CONTENTS. ix 



PAGE 



Bulletin 162. Phosphates in Massachusetts agriculture : importance, 



selection and use, 131 



Summary, 131 



Introduction, 133 



Relation of Massachusetts agriculture to soil composition, and 



results of chemical analj'sis, 135 



Composition of Massachusetts soils, 137 



Relative need of phosphoric acid and potash, .... 139 



Experimental results, 139 



The potato, 139 



The corn crop, 141 



The hay crop, 142 



Asparagus, 144 



Soy beans, oats and rye, 145 



Cniciferai, 145 



Experiments for comparison of different phosphates, . . . 147 

 Comparison of phosphates on the basis of equal money's 



worth, 147 



Phosphates compared on the basis of equal annual application 



of phosphoric acid, 148 



Plant-food elements apphed, 149 



General treatment, 149 



Crops grown, 150 



Relative profits on the different phosphates, . . .156 



Cumulative effect, 157 



Indirect or secondary effects, 158 



Effect on soil acidity, 159 



Sulfur supplied, 161 



Beneficial secondary effects from the use of soluble phos- 

 phates, 161 



Rapid early growth of both roots and tops, .... 161 



Increase in tillering of cereal grains, 162 



Earlier and more perfect ripening, 162 



Effect on the availability of soil constituents, . . . 163 



Larger gain of atmospheric nitrogen, 164 



Conclusions, 164 



Relative phosphate needs of different crops, .... 167 



