448 



STATE BOARD OF AGRICULTURE. 



The PhospJiorus Balance of Michigan Soils. The amount of phos- 

 phorus lost annually from Michigan's soils is of great concern to the com- 

 monwealth. The figures in table I show as nearly as can be estimated 

 the quantity of this element of plant-food removed by the staple crops 

 and pastures, but not including fruit, mint, chicory, or vegetables such 



^/; frozen 



Relative ^.mounts of nifrogen, phosphoric dc/c/ dfic/ pot^^h 



fd.rm manure 



in 



Figure 12. 



as the onion, cucumber, cabbage and others, and in addition the amount 

 of phosphorus returned to the soil in farm manures and commercial 

 fertilizers. The fertilizers are considered to carry 10 per cent phosphoric 

 acid. 



TABLE I.— PHOSPHORUS BALANCE OF MICHIGAN SOILS. 



Pouncis 

 annuaUy. 



Phosphorus removed from the soil 



Phosphorus returned in farm manures 



Phosphorus returned in commercial fertilizers 



Total phosphorus returned to soil 



Phosphorus lost from the soil 



77,999,678 

 46,304,763 

 8,732,000 

 55,036,763 

 22,962,915 



These figures reveal rather striking conditions. There are being lost 

 annually about 22,900,000 pounds of phosphorus from our soils. It is 

 true that as yet we are not ready to ignore the phosphorus content of 

 many of the soils, that is supply it in sufficient quantities to meet the 

 requirement of the crops grown. Yet we are approaching this situation 

 and in case of many fields it seems to have been reached, and to these 

 phosphorus should be added in excess of the amount removed by the 



