Abstract
Because farming fields have recently been get-ting consolidated and farmers land also have been getting large-scale, dry-seeding of rice is widely introduced by the farmers. Our objective of this paper was to clarify whether the penetration resistance distribution measured using a corn penetrometer (SR-II) can be used to diagnose soil-layers affecting rice establishment rate and to develop a formula to predict the averaged establishment rate level of rice based on the results of diagnoses. We measured the penetration resistance distribution using a corn penetrom-eter and evaluated the establishment rate of rice at 52 dry-seeding paddy fields with lower sowing rate in southern part of Okayama prefecture. We analyzed the trend of mea-sured penetration resistance distributions for each level of the establishment rate. We proposed 5 sets of the diagnose index and criterion based on the trends of penetration resis-tance distribution, and the previous cultivation guidelines for rice. By using these sets of index and criterion, we gave scores to all the fields, and calculated the averaged level of establishment rate for each field-score. There was a high correlation between the given field-score and the averaged levels of establishment rate. We concluded that the penetration resistance distribution can be used for the diagnosis on the soil-layers of paddy fields, and we developed a for-mula to predict the averaged establishment rate level of rice by using the field-score according to the indices and crite-ria.