Semester

Summer

Date of Graduation

2009

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Horticulture

Committee Chair

Sven Verlinden.

Abstract

In terms of cost and availability, it is important that new materials are tested as a hydroponics soil-less media, especially in areas where traditional hydroponic media such as rockwool and perlite are not available or cost prohibitive. Red lava rock or "Tezontle" has potential as a media due to its physical characteristics and cost. However, limited experience has been gained with this material as a hydroponic media for crops outside of tomato, pepper, melon, and tomatillo. In an attempt to diversify hydroponic crop production systems in semi-arid regions of Mexico, red lava rock (tezontle)-based hydroponic systems were tested in three experiments designed to study the effect of watering regimens on the growth and development of four herbs (basil, thyme, rosemary, and mint) and one ornamental (sunflowers). In Experiment 1 plants were watered at 80%, 100% and 120% of container capacity. In Experiments 2 and 3 plants were irrigated applying the same amount of water at each irrigation but at five different treatment levels (every other day, once a day, two times a day alternated with one time the next day, two times in a day, and three times in a day).;In general, the growth and performance of plants improved as the amount of irrigation water increased. In the three experiments, all plants suffered drought stress in treatments receiving the least irrigation and therefore also produced the lowest yields. However, each of the plant species included in this study showed different response patterns to irrigation amount and frequency. Thyme, despite its low yield in the low watering level (80%) in Experiment 1 and less frequent irrigation treatment (every other day irrigation) in Experiments 2 and 3, performed best in terms of marketable characteristics (width of stems and size of leaves), in these low water applications. In addition, thyme showed low yields in the treatments receiving the most irrigation suggesting that thyme can be grown with relatively low amounts of water at each application or less frequent water application than any of the other crops included in this study. In conclusion, basil, thyme, rosemary, sunflowers and mint can be successfully grown in a greenhouse tezontle-based hydroponic system with a low input of water. Although plants receiving the lowest irrigation showed low yields, they still showed acceptable marketable characteristics to be sold fresh or dried.

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