Doctoral Dissertations

Date of Award

12-2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

Jaehoon Lee

Committee Members

Neal S. Eash, Hubert J. Savoy, Xinhua Yin

Abstract

Soil physical and hydraulic properties control the major soil functions related to the imbibition, transmission and retention of water, air, heat and nutrients. Adoption of no-tillage in Tennessee through the last decades has considerably decreased the fluvial soil losses. However, the long-term effect of no-tillage on soil hydro-physical properties and its interaction with companion practices such as cover crops and crop sequence has not been fully discovered.In this project, three long-term experiments located in West Tennessee Research and Education Center in Milan and Jackson, TN were studied in 2015 and 2016 for soil hydro-physical properties. The effect of 34 years of tillage, fertilization and cover crop, 15 years of crop rotation on no-tillage with winter fallow and 37 years of a range of tillage intensities and no-tillage with and without cover crop on soil physical properties were assessed. Relationship between soil physical properties were determined and by relating the soil physical properties to corn, cotton and soybean yield and long-term yield stability, the most effective cropping and tillage managements were identified.Long-term no-tillage substantially improved soil aggregation, water infiltration and transmission and cotton yield than conventional tillage. Effect of cover crops on measured soil physical properties were less evident than the effect of no-tillage. However, planting hairy vetch and wheat cover crops improved the soil aggregation and increased the water infiltration and transmission significantly compared with no cover crop. No-tillage planted with hairy vetch cover crop experienced significantly higher quasi-steady and cumulative infiltration compared with the other treatment combinations in both years. Cropping corn, cotton and soybean in double cropping sequences did not favor soil in improved physical quality than monoculture while existence of corn in cropping system either as continuous cropping or in sequence improved soil physical quality. Corn rotated with soybean and cotton increased yield and decreased the long-term variance in soybean yield. Under sub-humid climate of Tennessee with relatively high decomposition rate of organic matter, the magnitude of residue turnover and below-ground root activity was found to be key factors increasing the no-tillage potential for additional improvement in soil quality and yield.

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