High-voltage electrostatic fields (HVEFs) can increase the nitrogen uptake of plants. An ammonium cation inhibitor, tetraethylammonium chloride, and a nitrate ion inhibitor, 5-nitro-2-(3-phenylpropylamino)-benzoate, were added to ammonium and nitrate growing solutions with and without exposure to HVEFs to investigate the effects of these fields on tomato seedlings. The seedlings were exposed to HVEFs with field intensities of 2.25 and 2.5 kV cm^-1, respectively, for 8 h and the dynamic absorption of nitrogen ions was comparatively analyzed. The seedlings exposed to HVEFs were planted in a greenhouse, the diameter and length of their stems were measured after a 20-d growth period, and their fruit yield was recorded after harvest. Results demonstrated that HVEFs with field intensities of 2.25 and 2.5 kV cm^-1 could respectively improve the dynamic absorption of and by the hydroponically grown tomato seedlings. Many channel proteins were also activated by HVEFs as nitrogen uptake increased. HVEF treatment in the seedling stage is a potential mechanism to enhance nitrogen uptake, cultivate shorter and stockier seedlings, and increase yield.