Abstract
This experiment was conducted to determine the relation between the volume of rockwool cube and the root density in the cube during seedling growth, and the plant growth and yield of tomatoes after transplanting to the rockwool system. Tomato seedlings were grown in three rockwool cubes with three different volumes (500 ml (large), 281 ml (medium) and 125 ml (small)). The cubes were piled to the same height of 5 cm. Shoot dry weight increased with the cube size, and differences in shoot dry weight between different cube sizes increased with the period of seedling growth. However, root dry weights were not significantly affected by the volume of rockwool cubes. The results indicated that shoot growth was restricted when the ratio of root dry weight to cube volume (rdw/cv) was over 2.0 mg/ml. The highest marketable yields in each cube size were observed when seedlings were grown for 4, 3 and 2 weeks in large, medium and small cubes, respectively. Regression analysis estimated that the highest yield could be produced when the seedlings were transplanted at rdw/cv ≒ 1.64 mg/ml.
