Research On Soil Electrical Properties And The Technology Of Killing Pests By Elcetronic Field

In this paper, soil electrical properties and the technology of killing pests by electronic field were studied. The high voltage pulse generator, soil testing system and pest holding device that were needed in the experiment were made. We discussed the effects on the electric shock tolerance of three different kinds of soil insect such as cutworm, mole cricket and grub under different discharging conditions, such as pulse voltage, the frequency, and the pulse duty factor, to find the optimum parameters of killing pests using electronic field. Meanwhile, the electric transmission characteristic of soil in different conditions such as soil kinds, bulk density, nature water content and temperature had been analyzed, to provide a theoretical basis for the technology of killing soil pests by electronic field. It includes four parts: the first part, design of testing equipment, including a set of high pulse generator, soil testing system and pest holding device; the second part, research on the tolerance of three different kinds of soil insect; the third part, discuss the soil basic physical parameters distribution properties and the factors affecting the soil electric transfer characteristic; the last part, the design method equipment. The main experiment results as follows:(1) The high voltage pulse generator is the core equipment. The generator developed in this study has two work patterns both inner and outer. The parameters are as follows: the power is 300W, frequency is 10-200Hz, voltage is 0-2000V and pulse duty factor is 0.1-0.9.(2) Pest type, pest instars, holding manner, discharging time, pulse voltage, pulse frequency and pulse duty factor are the main factors that influence the electric shock tolerance of soil pests. Under single factor experiment, the best pulse parameters and scopes are ensured. The best parameters for cutworm are as follows: pulse voltage is 55V, pulse frequency is 80Hz, pulse duty factor is 0.6. The parameters for grub are as follows: pulse voltage is 45V, pulse frequency is 40Hz and pulse duty factor is 0.5. The parameters for mole cricket are as follows: pulse voltage is 65V, pulse frequency is 90Hz and pulse duty factor is 0.7. Experimental results confirmed that these parameters can get a death rate more than 93%.(3) Using oven method to test the nature water content of the soil samples, the water content is 19.86%-30.15%. Using cutting ring method to test the bulk density of the samples, the bulk density is around 1.25g/cm3. The result of the soil temperature test shows that: the temperature varies from 7.1oC to 41.5 oC with lighting time and depth, the highest temperature comes on 13:00 and the inner soil temperature has inertia.(4) Soil type, under pressure time, nature water content, bulk density, soil temperature, pulse voltage, pulse frequency and pulse duty factor are the factors that influence the soil electric transfer characteristic. Soil resistivity varies greatly with the under pressure time, we choose 10 seconds with experimental condition.(5) Relation between soil resistivity and pulse voltage: soil resistivity goes down with the pulse voltage goes up, especially when the voltage in under 800V. Relation between soil resistivity and pulse frequency: soil resistivity goes up with the pulse frequency goes up. Relation between soil resistivity and soil water content: soil resistivity goes down with the water content goes up, and the line is approximately linear. Relation between soil resistivity and soil bulk density: soil resistivity goes down with soil bulk density goes up. Pulse duty ratio and soil temperature has little influence on soil resistivity.(6) Choosing the disc blades as electrode, based on the rotary cultivator model B-155 produced by Italy MASCHIO company, we discussed the choosing and calculating method of the pulse parameters such as voltage, frequency and duty ratio.