82 MASS. EXPERIMENT STATION BULLETIN 165. 



compound in water extracts were successful when a smaller ratio of soil 

 to water was used and the two left in contact a greater length of time. Soils 

 from the unhmed ends of plots 6 and 8 were used. The extracts were ob- 

 tained as follows: between 6 and 8 kilos of air-dried soil were placed in a 

 glass jar with an opening in the bottom plugged with glass wool and covered 

 ^v^th a linen filter. Enough water was added to just saturate the soil and 

 left for from twelve to twenty-four hours. In the first experiment only as 

 much water was percolated through the soil as was required originally to 

 satiu'ate it. After evaporating the percolate to a small volume, and making 

 slightl}^ acid with hydrochloric acid to decompose any carbonates present, 

 ammonium hydrate was added until the solution was shghtly alkahne. A 

 heavy flocculent precipitate, brick red in color, separated out. On filter- 

 ing, drying and analyzing the precipitate it was fomid to contain organic 

 matter, calcium, iron and aluminium and sihca. The composition of this 

 precipitate varied somewhat from the compoimd obtained wdth the am- 

 monium-sulfate solutions. In the ammonium-sulfate extracts the amount 

 of iron and aluminium oxides was about three times the amount of silica 

 found, while with water the percentage of iron and aluminium oxides was 

 almost the same as the per cent, of silica. In the extract made in a similar 

 manner with soil from the unlimed end of plot 8 a precipitate similar in 

 appelarlance but of a somewhat different composition was found. More 

 silica than iron 'and aluminium oxides was found. 



The increased amount of iron and aluminium fomid in the extracts wdth 

 ammonium sulfate over that found in water extracts seems to indicate 

 that in the absence of an available calcium compound the ammonium 

 sulfate attacks the iron and ahmiinium compounds in the soil. 



Investigations in regard to this solvent action of ammonium sulfate on 

 iron and almninium compounds in the soil are at present being conducted. 



Calcium Absorption. 



The absorption of calcium by the soil was studied in comiection with 

 the determination of soil acidity by the Veitch method. This method is 

 essentially a measure of the absorption of lime by the soil and not a measure 

 of any free acid. 



The Veitch method was used on soil from the unhmed and limed ends 

 of plot 6. No difference in the amount of absorbed calcium was noted 

 between the limed and unhmed areas, both having absorbed at the rate of 

 2,545 pounds of calcimn oxide per acre (2,000,000 pounds of soil per acre). 



A second method, using the same substance, was also tried. In this 

 method 100 grams of air-dried soil were shaken with 500 cubic centimeters 

 of a saturated calcium-hydrate solution and filtered after two hours. An 

 aliquot of the filtrate was then titrated and the amount of absorbed Ume 

 determined. This method gave a much higher absorption than was found 

 by the Veitch method. No difference in the amount of calcium absorbed 

 between the hmed and unlimed ends was observed. The calcium oxide 

 absorbed was equal to 11,776 pounds per acre. 



