444 EXPERIMENT STATION RECORD. 



The means of correcting present conditions proposed are (1) extension of the area 

 of the sewage farms, (2) substitution of bacteriological treatment for sewage irriga- 

 tion, and (3) a combination of the two. The last seems to offer many advantages. 

 An account of the Berlin sewage farm and its successful operation is given. 



SOILS— FERTILIZERS. 



The availability of potash and phosphoric acid in soil, (i. S. Fraps {North 

 Carolina Sta. Rpt. 1904, pp. 26-47). — This article discusses and reviews investiga- 

 tions relating to the "influences which art to release the plant food locked up in the 

 soil," grouping and defining these influences under three ''factors of availability,' 1 

 viz, (1 ) chemical availability, (2) physical availability, and (3) weathering availa- 

 bility. These should take into account "the amount of plant food which is present 

 in forms of combination that can be taken up by the plant; the physical condition 

 of the soil; the amount of plant food converted into assimilable forms during the 

 period of growth of the plant; the feeding power of the plants.*' 



A study of the changes caused by weathering and by varying conditions of mois- 

 ture, organic matter, and calcium compounds in 3 typical North Carolina soils is 

 reported. The results show that " nitric acid of 1/50 normal strength dissolved from 

 40 to 80 per cent as much potash as 1 5 normal nitric acid from samples (differently 

 treated) of one soil, ami from 50 to 90 per cent from another. The amount of phos- 

 phoric acid soluble in 1 5 normal nitric acid may increase or decrease in a moist soil 

 after standing 4 months, but increases if calcium sulphate is present. An increase 

 in the amount of potash soluble in 1/5 normal nitric acid took place in a soil kept 

 moist 4 months, with or without the presence of calcium sulphate. 



"The presence of calcium carbonate had a tendency to decrease the amount of pot- 

 ash dissolved. There was a difference in the behavior of the three soils, one show- 

 ing a tendency to decrease in soluble potash, while the other two increased. In the 

 same samples the quantity of potash soluble in 1/50 normal acid had decreased. The 

 effect of moist calcium carbonate was to reduce the solubility of phosphoric acid 

 in 1 5 normal acid as compared with dry calcium carbonate. In one soil calcium 

 carbonate increased decidedly the amount of phosphoric acid soluble in 1/5 normal 

 acid, and in two soils it decreased the amount. It caused a decrease in the amount 

 of soluble potash in every case. Calcium sulphate increased the amount of phos- 

 phoric acid soluble in 1 5 normal acid, particularly in one of the soils. It caused a 

 decrease in the solubility of potash in two cases ami a decided increase in one. 



"There is no contradiction in the fact here brought out.that calcium salts decrease 

 the amount of potash dissolved by 1/5 normal or 1/50 normal nitric acid, and the fact 

 that calcium salts cause more potash to go into solution in an aqueous extract of 

 the soil — 'liberate:- potash.' 



"The decay of organic matter (starch or sawdust ) in a soil caused a decrease in the 

 amount of phosphoric acid dissolved, but a great increase in the amount of potash, 

 from 9,0 to 99 per cent with 1 5 normal acid, and from 11 to 20 percent with 1 50 nor- 

 mal acid. . . . 



"There was a variation in the power of soils to convert organic matter into humus 

 and retain it. In three soils, the amount of humus gained from starch at the end of 

 6i months was 0.0, 0.06, 0.18; and from sawdust 0.03, 0.14, 0.30 per cent of the ignited 

 soil. A relatively small amount of organic matter added to soils was converted into 

 humus. The maximum obtained in this work was 3 per cent of the starch and 4.1 

 per, cent of the sawdust, though from 75 to 95 per cent of the starch and from 30 to 

 .".7 per cent of the sawdust disappeared during the 4 months." 



On the source, amount, and importance of carbon dioxid in soil, J. Stok- 

 lasa and A. Ernest (Cenibl Bakt. [«fc.], 2. AbL, U (1905), No. 22-23, pp. 723-736; 

 abs, in Chem. Ztg., 29 (1905), No. 68, Repert. No, 17, p. 249; .Jour. Chem. Soc. [Lou- 



