Masters Theses

Date of Award

5-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Donald D. Tyler

Committee Members

Tom Ammons, Michael Mullen, Glenn Wilson

Abstract

No-tillage farming has become an important practice in many areas of the United States. Because of the loessal soils that exist in West Tennessee and their highly erodible nature, no-till farming is becoming the primary cropping technique with which to reduce erosion and conserve topsoil. Many aspects of no-till farming have been researched in past years; the effects of no-tillage on earthworm population have received little attention in Tennessee agriculture. Earthworms significantly influence the structure and fertility of soils and in turn effect root growth, infiltration of soil water, microbial populations, soil aggregation, and other properties. This research project was conducted to determine and compare the population dynamics of earthworms in cultivated production fields versus no-till production fields. Sites located at the University of Tennessee Milan Experiment Station were chosen for sampling. The sampling was done 4/94, 10/94, and 4/95. Samples for determining the effect of no-till were taken from three no-till and two tilled production fields and from an ongoing experiment containing both no-till and tilled plots. Samples were also taken from a long term no-till cover crop experiment to compare the effects of various covers. Six 30cm X 30cm X 15cm deep volumes of soil were taken from each production field and one sample per plot from the ongoing experiments. Soil samples were taken to determine bulk density, volumetric water content, total carbon, and pH. Surface residue samples were also taken at each no-till sample site. Earthworms were extracted by hand sorting and preserved in 10% formalin solution for identification. Three seperate species were identified: two native species; Diplocardia caroliniana and Bimastos longicinctus and one exotic; Apporectodea trapeszoides No-till cropping systems had a significant effect on earthworm populations for the 10/94 and 4/95 sampling periods and over the entire period due to the availability of food and limited soil disturbance. Length of time in no-till also had a significant effect on population for the 4/94 and 10/94 sampling periods and over the entire sampling period. Cover crop showed no significant difference for the 10/94 and 4/95 periods, but did for the 4/94 sample period. The results of the analysis performed had a high rate of variability overall.

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