PHOSPHATES m MASSACHUSETTS AGRICUL- 

 TURE; IMPORTANCE, SELECTION AND USE. 



WM. P. BROOKS. 



SUMMARY. 



A. In some of the corn-belt States farmers are advised that phos- 

 phorus is the key to permanent and profitable agriculture, and that fine- 

 ground rock phosphates should be used to supply that element. 



B. It is pointed out in support of this position that in the agriculture 

 of that section the soils contain relatively little phosphorus and are being 

 rapidly depleted in that element; that they contain practically exhaust- 

 less stores of potash; and that by suitable use of lime and the growth of 

 legumes their need for nitrogen can be met. 



C. It will be the purpose of this bulletin to show to what extent these 

 statements apply under Massachusetts conditions. 



D. It is believed that the facts and results presented will justify the 

 following conclusions : — 



1. Massachusetts soils, though not usually supplying as much phos- 

 phoric acid as maximum crops require, show a much less signal relative 

 deficienc}^ in that element than corn-belt soils. 



2. In our system of agriculture our soils are not being depleted in phos- 

 phoric acid, some of the more important reasons being: — 



(a) The products sold carry relatively little phosphoric acid. 



(b) Purchased grain and by-products, fed largely on our farms, contain 

 large amounts of phosphoric acid which finds its way to our soils in farm 

 manures, since phosphoric acid, voided in the dung, does not waste ap- 

 preciably between the stable and the field. 



(c) The practice of supplementing manures with commercial fertihzers, 

 except where the former as in some types of market gardening are applied 

 in enormous quantities, has been for many years and is now practically 

 universal, and as a rule these commercial fertilizers contain a high pro- 

 portion of phosphoric acid. 



(d) Phosphoric acid, even when applied in soluble forms, is fixed and 

 retained in the soil under ordinary soil conditions. This compound is 

 subject to little or no loss by leaching. 



3. Experiments in this station and elsewhere in the State indicate that 

 for most of our leading crops potash far more frequently than phosphoric 

 acid is the dominant food requirement. The only prominent exceptions 

 are the crucifers, — cabbage, turnip, etc. 



