Abstract
Exchangeable bases and related properties were important indicators of soil conditions. Under natural conditions, most Japanese upland soils are acid and have low exchangeable bases. However, on arable land, soil acidity had been reclaimed by liming and chemical fertilizer application. Under those kinds of agricultural practices, imbalance of bases, for example low Mg-K ratio, have been warned against in recent decades. General monitoring survey of soil properties of arable land were carried out by the Ministry of Agriculture and prefecture agricultural experiment stations from 1979 to 1997. In this report, we describe the state of exchangeable bases and related properties from the monitoring survey data. Exchangeable Ca switched from increase to decrease during the monitoring period in upland crop fields and orchards. The pH showed decreasing trend on orchards and tea gardens. Exchangeable Mg also showed decrease on paddy fields and orchards. On the other hand, exchangeable K showed rather higher increasing trend than Ca and Mg. Exchangeable Mg was clearly decreased in fine textured Gley soils of paddy fields. On the balance of exchangeable bases, ratio of Mg/K was decreased and stayed at low level in most land uses. Base saturation stayed at rather high level during the period, especially on greenhouses and vegetable fields.
