Impact of Pre-planting NO3:NH4 Ratios in Root Media on the Growth of Tomato Plug Seedlings

摘要

This research was conducted to investigate the influence of various pre-planting NO3:NH4 ratios in the coir dust+peatmoss+perlite (3.5:3.5:3, v/v/v) medium on the growth of tomato plug seedlings (cv. Dotaerang Dia), changes in chemical properties of root media, and tissue nutrient contents. With the fixation of N concentration to 300 mg.L-1, the NO3:NH4 ratios were adjusted to 100:0, 73:27, 50:50, 27:73, 0:100. Then, root media containing various NO3:NH4 ratios and equal concentration of other essential nutrients were filled into 50-cell plug trays and the seeds of 'Dotaerang Die' tomato were sown. The investigation of seedling growth and tissue analysis for mineral nutrient contents based on the dry weight of above-ground tissue were conducted 6 weeks after sowing. As seedlings grew, the EC decreased quickly and pH increased gradually in the all treatment media. The plant height, fresh weight and dry weight of seedlings in the treatment of 50:50 (NO3:NH4) were 29.0 cm, 13.7 g, and 1.21 g, respectively, which were the highest among treatments tested. However, the seedlings in the treatment of 0: 100 (NO3:NH4) had 26.5 cm, 11.2 g, and 0.92 g in plant height, fresh weight and dry weight, respectively. These were the poorest among the treatments tested. The tissue contents of N were 2.77 to 3.22% in all the treatments. The treatment of 27: 73 (NO3:NH4) had the highest contents of Fe, Mn and Zn and that of 0:100 (NO3:NH4) had the lowest contents of Mg, Na, Cu, Mn and Zn among the treatments tested. The results indicate that NH4 ratio should be lower than 50% in the coir dust+peatmoss+perlite (3.5:3.5:3, v/v/v) medium for seedling growth of tomato and the optimum ratio will be used to draw up guide lines for plug seedling production.