Nitrogen accumulation and partitioning in field‐grown heirloom tomato cultivar ‘brandywine’

Heirloom tomato (Solanum lycopersicum L.) are a high-value crop for organic vegetable growers. Tomato plants have a high N requirement and are adversely affected by insufficient, excessive, and poorly timed N fertilization. However, little information is available about N dynamics in heirloom tomato and whether their nutritional needs differ from those of hybrid fresh-market (HFM) tomato. The project's goals were to (a) develop seasonal N accumulation curves for the popular heirloom tomato cultivar Brandywine, (b) measure the N removed with the harvested fruits, and (c) determine whether N concentrations from recently matured leaves from adequately and underfertilized fields as well as N accumulation and partitioning fell within published thresholds for HFM tomato plants. We tracked the leaf N concentrations, growth, yields and N accumulation of organically grown Brandywine tomato in a 2-yr replicated field trial under low- and high-N availability treatments. We also collected leaf and fruit samples from fertilized and unfertilized plots on local commercial organic fields. Total N accumulation ranged between 25 to 45 g N per linear bed meter and did not differ with N treatment. The N removed with the harvested fruit averaged 1.14 kg Mg-1 fresh fruit across all sites and years and differed by site but not N fertility. On average, 70-80% of tomato N demand occurred between full bloom and early harvest. The observed N accumulation per unit yield, seasonal N accumulation pattern, and leaf sufficiency thresholds for Brandywine tomato were within the ranges published for HFM tomato varieties.