Abstract
In the preceding paper, the basic characteritics of the new soil sterilizing method in which soil was sterilized by the heat transmitted from the radiating pipes buried in the soil were clarified. The outline were as follows: The lethal temperature of main soil borne pathogens of indoor horticultural crops was 60°C. And initial air temperature and air velocity following in the radiating pipe of 10cm diameter, 20m length were 120°C and 8 to 10m/s respectively. In the present paper, various problems regarding the design of sterilizing device was discussed and also, results of trial production of the device and field experiments were detailed. These results are as follows.
In application of commercial greenhouse heaters to the soil sterilization a number of problems to be solved were found. These were as follows: 1) insufficient adiabatic processing of the heater shell plate. 2) shortage of the wind power of fan. 3) lacks of air exhaust port numbers. 4) uniform temperature and velocity of heated air between increased ports. 5) mobility of the heater.
The air heater for soil sterilization was fabricated. The brief specifications and outline drawing are shown in table 4 and figure 1. The results of experiments on the practical scale were as follows.
1) The fusarium wilt with cucumber died completely with treatment of 60°C during 10 minutes. 2) As a result of the experiments on the effect of the sterilization on the growth, the yields and the weed controls, the satisfactory results were obtained respectively. The comparison of the cost analysis of the heated air method and steaming method was investigated. The total cost including the depreciations of air heater and other instrument in this method was equivalent about 58% to the steaming method.
The new system of soil sterilization developed by the authors was considered to have reached the stage for practical use.
