Date of Graduation

12-2016

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

Larry C. Purcell

Second Committee Member

Mary C. Savin

Third Committee Member

W. Jeremy Ross

Fourth Committee Member

Edward E. Gbur

Keywords

Biological sciences; Agronomy; Soil science; Soybean

Abstract

Continued achievement of soybean [Glycine max (L.) Merr.] yields greater than 6719 kg ha-1 (100 bu ac-1) will depend on decreasing the yield gap, which is contingent on gathering more information regarding the soil physical, chemical, and microbiological environment and the main plant factors contributing to high-yield soybean. Therefore, understanding the main factor differences between high- and average-yield areas may provide insight for making management decisions to increase yields. The objectives of this study were i) to evaluate the effects of region and soil depth on soil property differences between high- and average-soybean-yielding areas, ii) to determine which soil properties are most related to ultra-high soybean yields, and iii) to identify correlations among aboveground biomass and seed nutrient concentrations from various growth stages and soil properties for high- and average-yielding fields. In each of seven regions of the “Grow for the Green” yield contest in Arkansas, one contest-entered, high-yield (HY) area in close proximity to one average-yield (AY) area were plant-sampled at three growth stages in 2015 and soil sampled from two depth intervals (0- to 10- and 10- to 20-cm) in each yield area immediately prior to or just after harvest in 2014 and 2015. In 2014 and 2015, yields in the AY areas averaged 4633 kg ha-1 (69 bu ac-1), while yields in the HY areas averaged 5647 kg ha-1 (84 bu ac-1). Averaged across soil depth and years, selected measured soil properties differed (P < 0.05) between HY and AY areas within at least one region. Averaged across regions, Shannon’s microbial diversity was greater (P < 0.05) in HY than in AY areas. Averaged across growth stage, some plant properties were greater (P < 0.05) in HY areas, while others were greater (P < 0.05) in AY areas across regions. Since this study encompassed a wide variety of landscapes and soybean management systems across Arkansas, results of this study have the potential to help growers better understand soil and plant properties in their own fields that contribute to or hinder achieving ultra-high soybean yields, which may contribute to minimizing the soybean yield gap.

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