Date of Award:

2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Advisor/Chair:

Jennifer W. MacAdam

Abstract

Three studies applicable to organic management and cultivation of birdsfoot trefoil (BFT, Lotus corniculatus L.) are presented here. The first is a histological 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 to break BFT stems. The sixth internodes from the base of 10 BFT and two alfalfa plants were sampled during 15 weeks of midsummer regrowth. The lignified xylary ring reached its maximum radial width by 7.5 weeks of regrowth, and full bloom was reached by 6.5 weeks of regrowth.

The second study evaluated establishment of BFT, which competes poorly with weeds and produces low yields during establishment. At an organic, irrigated site in northern Utah the effects of autumn vs. spring seeding, seeding rates of 3, 7 20, and 34 kg pure live seed (PLS) ha-1 and use of a companion crop on 3 years of annual yields and foliar cover of mature stands were determined. First year yields increased linearly with seeding rate (P≤0.05). Use of a companion crop reduced first year yields, and did not reduce weed cover. Autumn seeding of BFT alone, following harvest of a summer crop, is recommended for irrigated production.

The final study evaluated BFT establishment on five organic dairy farms in souther 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 achieved high 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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