66 SCIENCE AND SOIL 



These abnormal soils are likewise characterized by a high phos- 

 phorus content. The coral soil is also abnormal in its extremely 

 low potassium content, when compared with ordinary soils. 



Leather reports the average acid-soluble phosphorus of the 

 " black cotton soils " of India as 520 pounds in 2 million of soil, 

 and the analyses of eighteen other types of Indian soils show the 

 phosphorus as varying from a " trace " to 790 pounds; while 

 among the other four types described by him, one abnormal 

 soil (essentially an iron ore) contained 34.10 per cent of iron and 

 .28 per cent of phosphorus, corresponding to 5600 pounds of phos- 

 phorus per acre in a 6|-inch stratum. 



Von Ugrimov's analyses 1 of the cultivated " black earth " soil 

 of southwest Russia shows only 260 pound's of acid-soluble phos- 

 phorus in 2 million of soil; while Hilgard 2 gives .13 per cent of 

 P 2 O 5 , corresponding to 1130 pounds of phosphorus in 2 million of 

 cultivated soil, and .14 per cent of P 2 O 5 , or 1220 pounds of phos- 

 phorus, in 2 million of virgin soil. The fact that the samples se- 

 cured upon his request and analyzed by Hilgard showed 5.54 per 

 cent of humus in the cultivated soil and only 5.11 per cent in the 

 virgin soil, leads one to question whether the sample referred to as 

 cultivated soil, containing 4800 pounds of nitrogen, and acid- 

 soluble minerals amounting to 1130 pounds of phosphorus, 8600 

 of potassium, 9000 pounds of magnesium, and 18,300 of calcium 

 (in 2 million of soil), can fairly represent the black earth soil of 

 Russia whose average yield of wheat for 20-year periods is less than 

 10 bushels per acre in a three-year rotation, including one year of 

 green fallow. (See Bulletin 42, Bureau of Statistics, United States 

 Department of Agriculture.) 



The report of Von Ugrimov's investigations states that "pot and 

 field experiments with wheat, and analyses of the crop produced, 

 bear out the chemical analysis in indicating that phosphorus is 

 the element of plant food especially needed in this soil." 



Analysis of " typical soils " of British East Africa shows that 

 they are fairly well supplied with nitrogen and potassium, but 

 deficient in phosphorus, "a deficiency which is stated to .be 

 common throughout East Africa." 3 



1 Experiment Station Record, 10, 1015. 2 "Soils," page 364. 



3 Experiment Station Record (1908), 10, 1015. 



