SOIL MANAGEMENT — FERTILIZATION OF ORCHARDS. 41 



The yields have been light, averaging only about 2\ barrels per j'ear 

 per tree for the period from 1912 to 1920, inclusive, when the trees were 

 practically mature. Rhode Island Greening has been the heaviest pro- 

 ducer, deriving its superiority largelj^ from plots 1 and 2. Baldwin is 

 second, due in part to its superiority on plot 5. Roxbury Russet is third, 

 and Gravenstein fourth, this variety being considerably inferior to the 

 others in yield. 



In total yields of all varieties by plots, the order is the same as for the 

 size of the trees measured by trunk circumference. Plot 1 is ahead, fol- 

 lowed by plots 5, 2, 4 and 3 in order. 



All varieties increased their yield strikingly in the second period on 

 nearly all plots, and especially on plot 3, the unfertilized plot. Here the 

 total yield of all varieties was nearly fourfold. Baldwin increased nearly 

 fivefold despite the loss of one of the three trees in 1913. On plot 1 the 

 increase of all varieties was a little less than 50 per cent, though the yield 

 of Gravenstein fell off, owing to the death of one tree before 1907, and the 

 decline and death of another in 1919. If we assume that the normal in- 

 crease due to growth of the trees is about 50 per cent, then plot 3 has in- 

 creased its yield about two and one-half times over its normal, while the 

 increase on plot 2 was about 40 per cent more than this assumed normal 

 increase. Plot 4 has increased slightly more than the normal, while plot 

 5 has failed to make the normal gain. 



There are several suggestive things that can be noted concerning the 

 response of the different varieties to strip cultivation, but the small number 

 of trees involved makes it rather doubtful if these differences have real 

 significance. 



The total yield of apples from the five plots from 1902 to 1920, inclusive, 

 is shown graphically in Fig. 4. The heavy crops have been in the odd 

 years, and are shown by heavy lines, while the light yields of the even 

 years are shown by the lighter lines. The heavy perpendicular line be- 

 tween 1910 and 1911 marks the transition from sod mulch to strip culti- 

 vation. 



This chart shows that in the off years there were no very great nor con- 

 sistent differences between the plots until the 1920 crop. Nor has there 

 been a very great increase in yield with the larger size of the trees in 

 succeeding years. The off-year crop on the unfertilized plot has been the 

 lowest of all in most years until the last two crops, when it has been about 

 the average of the whole orchard. This better showing probably is the 

 result of the increased growth of these trees since strip cultivation has been 

 practiced. The crop of 1920 was heavier than that in any other off year, . 

 and, together with the light crop set in 1921 at the time of this writing, 

 may mark a reversal of the off and on years. In 1920 the crops on the 

 several plots were in much the same order as in the on years. 



The off-year jaelds of the muriate and sulfate plots have been closely 

 parallel, and the same is true of the on-year yields, yet the yields of the 

 muriate plot have been distinctly inferior to those of the sulfate plot. 

 This difference is less since 1911 than before, and may be due merely to 



