Objectives To optimize the nutrient solution management for substrate cultured tomato, we studied effects of regulating nutrient solution based on leaf number growth dynamic on growth, yield and quality of tomatoes.
Methods In greenhouse, tomatoes were used as experimental material, and four nutrient solution supplying modes with different frequency of increasing the concentration of nutrient solution were conducted. The nutrient solution concentrations were respectively increased by 0.1, 0.2 and 0.3 mS/cm in TR0.1, TR0.2 and TR0.3, while leaf number in the corresponding treatments increased by one, two, and three respectively. In the CK, the nutrient solution concentrations of 1.5, 2.1 and 2.7 mS/cm were respectively set at three growth stages of tomato, from the planting to before the flowering, flowering to the first cluster, and the first cluster until the end of the harvest. There were four treatments with four repetitions. The plant height, stem diameter, leaf number, yield and quality of tomatoes, as well as the total salt content and utilization efficiency of nutrient solution were measured to determine the effects.
Results The frequencies of increasing nutrient solution concentration in the TR0.1, TR0.2 and TR0.3 were 2.0–5.6 times of that of the treatment CK. The order of total salt contents of nutrient solution, total contents of macroelements and microelements all showed as CK > TR0.1 > TR0.2 > TR0.3. No significant differences were detected in the stem diameters and leaf numbers among all treatments. Compared with the CK, the yield and nutrient utilization efficiency of the TR0.1 increased by 30.4% and 37.7% ( P < 0.05) respectively. Also, in comparison with the CK, the contents of nitrate and titratable acid in TR0.1, TR0.2 and TR0.3 respectively decreased by 19.4%–68.6% and 16.7%–23.2% ( P < 0.05), while the total soluble solid and sugar-acid ratios respectively increased by 0.8%–12.9% ( P < 0.05, except TR0.3) and 31.3%–34.7% ( P < 0.05), which indicated that the quality of tomato in the TR0.1, TR0.2 and TR0.3 which were based on leaf number growth dynamic was better than that of the CK which was regarded as the conventional nutrient solution supplying mode for tomato. In addition, compared with the TR0.3, the plant height in TR0.1 increased by7.5 cm ( P < 0.05), and the total yield and the nutrient utilization efficiency increased by 30.7% and 29.4% ( P < 0.05) respectively. Moreover, the highest contents of nitrate, titratable acid and soluble solid as well as the sugar-acid ratio were all observed in the TR0.1, and there were significant differences among the treatments, except for the sugar-acid ratio.
Conclusions The controlling mode of tomato nutrient solution based on leaf number growth dynamic is better than the conventional management mode based on the three growth stages, resulting in higher yield and better quality of tomato, and high utilization efficiency of nutrient solution. Additionally, the TR0.1, whose nutrient solution concentration was increased by 0.1 mS/cm while leaf number increased by one, showed the best effects on the promotion of growth and nutrient absorption, as well as yield and quality of tomato. Therefore, TR0.1 was considered as the most optimal controlling method of tomato nutrient solution.
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