426 EXPERIMENT STATION KECOED. 



The only Injurious effects which are attributed to earthworms are said to 

 be an insignificant danger to ungerminated seeds and a slight injury to potato 

 roots and potted plants. 



Soil fatigue, F. T. Peeitubin (Izv. Moskov. Selsk. Khoz. Inst. {Ann. Inst. 

 Agron. Moscou), 19 (1913^, No. 4, pp. 1-lU, figs. 36).— The author briefly 

 reviews the literature on the subject of tired soils and reports a series of 

 cereal cropping experiments conducted to determine the origin of injurious 

 substances said by American investigators to originate in the soil and cause 

 fatigue. 



Three successive growths of oats in distilled water, each of two weeks' 

 duration, showed no difference in weight or external appearance. 



Several different kinds of plants were seeded in varying alternations in 

 sand cultures, using clean quartz sand and Hellriegel's nutritive solution. 

 The second seeding in all cases produced a weak growth of poor appearance. 

 Repeated seeding in the same pot brought out abnormal characteristics in all 

 the plants, and plants of the second seeding showed the same poor develop- 

 ment when following a first seeding of their own kind as when alternated with 

 plants of different botanical groups. The addition of 15 gm. of clean pul- 

 verized charcoal to a pot after the first seeding was followed by normal de- 

 velopment of the second seeding. The decrease in yield in the second seeding 

 is attributed in part to the action of the decomposing root residue from the 

 first seeding, and not wholly to the alkalinity of the culture medium. 



Growths of wheat and oats from the second of two successive seedings- in 

 soil, each grown for six weeks, developed abnormally with greatly decreased 

 yield. CJomplete fertilization of the soil between seedings decreased the ab- 

 normal development very little. 



Oats and buckwheat were grown in water cultures, using soil extracts to 

 which the Hellriegel nutritive solution was added. Part of the solutions was 

 used in its original state, part was filtered through charcoal, and part was 

 boiled. The filtered solutions produced normal growths, while the boiled solu- 

 tions produced both normal and abnormal growths, depending on the solu- 

 tion. The untreated solutions in which there had been no previous growth 

 produced a normal growth. 



It is concluded that extracts from soils cropped as indicated probably con- 

 tain substances injurious to plants which are removed by filtration through 

 ckarcoal, and that boiling destroys them only in certain soils. No injurious 

 substances were found in soils which had not been cropped with cereals, and 

 it is thought probable that these soil extracts are injurious to plant growth 

 in general. 



The Illinois system of permanent fertility, C. G. Hopkins (Pop. Sci. Mo., 

 84 (1914), No. 1, pp. 52-63, figs. 5). — In this system "those materials which 

 are naturally contained in the soil in inexhaustible amounts are liberated 

 from the soil and thus made available for crop production; those contained in 

 the air are likewise drawn upon as needed ; while those materials which must 

 be purchased are bought and applied in liberal quantities, but in low-priced 

 forms, and then made available on the farm by economic natural methods." 



The system involves liberal applications of barnyard manure, ground lime- 

 stone, and raw rock phosphate, and rotations including a legume to supply 

 nitrogen. The practically inexhaustible supply of potash in the soil is drawn 

 upon to furnish the necessary amounts of this element of plant food. The 

 successful application of the system on a farm of poor gray prairie soil in 

 southern Illinois is described. See also a previous note (E. S. R., 29, p. 623). 



Comparative tests of various fertilizers, G. Smets and E. Thomas (A 65. in 

 ZentU. Agr. Chem., 42 {191S), No. 10, pp. 667-669) .—Fot tests on com of 



