PHOSPHATES IN MASSACHUSETTS AGRICULTURE. 143 



included in the rotations which have been followed on both has included 

 mixed timothy, redtop and red and alsike clovers. On the phosphate 

 field materials furnishing nitrogen and potash are annually equally and 

 hberally appUed to all plots. There are 3 no-phosphate plots and 10 

 receive phosphoric acid. On field G there are 5 similar series of plots, 

 each series including 1 no-potash plot and 7 receiving potash. All plots 

 annually receive materials furnishing equal nitrogen and phosphoric 

 acid. Average results only are here presented. ^ 



Effects of Phosphoric Acid on the Hay Crop {Phosphate Field). 



Effects of Potash on the Hay Crop {Field G). 



It will be noted that neither phosphoric acid nor potash produced a 

 large increase in the first cut of the season ("hay") except in one year, 

 1911, when the potash appeared greatly to improve the crop. Neither, 

 as is well understood, is the dominant requirement for either timothy 

 or redtop which predominate in the first cut. The increase in hay pro- 

 duced by the potash is, however, greater even when lowest than that 

 produced by the phosphoric acid at its best. 



The far greater proportional increase in the rowen crop produced by 

 the potash is explained by its relation to clover, which cannot be suc- 

 cessfully produced in our soils without it. The lesser increase in the 



1 For details see annual reports for 1907, 1908, 1910, 1911 and 1912. The great variations in yield, 

 even with full fertilization in different years, were doubtless due chiefly to seasonal variations in 

 rainfall. 



