Masters Theses

Date of Award

5-1994

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Donald D. Tyler

Committee Members

H. Paul Denton, Gary Lessman, Fred Allen, Robert Freeland

Abstract

No-tillage crop production has gained popularity in Tennessee due to the following reasons: demand to meet conservation compliance requirements regarding soil erosion, less time spent in spring planting operations, savings in fuel and labor, and improvements in weed control. Differences have been measured in soil properties between no-till and conventional tillage. These differences have raised concerns about effects on plant growth and rooting characteristics. An experiment was designed to evaluate soybean (Glycine max L., Merr.) root distribution under conventional and no-tillage, to evaluate traffickability of conventional and no-tillage and to evaluate the effect of trafficking on soybean root distribution. The experiment was conducted on long term tillage plots on Lexington silt loam soil (fine silty, mixed, thermic, Typic Paleudalf) located at the West Tennessee Experiment Station at Jackson, Tennessee. The experimental design in 1992 was a randomized complete block with tillage as the treatment, replicated four times. In 1993 the design was a randomized complete block with a split- plot arrangement of treatments replicated four times. Tillage was the whole plot treatment and traffic was the subplot treatment, and there were four replications. Soybean root distribution was evaluated using minirhizotrons. Trafficking was done in 1993 using an 8,100 kg tractor and evaluated by measuring changes in soil surface elevation, bulk density and penetrometer resistance. In 1992 there were no differences in root distribution until late in the season. Soybeans had greater root length under conventional tillage at deep (>60 cm) depths than soybeans grown under no-till. In 1993, 30 days after emergence, no-tillage plots had greater root length at shallow (< 25 cm) depths and conventional tillage plots had greater root length below 25 cm. Within row position had greater root lengths at depths less than 20 cm while between row positions had greater root length below 30 cm. At 30 days after emergence there were greater root lengths within row in the trafficked zone of the traffic treatment, but by 60 days after emergence there were no differences in root lengths related to traffic. The no-tillage treatment had greater traffickability, as indicated by less soil displacement, smaller bulk density increases and smaller penetrometer resistance increases than in conventional tillage. Due to high soil displacement in conventional tillage from trafficking, soil leveling was required before planting. In 1992 no-tillage had significantly greater yields than conventional tillage but in 1993 there were no differences in yields from tillage or traffic treatments. There were no agronomically significant differences observed in yield or root lengths from either tillage or traffic effects in this study.

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