Agronomy and Horticulture, Department of

 

First Advisor

Andrea D. Basche

Committee Members

Caro Cordova, Jenny Keshwani

Date of this Version

11-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree of Master of Science

Major: Agronomy

Under the supervision of Professor Andrea D. Basche

Lincoln, Nebraska, November 2024

Comments

Copyright 2024, Bridget McKinley. Used by permission

Abstract

Cover crops (CC) provide essential ecosystem services including soil conservation, nutrient cycling, and weed suppression, through the accumulation of aboveground (AGB) and belowground (BGB) biomass. While AGB has been widely studied, BGB contributions, particularly root development and distribution, remain less understood. This study evaluated fall-planted CC across three Nebraska ecoregions, assessing AGB productivity, BGB biomass, and correlations between ground cover, plant height, and AGB.

Thirty treatments, including grasses, legumes, brassicas, and mixtures, were evaluated over two fall growing seasons (2022–2023 and 2023–2024) at three UNL research centers in northeast, west central, and west Nebraska. AGB was highest at west site (1,778 kg ha⁻¹), followed by northeast (1,364 kg ha⁻¹) and west central (1,102 kg ha⁻¹). Elbon rye produced the greatest biomass, reaching 9,608 kg ha⁻¹ in the west in spring 2024, while legumes including hairy vetch, and pea yielded less than 470 kg ha⁻¹ and had higher weed densities. Correlations (R = 0.43–0.91) were observed between fall ground cover and spring biomass, with cultivars including Elbon rye supporting higher productivity into spring. Treatments with > 80% ground cover produced > 3,000 kg ha⁻¹ of biomass, while those with

For belowground productivity, selected treatments (AU-Merit hairy vetch, Gore wheat, Montech triticale, Elbon and Yankee rye and mixture of Elbon rye and AU-Merit hairy vetch) were evaluated for root biomass, root depth distribution (0-5 cm and 5-30 cm), and root-to-shoot ratios. Total root biomass varied, with grasses consistently producing more than the control, and hairy vetch. Rye cultivars also produced greater root biomass at both depths across locations, averaging 73% higher than controls. In northeast Nebraska, Elbon and Yankee rye produced root biomass over 0.57 g, significantly outperforming other species. Root-to-shoot ratios varied by species and region, with AU-Merit hairy vetch showing a high ratio, indicating greater root investment despite lower AGB.

These findings highlight the potential of certain CC, particularly rye cultivars, to deliver reliable biomass accumulation across Nebraska’s varied climates.

Advisor: Andrea D. Basche

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