Substrate Water Content and Nitrogen Interactions in Growing Media: Yield, Fruit Quality, Water Consumption and Water Use Efficiency on Tomato

Substrates water content x N rate experiments were conducted using a D-saturation design in media pot planting tomato (Solanum lycopersicum L.) during September 2006 to February 2007 in Beijing. A range of substrate water content and N rates were selected to permit the calculation of appropriate water x N production functions. The results indicated that under the same nitrogen level, tomato yield increased significantly with the water amount applied, T-2 and T-7 was 108.12%, 214.96% higher than T-1 and T-3 respectively. However, under the same water level, tomato yield decreased with N rate, T-3 was 42.51% lower than T-1, and T-7 was 12.99% lower than T-2. Water consumption increased significantly with water applied under the same N rate, and decreased with N rate under the same water level but not significant, T-3 and T-7 was 33.12%, 20.29% less than T-1 and T-2 respectively. There was a positive effect by interaction between water and nitrogen on water use efficiency but not significant. Fruit vitamin C, sugar, acids, nitrate, and TSS contents were decreased with water and increased with N rate. An over-irrigation with under-N treatment or under-irrigation with over-N treatment in tomato will produce a low soluble solids content but high crop yield and poor crop yield but high soluble solids content respectively. Our results recommend that the optimum levels of water and nitrogen for the high yield, good quality under the study condition were the substrates' water content of 90%, and pure nitrogen rate of 0.58-0.74 g/pot/time.