Honolulu County, HI Extension Office & Soil Testing Directory
Welcome to the official directory resource for Honolulu County, HI. Connecting local homeowners, urban gardeners, and commercial growers with Hawaii's land-grant university extension resources, state soil testing lab services, and Master Gardener volunteer clinics.
1. Extension Office Contact Details & Operational Hours
The UH CTAHR Extension - Oahu County serves as the primary educational extension center in Honolulu County. Visit or call during standard operational hours for agricultural advice, soil sample kits, and youth 4-H programs.
| Official Office Name: | UH CTAHR Extension - Oahu County |
| Physical Address: | 1955 East-West Road, AgSci 217, Honolulu, HI 96822 |
| Direct Phone Desk: | (808) 956-6007 |
| Email Contact: | oahu-ext@ctahr.hawaii.edu |
| Office Hours: | Monday – Friday: 7:45 AM – 4:30 PM |
| Official Web Portal: | https://www.ctahr.hawaii.edu/site/ext.aspx |
2. Official Soil Testing Laboratory & Pricing
Testing your soil is the single most important step before adding fertilizers or agricultural lime. The official testing laboratory serving Honolulu County is UH Agricultural Diagnostic Service Center (ADSC).
| Official Testing Lab: | UH Agricultural Diagnostic Service Center (ADSC) |
| Lab Location: | 1920 Maile Way, Gilmore 134, Honolulu, HI 96822 |
| Routine Sample Fee: | $12 per routine soil test |
| Expected Turnaround: | 10 to 14 business days |
| Official Lab Website: | https://www.ctahr.hawaii.edu/adsc/ |
How to Collect and Submit a Soil Sample in Honolulu County:
- Pick up a Soil Kit: Pick up official sample boxes and submittal forms at the UH CTAHR Extension - Oahu County (1955 East-West Road, AgSci 217, Honolulu, HI 96822).
- Collect Sub-Samples: Use a clean stainless steel trowel to take 10 to 12 soil cores from a 4-to-6-inch depth across your garden or lawn area.
- Air-Dry: Mix sub-samples in a clean plastic bucket and air-dry on clean paper at room temperature (never use an oven).
- Submit Sample: Return your filled soil box to the extension office or mail directly to UH Agricultural Diagnostic Service Center (ADSC).
3. Master Gardener Volunteer Program & Plant Clinic
The Oahu Master Gardeners provides free plant disease diagnostics, lawn care advice, and eco-friendly pest management tips.
| Program Name: | Oahu Master Gardeners |
| Plant Clinic Hours: | Monday & Wednesday: 9:00 AM – 12:00 PM (Note: Plant clinics run seasonally; call office during winter months) |
| Direct Helpline Phone: | (808) 453-6055 |
| Program Portal: | https://www.ctahr.hawaii.edu/uhm/mg/ |
Volunteer Training: UH CTAHR tropical horticulture certification.
4. Regional Soil & Growing Snapshot for Honolulu County
USDA Plant Hardiness Zone: Zone 11a / 12a
Natural Soil Profile: Tropical Volcanic Oxisols & Ultisols
Popular Local Crops: Papayas, bananas, taro, citrus, plumeria, sweet potatoes
Extension Specialist Tip: Tropical volcanic soils bind phosphorus tightly; use rock phosphate and organic compost.
5. 🧮 Interactive Soil Amendment Calculator for Honolulu County
Estimate the recommended agricultural limestone or elemental sulfur needed to adjust your garden soil pH based on local Tropical Volcanic Oxisols & Ultisols characteristics.
📚 Recommended Extension Guides & Soil Articles
Learn more about interpreting your Honolulu County extension soil test report and managing plant nutrients:
Frequently Asked Questions (Honolulu County Directory)
The UH CTAHR Extension - Oahu County is located at 1955 East-West Road, AgSci 217, Honolulu, HI 96822. You can call their main desk directly at (808) 956-6007 during standard business hours (Monday – Friday: 7:45 AM – 4:30 PM).
Standard soil analysis for Honolulu County garden samples through UH Agricultural Diagnostic Service Center (ADSC) costs $12 per routine soil test. Check with the office for special sample types.
You can reach the Oahu Master Gardeners hotline by calling (808) 453-6055 during plant clinic hours (Monday & Wednesday: 9:00 AM – 12:00 PM).
Honolulu County falls primarily within USDA Plant Hardiness Zone 11a / 12a. Local soil is characterized as Tropical Volcanic Oxisols & Ultisols.
Written & Verified by Sahajul
Verified Author & Founder
Sahajul is an independent agricultural data researcher based in India and founder of LocalSoilLab.com. He specializes in compiling, structuring, and verifying US land-grant university extension services, soil lab testing fee schedules, and county Master Gardener contact directories directly from official .edu and USDA NIFA portals.