Doctoral Dissertations

Date of Award

12-1974

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Biosystems Engineering

Major Professor

B. L. Bledsoe

Committee Members

Houston Luttrell, John I. Sewell, Stanley E. Becker, Maxwell E. Springer

Abstract

Minimum tillage practices enhance conservation of soil and moisture resources and reduce the mechanical and labor energy inputs required for crop production. However, obtaining crop stands which are comparable to those established by conventional tillage methods has been difficult with minimum tillage equipment. Also, draft force requirements for minimum tillage systems are substantial, particularly when the system is operated under conditions where adequate soil penetration can be achieved only by adding weight to the machine. In an attempt to overcome these problems, an experimental vibratory furrow opening tool was designed for use with a minimum tillage planter system. The vibratory opener was selected because of reports that vibratory tillage tools can reduce draft force requirements and increase soil fragmentation. A one-row planter system using the vibratory opener and commercial seed metering and covering components was designed and constructed. The machine was field tested in chemically killed sod on two soil types at The University of Tennessee Plant Science Farm. The vibratory opener was operated at frequencies of 10, 20, and 30 Hz with amplitudes of 6 and 15 mm (0.236 and 0.590 inches). Two soil-contacting tools with lift angles of 25 and 45 degrees were tested. The performance of the vibratory system was compared with that of a conventional system using a fluted coulter furrow opener. The tillage accomplished by each treatment combination was determined by measuring the change in soil bulk density and by determining the mean weight clod diameter. Energy inputs to the systems were monitored by measuring both the draft force and the torque input to the oscillator mechanism. Seed emergence ratio was used to indicate stand establishment ability of the systems. The vibratory tool reduced draft force while requiring no increase in total power consumption. Changes in soil bulk density were greater and mean weight clod diameter values were smaller for the vibratory tool. The vibratory tool readily penetrated the soil, whereas up to 180 kg (400 lbs) of additional weight were added to the machine to achieve adequate soil penetration with the fluted coulter. Mean seed emergence ratio values for all treatments in the Etowah silt loam and Sequatchie loam were about 0.76 and 0.87, respectively. The 25-deg blade oscillating at a frequency of 20 Hz with an amplitude of 6 mm (0.236 inches) produced the greatest change in soil bulk density while requiring the smallest draft force and least total operating power. The 45-deg tool oscillating at 30 Hz with an amplitude of 6 mm (0.236 inches) produced the smallest mean weight clod diameter values and the highest seed emergence ratio. However, the values of these various response variables for the two particular treatment combinations were not statistically different from corresponding values of some other treatments.

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