1916] FIELD CROPS. 29 



Inventory of seeds and plants imported by the Office of Foreign Seed and 

 Plant Introduction during the period from October 1 to December 31, 1913 

 {U. S. Dcpt. Ayr., Bur. Plant Indus. Inventory No. 37 {HUG), pp. 95, pis. G).— 

 Notes are given of seeds and plants imported from various sources from Oc- 

 tober 1 to December 31, 1913, about 700 numbers being included. These were 

 largely obtained from an expedition to Brazil made by P. H. Dorsett, A. D. 

 Shamel, and W. Popenoe, a collection by S. C. Mason in Egypt and Nubia, and 

 collections by F. N. IMeyer in Cliina. 



International catalogue of scientific literature. M — Botany {Internat. Cat. 

 Sci. Lit., 11 (1914), pp. yiII-\-856). — The literature heroin catalogued is said to 

 be mainly that of 1911, but to include some entries dated 1912 and portions of 

 the literature of 1901 to 1910, the index slips for which were received too late 

 for inclusion in previous volumes (E. S. R., 29, p. 327). 



International catalogue of scientific literature. M — Botany {Internat. Cat. 

 Sci. Lit., 12 {1915), pp. VIH+SSo). — The literature indexed herein is mainly 

 that of 1912 and 1913, but includes also material received too late for inser- 

 tion in previous issues. 



FIELD CEOPS. 



The influence of relative area in intertilled and other classes of crops on 

 crop yield, D. A. Brodie {U. S. Dept. Agr., Office Sec. Circ. 57 {1916), pp. 8, 

 fiy. 1). — A report is presented on studies as to the relation of the type of farm- 

 ing to the maintenance of crop yield made in 1914 and 1915 on 240 farms in 

 Chester County, Pa., and on 303 fai-ms in Central Illinios. The labor income 

 was used as the measure of efficiency in producing profits, and the crop index or 

 percentage relation of the crop yields of a particular farm to the average crop 

 yields of all the farms in the community as the measure of efficiency in main- 

 taining crop yield. Use was also made of two other studies furnishing data on 

 this subject, one covering 377 Chester County, Pa., farms, antl the other, 300 

 farms in Lenawee County, Mich. Tlie relation of different groups of crops to 

 crop yield is shown in tables and discussed. 



For the purpose of this study the farm crops were divided into intertilled, 

 annual not intertilled, and perennial crops. The results indicated that in all 

 the districts so far studied an optimum percentage of the crop area of the 

 farm may be devoted to a single class of crops and maximum yields main- 

 tained. Under tl>e rather intensive types of farming studied in IV'nIlr^vlvallia 

 and Michigan and under the more extensive type practiced in Central Uliuoifl, 

 the optimum area of intertilled crops in each case was found to fall with in 

 5 per cent of each other, the range being about from 32 to 36 per cent. It 

 ^^•as further indicated that when more than this percentage of area is devoted to 

 a single class of crops, yields decrease even where there is an increase in the 

 number of live stock per acre. 



The area devoted to small grain in the Pennsylvania area is so small that it 

 is regarded as either not directly affecting crop yield or that its inlluence is 

 completely masked by the effect of the amount of manure available. The opti- 

 mum percentage area for perennial grass, which is mainly timothy and clover 

 in Chester County, Pa., was aljout 30 per cent of the crop area of the farm. 



A cropping system constructed from data brought out in a survey made in 

 1912 was found to correspond very closely to the practice of those farmers on 

 the one hand who maintain high yields and with those on the other hand who 

 made the highest profits. Taking the data secured in Chester County, it is 

 stated tiiat with the allowance of about 10 per cent of the crop area of various 

 crops not in the rotation such as garden, orchard, soiling crops, and the like. 



