Date of Graduation

7-2015

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor

Kristofor R. Brye

Committee Member

Pengyin Chen

Second Committee Member

Edward E. Gbur

Third Committee Member

John C. Rupe

Abstract

Adoption of management practices that maintain or increase soil organic matter (SOM), which contains 58% carbon (C) on average, may help to mitigate climate change by sequestering atmospheric C. Therefore, the main objective of this study was to determine the long-term trends in SOM, soil C and nitrogen (N), bulk density, various soil chemical properties (i.e., pH, electrical conductivity [EC], and Mehlich-3-extractable nutrients) in the top 10 cm, and soybean yield as affected by residue burning (burning and non-burning), tillage (conventional and no-tillage), irrigation (irrigated and non-irrigated), and N-fertilization/residue level (high and low) in a wheat (Triticum aestivum L.)-soybean [Glycine max (L.) Merr.], double-crop system in eastern Arkansas. The secondary objective was to determine the relationship between soil water potential (-MPa) and soil water content (g g-1) in the top 7.5 cm as affected by residue treatments. The field site has been consistently managed for 13 years at the University of Arkansas Lon Mann Cotton Research Station near Marianna, Arkansas on a Calloway silt loam (fine silty, mixed, active, thermic Glossaquic Fraglossudalf). Averaged across all other factors, SOM did not differ over time (P > 0.05) under irrigation, while SOM content increased over time (P < 0.05) until approximately nine years after initial conversion when SOM decreased thereafter under dryland production. Results indicated that irrigation management caused many of the largest differences in near-surface soil property trends over time, namely SOM and C, compared to the other field treatments. The relationship between the natural logarithm of soil water potential and the gravimetric soil water content was only affected (P < 0.05) by the N-fertilization/residue level treatment. Averaged across tillage, burning, and irrigation, soil water contents under high residue treatment exceeded those water contents under low residue treatment at the same water potential. The increased soil water retention under high residue treatment may be related to increased biomass inputs, SOM accumulation, and soil aggregation at the < 2mm level compared with low residue treatment. Understanding the long-term effects of growing-season weather patterns as well as irrigation, burning, tillage, and fertilization management on near-surface soil properties is critical to developing sustainable agricultural practices in the mid-South.

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