Date of Award

5-2018

Document Type

Thesis

Degree Name

Master of Science (MS)

Committee Member

Dr. Young Han, Committee Co-Chair

Committee Member

Dr. Ahmad Khalilian, Committee Co-Chair

Committee Member

Dr. Joe Mari Maja

Abstract

Cotton is one of the most important crops in the southern USA with an estimated production value of $6 billion. Cotton root growth is often hindered in the Southeastern U.S. due to the presence of root-restricting soil layers. Soils in this region have three distinct layers, the A horizon, the E horizon and the Bt horizon. The E horizon is often plagued with a hardpan layer that has a much higher bulk density than optimum for crop production. This limits the ability of the plant roots to penetrate into the Bt horizon for uptake of water and nutrients, therefore, reducing yields, limiting productivity, and making plants more susceptible to drought stress. Tillage must be used to temporarily remove this compacted soil layer to allow root growth to depths needed to sustain plants during periods of drought. However, due to significant variability in depth and thickness of hardpan layers in Coastal Plain soils, applying uniform-depth tillage over the entire field may be either too shallow to fracture the hardpan or deeper than required resulting in excess fuel consumption and inefficient use of energy. Therefore, significant savings in tillage energy could be achieved by adjusting tillage depth to match soil’s physical properties. However, there is currently no equipment commercially available to automatically control the tillage depth to match the soil physical properties. Therefore, the objective of this project was to develop and test equipment for controlling tillage depth “on-the-go” to match soil physical parameters, and plant responses in cotton production. The “Clemson Intelligent Plow” was developed by modifying an existing four-row subsoiler into a variable depth tillage platform, which could change the tillage depth from zero to 45 cm (18 in) on-the-go. Site-specific tillage operations reduced fuel consumption by 45% compared to conventional constant-depth tillage. Only 20% of the test field required tillage at recommended depth for Coastal Plain regions (15 inches deep). Cotton taproots in the variable-depth tillage plots were 96% longer than those in the no-till plots (15.4 vs. 7.8 inches). Statistically, there were no differences in cotton lint yield between conventional and the variable-depth tillage. Deep tillage (conventional or variable-rate) increased cotton lint yields by 20% compared to no-till.

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