Seasonal change of moisture tension and inorganic nitrogen contents in apple [Malus] orchard soil

For studies of nitrogen fertilizer application system and soil management that are based on soil properties and weather conditions, we investigated the seasonal variation of moisture tension and inorganic nitrogen contents of about six apple orchards in Yokote-Hiraka region, Akita Prefecture. The investigations were continued during apple growth season from l993 to l995, and the measurement data of the differences among six orchards (as soil properties) and three years (as weather conditions) here analyzed. 1) Weather conditions of investigated periods were extremely different. The characteristics are as follows. In 1993, the temperature was lower than the average year through growing season. The tendency was particularly strong then in July and August. In 1994, it was very hot and dry summer. In l995, it was characterized by having much rainfall and short daylight from June to August. 2) Significant differences among the orchards were recognized in seasonal soil pF values. pF values of Andosol soil orchard we1-e always lower than other orchards. It seemed that the fluctuation of pF value according to seasonal weather change was different among. the orchards, wherein the scale of brown Forest soil orchard was great, in contrast to Wet Andosol soil orchard, which was small. 3) The annual difference of soil pF value was distinct in June, July and August. In 1993, soil moisture tension moved in the range of field capacity through growth season. In l994, moisture content for optimum growth reached until near depletion in midsummer. On the other hand, it was supposed that the condition where gravitational water existed in soil continued from July to August 1995. 4) Significant differences among six orchards were not recognized in the inorganic nitrogen content. It was suggested that the behavior of inorganic nitrog-en in product field was various and complicated