatial and temporal scales and their associations with uniform and variable-rate N management. We established a 2-yr winter wheat (Triticum aestivum L.)-double-crop soybean [Glycine max (L.) Merr.]-corn (Zea mays L.) rotation in a North Carolina coastal plain field and in a randomized complete block design, applied one VR-N and two uniform-N treatments to wheat and corn. We measured groundwater NO₃-N and water table depths every 2 wk at 60 well nests sampling 0.9 to 3.7-m depth. Field-mean groundwater NO₃-N exhibited temporal patterns and correlations associated primarily with water table elevation and depth. Mean groundwater NO₃-N exhibited two preferred states: high when the water table was shallow and low when the water table was deep. Temporal NO₃-N fluctuations greatly exceeded treatment effects. Treatments appeared to affect NO₃-N temporal covariance structure. Groundwater NO₃-N exhibited distinct spatial patterns and correlations with spatial ranges of 0 to 551 m. Early N treatment effects were minor; groundwater NO₃-N spatial patterns and correlations were associated mostly with saturated hydraulic conductivity and water table fluctuations and appeared influenced by subsurface lateral flow. When N treatments became consistently significant later in the study, they overrode natural controls, and NO₃-N was spatially uncorrelated or exhibited shorter spatial correlation ranges and patterns associated predominantly with N management treatments.