Document Type

Thesis - Open Access

Award Date

2020

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Sharon Clay

Keywords

Northern Great Plains, perennial, phytoremediation, saline, sodic, South Dakota

Abstract

Several decades of above average precipitation in South Dakota has increased the area of saline and sodic soils, which reduce crop yields and inhibit sensitive plant growth. Saline and sodic soils are difficult to remediate using traditional agricultural crops. Establishing salt tolerant perennial species may restore productivity to salt affected areas. Two perennial grass mixtures (mix 1: slender wheatgrass, beardless wildrye; mix 2: slender wheatgrass, western wheatgrass, green wheatgrass, creeping meadow foxtail) were dormant frost seeded along a topographic gradient in Clark Co., SD. Soils were Forman-Cresbard loam and a Cresbard-Cavour loam with surface electrical conductivity (EC1:1) that ranged from < 0.5 to >15 dS m-1 and sodium < 400 to >2500 ug g-1. Perennial grass and corn biomass, soil chemical properties, weed cover, and greenhouse gas emissions were quantified in two growing seasons (2018 and 2019). By 2019 perennial grass mixtures and corn reduced soil EC1:1 and sodium similarly. Slender wheatgrass was the dominant species in mix 1, comprising up to 65% of September 2018 total biomass (246-1705 kg ha-1) and 83% in 2019 (6400-9700 kg ha-1). AC Saltlander was the dominant species in mix 2 comprising up to 61% of 2018 total September biomass (604- 2646 kg ha-1) and 81% in July, 2019 (5853-10663 kg ha-1). In July, 2019 mix 1 and mix 2 saline plots had 16% and 3% weed cover (kochia/foxtail barley), respectively, compared to 75% in corn. Over a 7 d period in July, 2018 and 2019 non-fertilized barren saline soils emitted 2.09 and 4.89 g N2O-N ha-1 hr-1, respectively; and 611 and 324 g CO2-C ha-1 hr-1, respectively. During the same time period, grass vegetated non-saline soil emitted 0.38 and 0.46 g N2O-N ha-1 hr-1 in 2018 and 2019, respectively; and 1589 and 2538 g CO2-C ha-1 hr-1, respectively. Corn vegetated non-saline soil emitted 0.01 and 0.62 g N2O-N ha-1 hr-1 in 2018 and 2019, respectively; and 1821 and 1812 g CO2-C ha-1 hr-1, respectively. Urea application (224 kg-1 ha-1) increased CO2 emissions in all treatments both years from 19-155%, but increased N2O emissions by 102-704% in 2019 only. Simulated root exudates, plant residue decomposition, simulated root respiration, and barley growth increased greenhouse gas emissions compared with nontreated controls in laboratory studies on a saline Cresbard-Cavour loam. Growing barley plants reduced soil EC1:1 from 6.3 dS m-1 to 5.9 dS m-1 and reduced soil NO3- from 509 ug g-1 to 428 ug g-1 after 7 weeks and increased N2O-N and CO2-C flux by 224% and 244%, respectively, from baselines of 0.359 ug N2O-N kg-1 hr-1 and 206 ug CO2-C kg-1 hr-1. Revegetating salt affected soils with perennial grasses may reduce soil EC1:1, NO3-, Na, and weed cover and also may improve soil microbial activity and nutrient cycling.

Library of Congress Subject Headings

Phytoremediation -- South Dakota.
Soils -- South Dakota -- Analysis.
Soil management -- South Dakota.
Soils, Salts in.
Sodic soils.
Salinity. 6
Perennials.
Grasses.

Format

application/pdf

Number of Pages

186

Publisher

South Dakota State University

Rights

Copyright © 2020 Douglas J, Fiedler

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