Responses of field-grown tomatoes to nitrogen sources

Abstract

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 greenhouse studies. The objective of this research was to examine the effect of N fertilizer sources (ammonium nitrate (NH4NO3), potassium nitrate (KNO3), urea (CO(NH2)2), urea ammonium nitrate (UAN), and calcium nitrate (Ca(NO3)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 (CaCl2). 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 wood be suitable for tomato production, if price of N fertilizer materials are the same.