Nitrogen Rate and Application Method Management of Fresh Market Tomato On Sandy Loam Soils.

Nitrogen (N) rate and application methods for fresh market tomatoes in the Mid-Atlantic may impact nutrient loading in fresh and saltwater ecosystems. The objective of this study was to define a nitrogen rate and application method regime for plastic mulched tomatoes grown on sandy loam soils in the Mid-Atlantic. Nine treatments were implemented in a 4 N rate × 2 N application method factorial arrangement to determine N management’s effect on yield. A 0-N treatment was also included. For all treatments, N rates totaling 112, 224, 336, and 448 kg N ha^-1 were applied and split with 50% of total N applied under plastic mulch and 50% applied through biweekly fertigation over the growing season. The incorporated method consisted of 50% total N (100% total pre-plant N) being incorporated into the plant beds immediately before plastic mulch was laid. The second application method, the banded method, consisted of 16.7% total N (1/3 total pre-plant N) being incorporated into the plant beds and 33.3% total N (2/3 total pre-plant N) being applied as a band on the top of the beds immediately before plastic mulch was laid. The band was located halfway between the drip tape and edge of the plant bed. Total marketable yields were weighed, graded, and regressed against N rates. In 2009, there was a quadratic relationship between yield and N rate for the incorporated method (y = -0.6802x² + 249.95x + 47830, R² = 0.93) and the banded method (y = -0.4153x² + 200.81x + 48524, R² = 0.88). Overall, a N rate of 184 kg ha^-1 produced highest yields with the incorporation method and 242 kg ha^-1 with the banded method. Virginia Extension N rate methods should be revised for current plastic mulch production systems and include a variety of application methods.