Studies on the Soil Sickness of the Tomatos.

Abstract

A study was made concerning to the nature and extent of soil-sickness on the tomato. The experiments are excuted by continuous planting in pots. Emp. hasis was placed on the nature of soil-sickness and on the chemical composition of the sicked soils. The results are summarized as follows : 1) In the optimum soil reaction, (pH 5.26〜5.18 N KCl, soluble CaO 0.30〜0.35%) the soil sickness does not occur till at least the third planting. The former planting seems to stimulate the growth of the next planting. 2) In the unsuitable soil reaction (over the pH 6.4 KCl, soluble CaO 0.37%) the first planting of tomato got some growing, great curtails, to a great extent, the growth of the next plantings and the amount of the third yield was smaller than that of the second. 3) The critical point at which the soil showed the phenomenon of soil sickness to the tomato is indicated by the curve of Fig I. According to the figure, seems to be about the place where is contained 28% exchangeable hydrogen against the total base exchangeable capacity. From this fact it is clear that continuous planting may be possible on the soil containing more than 28% hydrogen, and that if the percentage of hydrogen is decreased and that of calcium is increased instead, soil-sickness will appear. 4) The decomposition products of tomato root is a cause of soil sickness of next plantings.