The ADSC staff: Desmond Ogata, Ray Uchida, Sharon Yee, Sonia
Campbell, Julana Abe, and Robert Huang.
What’s in your ground?
Representative areas for the various soil types have been generally established,
and knowing them is an important first step. But there’s so much more to learn
about any individual plot of soil: does it harbor fungi, viruses, or other
pathogens? Has it been tainted by chemicals, such as pesticide residues or
gasoline spills? Is there a high buildup of salt? What is its nutrient content,
and what should be added to nourish what will be planted there?
Diagnostic Service Center (ADSC) research staff conduct chemical analyses of
soils, plant tissue, and water and nutrient solutions, and then give recommendations
about the conditions they’ve discovered. They receive around 25 requests and
questions a week from home gardeners and commercial farmers, estimates Raymond
Uchida, O‘ahu County administrator and the director of ADSC. The office also
provides workshops and other training, including a recent briefing for managers
of a popular home and garden chain on the importance of soil analysis.
ADSC processes approximately 2,000–2,500 soil analyses per
are performed on a small sample of soil from an entire garden or field, the
sample must be representative. Home gardeners should gather a composite sample made
up of 5–10 subsamples per 100 sq. ft., collected over the entire planting area.
One-inch-thick slices of the soil, cut 4–8 inches deep, are mixed well in a
bucket, and 2 cups’ worth is removed for the sample. It can be dropped off at
the nearest county Extension office, at the Pearl City Urban Garden Center, or at the ADSC office on the UH Manoa
campus. Also necessary is the soil sample information form appended to this
CTAHR publication, which also provides more
detailed instructions about collecting the sample: www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-9.pdf.
suggests that at the very least, gardeners should buy a kit from a garden store
to determine soil pH—that’s the most important information. But the ADSC’s full analyses and recommendations
are well worth getting: they can help growers enhance yields, more efficiently utilize
resources, save money, and preserve the environment. Commercial taro growers,
for example, learned they could reduce the amount of nitrogen they added to
their lo‘i by 25%, increasing profits and improving the surrounding soil
quality. Isn’t it time to do a little digging?