Date of Graduation

12-2017

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

Edward E. Gbur Jr.

Second Committee Member

Mary C. Savin

Third Committee Member

R. Esten Mason

Keywords

Infiltration, light fraction, microbial biomass, particulate organic matter, wheat-soybean, double crop

Abstract

Improving the understanding of conventional and alternative management practices and their interactions on aggregate-derived particulate organic matter (POM) fractions and soil hydraulic properties, particularly infiltration, is instrumental to soil and groundwater management and long-term sustainability in the Lower Mississippi River Delta (LMRD) region of eastern Arkansas. The objective of this long-term wheat (Triticum aestivum L.)-soybean (Glycine max [L.] Merr.), double-crop (WSDC) field study in a silt-loam soil (Glossaquic Fraglossudalf) in the LMRD region of eastern Arkansas was to evaluate the effects of conventional and alternative management practices, including wheat-residue level, residue burning, tillage and irrigation, on i) POM fractions and the distribution of C and N among POM fractions, including the total POM, light fraction (LF) and intra-POM (iPOM) fraction, in the top 10 cm of soil after 14 years of consistent management and ii) falling-head and tension infiltration after 11 and 14 years of consistent management. Long-term treatment combinations affected (P < 0.05) several macro- (53-250 μm) and micro-aggregate-(<53 μm)-derived coarse and fine POM fractions. Averaged across tillage and burn treatments, the coarse LF C content was 20.3% greater (P ≤ 0.02) in the irrigated-low- (107.3 g m-2) compared to the irrigated-high-residue (89.2 g m-2) and 65.4% greater than in the non-irrigated treatment combinations, which did not differ and averaged 64.8 g m-2. Adjusted for differences in initial volumetric water content (VWC) across sampling dates and averaged across burning and tillage, the falling-head overall infiltration rate in the 2012-non-irrigated-high-residue combination (8.3 cm hr-1) was 2.7 times greater (P = 0.02) than the combined average of all 2015 irrigation-residue-level combinations, which did not differ and averaged 2.2 cm hr-1. The effects of alternative management practices in a WSDC on POM fractions’ C and N contents and water infiltration can lead to greater C and N storage as well as direct and indirect improvements in soil health, aquifer recharge, and crop yields in the LMRD region.

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