The main constituents and physical and chemical properties of water filtering sludge in Okinawa island (Department of Environmemtal Sciences and Technology)

農業用客土資材として有効利用するために,沖縄島の石川,北谷,コザ,西原の各浄水汚泥の主要構成成分と理化学性とを調べ,さらに県内の代表的耕地土壌の理化学性とも比較した。得られた結果は,次のように要約することができる。1)一次鉱物はいずれも石英が主体で,その他に石川汚泥では長石,コザ汚泥では方解石が附随した。二次鉱物はいずれもカオリナイトやイライトが主体で,それらの他にバーミキュライトークロライト中間種鉱物が附随した。石川および北谷汚泥ではゲーサイトも随伴した。2)有機物含量は約5∿16%で,いずれも耕地土壌の約2%より高かった。3)土性は一般に粘土含量が高く,西原汚泥で砂含量,コザ汚泥でシルト含量がそれぞれ高かった。4)pH(H_2O)はいずれも弱アルカリ性を示し,全窒素含量はいずれも耕地土壌より倍以上高かった。5)CECは約5∿16me/100gを示した。交換性Ca含量は約7∿53me/100gで,いずれも酸性土壌の国頭マージよりかなり高かった。6)可給態リン酸含量は西原汚泥で約7∿8mg/100gで,他の汚泥より17倍以上も高かった。リン酸吸収係数は約2,400∿2,700mg/100gで,耕地土壌より3∿5倍も著しく高い値を示した。以上のことから,浄水汚泥の資材特性は耕地土壌に対して全体的には優るものが多く,農業用客土資材として有効利用できる可能性が高いと考えられる。For the purpose of effective using the water filtering sludge as a soil dressing material in Okinawa island, the sludges which were collected from Ishikawa, Chatan, Koza and Nishihara water purification plant were studied on the main constituents and physical and chemical properties. And furthermore these properties of the sludge were compared with these of arable soils. The results are summarized as follows. 1) The primary mineral of the sludges was mainly consisted of quarts accompanied by a small amount of feldspars in Ishikawa's and calcite in Koza's sludge. In the clay fraction the sludges included kaolinite and illite as the main minerals accompanied by a moderate amount of vermiculite-chlorite intergrade, in addition, goethite in both Ishikawa's and Chatan's sludge. 2) It was contained about 5 to 16% in organic matter which was higher than 2% in arable soils. 3) The texture was clayey in both Ishikawa's and Chatan's, sandy in Nishihara's and silty in Koza's sludge, respectively. 4) The sludges showed slightly alkaline reaction, and their total nitrogen were higher twice than this in arable soils. 5) The CEC was about 5 to 16me/100g. The value for exchangeable calcium was about 7 to 53me/100g and was considerably higher in the sludges than this in acidic Kunigami mahji soil. 6) The value for available phosphate was about 7 to 8mg/100g in Nishihara's sludge and the value was larger 17 times than this in the other sludge. The phosphorus absorption coefficient was about 2,400 to 2,700mg/100g and the value was considerably higher 3 to 5 times than this in arable soils. From the results of these expriments, it was considered that it will be possible to use the sludge effectively as a soil dressing material in Okinawa island because the physical and chemical properties of the sludges were better on the whole than these in arable soils

Studies on methods of available phosphate determination : (I) Comparative examination of Truog, Bray No.2 and HSPA methods (Department of Agricultural Chemistry)

沖縄県の土壌に対して各可給態リン酸測定法の比較の1過程として, Truog法, Bray No.2法及びHSPA法を比較検討した。Truog法とHSPA法及びBray No.2法の間に有意差がみられ, Truogリン酸はHSPAリン酸及びBray No.2リン酸より低い値を示した。HSPA法とBray No.2法の間には有意差がみられなかった。Truog法(浸出液0.002N硫酸)とHSPA法(浸出液0.02N硫酸)は, 赤黄色土壌において高い相関関係(r=0.978)がみられ, 回帰式はY=2.40X+2.20であった。Truog法とBray No.2法は, 相関関係がみられるものの, 回帰直線からはずれる土壌がみられた。また, Bray No.2法とHSPA法は相関が認められるものの, 二つのグループに分けられた。灰色台地土及び泥灰岩において, HSPAリン酸及びBray No.2リン酸はTruogリン酸より非常に高い値を示した。Truog, Bray No.2 and HSPA (Hawaiian Suger Planters' Association) methods were compared in determining available phosphate in selected soils of Okinawa. Available phosphate determined by the Truog method was found significantly lower than that determined by the Bray No.2 and HSPA methods. There was no significant difference between the levels of available phosphate with the later two methods. There was a close correlation (r=0.978) between the levels of available phosphate with the Truog and HSPA methods, and the regression equation was expressed as Y=2.40X+2.20 on red and yellow soils. There was a correlation (r=0.778) between the levels of available phosphate with the Truog and Bray No.2 methods, but some soils showed deviation from the correlation curve to some extent. There was a correlation (r=0.540) between the levels of available phosphate with the Bray No. 2 and HSPA methods, and there appeared 2 groups in the tested soils from the difference in the correlation curve. The Bray No.2 and HSPA methods indicated much higher levels of available phosphate than the Truog method when applied to Jahgaru (soils derived from marl) and Marl