Date of Award


Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)


Plant, Soil, and Environmental Sciences


Ellen Mallory

Second Committee Member

Dave Lambert

Third Committee Member

M. Susan Erich


Currently, local bread wheat production in Maine is of growing interest for farmers, bakers, millers and consumers. Soil fertility practices are a major concern for bread wheat growers. The aim of this project was to evaluate organic sources of plant nutrition for high quality bread wheat production in the Northeast. The research involved two distinct experiments with hard red spring wheat. The first evaluated the effects of different organic nitrogen (N) sources on N availability, grain yield and protein, and N utilization efficiency. The second investigated the efficacy of microbial inoculants on wheat arbuscular mycorrhizal fungus (AMF) colonization, biomass accumulation, nutrient uptake, and grain yield and protein.

The N source experiment was a two year field trial with four organic N sources: broiler litter (broiler), caged layer manure (layer), solid dairy manure (dairy) and red clover (Trifolium pratense, clover), and a 0-N control. Chilean nitrate (CN) was used as an inorganic N source check. Among N sources, poultry manures enhanced early season N availability compared with the control, but dairy did not. Early season N availability was likely related to yield as all N source treatments except for dairy enhanced grain yield over the 0-N control. There were no N source effects on grain protein concentration or N utilization efficiencies. In this trial, spring wheat performance was similar with organic N sources and Chilean nitrate, which implies that animal and green manures may be practical substitutes for synthetic N sources.

The microbial inoculant experiment involved one year of a containerized greenhouse trial and 2 years of field trials. We used a commercially available AMF inoculant, an on-farm produced AMF inoculant, and an on-farm produced indigenous microbial inoculant. The impact of the inoculants was compared with their relative controls, which were sterilized inoculants. In the greenhouse, both AMF inoculants enhanced AMF colonization rates as compared with their relative controls, but only the on-farm produced AMF increased aboveground biomass, and phosphorus (P) uptake. No treatment differences were observed in the field. The indigenous microbial inoculant (IMO+) increased wheat aboveground biomass, nutrient uptake, and grain yield when compared with the mycorrhizal inoculants, but no increases were observed when contrasted against its relative control (IMO-). Therefore, wheat growth enhancements from IMO were likely due to nutrient supply from the compost-based carrier material. Results demonstrate that an AMF inoculant produced on-farm can increase wheat AMF colonization, aboveground biomass and P uptake in a containerized setting. In the field, differences between inoculants and their relative controls were limited, which was likely due to competition from the native soil microbial community.