286 



Journal of Agricultural Research 



Vol. XIX, No. 7 



correlation between the most closely associated plants — that is ra'b' > 

 rob- Apparently the reverse condition, ra'v < rah, is due to some 



influence of the open space adjoining a 

 and h, which allows the fuller development 

 of those plants and in consequence renders 

 them more representative of the extremely 

 localized soil influences to which they are 

 subjected.^ 



3. TIMOTHY HAY 



The records of plot yields of timothy 

 hay published by Holtsmark and Larsen 

 (r?) have been shown elsewhere (5) to 

 present a correlation between the yield of 

 ultimate plots, combined in a 2 by 2 fold 

 manner, of 



y = o.6ii +0.027, r/Ef. = 22.4. 

 Clearly the field was highly heterogeneous. 



4. — ALFALFA HAY 



Records of the yields of a series of 46 

 plots on the Huntley Experiment Farm, 

 Montana, may be used to test further the 

 influence of heterogeneity on the yields of 

 alfalfa hay. Data were kindly placed at 

 my disposal by Mr. C. S. Scofield. 



Alfalfa should be of especial interest in 

 the present discussion since it is a deep- 

 rooted perennial herb, whereas all other 

 herbaceous crops investigated have been 

 annuals, or at most biennials. 



In field B of this experimental farm 

 there are two series, II and III, each of 23 

 plots. The 46 plots form a solid block 

 which has been planted each year to one 

 crop just as if it were an ordinary field. 



The two series of plots are separated 

 from each other only by a temporary irriga- 

 tion ditch. Each plot is 23^ feet wide, 

 317 feet long, and contains approximately 

 0.17 acre. These plots have in certain 

 cases been harvested in subplots of 0.085 ^cre when the division 

 has been into halves, of 0.0,567 acre when the division has been 



Fig. '2. — Diagram showing yield of al- 

 falfa in first cutting, 1913, on the 

 Huntley experimental tract. The 

 yield is expressed in pounds per half 

 plot. 



1 Possibly competition between closely associated a' and 6' plants tends to make the yield of one 

 lew when that of the other is high* 



