Semester

Spring

Date of Graduation

2007

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Applied and Environmental Biology

Committee Chair

Todd P West

Abstract

Dissolved nitrogen (N) and phosphorus (P) present in flow-through aquaculture effluent can pose the risk of eutrophication to receiving streams when discharged from flow-through systems. One potential solution to prevent nutrient loading is the establishment of an integrated system that cultures green plants in the effluent. The objectives of this research were to determine watercress' (Nasturtium officinale) growth and nutrient contents in both a hydroponic controlled environment and a flow-through aquaponic production system utilizing brook trout (Salvelinus fontinalis) aquaculture effluent; and to evaluate various treatments to determine the best cultural conditions for watercress in the aquaponic system for optimization as a nutrient recovery option for and value-added by-product to fish production. A 6-week long hydroponic and three 12-week long aquaponic experiments were conducted to meet these objectives. The hydroponic experiment studied the effects of light intensity and nutrient solution concentration and the aquaponic experiments studied the effects of water velocity, plant density, growing media, location, and season on watercress growth and nutrient contents. Whole plants were sampled for growth data (fresh weights, lengths, and dry weights) and dried tissue was analyzed for total N and P content. All experiments were randomized complete block (RCB) designs with three replications per treatment. Growth and nutrient data were analyzed separately and all significance was determined using SAS software. Data from the hydroponic experiment indicated that watercress growth and nutrient contents were greatest in the intermediate light intensity. The half-strength Hoagland's nutrient solution treatment resulted in significantly longer plants but had no significance on fresh weight or nutrient content versus the full-strength nutrient solution treatment. Overall, results from the aquaponic experiments provided that watercress growth was significantly greater when grown in the high water velocity, high plant density, paper growing medium, Aquaponic Production Greenhouse (APG), and spring season treatments. These treatments also resulted in greater nutrient contents in dry tissue, with the exception of greater nutrient contents in plants grown during the winter season. Nutrient sufficiency ranges may or may not have been met in the various experiments which suggest that the effluent may be nutrient limiting at times. In conclusion, watercress production is possible utilizing brook trout flow-through aquaculture effluent. The risk of nutrient loading from the system studied is insignificant because watercress growth and nutrient contents were not significant among treatments exposed and not exposed to effluent. Therefore, the focus of this integrated watercress and trout production system becomes a sustainable agriculture versus a phytoremediation approach that takes advantage of resources already available. Watercress could also serve as a secondary marketable crop for farmers to potentially increase farm income.

Download

Share

COinS