Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Jennifer W. MacAdam

Committee

Jennifer W. MacAdam

Abstract

Birdsfoot trefoil (BFT, Lotus corniculatus L.) is a non-bloating, productive forage legume well suited to grazing-based ruminant production. This thesis presents three studies conducted in the Mountain West applicable to organic management and cultivation of BFT. The first is an analysis of lignification in BFT stems that supports recommendations to harvest BFT at approximately 6 weeks of regrowth, or early bloom. Lignification decreases digestibility and is correlated with high shear force required for grazing animals to break BFT stems. The process of stem lignification was observed by harvesting increasingly mature stems; cutting thin sections of the sixth stem internode, which is located low on the plant at a recommendable harvest height; and then staining stem sections for lignin, viewing and photographing them under a microscope. Lignification was apparent in the 6th stem internode of BFT by 5 weeks of regrowth and reached maximum extent by 7.5 weeks of regrowth. Flowering in BFT began at 5.5 weeks of regrowth, and full bloom was reached by 6.5 weeks of regrowth.

The second study evaluated establishment of BFT, which often competes poorly with weeds and produces low yields during establishment. At an organic, irrigated site in northern Utah the effects of different establishment methods on 3 years of annual yields and foliar cover of mature stands were evaluated. The establishment approaches tested were autumn and spring seeding, seeding rates of 3, 7, 20, and 34 kg pure live seed (PLS) ha-1 and seeding with or without a companion crop. Rates of 7 and 20 kg PLS ha-1 produced high first year yields and mature stands with low weed cover. Use of a companion crop reduced first year yields and did not reduce weed cover in mature stands, so is not recommendable. Autumn seeding of BFT at a rate between 14 and 18 kg PLS ha-1, following harvest of a summer crop, is recommended for irrigated production.

The first study evaluated BFT establishment on five commercial organic dairy farms in southern Idaho and northern Utah. Participating producers broadcast seeded 4-ha BFT pastures in the fall at a rate of 25 kg PLS ha-1. All farms established hight BFT density, but only two farms had higher BFT than weed density. These two farms also had high BFT cover the spring following autumn seeding, and their pastures produced 6000 to 7600 kg of dry matter ha-1 by 20 June 2012 and supported grazing for the remainder of the summer. Establishment was enhanced by crop rotation and sprinkler irrigation.

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