FIELD CEOPS. 435 



International catalogue of scientific literature. M — Botany (Inteniat. Cat. 

 Sci. Lit., o (1908), ;>/>. VIII+1210). — This is the fifth annual issue of the cata- 

 logue of scientific papers compiled and published by the International Council 

 of the Royal Society of England, the arrangement and grouping being essentially 

 the same as in previous issues ( E. S. R., 18, p. 435) . The number of papers noted 

 is about 7,000, the literature iuchuled being mainly that of 1905. As in the pre- 

 vious numbers, the American literature is inadequately catalogued, the publica- 

 tions of this Department and the experiment stations being almost wholly 

 neglected. In the section listing titles realting to the treatment of plant dis- 

 eases, not a single reference to American literature is given. 



FIELD CROPS. 



The rotation of crops, W. M. Hays et al. {Minnesota Sta. Bui. 109, pp. 

 281-35S, jigs. 12). — The plan of this experiment, together with earlier results, 

 has been previously noted (E. S. R., 7, p. 122). This bulletin reports the results 

 of 10 years' work. 



Of the different cropping systems tried those in which corn, small grains, and 

 timothy and clover for 1 to 4 years were arranged in a 4 to a 7 year rotation 

 with light manuring once during the course, gave large net profits. The stand- 

 ard 5-year rotation was as follows: First year corn following the application 

 of 8 tons of manure per acre, second year wheat, third and fourth years meadow, 

 and fifth year oats. The average gross income per year from this rotation 

 based on average farm prices was $14.08 per acre and the cost of production, 

 including .$3.50 land rental, was $9.05. The best rotations yielded a product 

 worth from $4 to $(> per acre more than is obtained on the average farm 

 throughout :\Iinnesota. All systems of cropping which provided for the main- 

 tenance of vegetable matter in the soil either by manuring or by growing pas- 

 ture or meadow crops gave profitable returns. 



The plats growing hoed crops such as corn, potatoes, and mangels continu- 

 ously without manure gave poorer returns than the plats growing grain continu- 

 ously without manure. It is believed that the intertillage given these crops 

 caused a more rapid depletion of vegetable matter than took place in the con- 

 tinued grain fields. The 4-year rotation, millet, barley, corn, and oats, gave no 

 better returns than wheat grown continuously. All these crops are considered 

 exhaustive as they decrease rather than increase the supply of vegetable matter 

 in the soil. Sowing grass seed with graih on corn land that is disked in the 

 spring, in place of fall plowing, proved to be the surest method of obtaining a 

 grass stand at the university farm. 



In studying the influence of crop rotation and continuous cultivation upon the 

 composition and fertility of soils at the beginning and close of the 10-year 

 period on the 44 experimental plats, it was found that when wheat, com, pota- 

 toes, and mangels were grown continuously the average loss of nitrogen 

 amounted to 0.034 per cent, or 1,100 lbs. per acre. The maximum amount of 

 nitrogen was lost in the continuous cultivation of these crops. In the case of 

 wheat two-thirds of the nitrogen removed was not utilized as plant food but was 

 lost by the rapid decay of the humus with tlie formation of soluble and volatile 

 nitrogen compounds. When the crops were grown continuously the soils lost 

 0.5 per cent of carbon, representing over 1 per cent of humus or 20,000 lbs., 

 equivalent to an annual loss of 1 ton per acre. On the plats growing the stand- 

 ard rotations there was an average gain of 0.014 per cent of nitrogen, equivalent 

 to about 300 lbs. per acre. The results show that the nitrogen content is main- 

 tained when clover is grown 2 years in a 5-course rotation. The data also indi- 

 cate that any substitution of crops in the rotation could be made without mate- 



