356 Journal of Agricultural Research vol. xx, No. s 



the alfalfa upon the yield of subsequent crops decreases with the lapse 

 of time from the maximum correlation found for ear corn in 191 6. The 

 residual influence of the alfalfa is clearly marked in the oat crop of 191 7 

 and may still be evident in the silage corn and barley crops of 191 8 

 and 1 91 9. 



In view of the early introduction of alfalfa into the rotation, it is 

 impossible to determine whether the correlations between yields other 

 than those for alfalfa are due to the variation from plot to plot of the 

 amount of nitrogen fixed by the alfalfa or whether it is to a considerable 

 extent due to the original heterogeneity of the plots. This and other 

 problems which will suggest themselves to the reader can be solved only 

 by the analysis of further experimental data. The illustrations of the 

 present paper are sufficient to show the value of the application of the 

 interannual correlation method to agronomic problems. 



LITERATURE CITED 

 (1) Harris, J. Arthur. 



1915. ON A CRITERION OF SUBSTRATUM HOMOGENEITY (OR HETEROGENEITY) 

 IN FIELD experiments. In Amcr. Nat., v. 49, no. 583, p. 430-454. 

 (2) 



1915. the value OF inter-annual correlations. In Amer. Nat., v. 49, no. 



587, p. 7°7-/ 12 - 



(3) — 



1920. practical universality of field heterogeneity as a factor in- 

 fluencing PLOT YIELDS. In Jour. Agr. Research, v. 19, no. 7, p. 279- 

 314. Literature cited, p. 313-314. 



(4) Lehmann, A. 



1907. SEVENTH ANNUAL REPORT OF THE AGRICULTURAL CHEMIST FOR THE YEAR 



1905-1906. [Department of Agriculture, Mysore State.] 53 p. 

 Bangalore . 



(5) Lyon, T. L. 



1912. SOME EXPERIMENTS TO ESTIMATE ERRORS IN FIELD PLAT TESTS. In 



Proc Amer. Soc Agron., v. 3, p. 89-114, 5 fig. 



(6) Smith, Louie H. 



1910. PLOT ARRANGEMENTS FOR VARIETY EXPERIMENTS WITH CORN. In ProC. 



Amer. Soc. Agron., v. 1, 1907/09, p. 84-S9. 



(7) Stockberger, W. W. 



1912. A STUDY OF individual performance in hops. In Ann. Rpt. Amer. 

 Breeders' Assoc, v. 7/8, p. 452-457. 

 (8) 



1916. relative precision of formulae for calculating normal plot 



yields. In Jour. Amer. Soc. Agron., v. 8, no. 3, p. 167-175. 



