426 GROWTH OF PLANTS 



several peat soils as the pressure rose. The pressure varied from that of a 

 screw hand press to 30,000 pounds per square inch exerted by a hydrauhc 

 press and rose in steps of 1000 or several thousand pounds per square 

 inch. The acidity fell as the pressure to squeeze out the successive water 

 fraction rose. In the more acid peats the acidity fell as much as 3 pH, 

 from 3.64 pH at low pressures to 6.77 pH at high pressures. The most 

 marked fall was from minimal pressures to 1000 to 4000 pounds, but there 

 were sUght falls above 4000 pounds. In peat soils the phosphorus content 

 of the water fractions pressed out by increasing pressures fell markedly. 

 In a brown sphagnum peat, phosphorus content fell from 50 to 55 ppm 

 with slight pressure to 3 to 4 ppm with 20,000 to 30,000 pounds. The 

 phosphorus content of expressed water continued to fall noticeably even 

 above 4000 pounds. Even a sandy loam showed similar changes in phos- 

 phorus content of water fractions as the pressure increased. The supply of 

 acids and phosphorus was not exhausted by the pressure; for on rewetting 

 these materials give fractions similar to those initially observed as far as 

 the hydrogen-ion concentration and phosphorus content are concerned. The 

 authors suggest that high pressures may form semi-permeable membranes 

 in the materials and mention Bouyoucos' suggestion that the small capillary 

 spaces may contam more dilute solutions. They feel, however, that the real 

 explanation of the phenomenon is still to be learned. 



Insoluble organic sources of nitrogen. In mixed fertilizers insoluble 

 organic nitrogen sources that gradually become available during the crop 

 season are supposed by some to have an advantage over nitrates and other 

 soluble compounds which are subject to leaching in light soils under 

 heavy rainfall. Such nitrogen sources also add to organic content of soil. 

 McCool *■* has made a study of several insoluble organic nitrogen com- 

 pounds as to rate of ammonification and nitrification in soils and as to 

 their relative values as nitrogen sources for crop growth. 



A patented mixture of fermented molasses concentrate, after distilling 

 off alcohol, and calcium cyanamide, bearmg about 55 per cent soluble nitro- 

 gen, was compared as such and after leaching out the soluble nitrogen 

 with two grades of tankage. While there was considerable variation in the 

 relative rate of ammonification of the four materials in Gloucester loam 

 and Norfolk fine sand the two tankages early showed most rapid nitrifica- 

 tion in both soils; but later the nitrification of tankage was no more rapid 

 in Gloucester loam than that of the molasses mixture. The molasses 

 mixture was equal to high-grade tankage for production of snap beans, 

 tobacco, and corn, and superior to tankage for cotton, rye grass, and millet. 

 Also the slower rate of nitrification of the molasses mixture should lead 

 to lower rate of loss of nitrogen by leaching in soils. McCool also made a 

 similar study ^'' of the du Pont Urea- Ammonia Liquor-37 (UAL-37) which, 

 when mixed with acid phosphate, potash, and other materials, forms an 

 insoluble nitrogenous material. This proved a little less effective for 

 millet growth ui Norfolk fine sandy loam than the insoluble nitrogen of 



