By Russell T. Nagata
University of Hawaii at Manoa College of Tropical Agriculture and Human Resources Komohana Research and Extension Center-Hilo
As many gardeners know, for all of the items that you can control, the success of your garden depends greatly on the soil that it is planted in. No matter what type of soli you have, knowing the nutrient requirements for that plant and what must be done to achieve that goal, will contribute greatly to success.
It’s fortunate for us, that one of the best kept gardening secret of the University of Hawaii at Manoa, College of Tropical Agriculture and Human Resources is the Agricultural Diagnostic Service Center or ADSC. The ADSC conducts analyses and diagnostic test for on going UHM research, other government agencies, businesses, farms and for the knowledgeable gardeners of Hawaii.
The analysis that the ADSC performs can be listed under the general heading of plant disease identification, insect identification, feed and forage analysis, chemical analysis of soil, chemical analysis of plant tissue and chemical analysis of water and nutrient solutions. The menu of services and the cost for different analysis can be found on the ADSC website at www.ctahr.hawaii.edu/site/ADSC.aspx. or web search for ADSC Hawaii. While 35 analyses are listed, most of us will use only a few of the services. Most widely use services are disease and insect identification, soil pH and extractable nutrients. Although not listed, the ADSC also will test papaya plants to determine if it contains genetic traits associated with genetic engineered characters.
The Service Center is headquartered on the University of Hawaii at Manoa campus on Oahu and is staffed by a group of dedicated individuals. On the Big Island located at the Komohana Research and Education Center in Hilo, we have Mr. Brian Bushe who is an award winning diagnostician. Brian handles disease and insect identification for the Big Island as well as to coordinate soil and plant tissue sample delivery to Oahu for analysis. Brian was selected for the State of Hawaii Governor’s Award in the category of the best individual State employee for 2009-2010.
One of the most important things to remember when submitting a sample is to submit a properly collected sample, one that will be representative of the surveyed item. For insect identification, collect more than one insect if possible and collect different growth stages if available. Additional information like host plant name, infested plant part and location on the island where insect sample was collected will be beneficial to the identification.
For plant disease samples it is best to submit samples that express the disease symptoms. A common mistake is to submit samples that are dead and rotting. Identification of the organism that caused the disease at this stage is made more difficult, if not impossible due to the exponential growth of opportunistic organism moving in after the kill. For diseases that cause necrosis or rots, the best place to identify the causal disease organism is the zone between healthy and diseased tissue. In this intermediate zone, the disease organism can most likely be isolated without the opportunistic organisms. It is also important to submit your sample shortly after collection.
Sample size should be appropriate and proportional to the sample of the host plant being submitted. A few leaves is fine for a foliar disease, but a section of a tree trunk and/or roots may be more appropriate when finding out what killed your tree. It’s always a good idea to place your insect or diseased sample in a bag or sealed container to prevent their spread or escape.
For a good soil test, it is important to get a representative sample for the location you wish to evaluate. Divide the plot into fairly uniform soil type or common use history. Each soil type or those with different history of use will need a separate test in order to correctly recommend the correct amount of fertilizer and other soil amendments required to grow a specific crop. The submitted soil sample size will need to be 2 cups, which is half of a quart storage bag.
Samples too small may not allow for a proper test, while too large a sample leads to waste since all samples are shipped to Honolulu, and soil sample remaining after the test are heat sterilized before placing into the landscape. To begin, use a shovel to dig out a section of soil 6 inches deep and place it to the side. Cut a second section about one-inch thick and place the vertical middle 2 inches of the section into a clean bucket.
Repeat collection in several locations to get a representative sample of your field site. A zigzag pattern across the field, stopping at various points to sample is a good procedure to collect a representative sample. After collecting the soil sample from the field location, mix soil sample well, breaking clumps and removing large rocks and place 2 cups of soil in a plastic bag. If you have more than one sample to submit, remember to label each bag as you collect it.
To submit any sample for analysis, bring it by any of the Cooperative Extension Service office on the Big Island. The Hilo office is located in the Komohana Research and Extension Center, phone 981-5199. The office in Waimea is located in the Public Safety Complex next to the Hawaii Department of Health, phone 887-6183. Submit soil samples in Kona at the Kona Cooperative Extension Service office at 79-7381 Mamalahoa Highway in Kainaliu, opposite the Aloha Theater. Payment can be made by cash or check. Credit cards are not accepted at this time.
For more information on this and other gardening topics, please visit the CTAHR electronic publication website at http://www.ctahr.hawaii.edu/Site/Info.aspx or visit any of the local Cooperative Extension Service offices around the island. I can be reached at firstname.lastname@example.org.