1919] ' FIELD CROPS. 438 



to the plats on the series mentioned. It appears, liowever, that where determi- 

 nations are sufficiently large in number and are made covering varying condi- 

 tions of soil and climate, probable errors for areas of given size are very 

 similar." 



Tabulated data are presented and discussed comparing the increases in yield 

 following the different fertilizer treatments on the various experiment fields as 

 ascertained by the tenth-acre plat and the square-yard methods, together with 

 data showing the yields secured from the entire tenth-acre plats and from the 

 square-yard areas removed from them. The effect on yields of alleys along the 

 sides of plats and of cultivated roadways at the ends, as indicated by investi- 

 gations described by Arny and Hayes (E. S. R., 40, p. 226), is pointed out, and 

 the statement made that the yield of entire plats subject to this effect should 

 ordinarily be about 5 to 10 per cent higher than that of square-yard areas not 

 subject to border effect. The cost of removing 10 square-yard areas from a 

 tenth-acre plat, thrashing, and weighing the product is said to be approximately 

 the same as for harvesting the entire area with the binder, thrashing the grain 

 with the ordinary thrashing machine, and weighing the product. 



The authors conclude that " the variations in the calculated probable error 

 for the yield determinations at the different locations emphasizes the desira- 

 bility of deriving probable error for use in the interpretation of the results of 

 each test. The pairing method may be used to advantage in deriving probable 

 error where the yields from a sufficient number of check plats Is not available 

 for this purpose. Yields determined from 4 to 5 systematically distributed 

 square-yard areas removed from plats one-tenth acre in size or less of rela- 

 tively uniform crop may be confidently substituted for those from the entire 

 plats. Under similar circumstances the yields from a greater number of square- 

 yard areas may be considered more accurate than those from the entire plats. 

 From Very nonuniform crops the yield from 10 square-yard areas systematically 

 distributed may not be as accurate as the yields from the entire plats. The 

 method of determining yields by the removal of relatively small systematically 

 distributed areas, square yards or rod rows, from plats may be used to ad- 

 vantage: (a) Where facilities for making yield determinations from entire plats 

 are lacking, (b) to check the accuracy of yield determinations on plats, [and] 

 (c) where more accurate determinations of yield are desired than can be se- 

 cured from the limited number of larger plats that can ordinarily be devoted 

 to a series of tests." 



[Report of field crops work in Nebraska] (Nebraska Sta. Rpt. 1918, pp. 21, 

 ^2-2//).— This briefly describes work conducted during 1918 on the North 

 Platte, Scottsbluff, and Valentine substations. 



The average yield of spring wheat at North Platte was 8.9 bu. per acre, and 

 of winter wheat 7 bu. per acre, although most of the latter was winterkilled. 

 Spring wheat following summer tillage produced 17.5 bu., as compared with 3.7 

 bu. under continuous cropping. Winter wheat following corn produced 5.6 bu., 

 and after summer tillage 19 bu. Without irrigation potatoes yielded S4.5 bu. 

 per acre, corn for silage 4.5 tons, and winter wheat 8.3 bu., as compared with 

 185 bu., 9.1 tons, and 26.2 bu. per acre, respectively, with irrigation. 



Observations on irrigated crop rotations at Scottsbluff showed that low yields 

 followed continuous cropping ; that poor grade and extremely scabby potatoes 

 were secured from short rotations ; that, fall seeding of alfalfa in grain stubble 

 gave better results than seeding alone in the spring except during seasons when 

 grasshoppers were bad, when early spring seeding is deemed preferable; that 

 barnyard manui-e was beneficial ; and that there was a marked residual effect 

 from alfalfa. Sugar beets grown on manured plats produced at the rate of 21.3 



