The Effect of Nitrogen Sources and Rate on Tomato Bacterial Spots.

The pot experiment was conducted in the greenhouse at the Tropical Research and Education Center, University of Florida to test the effect of nitrogen source and rate on tomato bacterial spots. Treatments were no nitrogen (CK), Urea (UF) and Ammonium Nitrate (ANF) each at 114.3 mg N kg^-1 soil^-1 ( F1), 171.4 mg N kg-1 soil-1 ( F2), 228.6 mg N kg-1 soil-1 ( F3) and 342.9 mg N kg^-1soil^-1 (High N as F4). Starting evaluating the percentage of bacterial spot on tomato leaves was on 5 weeks after transplanting tomato seedlings. Adding N fertilizer significantly reduced the percentage of bacterial spot on tomato leaves compared with CK on 5 weeks after transplanting. On 6 weeks after transplanting only CK and UF1 had significantly higher percentage of bacterial spot on tomato than other treatments. On 7 weeks after transplanting, all ANF treatment had significantly lower percentage of bacterial spot than all UF treatment and the treatment with high N rate had significantly lower percentage of bacterial spot than the treatment with low N rate. The result from this experiment indicated N source of ammonium nitrate and high N rate could significantly reduce bacterial spots on tomato leaves. The mechanism needs to be investigated further.