In this paper, the quantitative determination of available copper in soils by Aspergillus niger method and comparison of the results with chemical methods are described. Satisfactory purification of the basal medium is obtained by autoclaving with 15 g/l Al2O3 (chromatographic analysis material) for 20 min. at 10 lb. pressure. The spore colour sensitivity of Asp. niger to trace amount of copper is confirmed, and the amount of available copper in soils can be estimated by visual comparison of the spore colour of similar cultures with from 0.05 to 0.10 g of dry soil replacing copper with that of series of copper standard cultures containing from 0 to 3.0 γ of added copper per 25 cc nutrient solution after 7 days' incubation at 30℃. The results obtained by Asp. niger method compare fairly favorably with the chemical method, and except in a few soils the bioassay generally gives from 1*1/2 to 2-fold as high values as the avalable copper contents by chemical method (Hibbard's method.) These higher values are probably attributable to the fact that organic acids produced by Asp. niger may release more copper than chemical exchanging solution and the soils remain in contact with the acid nutrient solution during several days of incubation.
1) 九大農学部構内の土壌より分離した Asp. niger を試験薗とし, 再結晶法とクロマトグラフ用活性アルミナによる吸着法の併用により純化した培養液を用いて30℃で7日間培養後, その胞子の色調を Standard series のそれと比較する方法によつて土壌中の可給態銅の Bioassay を行つた. 2) sample の使用量は通常の土壌では 0.05～0.10 g/25cc medium 位, 果樹園土壌の如く銅含量が明かに多いと思われる土壌では更に少量が適当と思われる. 3) Asp. niger法による可給熊銅の定量値は, Hibbard法による化学的定量の結果とかなり同一の傾向を示すが, 若干の例外を除いてその絶体値は大約1.5～2倍の値を示した.
Mendeley出力
