Date of Award:

12-2008

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Plants, Soils, and Climate

Committee Chair(s)

Heidi A. Kratsch

Committee

Heidi A. Kratsch

Committee

Paul R. Grossl

Committee

Michael R. Kuhns

Committee

William A. Varga

Abstract

An important aspect of sustainable landscaping includes utilization of plants requiring few to no inputs once installed. Limited research exists for many of these species. For this research, we chose four with potential for use: Mexican cliffrose (Purshia mexicana), silver buffaloberry (Shepherdia argentea), roundleaf buffaloberry (Shepherdia rotundifolia), and seaside alder (Alnus maritima). All are actinorhizal, meaning they form a symbiotic relationship with soil-borne Frankia bacteria that fix atmospheric N2 for plant use. Many actinorhizal species are also native to arid environments where soils have low organic matter (OM) content. We suspect that these species are detrimentally impacted by traditional growing substrates high in OM due to OM effects on water-holding porosity characteristics. We sowed previously stratified seeds of roundleaf buffaloberry and silver buffaloberry in three substrates with varying amounts of OM and found that roundleaf buffaloberry germination rate was maximized in a calcined clay (66.2%) containing no OM and had low germination rates (12.7 - 21.8%) in the substrates containing OM. Silver buffaloberry germination rates varied from 42.3 to 53.7%, and germination rates were similar across substrates. This shows that substrate water-holding properties can impact germination of some species native to arid environments. Poor seed quality made the research concerning Mexican cliffrose inconclusive.

We also investigated effects of controlled release fertilizer (CRF) on nodule formation in seaside alder and specifically sought to determine if previously inoculated plants treated with CRF would form nodules, and what level of CRF maximizes nodule formation. These plants were topdressed with CRF at rates from 0-32g, while a group of uninoculated plants received the manufacturer prescribed rate of 6 g. We found that 2 g CRF maximized root nodule formation (26 nodules; 110 mg dry weight). Plant growth parameters and leaf N content of 2-g treated plants were similar (P < 0.10) to those of uninoculated plants receiving the prescribed rate of CRF.

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