Integrated approach for Rehabilitation of Severely Eroded Soils for Agricultural Sustainability and Natural Resources Preservation of the Micronesian island of Guam Mohammad H. Golabi, Ph.D., Soil Scientist Margaret J. Denney, past graduate student Clancy Iyekar, Soil Lab Tech College of Natural and Applied Sciences University of Guam

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Soils of Guam Nineteen different soil series have been mapped on Guam Soils of Guam can be grouped into three primary categories: Soils over limestone Soils on volcanic uplands Soils on bottomlands and coastal margins

Soils of Guam (cont’d) Predominant location of Limestone-derived soils is in Northern Guam Predominant location of Volcanic soils is in Southern Guam Shallow - limestone-derived Guam soil series covers approximately 24% of total land area (55,445 hectares or 214 square miles)

Conditions Threatening Guam’s Soils Approximately 1,644 hectares of land (30% of total) are at risk of erosion Severe erosion of the varied soil series on Guam exposes infertile subsoil restricting regrowth of vegetation and having negative effect on crop productivity A major problem of agricultural soils in Guam is the low organic matter content

A typical Badland area in Southern Guam

Farmers and hunters burn natural vegetation for clearing purposes

Challenges facing Guam’s agricultural and the soil scientists Soil and agricultural scientists must develop strategies to control erosion on the farms, rangelands as well as the watershed areas New techniques must be introduced for soil conservation and natural resources protection both in the farm fields as well as on the watershed areas in the southern mountains.

Facing the challenges - Research Objectives Evaluate the use of composted organic wastes as soil amendment for the enhancement of the overall quality of soils for crop productivity and agricultural sustainability as well as for erosion control purposes Evaluate the effect of Vetiver Grass Systems (VGS) to prevent sediment loss and control soil erosion at the watershed level Evaluate the effect of conservation techniques on soil erosion and crop productivity

Case study No. 1 Effect of Compost Application Rates on Crop Growth

Manual spreading of Compost

Completed Compost Application

Some of the Results

Corn performance after compost application ↑ 0 tons/acre ↑ 120 tons/acre

Inarajan Corn Plots ↑ 30 tons/acre ↑ 0 tons/acre

Corn cups produced under different treatment (compost application rate)

Soil Quality parameters affected by different application rate Treatment O.M % Bulk Density (gr/cm3) Moisture 0 t/acre 2.78 1.06 25.86 30 t/acre 5.52 0.99 26.01 60 t/ace 6.40 1.02 28.07 120 t/acre 10.34 0.95 32.16

Average yield per treatment following different application rates

Effect of Application Rate on Some Chemical Properties of the Soil under study

Effect of Compost Application Rate on Some of the Soil Nutrients

Conclusion These findings clearly showed that productivity can be improved by proper use of organic materials and the environment also benefits through the re-use of organic wastes that otherwise would be buried in the land fill.

The effect of conservation tillage on soil erosion Case Study No. 2 The effect of conservation tillage on soil erosion and its impact on crop productivity on the following soil: Oxide rich, highly weathered acid soils (very fine, kaolinitic, isohypothermic oxic Haplustalf) derived from the volcanic deposit.

No-Till and Reduced Till

Conventional Till (CT) and No-Till

Using rainfall simulator for measuring infiltration

Rainfall simulator (cont’d)

Effect of conservation tillage practices on infiltration

Effect of conservation tillage practices on crop yield

2006 yield results Treatment Yield (t/ha) Reduced Till 1.44 No Till   2006 yield results Treatment Yield (t/ha) Reduced Till 1.44 No Till 0.51 Conv. Till 1.25 Conv. Till/SH 1.45  

Case Study No. 3 Use of Vetiver Technology to control erosion as a watershed management technique for water quality improvement and natural resource preservation

Project Importance Watershed Degradation Water Quality Problems Limited Water Sources Coral Reef Degradation Economic Impacts

What Causes Erosion? Occurs Naturally - Wind - Rain

Water Erosion in the Fields

Human Activities Construction Burning Farming ATV’s, Off-Road

Mud in Pauliluc Bay Courtesy of Dr. Minton, NPS

Healthy Coral Reef

Coral reef degradation as the result of Severe Soil Erosion

What can be done? Erosion Mitigation - Surface Cover - Education - Stop Burning - Farming BMP’s - Use of Vetiver Technology to reduce Sedimentation

About Vetiver

What Is Vetiver Grass Scientific Name; Vetiveria Zizanioides Seedlings Vetiver in Nature

Mainly found in Thailand Vetiver Origin Mainly found in Thailand Also found and Used In: * China * Indonesia * Australia * South Africa * Madagascar * Guam * Persia

Special Characteristics Adoptable to Various Soil Conditions: * Low pH: < 4 * High pH: > 12 Able to take up heavy metals * Zn, As, Mn, Cu, Al, & Pb Water Purifier (Sediment & Nutrients) * Nitrates & Phosphates

Vetiver Root System Scientific Name; Vetiveria Zizanioides

Comparing root systems of common Savanna Sword grass with Vetiver Local Sword Grass Vetiver Grass

Main Uses of Vetiver Badland Six Months after Planting

End Goal Stop Erosion From Source Stop Major Sediment Outfalls

Vetiver Technology experimentation in the island of Guam using flume enclosures

Evaluating sedimentation under 4 different watershed conditions Burned Vetiver & Sunn Hemp Tilled (simulating badland) Natural condition

Runoff & sediment sampling techniques Flume Drain Sampling Design Sampling Protocol Tank Drainage

Results

Table 1.: Soil characterization prior and following the treatments.   Management Practices 3.9 54.4 24.9 20.7 Initial soil characteristics Soil characteristics as affected by study treatments Soil Texture (%) O.M. Clay Sand Silt Avg. % O.M. Burn 57.2 20.5 22.3 5.1 Vetiver 51.8 28.2 20.0 5.4 Till 54.8 26.1 19.1 3.0 Natural 56.8 25.7 17.5 3.8 Table 1.: Soil characterization prior and following the treatments.

(Soil surface conditions) Size and slope of the study plots Management practices (Soil surface conditions) Soil loss (tons/ha/yr) Area ha Length m Slope % 0.0037 21.95 12 Burn 14.13 Vetiver 1.47 Till 104.75 Natural 5.22 Table 2: Annual Soil loss from each plot with different treatments.

Concluding Remarks Vetiver Technology is a viable system to mitigate sedimentation at the watershed level for water quality improvement and natural resources preservation and the environmental protection

Overall Conclusion Preserving natural resources and protecting the environment requires: Highly coordinated holistic approach towards natural resource management that include: Soil Water Rangelands Forests And watershed protection

Overall conclusion (cont’d) Holistic approach towards natural resource management also include: Inspirational leadership and intelligent national efforts from: government leaders, educators, business and public sectors Good Scientific information and monitoring Broad educational efforts for conservation of natural resources

Thank You