1919] SOILS — FERTILIZERS. 315 



ported thai the sulphuric acid I s< >, | content of snow and rain water varied with 

 the proximity of Industrial centers and the prevailing direction of the wind. 

 In an industrial district, freshly fallen snow was found t<> contain <>n an aver- 

 age I'm ni in to 20 nig. per kilogram and fresb rain water from 17 to 18 m.u r . 

 per liter of sulphuric acid, much lower amounts than have been recorded for 

 certain agricultural stations. Distilled water exposed in an Industrial district 

 absorbed 1.2 rag. of sulphuric acid per LOO square meters in 24 hours. The 

 true sulphuric acid content of snow and rain was obtained only with freshly 

 fallen samples. 



SOILS— FERTILIZERS. 



Soil factors affecting 1 the toxicity of alkali, F. S. 1 1 akkis and D. W. Pitt- 

 man {Jour. Agr. Research [(. ST.], 15 {1918), No. 5, pp. 281-S1U, figs. 21). — 

 Continuing previous work at the Utah Experiment Station, an attempt was 

 made to determine with more exactness the quantities. of the various salts that 

 prohibit crop growth under different soil conditions. The general method of 

 procedure was the same as was used previously (E. S. K., 34, p. 12.~>) in study- 

 ing the effects of different salts and combinations of salts. In these experi- 

 ments, sodium carbonate and sodium sulphate were used at rates of 500, 1,000. 

 3,000, 5,000. 7.000, and 10.000 parts per million of dry soil, and sodium eWorld 

 at rates of 400. 1,000, 2.000, 3,000, and 4,000 parts. Wheat plants were grown 

 in the glass tumblers for 21 days in sand, loam, clay, and garden soil, with and 

 without addition of peat or manure and with varying amounts of moisture. 

 About 12,00(1 determinations of the effect of the salts on germination and growth 

 under the different conditions were made. 



Summarizing the results, it is stated that "size of particles of a sand inde- 

 pendent of other factors does not seem appreciably to influence the toxicity of 

 alkali. Loam soils are more tolerant of alkali than either sand or clay. The 

 coarser loams are more tolerant than the liner at the same moisture content, 

 but if the heavier loams are maintained at an equivalent moisture content they 

 are more tolerant. 



"Organic matter increases the resistance to alkali when the soil containing 

 it is given sufficient moisture, but where present in large quantities organic 

 matter decreases the resistance if the moisture supply is low. Increasing the 

 moisture content of a soil up to the maximum that will produce good crops in- 

 creases resistance to alkali. 



" The toxicity of sodium chlorid and sodium sulphate seems to depend to 

 quite an extent on the relation between concentration of salt and percentage of 

 moisture present, while the toxicity of sodium carbonate is more largely 

 affected by the presence of organic matter. Organic matter in the soil seems 

 actually to remove sodium carbonate from the soil solution in large quantities, 

 This probably explains why in experiments where sodium carbonate is added 

 to a loam soil, it is less toxic than sodium chlorid. while in Held studies where 

 the salt is determined by analyses and in solution and sand culture studies 

 the sodium carbonate is more toxic. 



"Practical conclusions that may be drawn from these experiments are: (1) 

 Loam soils and soils with a high water-holding capacity may be successfully 

 farmed at a higher alkali content than others; (2) soils in which alkali re- 

 duces crop yields should be kept as moist as is compatible with good plant 

 growth; and (3) manure, or other organic matter, should be beneficial to alkali 

 soils, especially those high in carbonates." 



Determining the absolute salt content of soils by means of the freezing- 

 point method, G. J. Bouyoucos and M. M. McCool (Jour. Agr. Research 

 [U. S.], 15 (1918), No. 6, pp. 331-336).— In investigations at the Michigan Ex- 



