XV.—On the analytical determination of probably available “mineral” plant food in soils

Abstract

Wiklund, &c.; whilst a vast storehouse of data of information for future use has been accumulated, and is being yearly accumulated, in the field experiments of Lawes and Gilbert, at Rothamsted, followed up by those of late years carried on at Wobnrn by A. Voelcker and J. A. Voelcker. Most of the memoirs touching these subjects published by the various authors have: however, had to do rather with manures than directly with soils, and for the moment it is proposed to select for CORsideration such work as has borne more directly on the question of soil analysis, so far as concerns phosphoric acid and potash. The memoirs coming strictly under this head to be found in modern chemical literature are comparatively few. The earliest paper of any importance that the author has been able to find is that of 3. v. Liebig (Zeitschrift d. Landwirth. Vereines, 1872), who worked on soils obtained from the permanent wheat field at Rothamsted. The attention of the present author was directed to Liebig's investigation by Dr. (now Sir J. Henry) Gilbert, when some three or four years ago he discussed with him the lines on which it was proposed to pursue the investigation which forms the principal subject of the present paper. I n the light of the results of the experiments since made with soils from other Rothamsted plots, plots not only more numerous, but experimentally nearly twenty yeare older, than those worked on by Liebig in 1872, it appears to be desirable to quote here some of Liebig's figures. The specimens of soil used by Liebig were from Broadbalk WheaG field, Rothamsted, and represented the 1st and 2nd depths of 9 inches each. No. 3 soil had been continuously unmanured for nearly thirty years. Liebig determined in it several of the mineral constituents solnble in L ' dilute hydrochloric acid'' and in " dilute acetic acid." As the present paper is concerned only with potash and phosphoric acid, it is unnecessary to quote Liebig's determinations of lime, magnesb, soda, &c. The other soils were 10 A, which for nearly 30 years had received an annual dressing of 400 lbs. ammonia salts, without mineral manure ; 5 A, which for a like time had received a complete annual dressing of mineral manures, without nitrogen ; 7 A, which had received annually both 400 lbs. ammonia salts and a complete mineral manure; and 2, which had received an annual dressing of 14 t~n s of farmyard manure. K 2

Photosynthesis, water-use efficiency and δ¹³C of five cowpea genotypes grown in mixed culture and at different densities with sorghum

“…Determination of plant-available minerals in rhizosphere soils: Extractable P, K, Ca, and Mg were determined by the citric acid method as developed by Dyer (1894) and modified by the Division of Chemical Services (DCS 1956) and Du Plessis and Burger (1964). A 20 g of the air-dried soil sample was extracted in 200 ml of 1% (w/v) citric acid, heated to 80°C, shaken for 2 min at 10-min intervals over 1-h period and filtered.…”

Phosphorus in Finnish soils in the 1900s with particular reference to the acid ammonium acetate soil test

“…This assumed natural process was simulated in the laboratory with weak acids or with diluted solutions of strong acids. An internationally widely used method for measuring plant available P was the extraction of soils with 1% solution of citric acid introduced by Dyer (1894). Distilled water had already been tested as the extracting agent, both as pure water and saturated with carbon dioxide, as suggested by Mitscherlich (Rindell 1910).…”

Effect of phosphate topdressing on a soil from Andesitic Volcanic Ash

“…The following soil phosphorus extractions with dilute acid have been done: 2.5% acetic acid (Williams and Stewart 1943) using a soil extractant ratio of 1 : 200 instead of 1 : 40, 1 % citric acid (Dyer 1894), 0.002 N H 2 S0 4 (Truog 1930), 0.02 N calcium lactate in 0.01 N HCI) (Egner 1932), neutral 0.5 N ammonium fluoride (Bray and Kurtz 1945) . The inorganic phosphorus extracted by these methods was determined colorimetrically (Williams and Stewart 1941) in an aliquot of the clear filtrate.…”