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?
CTAHR’s Agricultural 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.
Since analyses 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.
Mr. Uchida 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?
