Study on minor elements of Ryukyuan soils. 1. Preliminary test by Spurway Soil Test Kit. 3. Soils from Miyako Island.

摘要

1. Fifty soil samples from seventeen localities in Miyako Island were tested by Spurway Soil Test Kit for the same purpose as in the previous reports. 2· Magnesium was contained moderately in most soil samples, so there is little possibility of magnesium deficiency. However, tow samples of the first horizon gave negative, or trace test results, which indicate that much magnesium has been lost from the top soil which are naturally high in magnesium. 3. Two samples gave negative, or trace reserve test results for iron which indicate the possibility of iron deficiency. 4. In the case of manganese, samples from thirteen locations of seventeen localities gave negative, or trace active test results. The other four samples also gave low test results. Therefore, there is high possibility of manganese deficiency in most of these soils. 5. Test results for sulfates were negative in all of the soil samples. However, soils may not always be deficient in sulfur because the lower limit of the sulfate test of the Spurway Soil Test Kit is 20 ppm. 6. Test other than above elements were also made and the results are summarized as follows: a) Slightly higher test results of available nitrogen in most of the soil samples were obtained when compared with previous samples. b) Phosphorus content in most soil samples were very low, but two samples gave high test results. One of the two gave extremely high reserve test result, abnormally so-100 ppm., but its cause is unkown. c) Active test results for potassium were negative in most soil samples, and when compared to Ishigaki and Iriomote Islands there were a greater number of samples containing less than 20 ppm. d) In spite of the fact that the Miyako Island soils are developed from lime stone or marl, a comparatively large number of soil samples gave low test results for calcium. It is suggested that even in Miyako Island, acid-soil crops may be grown in some place, if they are shallow-rooted crops. And also in the early growing stages of high-lime crops, consideration for lime fertilization might have to be paid. e) Aluminium, chlorides and nitrites were all below toxic levels. 7. Elements other than the above were not checked because the Spurway Soil Test Kit does not include such testing methods.