TOMATO GROWTH AND NUTRIENT-UPTAKE PATTERN AS INFLUENCED BY NITROGEN FORM RATIO

Although most plants can use ammonium (NH4) or nitrate (NO3) as a source of N, the degree of effectiveness of these two N forms on tomato growth was found to be dependent on the NH4:N03 ratio. The addition of small amounts of NH4 to NO3 solutions, up to 14 ppm, improved plant growth but did not significantly change the uptake of K, Ca, and Mg as compared to NO3 alone. However, with 28 ppm NH4-N and above, dry weights and cation accumulations decreased in amounts of about 35 to 50% and in a 12-day period. The decreased dry weight and cation uptake with 77:77 ppm NH4:NO3 ratio was comparable to that obtained with a O N treatment for the same interval. © 1990, Taylor & Francis Group, LLC. All rights reserved.