Theses and Dissertations

ORCID

https://orcid.org/0009-0004-6237-6772

Advisor

Gholson, Drew M.

Committee Member

Spencer, Gene Dave, III

Committee Member

Ashwell, Nicolas Quintana

Committee Member

Locke, Martin A.

Committee Member

Pieralisi, Brian K.

Date of Degree

5-10-2024

Original embargo terms

Visible MSU only 1 year

Document Type

Graduate Thesis - Campus Access Only

Major

Plant and Soil Sciences (Agronomy)

Degree Name

Doctor of Philosophy (Ph.D)

College

College of Agriculture and Life Sciences

Department

Department of Plant and Soil Sciences

Abstract

Aquifer resources in the mid-southern USA are declining because of irrigation water use in row crops. This study assesses the effectiveness of conservation tillage and cover cropping systems in reducing irrigation water use while improving or maintaining cotton yield and profitability. The effects of different tillage and cover crop cropping systems on soil moisture, irrigation water use, cotton yield, and profitability were investigated near Stoneville, MS on a Dubbs silt loam (fine-silty, mixed, active, thermic Typic Hapludalfs) and a Bosket very fine sandy loam (fine-loamy, mixed, active, thermic Mollic Hapludalfs). Reducing tillage reduced irrigation water use by 3.3 cm ha-1, and adding cover crops to conservation tillage practices further reduced irrigation water use to nearly zero (0.5 cm ha-1). Before irrigation, the conventionally-tilled soils had at least 59% greater soil tension (less soil moisture; P>F = 5.41×10-8) than all other conservation practices. Soil moisture was higher where cover crops were sown (20 kPa) than where treatments were winter fallowed (34 kPa). Prescribed irrigation to replenish treatments that reached the irrigation threshold (80 kPa) did not change the trend in soil moisture among treatments. The use of any conservation practice improved season-long soul moisture by at least 19 kPa (P>F = 3.8×10-12). Cover crops infiltrated 13% (P>F = 0.003) more rainwater than winter fallow, and subsoiling improved precipitation infiltration by 16% over non-subsoiled systems (P>F = 0.009). Lint yields were similar across all treatments in 2021 and 2022, but they were 222 kg ha-1 less (P>F = 0.029) in treatments with a cover crop than the control in 2023. The lowest costs acre-1 were realized when the no-seedbed-tillage with winter fallow treatment was used. Utilizing a cover crop reduced irrigation expenses by $7.40 acre-1 compared to the conventionally-tilled control. However, gross returns were reduced by $113 acre-1 where cover crops were sown and reduced overall net returns by $201 acre-1. The strip-tillage and no-seedbed tillage systems with winter fallow reduced overall risk of production when compared to the conventional control and treatments with a cover crop. Conservation systems successfully reduced irrigation water use, but systems with a cover crop may not be economically viable because of low yields and high costs.

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