Author ORCID Identifier

https://orcid.org/0009-0004-6928-0570

Semester

Summer

Date of Graduation

2023

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Division of Plant and Soil Sciences

Committee Chair

James Kotcon

Committee Member

Thomas Griggs

Committee Member

Michael Gutensohn

Committee Member

Rakesh Chandran

Abstract

Birdsfoot trefoil (Lotus corniculatus L.) (BFT) is a high quality, tanniniferous forage legume that has been shown to mitigate gastrointestinal nematode (GIN) infection in sheep. Reliable establishment of birdsfoot trefoil in existing pastures is difficult due to BFT’s poor seedling vigor, susceptibility to crown and root rot, and, perhaps chiefly, competition from other pasture plants. Most existing pastures in the Northeastern United States are primarily composed of cool-season grasses, many of which can be highly competitive. A common form of interplant competition is allelopathy, which occurs when secondary metabolites produced by a plant inhibit a necessary growth process of another plant. Allelopathic competition in cropping systems has been extensively studied, however very little has been done to assess allelopathic relationships between common cool-season forages and BFT. We investigated the presence and effect of allelopathic relationships of eight common cool-season forage grasses (Kentucky bluegrass, meadow fescue, orchardgrass, perennial ryegrass, reed canarygrass, smooth brome, tall fescue, and timothy) on BFT germination and radicle emergence. BFT seeds were germinated in a bioassay using serial dilutions of leaf tissue extracts and root leachates from the eight grasses, as well as from root and stem + leaf tissue from BFT to assess autotoxicity. We found that BFT germination and radicle length was allelopathically inhibited by the forage grasses and BFT. Inhibition varied widely by concentration, grass species, and source. Some grasses, such as orchardgrass and timothy, were inhibitory only at the highest concentration, while the more inhibitory grasses (reed canarygrass, tall fescue, and meadow fescue) were highly inhibitory at lower levels. BFT leaf + stem tissue extracts were found to inhibit BFT germination by up to 100%. Root leachate was overall much less inhibitory, though reed canarygrass root leachates inhibited BFT mean radicle length. Our results suggest that pasture establishment of BFT could be limited by the presence of severely inhibitory allelopathic relationships between BFT and the grasses into which it is commonly seeded.

Growth patterns of forage grasses may be categorized as bunch-type or rhizomatous. Bunch-type grasses form discrete clumps and spread via tillering. Rhizomatous grasses are sod-forming and spread through rhizomes and stolons, increasing competition by decreasing space available to other pasture plants. Birdsfoot trefoil (Lotus corniculatus L.) (BFT) is a high quality, tanniniferous forage legume that has been shown to mitigate gastrointestinal nematode (GIN) infection in sheep. Pasture establishment of birdsfoot trefoil is chiefly inhibited by competition from other pasture plants. Though it has been anecdotally suggested that pasture seedings of Birdsfoot trefoil (Lotus corniculatus L.) (BFT) into bunchgrass swards may increase the likelihood of establishment, very little has been done to assess the role of grass morphology (bunch-type or rhizomatous) on BFT pasture seedings. We investigated the influence of grass growth habit on BFT seeding success in a field plot trial. Norcen BFT was planted via one of three no-till seeding treatments (coulter, coulter + Danish shovel, and rototill swath) into either a pure stand of one of seven cool-season grasses or a mixed sward consisting primarily of bunchgrasses or rhizomatous grasses. Stand counts of BFT and percent ground cover were used to quantify the influence of grass type on BFT seeding, with initial counts being taken in 2021 and emergence data being taken in 2022. In 2021, grass type significantly influenced BFT seeding success, with bunchgrass swards having higher BFT emergence, establishment, and persistence than in the rhizomatous swards. Rhizomatous swards had lower BFT counts and experienced total BFT stand declines earlier in the trial than bunchgrass BFT seedings. Seeding method was not a significant factor when analyzed by grass type. All BFT stands experienced a 100% decline in stand counts by the end of the 2021 season. In June of 2022, BFT counts were compared by seeding method and grass type to June 2021 emergence data. Over both years, only seeding method, year, and grass type*year were significant, with no overall differences existing between BFT emergence in bunch grass swards and rhizomatous sod. Seeding method significantly impacted BFT emergence, with the coulter + Danish shovel having the highest 2022 emergence and the rototill swath resulting in negligible 2022 emergence. Our study shows that no-till seeding methods can impact the success of a BFT seeding, however mean BFT emergence counts were so low in both years, that efficacy of BFT seeding methods may be negligible when planting BFT in an established pasture as a preventative anthelmintic treatment.

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