Responses of field-grown tomatoes to nitrogen sources

Although the effect of various N fertilizers on tomato yield and quality has been previously examined, much of this research was conducted in hydroponic or green-house studies. The objective of this research was to examine the effect of N fertilizer sources (ammonium nitrate (NH 4 NO 3 ), potassium nitrate (KNO 3 ), urea (CO(NH 2 ) 2 ), urea ammonium nitrate (UAN), and calcium nitrate (Ca(NO 3 ) 2 ) on tomato ( Lycopersicon esculentum Mill.) growth, yield, and fruit quality. The 2-year experiment was conducted using black plastic mulch covered raised beds with drip fertigation. A total of 180 lb acre (202 Kg·ha −1 ) N was applied with each N source, with 25% applied preplant and premulch and remaining N applied as 10 weekly applications of 13.5 lb/acre (15.2 kg·ha −1 ). If an N source contained Ca or K, that amount was applied to all other N sources (preplant and fertigated) as potassium chloride (KCl) or calcium chloride (CaCl 2 ). Collected data included plant height, leaf N concentration, and yield. Different N sources had varying and inconsistent effects on fruit yield and quality. Although plant height and stem diameter from UAN treatments were always smaller than those from other N sources, this effect did not extrapolate to decreased total marketable yield. Differences in N concentration of tomato leaf tissue were not consistent with N source and were not related to differences in tomato yield. There were few differences in yield and quality of nonmarketable fruit due to N source. In this one-site, 2-year study, it appears that any of the N sources studied would be suitable for tomato production, if price of N fertilizer materials are the same.