Large-scale Composting as a Means of Managing Invasive Plants in the Rio Grande River Valley Basin




Meier, Erica Jane

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The ecological impacts of invasive species are primarily due to their rapid growth, clogging waterways as well as outcompeting, even completely displacing native species. As a waste management system within agriculture, the composting process kills plant pathogens and weed seeds if high enough temperatures are obtained for long enough periods of time. Compost is used in the horticulture industry to decrease plant disease(s), increase the accessibility of nutrients by plants, and as an effective weed control agent. The purpose of this study was to investigate the effectiveness of a large-scale composting operation to manage invasive plants, water hyacinth (Eichhornia crassipes), water lettuce {Pistia stratiotes), hydrilla (.Hydrilla verticillata), and Georgia cane (Arundo donax), by rendering the seeds and other propagules non-viable while producing a valuable compost product for the agricultural and horticultural industries. Samples of water hyacinth {Eichhornia crassipes), water lettuce (Pistia stratiotes), hydrilla {Hydrilla verticillata), and Georgia cane {Arundo donax) plants were obtained during the mid to late summer months (when flowering and fruiting). Oven mortality tests determined at which temperature seeds and other propagules were rendered nonviable. After being subjected to the oven mortality tests, analysis using tetrazolium tests (viability tests) revealed one water hyacinth (Eichhornia crassipes) seed to be viable from the 120.0 degrees Fahrenheit oven. However, all other seeds and propagules were rendered non-viable at all other temperatures. Therefore, in the field, achieving temperatures of at least 135.0 degrees Fahrenheit were necessary within the compost piles in order to effectively manage the invasive species. In the field, windrow compost piles were constructed using the recipe: 50% woodchips, 25% cafeteria food waste, and 25% invasive species. A total of approximately 45,000 pounds of food waste, 52,200 pounds of woodchips, 7,680 pounds of water hyacinth (Eichhornia crassipes), 8,000 pounds of water lettuce (Pistia stratiotes), and 4,628 pounds of hydrilla (Hydrilla verticillata) - a total of 20,308 pounds of invasive plant species - were collected and utilized in this study. Composite samples of compost were collected from each compost pile, where they were either screened for seeds and other propagules and then analyzed by the researcher, or sent for analysis to the certified Compost Tests for U.S. Compost Council’s Seal of Testing Assurance Program at Pennsylvania State University’s Agricultural Analytical Services Laboratory. All seeds and propagules found through hand screening by the researcher, when analyzed using the tetrazolium test, were found rendered non-viable through the high temperatures achieved in the composting process. All compost samples analyzed by the certified Compost Tests for U.S. Compost Council’s Seal of Testing Assurance Program, were determined as either within satisfactory to ideal levels for favorable compost and therefore, a valuable compost product. Results demonstrate that the invasive species water hyacinth (Eichhornia crassipes), water lettuce (Pistia stratiotes), and hydrilla (Hydrilla verticillata) can be used to produce a nutrient rich resource for various applications within the agriculture and horticulture industries, while also effectively managing invasive species.



compost, invasive plants, noxious weeds, biological control


Meier, E. J. (2011). Large-scale composting as a means of managing invasive plants in the Rio Grande River Valley basin (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.


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