44 



MASS. EXPERIMENT STATION BULLETIN 209. 



horizontal line along the abscissa of 20 per cent shows what we may call 

 the normal yield of each plot. 



The manure plot produced from 8 to 17 per cent excess over its normal 

 20 per cent under sod mulch in the on years, and only a little smaller 

 excess in the off years. Under strip cultivation since 1910 it has fallen 

 to an average excess of about 8 per cent in the on years, and in three of 

 the off years it has failed to produce its normal 20 per cent of the crop. 

 Of course this percentage loss of the manure plot is made up by the other 

 plots, and the ashes plot has helped do this. In all but two of the on years 

 under sod mulch it failed to produce its normal 20 per cent, while in three 

 out of five crops under strip cultivation it has exceeded its normal share. 

 In the off years since strip cultivation its excess is much more marked. 

 The unfertilized plot was far behind under the sod mulch system, but 

 shows fairly consistent gains since strip cultivation has been practiced, 

 and in one of the off years has exceeded its normal 20 per cent. 



Effect of Form of Potash. — The muriate and sulfate plots have usually 

 been in close accord in the off years, but in the on years there was marked 

 superiority in the sulfate plot up to and including 1911, with the exception 

 of 1905. Since 1911 the yields of these two plots have not differed widely. 



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Fig. 6. 



Yields by plots in percentages of total yields of the whole orchard. 

 Plots 4 and 5. 



