^(32)P로 標識된 Ca(H₂PO₄)₂·H₂O를 使用해서 母材와 利用 形態가 相異한 土壤에 施用된 燐酸의 行動을 把握하기 위하여 施用 ^(32)P의 Aℓ-P, Fe-P, Ca-P, 및 有機燐酸으로의 分配 樣狀과 Lancuster法으로 浸出되는 ^(32)P의 經時的 變動狀況을 調査했던 結果를 要約하면 다음과 같다. 1) 河成 沖積母材에서 發達한 논 土壤(風乾土, pH5.8 有效燐離 100ppm에 燐酸을 施用하고 湛水定溫(25℃)하는 過程에서 初期(1∼3週)에는 많은 部分의 施用燐離이 Aℓ-P로 結合 하나 時間이 經過함에 따라 Aℓ-P와 Ca-P로 結合됐든 燐酸中 相當部分이 Fe-P로 變換 되는것 같았다. 施用된 燐酸이 有機燐酸으로 되는 量은 比較的 적었고 그量은 經時的 變動이 별로 없었으며, 有效燐酸으로 浸出되는 ^(32)P量은 湛水初潮(1∼3週) 에는 時間의 經過에 따라 減少 했으나 그 뒤부터는 時間의 經過에 따라 增加하는 傾向이였다. 2) 火山灰土(pH, 5.2 有效燐酸 2.7ppm)에 燐酸을 施用하고 밭 狀態로 維持하면서 定溫한 境過 施用된 ^(32)P는 Fe-P에 特히 많이 分配 됐으며 時間의 經過에 따른 各 形態間의 轉換은 별로 뚜렷하지 않았다. 特히 이 土壤에서는 施用 燐酸의 有效燐酸으로의 浸出量이 極히 적었다. 3. 花崗岩風化物을 母材로 하는 土壤의 境過 旣耕地(pH5.2, 有效燐酸 4.8ppm) 또는 未耕地(pH4.6, 有效燐酸은 7.3ppm)에 無關하게, 施用 燐酸은 初期(1∼2週)에는 Ca-P에 많이 分配 됐지만 時間이 갈수록 Ca-P와 Aℓ-P는 줄고 Fe-P가 增加하여, 無機燐酸의 形態間轉換에 關한 限畓土壤의 鏡遇와 類似 했다. 施用燐酸의 有效燐酸으로의 浸出量은 두 土壤 共히 많은 便이였으며 經時的으로 보면 旣耕地의 境遇는 별로 變動이 없었으나 未耕地에서는 時間이 經過와 함께 減少하는 傾向이 뚜렷했다.

The present work was carried out to study the fate of applied priosphorus labelled with ^(32)P and its availability to plants in soils subjected to different management practices. The results can be summarized as follows (Table 3): 1. The applied phosphorus was transformed into different phosphorus compounds in the soils depending upon the management practices and soil characteristics. 2. In the flooded paddy soil (pH 5.8) added P after one week of incubation was transformed into various fractions, the order of abundance being: Al-P$gt; Ca-P○Fe-P$gt; Org.-P. After two weeks the order changed to: Fe-P$gt; Al-P$gt; Ca-P$gt; Org.-P. The amounts of the Fe-P and Al-P fractions were found to increase from the second week of incubation whereas a decrease in Ca-P was noticed with the organic-P remaining constant. The amount of available P decreased from the first to the third week of incubation, but increased thereafter. 3. In the volcanic ash soil a major proportion of the applied phosphorus was found in the Fe-P fraction during the whole experimental period. The interconversions of the ^(32)P among the different phosphate fractions was not as evident as in the case of flooded rice soil. The recovery of applied P was low and remained constant throughout the incubation period. 4. In the upland soils relatively more of the applied phosphorus was found in the Ca-P fraction as compared with those of the other soils. As in the flooded paddy soil ^(32)P in the Ca-P fraction decreased with increasing incubation time, whereas in the Fe-P fraction it increased with time. The recovery of added phosphate as available P followed different patterns for the cultivated and the uncultivated soils. In the cultivated soils lit was relatively high and remained nearly constant during the whole incubation period. In the uncultivated soil on the other hand, it was high at the earlier time of incubation, but decreased with incubation tune