Interactive Effects of Elevated CO(2) and N Fertilization on Yield and Quality of Tomato Grown Under Reduced Irrigation Regimes

The interactive effects of CO(2) elevation, N fertilization, and reduced irrigation regimes on fruit yield (FY) and quality in tomato (Solanum lycopersicum L.) were investigated in a split-root pot experiment. The plants were grown in two separate climate-controlled greenhouse cells at atmospheric [CO(2)] of 400 and 800 ppm, respectively. In each cell, the plants were fertilized at either 100 or 200 mg N kg(-1) soil and were either irrigated to full water holding capacity [i.e., a volumetric soil water content of 18%; full irrigation (FI)], or using 70% water of FI to the whole pot [deficit irrigation (DI)] or alternately to only half of the pot [partial root-zone irrigation (PRI)]. The yield and fruit quality attributes mainly from sugars (sucrose, fructose, and glucose) and organic acids (OAs; citric acid and malic acid) to various ionic (NH(4)(+), K(+), Mg(2+), Ca(2+), NO(3)(-), SO(4)(2-), and PO(4)(3-)) concentrations in fruit juice were determined. The results indicated that lower N supply reduced fruit number and yield, whereas it enhanced some of the quality attributes of fruit as indicated by greater firmness and higher concentrations of sugars and OAs. Elevated [CO(2)] (e[CO(2)]) attenuated the negative influence of reduced irrigation (DI and PRI) on FY. Principal component analysis revealed that the reduced irrigation regimes, especially PRI, in combination with e[CO(2)] could synergistically improve the comprehensive quality of tomato fruits at high N supply. These findings provide useful knowledge for sustaining tomato FY and quality in a future drier and CO(2)-enriched environment.