Growth Control by NO3-N Supply in Production of High Soluble Solids Tomato in a Recirculating Capillary Hydroponic System

We investigated how the supply of NO3-N to triple-truss tomatoes grown for high soluble solids content (SSC) in a recirculating capillary hydroponic system affected growth, fruit yield, and SSC. Although decreasing the NO3-N supply decreased the top fresh weight, top dry weight, leaf area, and fruit weight, SSC remained steady at > 9 % (Exp.1). Although leaf area was smaller in the S-M treatment (with a small amount of NO3-N until flowering of the second truss then a medium amount) than in M-M (with a medium amount of NO3-N before and after), the harvested fruits weight was almost equal, and SSC was > 10 % (Exp. 2). However, leaf area index (LAI) in S-L (with a small amount of NO3-N then a large amount) was smaller than that in M-M, relative light intensity in S-L was greater than that in M-M and fruit weight (SSC > 8 %) in S-L was greater than that in M-M at a planting density > 5.7 m-2 (Exp. 3). At LAI > 2.5, the increase in fruit weight per unit area tended to slow, although fruit weight per unit area in S-L was greater than that in the other treatments. These results suggest that changing of the NO3-N supply during the production of high SSC tomato improved fruit weight per unit area at high plant density.