82 MAINE AGRICULTURAL EXPE^RIMENT STATION. I914. 



ceedingly unsatisfactory. The best practice in plant breeding 

 work is to plant in a plot only what one wants to harvest there- 

 from. All in all, as long as conditions are similar for all varie- 

 ties of grain in trial in a field of fairly uniform soil, the results 

 of plot tests will show the relative yields of the varieties. 



The use of small unit areas in plant breeding work is neces- 

 sary in the propagation of selected plants, especially because of 

 the great number of such selections one must try out in the 

 search for superior individuals. It is often impossible during 

 the first season following propagatioai in head rows to carry 

 . out tests on units larger than a thousandth or a five hundredth 

 of an acre. The calculated yields per acre obtained on such 

 small areas are generally a great deal hig'her than those gotten 

 by growing the same variety in large plots. Mercer and Hall 

 have pointed out that a large error due to soil variation and 

 other factors is involved in tests on such small areas. These 

 authors show that in plots smaller than a fortieth or fiftieth 

 acre the error of the yields rises rapidly as the area of the plot 

 diminishes. However an increase in the size of a plot above a 

 fortieth or fiftieth acre does not give results of sufficiently 

 greater accuracy to warrant the greater expense involved in the 

 use of larger units. By testing varieties in .four or five units 

 of 40th or 50th acre size they show the error of the results to 

 be much smaller. In addition to the error worked out 'by these 

 authors there must be in plots surrounded by paths another 

 factor w'hich augments the productivity of the marginal plants. 

 As already pointed out this factor brings the shape as well as 

 the size of plot into consideration. 



From the "foregoing discussion it is evident that a means of 

 gauging approximately the cropping ability of a variety of 

 grain in a field on the basis of what it does in small areas would 

 be of some service. Undoubtedly an absolutely accurate meas- 

 ure can not be determined for forecasting on the basis of per- 

 formance in small areas the probable productivity of an oat 

 under field conditions. However, it may be possible to arrive 

 at a fair -estimate. To be able to do this would prove of great 

 assistance in judging the possible worth of pure lines which 

 have been propagated to the point of enabling tests in 500th 

 acre plots. Then, at the beginning of the search for superior 

 strains it is desirable to approximately estimate their worth as 



