Study on minor elements of Ryukyuan soils. 1. Preliminary test by Spurway Soil Test Kit. 2. Soils from Iriomote Island.

1. The Spurway Soil Test Kit was used for preliminary testing on soils from 22 locations in Iriomote Island for the same purpose as the previous report. 2. Magnesium was well supplied in all soil samples. Therefore, soils in Iriomote Island may not be deficient in magnesium. 3. Soil samples in several localities gave low reserve test results for iron which indicate the possibility of iron deficiency for plants. Further, soils which indicated the toxic level for iron were not found. 4. Low reserve test results for manganese were given in several soil samples. These results indicate the risk of the manganese defiiciecy. On the other hand, high test results for manganese which indicate toxic for plants were not found. The use of sea water may be suggested for such manganese deficient soils. 5. Test results for sulfates were negative in most soil samples. However, soils may not be deficient in sulfur because the lower limit of the sulfate test of the Spurway Soil Test Kit is 20 ppm. 6. Tests other than above elements were also made, and the results are summarized as follows: a) Most soils were low in nitrogen content. It is suggested that they need nitrogen fertilizers for most crops. b) All soils except one were very low in phosphorus content. One soil gave high reseve test results, 15 ppm. It is suggested that the fixed phosphorus through past several phosphate fertilizer applications gave such high reserve test result for phosphorus. c) High reserve test results for potassium were given in all soil samples. So it is pointed out that the more investigation of the extract method and precipitation procedure for potassium are necessary. d) Many soil samles gave low calcium test results which indicate the need of the calcium fertilization for high lime crops. e) High chloride test results were given in some soil samples. It is supposed that those samples might be contaminated with sea water on the way of the shipping by boat from Yaeyama Islands. f) Aluminum and nitrites were all below toxic levels. 7. Other elements besides the above were not examined because the Spurway Soil Test Kit does not have such testing methods