agInnovation Research Center | Soil Science
Soil scientists are engaged in research, extension, and instruction activities regarding the environmental aspects of soil science, soil quality improvement, and organic waste management.
Soils are an important part of our natural environment and are essential in providing our food and fiber needs. On Guam and in many other parts of the Pacific, agriculture holds an important place in island culture. Issues related to soil and water pollution have become increasingly important for all Pacific islands as they experience growing populations and urban development.
The soil science program is addressing many of these issues for Guam and the region with the objectives of improving agricultural production, reducing threats of environmental pollution and the importation of potential pests, and preserving natural soil resources.
Seventeen different soil series have been mapped on Guam and are described in the U.S. Natural Resources Service (U.S. Department of Agriculture) 1988 publication “Soil Survey of the Territory of Guam”.
The soils of Guam can be grouped into three primary categories: soils over limestone (pure or argillaceous), soils on volcanic uplands, and soils on bottomlands and coastal margins. The predominant location of limestone-derived soils is in northern Guam and the predominant location of volcanic soils is in southern Guam.
The shallow, limestone-derived Guam soil series covers approximately 24% of the total land area of the island of 55,445 hectares (214 square miles). Agricultural land use accounts for approximately one to three percent of the total land use of Guam.
Approximately 127 hectares (314 acres) of land are under cultivation each year. Approximately 16,545 hectares of land (30% of the total) on Guam are at risk for erosion unless close-growing vegetation is maintained. Severe erosion of the Akina soil series on Guam exposes an infertile subsoil restricting regrowth of vegetation.
Additional public institutions on Guam involved in soil science include the U.S. Natural Resources Conservation Service, the University of Guam Water and Energy Research Institute and the Guam Environmental Protection Agency.
Controlling soil erosion is imperative for the health of coral reefs surrounding tropical islands like Guam and her northern neighbor Rota. Soil erosion and run-off result in sedimentation and suffocation of the complex organisms that make up a reef system.
Soil scientist Dr. Mohammad Golabi has been monitoring water quality of Rota’s Talakhaya Watershed since the planting vetiver grass in eroding areas. “This watershed is located in an area containing steep slopes and experiences frequent wildfires in the dry season. Vetiver’s ability to tolerate high stress situations, adapt to a variety of conditions, develop a dense vertical root system, and powerful soil binding characteristics make it an ideal candidate for controlling soil erosion,” says Golabi.
The scientific name for vetiver is Chrysopogon zizaniodes and the thick, stiff-stemmed cultivars are used for controlling soil erosion. Researchers around the world have evaluated the application of vetiver grass and found it to be very effective when bioengineering technology is needed to stabilize soil on steep slopes like those in the Talakhaya. The plant’s spongy root system binds the soil beneath the plant to a depth of up to 3 meters forming a dense underground curtain that prevents gullying and tunneling. Once the hedge has been established, it can live up to 50 years and does not require further maintenance other than periodic trimming. Under certain circumstances thick hedges can be formed in one year, it generally takes two to three growing seasons to establish a hedge dense enough to withstand torrential rains and/or heavy storm events, and protect the shoreline from sedimentation.
Golabi’s team has analyzed 8 months of data and are expecting to find reduced run-off in areas of the watershed that have been planted with vetiver grass. “Streams with a higher rate of turbidity during heavy rainfall are in areas that have not yet been planted,” says Sydonia Manibusan research associate on the project. “We are using hydrological data collection techniques and collecting data from streams including water levels, stream discharge and water quality. Specific to water quality, we are using a probe to measure pH, total dissolved solids (TDS) and dissolved oxygen.”
The analysis of the soil and water sampling from the areas of the watershed planted with vetiver grass will be compared with areas of watershed without any vetiver plantation to evaluate the environmental impact of the vetiver plantings on the watershed. It is expected that the results of planting the new vegetation, especially vetiver grass, will show a positive impact on the environment especially the health of coral reefs in areas fed by the Talakhaya Watershed well as other marine life.
Funded by National Oceanic & Atmospheric Association (NOAA) Managed by National Fish & Wildlife Foundation (NFWF)
RESEARCHER:
Mohammad Golabi, Ph.D.
ALS Bldg., Room 302
Phone: (671) 735-2143/34
Email: mgolabi@triton.uog.edu
Clancy Iyekar, M.S.
Chemist
ALS Bldg., Room 216
Phone: (671) 735-2143
Email: soillab@triton.uog.edu
