146 MASS. EXPERIMENT STATION BULLETIN 162. 



bage, Swedish turnip and wliite mustard. ^ This is l^est shown in the 

 resuhs obtained on the north soil test in 1896 witli cabbages. With 

 Swedish turnips in that year the two materials gave equal increases. 



Cabbages and Turni'ps — Increases per Acre {North Soil Test) (Pounds). 



The experimental results presented appear to prove that potash appli- 

 cation may usually be depended upon to give greater increases in most 

 of our more important crops than phosphoric acid application. The 

 figures given very conclusively demonstrate this for our station grounds, 

 and, with little less conclusiveness, for widely divergent soil types in 

 most parts of the State for potatoes, corn, hay (especially the second 

 cut, which is usually chiefly clover) and soy beans. We know that the 

 requirements of other legumes, including alfalfa, are in general similar 

 to those of clovers and soy beans. We know, also, that potash applica- 

 tion exercises a far greater effect in determining the yields of most of 

 our fruits and garden crops than i^hosphoric acid application. 



In view of the fact so clearly demonstrated by the figures which have 

 been presented for our most important crops, no further argument would 

 seem to be needed to demonstrate that phosphoric acid is not the key to 

 "permanent" (successful and profitable) "agriculture" in Massachusetts. 

 It is true, indeed, that our soils and subsoils contain less phosphoric acid 

 than potash, but it is also true that under our system of agriculture the 

 phosphoric acid has not apparently been undergoing exhaustion, and that 

 it is not now being depleted. It is not true for most crops that phos- 

 phoric acid is the element present in our soils in niinimo. Potash for many 

 is the element which determines the crop more largely than anj^ other 

 element apphed. Without the apphcation of potash in available form, 

 either in manures or fertihzers, the profitable production of most crops is 

 impossible. 



On the other hand, profitable crops of most kinds may be produced for 

 a time without apphcation of phosphoric acid. This, indeed, is not a 

 practice which can be recommended. Such a sj^stem should be followed 

 as will at least maintain the proportion of phosphoric acid at present 

 existing in our soils. To reduce the percentage below its present level 

 would for most soils and crops be a mistake. 



I For discussion of this subject see Bulletin No. 58, Hatch Experiment Station. 



